Debunking "physics by experts"

[GregoryUrich]

Aircraft Impact Damage
Tomasz Wierzbicki, Professor of Applied Mechanics, MIT
Liang Xue, Ph.D. Candidate of Ocean Engineering, MIT
Meg Hendry-Brogan, Undergraduate student of Ocean Engineering, MIT

http://web.mit.edu/civenv/wtc/PDFfiles/Chapter%20IV%20Aircraft%20Impact.pdf

http://public.gregjenkins.promessage.com/Ningen1.jpg
http://public.gregjenkins.promessage.com/Ningen2.jpg
http://public.gregjenkins.promessage.com/Ningen3.jpg

Wierzbicki et al.'s conclusion regarding core damage is based on flawed assumptions. They arrive at the amount of energy left to damage the core by subtracting Eplane + Eext_col + Efloor from Ekinetic. The Ekinetic is based on the total mass of the airplane which includes the fuel mass (roughly 32% of KE for 10,000 gal).

Once the fuel tanks disintegrate the fuel is incapable of damaging the steel core columns in the same manner as the wings cut the exterior columns. In fact the fuel mass can only reasonably be assumed to apply a general shear force to the entire structure which the structure is perfectly capable of absorbing.

So essentially there is an energy deficit before any damage can be done to the core columns.

[T.A.M.]

so write them and tell them so...see what they say. Unless, of course, you think they are paid shills...

TAM;)

[T.A.M.]

and the reason I suggest this, is that any HONORABLE scientist, would take the proper channels, follow proper protocol, if they have a problem with scientific findings or a scientific paper...take it to the authors, and allow them to respond, not just come here and say they are wrong.

TAM:)

[Minadin]

Once the fuel tanks disintegrate the fuel is incapable of damaging the steel core columns in the same manner as the wings cut the exterior columns. In fact the fuel mass can only reasonably be assumed to apply a general shear force to the entire structure which the structure is perfectly capable of absorbing.

You don't think that liquid fuel travelling at 800+ KPH can do any structural damage? What about previously stationary objects that are in its path? Have you ever seen a high velocity stream of water? Just because it's liquid, doesn't mean that it's incapable of doing major damage to much more solid things. I'm sure you've seen videos of police using fire hoses against crowds of rioters / protesters.

[DGM]

Meaning..............

[GregoryUrich]

and the reason I suggest this, is that any HONORABLE scientist, would take the proper channels, follow proper protocol, if they have a problem with scientific findings or a scientific paper...take it to the authors, and allow them to respond, not just come here and say they are wrong.

TAM:)

I already wrote to all of them. They have not responded. Further, I have not suggested anything regarding the character of the scientists or their motives.

[The Almond]

[...]

Once the fuel tanks disintegrate the fuel is incapable of damaging the steel core columns in the same manner as the wings cut the exterior columns.

This is the type of comment I'd love to see referenced somehow.

In fact the fuel mass can only reasonably be assumed to apply a general shear force to the entire structure which the structure is perfectly capable of absorbing.

Same here. These are statements that you expect us to agree with based on your opinion alone. You do the calculations, do the research, reference the material, and then come back and talk to me.

So essentially there is an energy deficit before any damage can be done to the core columns.
This conclusion is not supported by evidence.

[GregoryUrich]

You don't think that liquid fuel travelling at 800+ KPH can do any structural damage? What about previously stationary objects that are in its path? Have you ever seen a high velocity stream of water? Just because it's liquid, doesn't mean that it's incapable of doing major damage to much more solid things. I'm sure you've seen videos of police using fire hoses against crowds of rioters / protesters.

So essentially a wave of debris and liquid hit the cross section of the core. What percentage of that KE actually acted on damaging the core columns?

[Dave Rogers]

The question is, what other energy sinks were present? The kinetic energy had to be absorbed, apart from a small fraction that was retained by debris exiting the opposite side of the towers; so if it wasn't absorbed by damage to the aircraft structure or damage to the building structure, where did it go?

Dave

[HeyLeroy]

Omfg!!!111!! Teh Titanick Wuz An Incide Job!!!!11!!!! Iceburgs R Onlee Water!!!!!11!!!!!

[beachnut]

Aircraft Impact Damage
Tomasz Wierzbicki, Professor of Applied Mechanics, MIT
Liang Xue, Ph.D. Candidate of Ocean Engineering, MIT
Meg Hendry-Brogan, Undergraduate student of Ocean Engineering, MIT

http://web.mit.edu/civenv/wtc/PDFfiles/Chapter%20IV%20Aircraft%20Impact.pdf

http://public.gregjenkins.promessage.com/Ningen1.jpg
http://public.gregjenkins.promessage.com/Ningen2.jpg
http://public.gregjenkins.promessage.com/Ningen3.jpg

Wierzbicki et al.'s conclusion regarding core damage is based on flawed assumptions. They arrive at the amount of energy left to damage the core by subtracting Eplane + Eext_col + Efloor from Ekinetic. The Ekinetic is based on the total mass of the airplane which includes the fuel mass (roughly 32% of KE for 10,000 gal).

Once the fuel tanks disintegrate the fuel is incapable of damaging the steel core columns in the same manner as the wings cut the exterior columns. In fact the fuel mass can only reasonably be assumed to apply a general shear force to the entire structure which the structure is perfectly capable of absorbing.

So essentially there is an energy deficit before any damage can be done to the core columns.
You better talk to the fuel going at 400 mph before you say it can not damage anything. I think fuel traveling at 400 mph, like my water pressure cleaner, can rip off heads, and rip off ever single piece of carpet, skin, wallboard, etc, it touches. Darn, you are an engineer? Wow.

I do not understand, the KE of the plane could cut all the exterior columns, and the core columns would not fair well.

What is your point? Seems like you, a truther poster at woo land, have an agenda. You have left your degree and academic achievement behind to join truther land, 9/11 lies RUs. What is the real deal. State your opinion, and stop hiding behind the standard veiled attempts to act like a real engineer.

You need to read the physics of Karate.

[Furcifer]

The reason we have a tendency to simplify these things is because they are very, very, very complex. You want to know where that kinetic energy went? Well lets talk about the columns that were severed, along with the debris that was swept up. All of that mass quite suddenly was imparted with the kinetic energy of the plane in an inelastic collision. All of that mass is now moving nearly 500 mph, in the same path as the plane. Some of the steel and debris may have centripetal acceleration as well. (pretty deadly if you think about a 10 foot section of steel spinning at 300 rpm and moving 400mph) And to borrow from another thread you've got the "wake vortex" inside the building picking up debris and slamming it into the core, don't forget that ;). See how easy it is to miss something when you look to closely at things? This is why we like to simplify. Give me a CM for the plane and a trajectory. From that I can roughly tell you how much was dissipated in the exterior, then the floors/trusses then the core. Plain, simple and effective. No offense Greg, but this should have been posted in the other thread. And your shortsight is probably the reason no one has got back to you. Point mass, trajectory, kinetic energy, basic physics.

[beachnut]

So essentially a wave of debris and liquid hit the cross section of the core. What percentage of that KE actually acted on damaging the core columns?
We will never know because the fires weakened the steel, now exposed after the fire insulation was pressure washed from the steel. The tower fell before anyone could see how many core columns were damaged, because they failed in the fire. You have asked questions now that many engineers have calculated.

At least you have not started telling us the wings can not enter the building, or the plane should have done something stupid. The plane was not going 70 mph, like the idiots in the truth movement show wrecks of planes hitting buildings at. The planes were not going 180 mph as in a landing accident. The planes were going 470 to 590 mph. 2.8 and 4.3 billion joules of energy, 1300 to 2200 pounds of TNT energy. So quibble if you will, let your engineering degree fall down and go with the woo land of 9/11 truth, where physics is suspended, and peer review is a sham.

Are you going to estimate the blast effect of 470 to 590 mph fuel atomized by the impact as the 700 degree C engine cores auto ignite it? I have not seen a critique of those who did the pressure and blast effect papers. Would those blast effects know off the insulation of the floors, which fell if you touched it or brushed it? What was all that stuff flying in the air after the impacts? The joules just in the fuel were equal to 315 tons of TNT, how much of that was blast effects? (heat in fuel due to burning energy)

I think the bigger question is how much insulation was blown off at impact. The unprotected steel would weaken very facts and fail in less than two hours. That is what we saw on 9/11. We saw two aircraft with impacts 7 to 11 times greater than the design impact according to the chief structural engineer Robertson. Then fires out of control, started by 10,000 gallons of fuel burning and exploding on multiple floors. Steel now stripped of insulation was exposed to fire. I have to ask a fireman what happens to steel in fire, he will tell me it fails to hold what it suppose to hold due to heat. Real world, steel fails, it has not indestructible features, it fails. Thousand of steel structures have failed and killed people due to fire.

Again, what is your goal. When will we hear "pull it" and squib?

[GregoryUrich]

This is the type of comment I'd love to see referenced somehow.

Same here. These are statements that you expect us to agree with based on your opinion alone. You do the calculations, do the research, reference the material, and then come back and talk to me.

This conclusion is not supported by evidence.

My point is that Wierzbicki's conclusion is not supported by evidence. Do you have the same problem with that conclusion?

I can't imagine there is any research regarding cutting steel by splashing liquids on them with varying debris content and granularity at any velocity. I make the value judgement that it is not worth my time to look for articles.

I don't expect anyone to just accept my opinion. I expect people to think.

If one wanted to model this, there are three basic scenarios and two important assumptions:

Assumptions:

Since all other energy is expended in destroying the external columns, floor and airplane, the only energy left is the KE of the fluid.
Any debris carried by the fluid will already have reduced the energy available due to momentum transfer. For example, if the weight of the debris was equal to the weight of the fluid, the KE would be reduced to 50% assuming no loss due to deformation of debris (actually energy will be lost to deformation of debris).


Scenarios:

Some part of the fluid and debris would impact the columns directly. This is less than 10% of the cross sectional area of the core. This impact will be distributed over time, over the height of the column, and reduced due to the fluid component flowing around the core.
Some portion of the fluid and debris would pass through the core or outside the core impacting nothing.
Some portion of the fluid and debris would impact the core partitions which would would act as a diaphram until they were breached. Since the diaphrams are relatively easily breached any force transferred to the columns will be a fraction of the force on the diaphram and also will be distributed across the height of the column.


Thus, the majority of energy available cannot act on the core. Furthermore, the forces acting on the core are distributed over the height of the columns which reduces the force per unit to such an extent that very little damage can occur.

[gumboot]

For what it's worth, the building performance study for the Pentagon concluded that most of the interior columns were severed by jet fuel, not solid debris.

In addition, the amount of damage required to undermine the core might not be as great as you think. Each of the four corner columns of the core carried 5% of the core's gravity load. The other 43 columns carried only 1.8% of the gravity load each.

One of the reasons WTC2 collapsed first is because UA175 hit a corner of the core, and probably severed at least one (possibly two) of the critical corner columns.

-Gumboot

[Newtons Bit]

Thus, the majority of energy available cannot act on the core. Furthermore, the forces acting on the core are distributed over the height of the columns which reduces the force per unit to such an extent that very little damage can occur.

A concentrated force acting on a member will produce a moment (bending, hence damage) only twice as large as that same force distributed over the entirety of that member.

[GregoryUrich]

The reason we have a tendency to simplify these things is because they are very, very, very complex. You want to know where that kinetic energy went? Well lets talk about the columns that were severed, along with the debris that was swept up. All of that mass quite suddenly was imparted with the kinetic energy of the plane in an inelastic collision. All of that mass is now moving nearly 500 mph, in the same path as the plane. Some of the steel and debris may have centripetal acceleration as well. (pretty deadly if you think about a 10 foot section of steel spinning at 300 rpm and moving 400mph) And to borrow from another thread you've got the "wake vortex" inside the building picking up debris and slamming it into the core, don't forget that ;). See how easy it is to miss something when you look to closely at things? This is why we like to simplify. Give me a CM for the plane and a trajectory. From that I can roughly tell you how much was dissipated in the exterior, then the floors/trusses then the core. Plain, simple and effective. No offense Greg, but this should have been posted in the other thread. And your shortsight is probably the reason no one has got back to you. Point mass, trajectory, kinetic energy, basic physics.

The other thread is about debunking physics by non-experts. I think the people here need to look critically at the experts as well.

You are forgetting that there is an energy deficit just for the other damage.

Any acceleration of debris is an energy sink that reduces the energy available to damage the core.

"Wake vortex"? I thought that was the air curling off the end of the wing which as seen from the NIST damage photos had no effect what so ever.

[GregoryUrich]

A concentrated force acting on a member will produce a moment (bending, hence damage) only twice as large as that same force distributed over the entirety of that member.

Didn't Wierzbicki assume a shear failure mode?

Edit: No sorry, it wasn't shear.

[DGM]

Any acceleration of debris is an energy sink that reduces the energy available to damage the core.

Would you mind defining damage.

[Furcifer]

The other thread is about debunking physics by non-experts. I think the people here need to look critically at the experts as well.

You are forgetting that there is an energy deficit just for the other damage.

Any acceleration of debris is an energy sink that reduces the energy available to damage the core.

"Wake vortex"? I thought that was the air curling off the end of the wing which as seen from the NIST damage photos had no effect what so ever.


Energy sink? The debris hits the core as well. That is the trajectory of the plane, hence the debris.

What deficit? The plane had X KE. 100% was absorbed by the building (perhaps there is an issue with the debris that passed completely through the building?) I'm not sure I'm following you at all. Are you suggesting a 5 gram bullet does more damage than a 5 gram bullet that is a shell filled with liquid? The type of damage may vary, but the kinetic energy remains the same.

[Newtons Bit]

Any acceleration of debris is an energy sink that reduces the energy available to damage the core.

In the other thread you went on and on about conservation of momentum, and now you're saying when two objects collide there's a LOSS of energy? No. The energy is transfered, the only loss is from deformation of the objects and friction which are extremely marginal when looking at MJ.

[Newtons Bit]

Didn't Wierzbicki assume a shear failure mode?

Edit: No sorry, it wasn't shear.

If it was a shear failure, it would be equal to or less than 2. A point load at the end of a member will produce shear equal to that force, a distributed force over the entire member will produce a shear equal to half that force at each end.

[The Almond]

My point is that Wierzbicki's conclusion is not supported by evidence.

And my point is that it's your opinion.

Do you have the same problem with that conclusion?
No, because I agree with Dr. Wierzbicki that a volume of fluid, traveling at a velocity, has kinetic energy. I also agree that when said fluid strikes an object, it will transfer an equal amount of energy to the object. That is the purpose of Wierzbicki's paper.

Your disagreement stems from the idea that the fluid will do no damage, less damage, less concentrated damage, bearing point only damage, or something else, to the columns in question. When asked to produce evidence and references for your conclusion you respond with this:

I can't imagine there is any research regarding cutting steel by splashing liquids on them with varying debris content and granularity at any velocity. I make the value judgement that it is not worth my time to look for articles.
Which amounts to an argument from personal incredulity.

I don't expect anyone to just accept my opinion. I expect people to think.
Then give us something other than your opinion to work with.

If one wanted to model this, there are three basic scenarios and two important assumptions:

Assumptions:
Since all other energy is expended in destroying the external columns, floor and airplane, the only energy left is the KE of the fluid.
Any debris carried by the fluid will already have reduced the energy available due to momentum transfer. For example, if the weight of the debris was equal to the weight of the fluid, the KE would be reduced to 50% assuming no loss due to deformation of debris (actually energy will be lost to deformation of debris).Scenarios:
Some part of the fluid and debris would impact the columns directly. This is less than 10% of the cross sectional area of the core. This impact will be distributed over time, over the height of the column, and reduced due to the fluid component flowing around the core.
Some portion of the fluid and debris would pass through the core or outside the core impacting nothing.
Some portion of the fluid and debris would impact the core partitions which would would act as a diaphram until they were breached. Since the diaphrams are relatively easily breached any force transferred to the columns will be a fraction of the force on the diaphram and also will be distributed across the height of the column.Thus, the majority of energy available cannot act on the core. Furthermore, the forces acting on the core are distributed over the height of the columns which reduces the force per unit to such an extent that very little damage can occur.

Again, your conclusions are not supported by evidence, theory, reference or anything other than your personal opinion. The phrase "some portion" is weasel language for "qualitative", meaning "useless". You could determine, from your experiment, whether or not damage was absorbed in those scenarios, but you cannot determine the extent. That makes your conclusion about the "majority of the energy available..." unsupported.

Didn't Wierzbicki assume a shear failure mode?Per Newton's Bit's comment, shear and moment are interrelated. Shear is defined as the derivative of the moment, and as the additive inverse of the integral of the distributed load. Any beam under load will undergo both shear and moment stresses, and shear failure mode simply indicates that the beams will fail in shear first. Check R.C. Hibbler Mechanics of Materials page 265 for more information.

[T.A.M.]

Well the purdue simulation has the fuel removing fireproofing, so that would take some KE, so perhaps this aspect of it needs to be looked into.

TAM:)

[Myriad]

I can't imagine there is any research regarding cutting steel by splashing liquids on them with varying debris content and granularity at any velocity. I make the value judgement that it is not worth my time to look for articles.

So, the manufacturers making and selling abrasive waterjet cutting tools for steel cutting just throw the machines together without any idea of whether they'll work or not? And then sell them without testing them first?

Or is there some fundamental physical principle that explains how an abrasive-carrying water stream less than 1mm in cross-section moving about 1400 mph can cut through steel, but masses of fluid with entrained debris at 1/3 that velocity and thousands of times greater cross-section will only "splash" on steel?

Respectfully,
Myriad

[GregoryUrich]

In the other thread you went on and on about conservation of momentum, and now you're saying when two objects collide there's a LOSS of energy? No. The energy is transfered, the only loss is from deformation of the objects and friction which are extremely marginal when looking at MJ.

You surprise me Newton. Energy is only conserved in perfectly elastic collisions. Fluids are definitely not elastic in behavior.

m1v1 = m1v2 + m2v2

to make it simple let m1=m2=m

so

mv1 = 2mv2 or v2 = v1/2

KE1 = (mv1^2)/2, KE2 = (2m(v1/2)^2)/2

KE1/KE2 = 2

[Minadin]

I can't imagine there is any research regarding cutting steel by splashing liquids on them with varying debris content and granularity at any velocity. I make the value judgement that it is not worth my time to look for articles.

I can't believe you said that.

http://en.wikipedia.org/wiki/Abrasive_water_jet_cutter

[T.A.M.]

interesting...so the fuel not only removed the fire proofing, but it is possible the fuel itself helped/contributed to the actual cutting of the columns...

TAM:)

[Furcifer]

Greg: Even if the plane was made of marshmallow, the same kinetic energy does the same amount of damage. Overall the collision was an exogenic one, due to the chemical energy in the fuel.

ps. Greg you're not allowed to use my powerwasher, ever ;)

[GregoryUrich]

Well the purdue simulation has the fuel removing fireproofing, so that would take some KE, so perhaps this aspect of it needs to be looked into.

TAM:)

Then there is the energy that went into the swaying of the tower.

[T.A.M.]

so in the end, I would say lets wait and hear what the authors have to say...

please bring their response here when it has arrived.

TAM:)

[T.A.M.]

I can see where he is coming from...Energy in has to equal energy out...in some form, for it to follow the laws of physics.

The question is, did the original authors account for all that Kinetic energy "in" had to do...ie...if they assumed 100% of KE from fuel went into cutting the columns, this is kind of incorrect, in that it doesnt account for the KE from the fuel to remove the fireproofing...

Am I on the right track here?

TAM:)

Edit: of course, the point is irrelivent, if the energy we are talking about is insignificant...meaning, if it is not enough to have played a role in the collapse initiation, or lack of, than it really is more of an academic question.

[GregoryUrich]

I can't believe you said that.

http://en.wikipedia.org/wiki/Abrasive_water_jet_cutter

So the columns' 2" thick gypsum fireproofing was abraded for a fraction of a second.

I can't believe you said that.

[GregoryUrich]

Greg: Even if the plane was made of marshmallow, the same kinetic energy does the same amount of damage. Overall the collision was an exogenic one, due to the chemical energy in the fuel.

ps. Greg you're not allowed to use my powerwasher, ever ;)

Does your power washer cut the plate or even break the plastic light lenses your car.

Can't I please borrow it. I need to wash the cat.

[pomeroo]

So the columns' 2" thick gypsum fireproofing was abraded for a fraction of a second.

I can't believe you said that.



Remember when you were still trying to pretend you weren't a twoofer?

We caught you.

[GregoryUrich]

So, the manufacturers making and selling abrasive waterjet cutting tools for steel cutting just throw the machines together without any idea of whether they'll work or not? And then sell them without testing them first?

Or is there some fundamental physical principle that explains how an abrasive-carrying water stream less than 1mm in cross-section moving about 1400 mph can cut through steel, but masses of fluid with entrained debris at 1/3 that velocity and thousands of times greater cross-section will only "splash" on steel?

Respectfully,
Myriad

You could also use an air jet. It is the abrasive material removing microscopically sized particles that does the cutting. So if there was no 2" gypsum fireproofing the columns probably would have surface scratches.

[R.Mackey]

Once the fuel tanks disintegrate the fuel is incapable of damaging the steel core columns in the same manner as the wings cut the exterior columns. In fact the fuel mass can only reasonably be assumed to apply a general shear force to the entire structure which the structure is perfectly capable of absorbing.

So essentially there is an energy deficit before any damage can be done to the core columns.
You surprise me Newton. Energy is only conserved in perfectly elastic collisions. Fluids are definitely not elastic in behavior.

Eh, no. Energy is conserved as well, it's just much harder to keep track of.

The NIST report treats the effect of fluid only in the Simplified Calculations section of NIST NCSTAR1-2B (http://wtc.nist.gov/NISTNCSTAR1-2B_Chaps9-11.pdf), section 10.5, pages 374 ff. This shows that all by itself, and taking dispersion at the perimeter into account, the fuel does not have enough momentum to fail core columns -- but it's pretty close. This matches observation, otherwise we would predict many more failed core columns across most of the wingspan. Still, the impact of the fuel is considerable.

If it weren't for the dispersion, the fuel would plow right through the first core columns it hit.

Combine this diffuse effect with the others, i.e. the cloud of smashed up aircraft bits, and you indeed do have enough momentum to fail core columns at the right places.

You absolutely cannot neglect this energy or this momentum. I'm not surprised that you haven't received a reply from the authors.

[GregoryUrich]

Remember when you were still trying to pretend you weren't a twoofer?

We caught you.

Sorry, does not compute...I don't get it.

[Minadin]

Try to picture, in your head, a 10,000 gallon water balloon hurtling at your house / apartment building / office at ~ 800 KPH (500 mph). What would you expect to happen when it impacted?

[pomeroo]

Sorry, does not compute...I don't get it.


Sure.

[Furcifer]

Does your power washer cut the plate or even break the plastic light lenses your car.

Can't I please borrow it. I need to wash the cat.

Yah, be careful, it's one of those "Hotsy" 2400 psi. jobbies with the heater. You're gonna end up with this cat (http://www.blog.morgaine-lefaye.net/images/sphynx.jpg)

[Newtons Bit]

You surprise me Newton. Energy is only conserved in perfectly elastic collisions. Fluids are definitely not elastic in behavior.

Whoops! And this is why I don't do dynamics for a living. I was thinking that since fluids (gasoline, water, etc) are non-compressible, they can't be inelastic and hence, elastic collisions. However as I think about that, it doesn't make a whole lot of sense.

Further clarification: all collisions are elastic to a degree, hence why I said energy losses due to deformation. I'm not a COMPLETE idiot.

[Furcifer]

Then there is the energy that went into the swaying of the tower.

This is about the only energy sink I can think of (acoustic perhaps) , at least in the plane/building collision. Some energy would go into sway, and be dissipated. Incidentally Greg, if you calculate the sway, you'll have your mass, they are of course interdependent. I guess you would work backwards from known values. I believe there was a study in 1994 in regards to this. Someone here will know.

[Apollo20]

Gregory:

There IS an energy sink that is being neglected here and that is the energy to break the fuel into droplets. Now this could be millimeter sized droplets, to micron sized droplets, to molecular sized droplets. In the molecular limit we are talking about the vaporization energy of jet fuel which would be about 3 gigajoules if all the fuel was vaporized, but this would appear to be unlikely! However, a very rough calculation, assuming a "fracture energy" of the fuel to be ~ 1 J/m^2 of surface area, shows it would require ~ 10 MJ to convert the fuel to 100 micron droplets.

[maccy]

You could also use an air jet. It is the abrasive material removing microscopically sized particles that does the cutting.

Not true. There are plenty of water jet cutting systems that do not uses abrasives. The abrasive are added only for the toughest materials.

In a similar way, it's not a good idea from fly through a rainstorm at supersonic speeds:

http://www.time.com/time/magazine/article/0,9171,823522,00.html

[Corsair 115]

Question: is this talk of the energy involved only about the kinetic energy from the movement of the aircraft? Considering that after both impacts there were huge explosions, I'm wondering if the energy from those explosions has been factored into the damage that may have been done to the structure.

[Furcifer]

Gregory:

There IS an energy sink that is being neglected here and that is the energy to break the fuel into droplets. Now this could be millimeter sized droplets, to micron sized droplets, to molecular sized droplets. In the molecular limit we are talking about the vaporization energy of jet fuel which would be about 3 gigajoules if all the fuel was vaporized, but this would appear to be unlikely! However, a very rough calculation, assuming a "fracture energy" of the fuel to be ~ 1 J/m^2 of surface area, shows it would require ~ 10 MJ to convert the fuel to 100 micron droplets.

10 MJ seems high for just vaporization. And wouldn't this just manifest in an increased temp in the fuel anyways? First Law sounds like its getting broken otherwise.

[GregoryUrich]

Eh, no. Energy is conserved as well, it's just much harder to keep track of.

The NIST report treats the effect of fluid only in the Simplified Calculations section of NIST NCSTAR1-2B (http://wtc.nist.gov/NISTNCSTAR1-2B_Chaps9-11.pdf), section 10.5, pages 374 ff. This shows that all by itself, and taking dispersion at the perimeter into account, the fuel does not have enough momentum to fail core columns. This matches observation, otherwise we would predict many more failed core columns across most of the wingspan.

If it weren't for the dispersion, the fuel would plow right through the first core columns it hit.

Combine this diffuse effect with the others, i.e. the cloud of smashed up aircraft bits, and you indeed do have enough momentum to fail core columns at the right places.

You absolutely cannot neglect this energy or this momentum. I'm not surprised that you haven't received a reply from the authors.

Of course you are correct--energy is always conserved. Kinetic energy is not conserved though. For fluid the energy will go into accellerating the fluid perpendicular to the impact vector so it can flow around things.

As you say "This shows that all by itself, and taking dispersion at the perimeter into account, the fuel does not have enough momentum to fail core columns." According to Wierzbicki all other energy went into deforming the external columns, floors and airplane so there is no energy left to damage the columns.

[Apollo20]

Corsair 115:

That's a good point, but it's not part of Wierzbicki's calculation as far as I remember....

[GregoryUrich]

Not true. There are plenty of water jet cutting systems that do not uses abrasives. The abrasive are added only for the toughest materials.

In a similar way, it's not a good idea from fly through a rainstorm at supersonic speeds:

http://www.time.com/time/magazine/article/0,9171,823522,00.html

Yes, but do commercial airliners slow down for rain?

[GregoryUrich]

10 MJ seems high for just vaporization. And wouldn't this just manifest in an increased temp in the fuel anyways? First Law sounds like its getting broken otherwise.

It's not just vaporization. Surface tension!

[Apollo20]

3bodyproblem:

I see no violation of anything. Imagine if the jet fuel was frozen... then you would have to add in the energy needed to FRACTURE it. Droplet formation is the same type of thing; it requires energy to overcome the Van der Waals forces holding the fluid together. In the limit of the smallest droplets possible you have the vaporization energy.

[GregoryUrich]

Yah, be careful, it's one of those "Hotsy" 2400 psi. jobbies with the heater. You're gonna end up with this cat (http://www.blog.morgaine-lefaye.net/images/sphynx.jpg)

A relation to Mr. Bigglesworth I presume.

[Corsair 115]

Yes, but do commercial airliners slow down for rain?The main time commerical airliners fly through rain is on approach to the airport for landing, at which point they are moving relatively slowly. There's an enormous difference between that speed and flying supersonic.

[GregoryUrich]

Sure.

Oh yeah, I forgot...my ironic post regarding arguments not to use against troofers.

I'm still a non-troofer though--committed purveyor of lies and misinformation.

[R.Mackey]

As you say "This shows that all by itself, and taking dispersion at the perimeter into account, the fuel does not have enough momentum to fail core columns." According to Wierzbicki all other energy went into deforming the external columns, floors and airplane so there is no energy left to damage the columns.

Greg, look -- in your OP, you said that the fuel, after entering the building, could only contribute to a "general shear" on the entire structure. This is simply wrong. Thus you cannot discount that large contribution, and there is no energy deficit.

You seem to be attempting to say energy from component X only went into damaging structural system Y -- it isn't so. There's a large energy input, and numerous energy sinks, but there isn't a specific order in which sinks are applied, possibly excepting the perimeter columns.

[GregoryUrich]

Not true. There are plenty of water jet cutting systems that do not uses abrasives. The abrasive are added only for the toughest materials.

In a similar way, it's not a good idea from fly through a rainstorm at supersonic speeds:

http://www.time.com/time/magazine/article/0,9171,823522,00.html

Isn't steel one of the toughest materials. Wikipedia points out that you can cut fish sticks without abrasive. Otherwise,

"In the 1950s, forestry engineer Dr. Norman Franz experimented with an early form of water jet cutter to cut lumber. However, the technology didn't advance notably until the 1970s when Dr. Mohamed Hashish created a technique to add abrasives to the waterjet cutter.[1]"

These cutters take time too, not the fraction of a second involved in an impact.

[Newtons Bit]

Isn't steel one of the toughest materials. Wikipedia points out that you can cut fish sticks without abrasive. Otherwise,

"In the 1950s, forestry engineer Dr. Norman Franz experimented with an early form of water jet cutter to cut lumber. However, the technology didn't advance notably until the 1970s when Dr. Mohamed Hashish created a technique to add abrasives to the waterjet cutter.[1]"

These cutters take time too, not the fraction of a second involved in an impact.

Not really, and it sort of depends on the grade of steel. Steel used for structures is actually easily machineable and malleable. These are almost at the bottom of the rung as far as steel grades go. Aerospace steel can be as much as 10 times stronger.

The stuff is tough, but it's not titanium.

[slyjoe]

Question: is this talk of the energy involved only about the kinetic energy from the movement of the aircraft? Considering that after both impacts there were huge explosions, I'm wondering if the energy from those explosions has been factored into the damage that may have been done to the structure.

The energy introduced by explosions and fire was explicitly excluded from the calculations being discussed. It was mentioned as the "general accepted" reason the towers collapsed. The paper was making an argument as to whether or not the impact ALONE could have caused the towers to fail.

[GregoryUrich]

Greg, look -- in your OP, you said that the fuel, after entering the building, could only contribute to a "general shear" on the entire structure. This is simply wrong. Thus you cannot discount that large contribution, and there is no energy deficit.

You seem to be attempting to say energy from component X only went into damaging structural system Y -- it isn't so. There's a large energy input, and numerous energy sinks, but there isn't a specific order in which sinks are applied, possibly excepting the perimeter columns.

No, Wierzbicki says the remaining energy after the deformation of the external columns, the floor and the airplane was left to destroy the core. But I see what you are saying.

Nonethless, the fluid is rather ineffective at destroying the core, the floor or the airplane and the fluid has 32% of the KE.

[GregoryUrich]

Not really, and it sort of depends on the grade of steel. Steel used for structures is actually easily machineable and malleable. These are almost at the bottom of the rung as far as steel grades go. Aerospace steel can be as much as 10 times stronger.

The stuff is tough, but it's not titanium.

Do you really think the fuel cut the columns in a fraction of a second?

[Furcifer]

3bodyproblem:

I see no violation of anything. Imagine if the jet fuel was frozen... then you would have to add in the energy needed to FRACTURE it. Droplet formation is the same type of thing; it requires energy to overcome the Van der Waals forces holding the fluid together. In the limit of the smallest droplets possible you have the vaporization energy.

Hmm...This goes back to my original post, and I think Mackey was thinking along the same lines. The CM of the plane has X kinetic energy, some goes into this, some goes into that. At the end of the day the only dissipative transfer of energy is the sway as heat energy is transfered away from the point of impact. The rest is contained in the area of impact and contributes to the structural destruction AFAIK. Fuel droplets before ignition make collisions with debris and accelerate it towards the core, that collision further vaporizes the fuel and so on. Some debris hits the core, some hits the floors. Some of the potential energy in the plane is converted to kinetic as well, which goes into the floors which goes into the walls which goes into vibration, which goes back into the core which goes into the sway which goes into the ground and on and on and on. Pure chaos. I'd say so far the only thing Greg's got going for him is the sway associated with the impact not being included as an energy sink in the grand scheme of things. Otherwise someone better calculate the amount of energy dissipated acoustically. :)

I think you would be perfectly justified to assume that a mass of fuel traveling 500 mph be considered "frozen" or in a solid form.

[Newtons Bit]

Do you really think the fuel cut the columns in a fraction of a second?

You mean cut in half columns the size of the ones at the WTC? Probably not in a fraction of a second. It would take a sustained stream that wasn't there. Damage on the other hand, very much so. Even small cuts would greatly affect the strength of the columns. Damage to the fire-proofing, to the connections, to the exterior of the columns are all very important.

Why are you even arguing this point? The plane obviously tore a big hole in the exterior columns, why is it anathema for you to admit that it probably caused damage to a couple or so columns only 60 feet further inside the building?

[T.A.M.]

You mean cut in half columns the size of the ones at the WTC? Probably not in a fraction of a second. It would take a sustained stream that wasn't there. Damage on the other hand, very much so. Even small cuts would greatly affect the strength of the columns. Damage to the fire-proofing, to the connections, to the exterior of the columns are all very important.

Why are you even arguing this point? The plane obviously tore a big hole in the exterior columns, why is it anathema for you to admit that it probably caused damage to a couple or so columns only 60 feet further inside the building?

Exactly, if you look at the NIST conclusions, in terms of the # Ext Columns sheared/severed, or even severely damaged via impact, it is only a few...

TAM:)

[AZCat]

You mean cut in half columns the size of the ones at the WTC? Probably not in a fraction of a second. It would take a sustained stream that wasn't there. Damage on the other hand, very much so. Even small cuts would greatly affect the strength of the columns. Damage to the fire-proofing, to the connections, to the exterior of the columns are all very important.

Why are you even arguing this point? The plane obviously tore a big hole in the exterior columns, why is it anathema for you to admit that it probably caused damage to a couple or so columns only 60 feet further inside the building?

It's been a while since I dealt with it, but IIRC stress risers from notches in beams or columns are significant detriments to the load capacity of the structural member, especially if the notches have sharp corners (like might be left from the impact with debris).

[Furcifer]

Anyone know what hurts more, getting hit with a ton of feathers or a ton of lead? :rolleyes:

[Newtons Bit]

Hmm... a ton of lead is about 3 cubic feet. A ton of feathers is likely an enormous silo. Imagine being tickled to death as you struggle to get out of the pile...

[beachnut]

Does your power washer cut the plate or even break the plastic light lenses your car.

Can't I please borrow it. I need to wash the cat.
My power washer will remove your paint, destroy your plastic light lens, skin and kill your cat. I can get a water cutter to cut your car in half. Check with Dr Jones, he can place some thermite on your car and with the help of gravity it will go right through the engine block. KE is a big bad buy, karate kids use it to defeat objects, KE helped doom the WTC.

A chicken hawk can enter a canopy of a jet and break your should bone, at and below the speeds of 9/11. Speed, velocity squared, it cut beams. The exterior of the building was just nothing. The energy of the planes could cut all the exterior columns, this means since the plane was not able to cut all the perimeter columns, there was energy left to cut core columns. A 4 inch light weight floor was not very much of a match for a 500 mph aircraft.

I must remind you again, the impacts on 9/11 were 7 to 11 times greater than the design was said to withstand. I do not understand what you are doing. Present your numbers and have at it. Show why, from the simple physics TLAR approach I use, to the more complicated studies, there is something wrong that means 9/11 WTC failure was not impact, fire, gravity collapse. Present some evidence. Or make it painstakingly clear what your problem is with this single study.

Your power washer must be too small. I can come over and clean your light right off your car, and clean your seats down to the metal.

[pomeroo]

I sent Prof. Wierzbicki an e-mail asking if he would care to respond to a critique of his paper posted on the JREF. He was gracious enough to reply:


Dear Mr. Wieck,

It looks that you are still following papers and discussions related to
the Twin
Towers. I stopped doing it a long time ago when the investigation led by NIST
turned from a technical into a more political matter.

Thank you for indicating to me the critique by Gregory Urich of our report and
book article. I don't think that he understands that deformation and fracture
of two impacting bodies are, to a large extent, controlled by the momentum
transfer rather than by the cutting process alone. It doesn't matter whether
this is a solid or a fluid, they both carry a momentum. The momentum of the
fuel-filled tanks was partially transferred to the exterior columns and a
remainder to the interior structure, including the core columns. Those
structures that acquire an initial velocity will then keep deforming until a
possible fracture. It is true that in this process, some of the fuel was
dispersed, and when entering the core of the building, there was no single
lumped mass of fuel. Therefore, our calculations provide an upper bound for
the worst-case scenario.

It should also be understood that the whole analysis that you refer to
was done
in the first 30 days after September 11. Other people work months and
years to
come with up with something.

I greatly appreciate you sending me this note, and providing an interesting
discussion of a difficult problem.

Best Regards,
Tom Wierzbicki

[beachnut]

Do you really think the fuel cut the columns in a fraction of a second?
In less than 0.01 second. That was fast, before the steel could cut the fuel, the fuel said sorry, and busted through the steel column. Do you think the JetA said, "pardon me"?

All the truthers told me that a flimsy aluminum aircraft can not cut steel, so there was a hole, so the fuel did it. What do you think about that? Or was it the fuel and the aluminum?

[Furcifer]

Hmm... a ton of lead is about 3 cubic feet. A ton of feathers is likely an enormous silo. Imagine being tickled to death as you struggle to get out of the pile...

I was thinking of that very same fact. But then again I'm a sick, sick individual.

[beachnut]

I sent Prof. Wierzbicki an e-mail asking if he would care to respond to a critique of his paper posted on the JREF. He was gracious enough to reply:


Dear Mr. Wieck,

It looks that you are still following papers and discussions related to
the Twin
Towers. I stopped doing it a long time ago when the investigation led by NIST
turned from a technical into a more political matter.

Thank you for indicating to me the critique by Gregory Urich of our report and
book article. I don't think that he understands that deformation and fracture
of two impacting bodies are, to a large extent, controlled by the momentum
transfer rather than by the cutting process alone. It doesn't matter whether
this is a solid or a fluid, they both carry a momentum. The momentum of the
fuel-filled tanks was partially transferred to the exterior columns and a
remainder to the interior structure, including the core columns. Those
structures that acquire an initial velocity will then keep deforming until a
possible fracture. It is true that in this process, some of the fuel was
dispersed, and when entering the core of the building, there was no single
lumped mass of fuel. Therefore, our calculations provide an upper bound for
the worst-case scenario.

It should also be understood that the whole analysis that you refer to
was done
in the first 30 days after September 11. Other people work months and
years to
come with up with something.

I greatly appreciate you sending me this note, and providing an interesting
discussion of a difficult problem.

Best Regards,
Tom Wierzbicki
Did Greg tell anyone what the author just imparted. The author, with an economy of words just explained more than Greg will ever understand. Why? I think Greg has left his degree at the door and entered truther land. He fails to pass on the whole story which the author did in one short email. I do recall a few papers out in the first month looking at energy in the WTC failure. This was one of them.

Thanks for work.

[Furcifer]

I sent Prof. Wierzbicki an e-mail asking if he would care to respond to a critique of his paper posted on the JREF. He was gracious enough to reply:


Dear Mr. Wieck,

It looks that you are still following papers and discussions related to
the Twin
Towers. I stopped doing it a long time ago when the investigation led by NIST
turned from a technical into a more political matter.

Thank you for indicating to me the critique by Gregory Urich of our report and
book article. I don't think that he understands that deformation and fracture
of two impacting bodies are, to a large extent, controlled by the momentum
transfer rather than by the cutting process alone. It doesn't matter whether
this is a solid or a fluid, they both carry a momentum. The momentum of the
fuel-filled tanks was partially transferred to the exterior columns and a
remainder to the interior structure, including the core columns. Those
structures that acquire an initial velocity will then keep deforming until a
possible fracture. It is true that in this process, some of the fuel was
dispersed, and when entering the core of the building, there was no single
lumped mass of fuel. Therefore, our calculations provide an upper bound for
the worst-case scenario.

It should also be understood that the whole analysis that you refer to
was done
in the first 30 days after September 11. Other people work months and
years to
come with up with something.

I greatly appreciate you sending me this note, and providing an interesting
discussion of a difficult problem.

Best Regards,
Tom Wierzbicki


I hate to say I told you so, but I told you so :) I just wish he would have commented on the sway, I'm not sure how much of that total kinetic energy was dissipated, it may have been enough to warrant further investigation. Oh, and I stand corrected, there is a response to Mr. Urich despite the short sightedness. Sorry Greg. You still can't borrow my power washer though!

[pomeroo]

Did Greg tell anyone what the author just imparted. The author, with an economy of words just explained more than Greg will ever understand. Why? I think Greg has left his degree at the door and entered truther land. He fails to pass on the whole story which the author did in one short email. I do recall a few papers out in the first month looking at energy in the WTC failure. This was one of them.

Thanks for work.



Beachnut, I have found that busy people are often more than willing to explain their work. You just have to take the trouble to ask them, something that the fantasists never seem to get around to.

[David Wong]

Now... is it off topic to ask Greg what he thinks damaged the towers if the planes were insufficient?

Is he suggesting some kind of flaw in the construction of the towers or maybe pre-existing degradation of the structure prior to the attacks that made the results worse than they should have been?

If so, that's a subject worth pursuing because perhaps without those factors the towers would have stood a little longer and more lives could have been saved. And I guess the "conspiracy" that makes the thread suitable for his subform is the conspiracy among building inspectors and whoever else spotted these problems and said nothing.

Right? Or are we talking about something else?

[Apollo20]

Pomeroo:

Thanks for providing those insights straight from the source!

I notice that Dr. Wierzbicki states that "It is true that in this process, some of the fuel was dispersed, and when entering the core of the building, there was no single lumped mass of fuel."

This is important because it raises the question is how much fuel was "dispersed" and because this "dispersion" represents the effective "atomization" of fuel that led to a fuel-air deflagration. Such a near-instantaneous, non-equilibrium and therefore ISOTHERMAL, vaporization of jet fuel requires ENERGY, a lot of energy, namely about 400 MJ for 1,000 kg of octane, although I suspect only a fraction of the available fuel was consumed this way. Nevertheless, this represents a significant (neglected) energy sink.

[AZCat]

Pomeroo:

Thanks for providing those insights straight from the source!

I notice that Dr. Wierzbicki states that "It is true that in this process, some of the fuel was dispersed, and when entering the core of the building, there was no single lumped mass of fuel."

This is important because it raises the question is how much fuel was "dispersed" and because this "dispersion" represents the effective "atomization" of fuel that led to a fuel-air deflagration. Such a near-instantaneous, non-equilibrium and therefore ISOTHERMAL, vaporization of jet fuel requires ENERGY, a lot of energy, namely about 400 MJ for 1,000 kg of octane, although I suspect only a fraction of the available fuel was consumed this way. Nevertheless, this represents a significant (neglected) energy sink. (emphasis mine)

You mean it's an adiabatic process like the mist coming from a champagne bottle when the cork is popped, right? (just trying to clarify)

[Furcifer]

Pomeroo:

Thanks for providing those insights straight from the source!

I notice that Dr. Wierzbicki states that "It is true that in this process, some of the fuel was dispersed, and when entering the core of the building, there was no single lumped mass of fuel."

This is important because it raises the question is how much fuel was "dispersed" and because this "dispersion" represents the effective "atomization" of fuel that led to a fuel-air deflagration. Such a near-instantaneous, non-equilibrium and therefore ISOTHERMAL, vaporization of jet fuel requires ENERGY, a lot of energy, namely about 400 MJ for 1,000 kg of octane, although I suspect only a fraction of the available fuel was consumed this way. Nevertheless, this represents a significant (neglected) energy sink.

Do you really think so? I understand the argument, and it certainly is something to ponder, the question is is it relevant? I'm not so sure that not treating it like a solid mass at impact has a considerable effect. 400 MJ represents 10% of the available kinetic energy, assuming a uniform distribution after impact this is a 5% decrease in kinetic energy to the floors and core. Even he sway would account for more than this alone. I'm still not convinced the nit picking seriously yields any worthwhile results. IMO.

[Apollo20]

3bodyproblem:

An estimate of the extent of building sway following an aircraft collision with the Towers may be made on the basis of simple momentum transfer theory. Let the mass of the aircraft be represented by Ma and its impact velocity by Va. We consider the impacted building to have an effective mass Mb, equal to the mass of the upper 1/3rd of the structure and assume a uniform mass distribution for the building. With a recoil velocity immediately after impact represented by Vb, conservation of linear momentum dictates that,

Vb = { Ma / Mb } x Va

Using known values for these quantities we have,

Vb = {124,000 / 170,000,000} x 220 m/s

Vb = 0.16 m/s

An estimate of the deflection of the top of a WTC tower induced by a dynamic load may be obtained from this recoil velocity by using the elastic response theory presented by W. Schueller. First we note that the natural period of vibration of a WTC tower, T, is equal to 11 seconds. Now if Vb is taken to be the maximum velocity of the top of the tower at its central position, it follows that the amplitude of vibration, Y, which is also the maximum displacement, is given by,

Y = { Vb xT } / 2p

Substituting for Vb and T in this equation we find that Y is only 0.28 meters. A WTC tower at a deflection 0.28 meters has converted all the initial kinetic energy of the swaying building to elastic strain energy that is ultimately dissipated as heat. This energy, equal to ½ MbVb^2 or 2.18 MJ, is less than 0.1 % of the initial kinetic energy of the impacting aircraft.

So who is nit-picking?

AZcat:

I am thinking of a fast, diabatic process.... It's like "fast-atom" chemistry!

[Furcifer]

3bodyproblem:

An estimate of the extent of building sway following an aircraft collision with the Towers may be made on the basis of simple momentum transfer theory. Let the mass of the aircraft be represented by Ma and its impact velocity by Va. We consider the impacted building to have an effective mass Mb, equal to the mass of the upper 1/3rd of the structure and assume a uniform mass distribution for the building. With a recoil velocity immediately after impact represented by Vb, conservation of linear momentum dictates that,

Vb = { Ma / Mb } x Va

Using known values for these quantities we have,

Vb = {124,000 / 170,000,000} x 220 m/s

Vb = 0.16 m/s

An estimate of the deflection of the top of a WTC tower induced by a dynamic load may be obtained from this recoil velocity by using the elastic response theory presented by W. Schueller. First we note that the natural period of vibration of a WTC tower, T, is equal to 11 seconds. Now if Vb is taken to be the maximum velocity of the top of the tower at its central position, it follows that the amplitude of vibration, Y, which is also the maximum displacement, is given by,

Y = { Vb xT } / 2p

Substituting for Vb and T in this equation we find that Y is only 0.28 meters. A WTC tower at a deflection 0.28 meters has converted all the initial kinetic energy of the swaying building to elastic strain energy that is ultimately dissipated as heat. This energy, equal to ½ MbVb^2 or 2.18 MJ, is less than 0.1 % of the initial kinetic energy of the impacting aircraft.

So who is nit-picking?

AZcat:

I am thinking of a fast, diabatic process.... It's like "fast-atom" chemistry!

Touche. :) I never realized this was as insignificant as you have calculated. I have not done my own calculation to compare, but I do respect yours and accept it (for now) This is not a total shock, as the building should have remained rigid during the impact, at least relatively. This however does not change my overall assumption that the kinetic energy imparted during the collision was directly responsible for the collapse. If we neglect the sway, we still arrive at what was the original assumption, 100% of the KE went destroying the exterior, floors and core. Even considering the small losses such as you have suggested. Sorry to have moved the goal posts, but you must admit it is a very small move overall ;)

[Dave Rogers]

However, a very rough calculation, assuming a "fracture energy" of the fuel to be ~ 1 J/m^2 of surface area, shows it would require ~ 10 MJ to convert the fuel to 100 micron droplets.

A quick google gives the surface tension of kerosene as 0.025Nm-1 (i.e. 0.025J/m^2 of surface area), so that modifies your figure to 250kJ - I don't think this is a significant energy loss.

Dave

[GregoryUrich]

The main time commerical airliners fly through rain is on approach to the airport for landing, at which point they are moving relatively slowly. There's an enormous difference between that speed and flying supersonic.

I checked with an American Airlines (MD-82/83 cruising speed = 504 mph) pilot. It is common to fly through rain at cruising speed. I.e. they don't slow down for it. Since the speeds associated with the WTC impacts are in that range it is useless to talk about super-sonic effects.

[GregoryUrich]

Beachnut, I have found that busy people are often more than willing to explain their work. You just have to take the trouble to ask them, something that the fantasists never seem to get around to.

Since I wrote to both Wierzbicki and Xue a number of months ago, that must qualify me as a non-fantasist. Too bad they didn't answer until they were challenged in a public forum.

[GregoryUrich]

I sent Prof. Wierzbicki an e-mail asking if he would care to respond to a critique of his paper posted on the JREF. He was gracious enough to reply:


Dear Mr. Wieck,

It looks that you are still following papers and discussions related to
the Twin
Towers. I stopped doing it a long time ago when the investigation led by NIST
turned from a technical into a more political matter.

Thank you for indicating to me the critique by Gregory Urich of our report and
book article. I don't think that he understands that deformation and fracture
of two impacting bodies are, to a large extent, controlled by the momentum
transfer rather than by the cutting process alone. It doesn't matter whether
this is a solid or a fluid, they both carry a momentum. The momentum of the
fuel-filled tanks was partially transferred to the exterior columns and a
remainder to the interior structure, including the core columns. Those
structures that acquire an initial velocity will then keep deforming until a
possible fracture. It is true that in this process, some of the fuel was
dispersed, and when entering the core of the building, there was no single
lumped mass of fuel. Therefore, our calculations provide an upper bound for
the worst-case scenario.

It should also be understood that the whole analysis that you refer to
was done
in the first 30 days after September 11. Other people work months and
years to
come with up with something.

I greatly appreciate you sending me this note, and providing an interesting
discussion of a difficult problem.

Best Regards,
Tom Wierzbicki

Pomeroo, thanks for your initiative and thanks also to Mr. Wierzbicki for taking the time to address this.

As I said in my original post, the fuel can not cut steel columns in the same way as the solid aircraft parts. Mr. Wierzbicki, (while suggesting that I do not understand the situation) confirms that the impact is dominated by momentum transfer rather than cutting/shear. Now we are getting somewhere.

Since the impacted surface area of the impacted core column (at least in WTC1) is less than 1% of the of the total impacted core area, less than 1% of the fluid/debris can actually impact a particular core column. Of course the impacting fluid/debris cloud is not evenly distributed. Most of the fluid and debris will impact at the center of the core due to the large belly fuel tank and the fuselage.

Wierzbicki states that for WTC1, 630MJ is dissipated in the core. The question remains, how much of this energy can be transferred to an individual column? Even if one assumes all of the impacting fluid/debris is distributed over the middle 20% of the core. The portion of the area occupied by a core column is only 3.6% of that area. Thus no more than 3.6% of the energy can be applied to an individual core column. This amounts to 22MJ or less than half of the energy required to sever the column by the most severe case (distribution over a single floor). For distribution over 2 floors this amounts to less than a forth of the energy required to sever the column. It is interesting to note that NIST used a distribution over four floors.

This points out a serious flaw in Wierzbicki's reasoning that you can simply divide the energy dissipated in the core by the energy necessary to sever a column to arrive at the number of severed columns. Mr. Wierzbicki admits that his calculation should be taken as an upper bound for the worst case scenario. Nonetheless, I do not find this caveat in the original article.

[T.A.M.]

Well why don't you take up an email corrispondence with the man, rather than depreciate his work and opinion (serious flaw in his reasoning?) on a public internet forum...if you REALLY are interested in the TRUTH. Seriously, all things aside, wouldn't it make things clearer for you, either way?

TAM:)

[HeyLeroy]

So, the manufacturers making and selling abrasive waterjet cutting tools for steel cutting just throw the machines together without any idea of whether they'll work or not? And then sell them without testing them first?

Or is there some fundamental physical principle that explains how an abrasive-carrying water stream less than 1mm in cross-section moving about 1400 mph can cut through steel, but masses of fluid with entrained debris at 1/3 that velocity and thousands of times greater cross-section will only "splash" on steel?

Respectfully,
Myriad
Does your power washer cut the plate or even break the plastic light lenses your car.

Can't I please borrow it. I need to wash the cat.

Water jet cutting steel:
http://liveu-44.vo.llnwd.net/vidilife/image/2006/10/10/946639/1231544L.jpg

Just an observation to counter the 'abrasive-free' jet-fuel; wouldn't the parts of shattered plane, as well as the exterior wall sections, office furniture, etc., act as abrasives against the fireproofing?

Not really, and it sort of depends on the grade of steel. Steel used for structures is actually easily machineable and malleable. These are almost at the bottom of the rung as far as steel grades go. Aerospace steel can be as much as 10 times stronger.

The stuff is tough, but it's not titanium.

Titanium machines like stainless steel. For fun stuff to cut, gotta go with porcerax (http://www.porcerax.com/).

[Newtons Bit]

Most stainless steel doesn't machine very well either :D

Mild carbon is used for reasons other than it's cheap. Weldability and machineability are very important for ease of fabrication.

[GregoryUrich]

Just an observation to counter the 'abrasive-free' jet-fuel; wouldn't the parts of shattered plane, as well as the exterior wall sections, office furniture, etc., act as abrasives against the fireproofing?


Yes, of course...for a fraction of a second.

I have never maintained that no fireproofing was damaged or even that no core columns were damaged. I was just trying to point out that the critics here would be well served to point their debunkulators at work done by experts once in a while.

[GlennB]

What if - the front landing gear "area" of the plane happened to impact on a window area of the building? i.e. a huge mass of very solid metal for that particular part of the plane, but little resistance, therefore the landing gear is relatively free to pass through at high velocity to damage the core structure?

A bit non-technical, I agree (I'm not a physicist), but it strikes me the OP - and much of the unsuing discussion - is dealing in averages and esoterics rather than specifics and practicalities. The KE of the solid part of the plane is 'deemed' to have been accounted for by the deformation of the outer columns, leaving only the fuel to damage the core columns. This is plain silly. The initial damage/ensuing debris would have been as random as the structure of the buildings/planes and the line of impact might decree.

(sorry, I've been away a while but came to have a browse and the new forum software nagged me into saying something)

[HeyLeroy]

Yes, of course...for a fraction of a second.

I have never maintained that no fireproofing was damaged or even that no core columns were damaged. I was just trying to point out that the critics here would be well served to point their debunkulators at work done by experts once in a while.

A bullet impacts in a fraction of a second. The tip of a whip cracks in a fraction of a second. I don't understand your issue with the amount of time it took for the planes to shred the fireproofing.

[GregoryUrich]

Well why don't you take up an email corrispondence with the man, rather than depreciate his work and opinion (serious flaw in his reasoning?) on a public internet forum...if you REALLY are interested in the TRUTH. Seriously, all things aside, wouldn't it make things clearer for you, either way?

TAM:)

As I have mentioned previously, I have written to two of the authors and received no response. Are you against public debate about published articles? Isn't this site about "discussing skepticism, critical thinking, the paranormal and science in a friendly and lively way"?

[GregoryUrich]

A bullet impacts in a fraction of a second. The tip of a whip cracks in a fraction of a second. I don't understand your issue with the amount of time it took for the planes to shred the fireproofing.

If you started from the beginning of the thread, you would know the issue at hand is how much damage was done to the core columns, not the fireproofing.

The time factor is in relation to abrasive waterjet cutting which takes more than a fraction of a second.

My opinion is that there must have been some damage to fireproofing but the extent of the damage is very difficult to know. Unfortunately, there is no evidence of damage to fireproofing beyond what can be seen in photographs.

[Apollo20]

Gregory:

I like your surface area argument!

The photos of the towers with the sun setting in the background show that those buildings were far from solid! That's why some aircraft parts went all the way through....

However, you cannot always expect an author to give a detailed response to every questioner that comes along.

I know, I have been on both ends of the stick!

[GregoryUrich]

What if - the front landing gear "area" of the plane happened to impact on a window area of the building? i.e. a huge mass of very solid metal for that particular part of the plane, but little resistance, therefore the landing gear is relatively free to pass through at high velocity to damage the core structure?

A bit non-technical, I agree (I'm not a physicist), but it strikes me the OP - and much of the unsuing discussion - is dealing in averages and esoterics rather than specifics and practicalities. The KE of the solid part of the plane is 'deemed' to have been accounted for by the deformation of the outer columns, leaving only the fuel to damage the core columns. This is plain silly. The initial damage/ensuing debris would have been as random as the structure of the buildings/planes and the line of impact might decree.

(sorry, I've been away a while but came to have a browse and the new forum software nagged me into saying something)

Sure, some debris must have hit the core. I am open to an engine hitting a core column straight on. The OP just reflects Wierzbicki's method of establishing the energy available to damage the core. My main point is that 32% of the KE was from fluid which is not capable of the same kind of damage as solid objects and that it is incorrect to assume all of the remaining energy (after damage to the airplane, external columns and floor) would act on the core columns.

Please read above where I demonstrate that whatever composite of fluid and debris hit the core, only a very small part of that could actually impact an individual column.

[GregoryUrich]

Gregory:

I like your surface area argument!

The photos of the towers with the sun setting in the background show that those buildings were far from solid! That's why some aircraft parts went all the way through....

However, you cannot always expect an author to give a detailed response to every questioner that comes along.

I know, I have been on both ends of the stick!

Thanks Apollo,

I am not criticizing the authors for not answering me, only responding to criticisms that I should take this up with the authors.

[Apollo20]

Gregory:

Actually when it comes to Prof. Wierzbicki's "Aircraft Impact Damage" paper I have a specific question concerning the validity of his equation 1:

E(kinetic) = E(plane) + E(ext col) + E(floor) + E(core)

My concern is that this equation neglects an energy dissipation term that I believe is quite important because it would significantly alter Prof W's estimate of the magnitude of the term E(core). My reason for claiming that an additional energy term is required for the energy balance comes from two statements from the NIST Report NCSTAR 1-5A:

On page 79, in reference to WTC 1: “…. the formation of the fireballs demonstrates that a fraction of the remaining fuel was expelled from the building most likely being forced out of openings as an atomized liquid …”

And on page 124, in reference to WTC 2: “As previously hypothesized, immediately after the aircraft struck the tower, the fuel tanks were ruptured, and much of the jet fuel was atomized.”

Based on the fact that the atomization of jet fuel during the aircraft impacts would require significant energy, I would argue that this energy could only be derived from the impact kinetic energy of the aircraft. In fact, I see the “flash-evaporation” of the jet fuel as a direct momentum transfer from the impacting aircraft to the escaping droplets of liquid.

But how much energy could be dissipated in this manner? Well, if we assume that jet fuel is essentially iso-octane, C8H18 (mol. wt. = 125.6; density = 0.7 g/cc), we can use the heat of vaporization of this liquid at 25° C, which is 41.5 kJ/mol or 330 kJ/kg, to calculate the energy required.

It is generally estimated that the Boeing aircraft were carrying about 10,000 gallons of fuel when they struck the towers. Unfortunately it is difficult to predict exactly how much fuel was vaporized when the wing tanks impacted with the towers but a figure ~ 800 gal would appear to be a reasonable estimate in line with values given by FEMA and NIST. This being the case, we have 2120 kg of fuel requiring 700 MJ to be vaporized, an amount of energy that is comparable to the “mechanical impact energies” derived in Prof. W's paper! It is perhaps significant that the kinetic energy of 10,000 gallons of jet fuel traveling at 220 m/s is ½ x 26,500 x (220)^2 joules or 640 MJ – an amount of energy close to the energy dissipated by vaporizing 800 gallons or 8 % of the fuel mass.

[GregoryUrich]

3bodyproblem:

An estimate of the extent of building sway following an aircraft collision with the Towers may be made on the basis of simple momentum transfer theory. Let the mass of the aircraft be represented by Ma and its impact velocity by Va. We consider the impacted building to have an effective mass Mb, equal to the mass of the upper 1/3rd of the structure and assume a uniform mass distribution for the building. With a recoil velocity immediately after impact represented by Vb, conservation of linear momentum dictates that,

Vb = { Ma / Mb } x Va

Using known values for these quantities we have,

Vb = {124,000 / 170,000,000} x 220 m/s

Vb = 0.16 m/s

An estimate of the deflection of the top of a WTC tower induced by a dynamic load may be obtained from this recoil velocity by using the elastic response theory presented by W. Schueller. First we note that the natural period of vibration of a WTC tower, T, is equal to 11 seconds. Now if Vb is taken to be the maximum velocity of the top of the tower at its central position, it follows that the amplitude of vibration, Y, which is also the maximum displacement, is given by,

Y = { Vb xT } / 2p

Substituting for Vb and T in this equation we find that Y is only 0.28 meters. A WTC tower at a deflection 0.28 meters has converted all the initial kinetic energy of the swaying building to elastic strain energy that is ultimately dissipated as heat. This energy, equal to ½ MbVb^2 or 2.18 MJ, is less than 0.1 % of the initial kinetic energy of the impacting aircraft.

So who is nit-picking?

AZcat:

I am thinking of a fast, diabatic process.... It's like "fast-atom" chemistry!

Some nit-picking:

NIST provides the following based on video analysis of the impact of wtc2:

maximum displacement at 70th floor = 16 in (0.4m) from the graph
maximum displacement of the top of the tower = 27 in (0.675m)

Where is the displacement value Y you are using?

Wouldn't wtc1 have a larger displacement due to the moment arm effect?

[Myriad]

Suppose the fluid current entrains desks, partitions, filing cabinets, pieces of floor. Desks, partitions, filing cabinets, floor structures impact core.

Consider the analogy to a bridge in a flood, which doesn't only have to resist the force of the water against its supports. It must also resist the impact of debris entrained in the water current. And, if debris logjams against the bridge supports, it must then resist the force of the water current against the debris as well. (Desks could not, of course, logjam in this way, but structural floor members could.)

If you flung 100 desks at the core, how many would pass through without striking a column?

Apollo, atomization is not vaporization. Most of the energy for vaporization (that actual liquid to gas phase change, that is) would have come from the combustion of the fuel, not from its kinetic energy.

Respectfully,
Myriad

[Apollo20]

Myriad:

I am talking about the events BEFORE fuel combustion. The fuel only has kinetic energy at this moment in time. After impact some of the fuel (all you need is 8 %!!!) is dispersed as fine droplets and/or vapor.

And when it comes to vaporization vs. atomization, I agree with your semantic quibble, but it's NIST and FEMA that use the term "atomization"..... more strictly they should have said "molecularization".

P.S. Even Prof Wierzbicki told me in an e-mail: "It would appear that the impact velocity of over 200 meters per second would be enough to break the fluid into an atomic level"

Perhaps you should raise your concerns about this with him?

[Apollo20]

Gregory:

My "building sway" calculation was done about 2 years ago and was a first stab at the problem.... hence the numbers are quite approximate.

[GregoryUrich]

Suppose the fluid current entrains desks, partitions, filing cabinets, pieces of floor. Desks, partitions, filing cabinets, floor structures impact core.

Consider the analogy to a bridge in a flood, which doesn't only have to resist the force of the water against its supports. It must also resist the impact of debris entrained in the water current. And, if debris logjams against the bridge supports, it must then resist the force of the water current against the debris as well. (Desks could not, of course, logjam in this way, but structural floor members could.)

If you flung 100 desks at the core, how many would pass through without striking a column?

Apollo, atomization is not vaporization. Most of the energy for vaporization (that actual liquid to gas phase change, that is) would have come from the combustion of the fuel, not from its kinetic energy.

Respectfully,
Myriad

Now you are making it complicated. What about partitions? What are the desks and partions made of? I would guess they are wood or wood metal composites and gypsum wall board repectively. I'm not sure it really makes a difference though. As Wierzbicki points out it's the momentum transfer that does the damage.

I think the office contents will impact each other dissipating some energy in plastic deformation before hitting the core. Also, the spaces between the columns were nearly 20 feet wide.

Regardless, some debris certainly impacted the core.

[T.A.M.]

As I have mentioned previously, I have written to two of the authors and received no response. Are you against public debate about published articles? Isn't this site about "discussing skepticism, critical thinking, the paranormal and science in a friendly and lively way"?

Of course I am not against public debate of articles, science, or otherwise. I just think that if you HONESTLY, simply want clarification on some points in the article, than asking the author would be the primary way to obtain those answers. You say you have tried to contact them, and I believe you, so this is most unfortunate.

I am glad you wish the debates to be friendly and lively, I wish they were like that more often, but when most of the truthers (I am not including you in this) come in here outright accusing people in the govt of mass murder, "lively" yes, "fun" not really.

TAM:)

[Corsair 115]

I checked with an American Airlines (MD-82/83 cruising speed = 504 mph) pilot. It is common to fly through rain at cruising speed.Considering that cruising speed is usually associated with cruising altitude (35,000 feet generally), I doubt it's that common to fly through rainstorms at that altitude. Sometimes, perhaps, but not common. Flights prefer to either fly around or over bad weather - headwinds slow the aircraft down causing delays in arrival time and more fuel being burned.

[Furcifer]

I'm stil not sure if I follow this correctly, so let's walk through this. We have a transfer of kinetic energy from the plane to the building. Almost all the kinetic energy was transfered to the building, very little of the plane actually exited. Can we safely assume 100% transfer here, or do we nit pick? ;) I'll give you 5% loss because that seems about right without ruining a perfectly good napkin. So we've got 95% of the KE striking the exterior and causing the damage we've all seen. It is at this moment that most of the vapourization of the fuel occurs correct? So you have some mass of fuel reduced to molecular size. I can see this, and it makes perfect sense. What I don't understand is how this in any way can be considered a "sink" in the overall energy equation. Yes it robs some KE from the impact to the core, but it only makes the resulting fireball more explosive. An atomized fuel is way more explosive than one in a liquid state, it destructive potential greatly increased. Any loss in this process is gained in the explosion. And if we consider the loss of energy in the process of atomizing the fuel, we also have to consider the mass of air that was caught up in the wake of the plane, and thrust into the hole it created. Doesn't this all just come out in the wash?

[Myriad]

It is generally estimated that the Boeing aircraft were carrying about 10,000 gallons of fuel when they struck the towers. Unfortunately it is difficult to predict exactly how much fuel was vaporized when the wing tanks impacted with the towers but a figure ~ 800 gal would appear to be a reasonable estimate in line with values given by FEMA and NIST. This being the case, we have 2120 kg of fuel requiring 700 MJ to be vaporized, an amount of energy that is comparable to the “mechanical impact energies” derived in Prof. W's paper! It is perhaps significant that the kinetic energy of 10,000 gallons of jet fuel traveling at 220 m/s is ½ x 26,500 x (220)^2 joules or 640 MJ – an amount of energy close to the energy dissipated by vaporizing 800 gallons or 8 % of the fuel mass. [emphasis added]


Do you have any explanation for how the vaporization of 8% of the fuel manages to transfer all the kinetic energy from the remaining 92%, thus stopping it dead in midair? (And if that happened, where did the fireball on the far side exterior of the building come from?) Or is this strange finding a clue that something is wrong with this calculation?

I am talking about the events BEFORE fuel combustion. The fuel only has kinetic energy at this moment in time. After impact some of the fuel (all you need is 8 %!!!) is dispersed as fine droplets and/or vapor.


Fine droplets and vapor are not interchangeable, and you cannot use the heat of vaporization to calculate the energy dissipated by atomizing (a correct, though misleading, term for breaking into fine liquid droplets e.g. by spraying) the liquid.

And just to be precise, the fuel does not have only kinetic energy, it also has thermal energy. Leave the fuel lying around in air, it will evaporate at its surface, cooling the remaining liquid in the process. Break it into fine droplets (by whatever means you prefer) and the evaporation and the cooling will happen much faster. Probably not a significant factor in the behavior of the fuel in this case (all the fuel would have to cool by about 50deg. C to supply the latent heat of vaporization to vaporize 8% of it), but it points again to two different physical processes.

And when it comes to vaporization vs. atomization, I agree with your semantic quibble, but it's NIST and FEMA that use the term "atomization"..... more strictly they should have said "molecularization".


There's no need for another term. "Atomization" correctly means breaking/spraying liquid into fine droplets of liquid. "Vaporization" means changing to gas phase, which is a behavior of and only of molecules. "Molecularization," presumably meaning separation into individual molecules in gas phase, would be entirely redundant with "vaporization."

It is not a semantic quibble that you are calculating the energy required for one physical process (atomization, spraying, separation into droplets) using the parameters of an entirely physically different process, vaporization.

P.S. Even Prof Wierzbicki told me in an e-mail: "It would appear that the impact velocity of over 200 meters per second would be enough to break the fluid into an atomic level"

Perhaps you should raise your concerns about this with him?


I don't doubt that some of the liquid, striking a barrier at high speed with resulting high pressures and temperatures at the surface, could have flash-vaporized as a result. This would be a very effective mechanism of momentum transfer to the barrier, essentially equivalent to a high-pressure vapor explosion occurring on the resisting surface, though it would of course dissipate some energy in the vaporization itself. But the amount of the fluid undergoing this process is unspecified; there's no reason to equate it with the amount (8%) separating into fine droplets due to other forms of mechanical agitation in the collision (such as, on the way out of the ruptured tanks).

After it starts burning, then we can pretty safely equate "atomized" with "vaporized," as only a tiny fraction of the heat of combustion is needed to supply the remaining latent heat of vaporization for all the droplets. But as you just reminded me, we're talking about before it ignites.

Respectfully,
Myriad

[Myriad]

Now you are making it complicated.


No, I'm not the one making it complicated. What happened was complicated.

Perhaps next time the terrorists will oblige us by crashing a spherical airplane into an infinite uniform two-dimensional membrane (at a zero angle from normal, please).

But in the meantime, there's nothing wrong with simplifying the analysis, such as by looking at it in terms of overall momentum transfer, as long as you're up-front about your simplifying assumptions. And there's also nothing wrong with looking into fine details, if you want to.

What you can't legitimately do is pick and choose which fine details to include, such as by taking into account the amount of fuel that would miss the core columns without also taking into account the effects of other debris entrained in the fluid stream.

Respectfully,
Myriad

[AZCat]

Perhaps next time the terrorists will oblige us by crashing a spherical airplane into an infinite uniform two-dimensional membrane (at a zero angle from normal, please).

It would be nice if it was also in space so we wouldn't have to worry about atmospheric drag or gravitational effect. Aahhhhh, the good old days when we were undergrads and every problem was simplified as much as possible.... </fade into the mists of time>

[GregoryUrich]

Considering that cruising speed is usually associated with cruising altitude (35,000 feet generally), I doubt it's that common to fly through rainstorms at that altitude. Sometimes, perhaps, but not common. Flights prefer to either fly around or over bad weather - headwinds slow the aircraft down causing delays in arrival time and more fuel being burned.

Common, as in more common than slowing down for rain. The point was that liquids at 500 knots don't wreck metal.

[T.A.M.]

I would qualify that, and say that individual droplets of water do not damage metal that strike them at 500 knots.

The question, is, can the same be said for a sheet of Jet Fuel Travelling into metal, at 500 knots?

TAM:)

[tsig]

My point is that Wierzbicki's conclusion is not supported by evidence. Do you have the same problem with that conclusion?

I can't imagine there is any research regarding cutting steel by splashing liquids on them with varying debris content and granularity at any velocity. I make the value judgement that it is not worth my time to look for articles.

I don't expect anyone to just accept my opinion. I expect people to think.

If one wanted to model this, there are three basic scenarios and two important assumptions:

Assumptions:

Since all other energy is expended in destroying the external columns, floor and airplane, the only energy left is the KE of the fluid.
Any debris carried by the fluid will already have reduced the energy available due to momentum transfer. For example, if the weight of the debris was equal to the weight of the fluid, the KE would be reduced to 50% assuming no loss due to deformation of debris (actually energy will be lost to deformation of debris).


Scenarios:

Some part of the fluid and debris would impact the columns directly. This is less than 10% of the cross sectional area of the core. This impact will be distributed over time, over the height of the column, and reduced due to the fluid component flowing around the core.
Some portion of the fluid and debris would pass through the core or outside the core impacting nothing.
Some portion of the fluid and debris would impact the core partitions which would would act as a diaphram until they were breached. Since the diaphrams are relatively easily breached any force transferred to the columns will be a fraction of the force on the diaphram and also will be distributed across the height of the column.


Thus, the majority of energy available cannot act on the core. Furthermore, the forces acting on the core are distributed over the height of the columns which reduces the force per unit to such an extent that very little damage can occur.

Physics was not your strong suit.

Do you have a degree in anything?

[einsteen]

The energy of the impact was tremendous, tons of TNT, nothing could withstand that impact, nothing is left when such an amount of energy is released, guys this is really a lot of energy, this is huge, this is a dramatic amount of energy, this is a monster amount of energy, horrible, even the strongest buildings cannot withstand it, massive utter strong columns capable to hold a complete flat block are just snapped like matchsticks and then don't forgot that dramatic fireball, that is just a couple of H-bombs, the tower was doomed. Nothing could survive it….. except a passport. :)

[T.A.M.]

Given many other things besides a passport survived, I see your strawman, and raise you with SOME FACTS.

TAM;)

[GregoryUrich]

I'm stil not sure if I follow this correctly, so let's walk through this. We have a transfer of kinetic energy from the plane to the building. Almost all the kinetic energy was transfered to the building, very little of the plane actually exited. Can we safely assume 100% transfer here, or do we nit pick? ;) I'll give you 5% loss because that seems about right without ruining a perfectly good napkin. So we've got 95% of the KE striking the exterior and causing the damage we've all seen. It is at this moment that most of the vapourization of the fuel occurs correct? So you have some mass of fuel reduced to molecular size. I can see this, and it makes perfect sense. What I don't understand is how this in any way can be considered a "sink" in the overall energy equation. Yes it robs some KE from the impact to the core, but it only makes the resulting fireball more explosive. An atomized fuel is way more explosive than one in a liquid state, it destructive potential greatly increased. Any loss in this process is gained in the explosion. And if we consider the loss of energy in the process of atomizing the fuel, we also have to consider the mass of air that was caught up in the wake of the plane, and thrust into the hole it created. Doesn't this all just come out in the wash?

The article in question makes no mention of the explosion in terms of the energy balance. You are essentially pointing out another limitation of the model presented.

While Wierzbicki admits the model/method needs to be refined, the basic conclusion still must be that damage to the core is extremely overestimated due to faulty logic.

If we are going to refine the model we need some way to gage the destructive potential of the fireball. My impression from the videos is that it was more like burning than a powerful fuel air explosion. If you look at the Naudet brothers video of wtc1 it looks like a huge amount of fuel falls outside the building. Windows are not shattered over the area covered by the burning. A fuel air explosion would have blown in every window in the vicinity. A fuel air explosion in the building would have blown out every window on the affected floors.

See: http://www.youtube.com/watch?v=mJAs_3MiV00

I'm not sure I agree with your conclusion regarding the timing of vaporisation. Most vaporisation probably occurs between the time that the exterior wall is breached and the fireball. There is free liquid flying through air for at least 60 ft.

Also, if the liquid was spread over four floors as proposed by NIST, it is likley that much less than 50% would have a free shot at the core due to desks and partitions outside the core as well as the 37.5" deep floor and truss system. Roughly 25% would result in a general shear on the floor and truss system. Core contents and partitions are probably a fairly large sink for liquid KE.

[GregoryUrich]

I would qualify that, and say that individual droplets of water do not damage metal that strike them at 500 knots.

The question, is, can the same be said for a sheet of Jet Fuel Travelling into metal, at 500 knots?

TAM:)

The answer is here (http://forums.randi.org/showthread.php?postid=2739589#post2739589).

[GregoryUrich]

The energy of the impact was tremendous, tons of TNT, nothing could withstand that impact, nothing is left when such an amount of energy is released, guys this is really a lot of energy, this is huge, this is a dramatic amount of energy, this is a monster amount of energy, horrible, even the strongest buildings cannot withstand it, massive utter strong columns capable to hold a complete flat block are just snapped like matchsticks and then don't forgot that dramatic fireball, that is just a couple of H-bombs, the tower was doomed. Nothing could survive it….. except a passport. :)

In case you missed it, the buildings stood after impact. According to NIST and FEMA, it was the fire that brought them down. The fireball was definitely dramatic, but not very destructive. See the fuel-air explosion (http://www.youtube.com/watch?v=mJAs_3MiV00).

[GregoryUrich]

Physics was not your strong suit.

Do you have a degree in anything?

I'm devastated, totally crushed by your astounding intellect and cogent logic. How can I possibly go on...

[westprog]

Fine droplets and vapor are not interchangeable, and you cannot use the heat of vaporization to calculate the energy dissipated by atomizing (a correct, though misleading, term for breaking into fine liquid droplets e.g. by spraying) the liquid.

And just to be precise, the fuel does not have only kinetic energy, it also has thermal energy. Leave the fuel lying around in air, it will evaporate at its surface, cooling the remaining liquid in the process. Break it into fine droplets (by whatever means you prefer) and the evaporation and the cooling will happen much faster. Probably not a significant factor in the behavior of the fuel in this case (all the fuel would have to cool by about 50deg. C to supply the latent heat of vaporization to vaporize 8% of it), but it points again to two different physical processes.




There's no need for another term. "Atomization" correctly means breaking/spraying liquid into fine droplets of liquid. "Vaporization" means changing to gas phase, which is a behavior of and only of molecules. "Molecularization," presumably meaning separation into individual molecules in gas phase, would be entirely redundant with "vaporization."

It is not a semantic quibble that you are calculating the energy required for one physical process (atomization, spraying, separation into droplets) using the parameters of an entirely physically different process, vaporization.




I don't doubt that some of the liquid, striking a barrier at high speed with resulting high pressures and temperatures at the surface, could have flash-vaporized as a result. This would be a very effective mechanism of momentum transfer to the barrier, essentially equivalent to a high-pressure vapor explosion occurring on the resisting surface, though it would of course dissipate some energy in the vaporization itself. But the amount of the fluid undergoing this process is unspecified; there's no reason to equate it with the amount (8%) separating into fine droplets due to other forms of mechanical agitation in the collision (such as, on the way out of the ruptured tanks).

After it starts burning, then we can pretty safely equate "atomized" with "vaporized," as only a tiny fraction of the heat of combustion is needed to supply the remaining latent heat of vaporization for all the droplets. But as you just reminded me, we're talking about before it ignites.



The problem of carburation is to burn a liquid fuel in a sufficiently short time. This isn't an issue so much with jet engines, but it's an important element in the internal combustion engine.

http://www.azcars.eu/wdfdi/

[T.A.M.]

The answer is not there, but your opinion is. That opinion differs from those who conducted the study, does it not?

Thanks for the link.

TAM:)

[Crungy]

The energy of the impact was tremendous, tons of TNT, nothing could withstand that impact, nothing is left when such an amount of energy is released, guys this is really a lot of energy, this is huge, this is a dramatic amount of energy, this is a monster amount of energy, horrible, even the strongest buildings cannot withstand it, massive utter strong columns capable to hold a complete flat block are just snapped like matchsticks and then don't forgot that dramatic fireball, that is just a couple of H-bombs, the tower was doomed. Nothing could survive it….. except a passport. :)

What about the three miracle Deep Purple CDs and live worm experiment that were found after the Columbia explosion?
http://forums.randi.org/showthread.p...43#post2017143

Always amazed that the "deep thinkers" go WOO-WOO by the passport. Time and time again history has shown plenty of odd anamolies following unique and chaotic events.

Looking at the comment below I see that at least T.A.M. hasn't gotten drunk on the purple Woo kool aid...

[Crungy]

Edit: Double post

[tsig]

I'm devastated, totally crushed by your astounding intellect and cogent logic. How can I possibly go on...

I don't know

Your figures do not figure.

They do not add up

Thanks for your understanding of my astounding intellect.

[tsig]

I'm devastated, totally crushed by your astounding intellect and cogent logic. How can I possibly go on...


I don't know

My astounding intellect tells me you have no clue.

[rwguinn]

I don't know

My astounding intellect tells me you have no clue.
I'll raise you 2 woos and a strawman.
My intellect applauds yours, but contends that there may be negative clues in that room...
First we have a "Chemist" who does not know that "atomization" is a long accepted term by physicists, chemists, engineers, and the perfume industry for the mechanical break-up of fluid into a very fine particle suspension. A chemist who then tries to equate that energy value with the heat of vaporization of the fluid.
Then, a guy who wants to ignore the details that don't fit, who has raindrops at 35000 feet MSL (Hint--clouds are composed of a much, MUCH finer droplet size than rain--that's why they are clouds and not rain), and apparently has never, ever, seen or heard of a waterjet cutter.

[tsig]

I'll raise you 2 woos and a strawman.
My intellect applauds yours, but contends that there may be negative clues in that room...
First we have a "Chemist" who does not know that "atomization" is a long accepted term by physicists, chemists, engineers, and the perfume industry for the mechanical break-up of fluid into a very fine particle suspension. A chemist who then tries to equate that energy value with the heat of vaporization of the fluid.
Then, a guy who wants to ignore the details that don't fit, who has raindrops at 35000 feet MSL (Hint--clouds are composed of a much, MUCH finer droplet size than rain--that's why they are clouds and not rain), and apparently has never, ever, seen or heard of a waterjet cutter.


Do I get to hit you hit in the head with a full can of beer.

[GregoryUrich]

I'll raise you 2 woos and a strawman.
My intellect applauds yours, but contends that there may be negative clues in that room...
First we have a "Chemist" who does not know that "atomization" is a long accepted term by physicists, chemists, engineers, and the perfume industry for the mechanical break-up of fluid into a very fine particle suspension. A chemist who then tries to equate that energy value with the heat of vaporization of the fluid.
Then, a guy who wants to ignore the details that don't fit, who has raindrops at 35000 feet MSL (Hint--clouds are composed of a much, MUCH finer droplet size than rain--that's why they are clouds and not rain), and apparently has never, ever, seen or heard of a waterjet cutter.

Show me the water jet cutter that severs W14 A36 steel I-beams with a 500 mph stream and no abrasive in 0.1 seconds. Water jets cut slowly. Without abrasive they are good for cutting fishsticks.

Show me the airline pilot who slows down for rain. At least I have a pilot (AA MD-82/83) that confirms that she flies through rain at crusing speed.

You guys are ignoring to topic which questions how 4-12 core columns magically get all of the remaining energy after destruction of the external columns, the plane and the floor. This is claimed by the famous MIT scientists which you guys seem incapable of questioning.

Talk about ignoring details. You guys are ignoring the most significant detail that most the remaining energy cannot possibly hit the core columns because they are only 12" wide (according to Wierzbicki) and have a gap of more than 20 ft between them. That's it. Your MIT guys failed you.

What will we do now? Who can we trust? Bush, Cheney, anyone with authority, please tell us some lies to make us feel better.

[tsig]

Oh yeah, I forgot...my ironic post regarding arguments not to use against troofers.

I'm still a non-troofer though--committed purveyor of lies and misinformation.


Pilots are flying

[tsig]

Then there is the energy that went into the swaying of the tower.were is your time.

[GregoryUrich]

were is your time.

Is that a koan or are you just high?

[apathoid]

Show me the airline pilot who slows down for rain. At least I have a pilot (AA MD-82/83) that confirms that she flies through rain at crusing speed.



Maybe she doesnt slow down for rain, but she should slow down for the 250 kt speed limit below 10,000'. Cruising speeds aren't reached until at least 15,000 ~ 20,000' or so and rain at that altitude is rare.

Perhaps your pilot friend simply said she doesnt slow down for rain?

[pomeroo]

What about the three miracle Deep Purple CDs and live worm experiment that were found after the Columbia explosion?
http://forums.randi.org/showthread.p...43#post2017143

Always amazed that the "deep thinkers" go WOO-WOO by the passport. Time and time again history has shown plenty of odd anamolies following unique and chaotic events.

Looking at the comment below I see that at least T.A.M. hasn't gotten drunk on the purple Woo kool aid...



It's fascinating that conspiracy liars fixate on the passport. If the Impossibly Vast Conspiracy wanted to plant evidence, why would they decide on something that arouses instant suspicion? Oh, I almost forgot: a real conspiracy wouldn't dream of creating any evidence that didn't help their scheme. The twoofers' Klown Kar Konspirators exist solely to provide clues for morons.

[pomeroo]

Show me the water jet cutter that severs W14 A36 steel I-beams with a 500 mph stream and no abrasive in 0.1 seconds. Water jets cut slowly. Without abrasive they are good for cutting fishsticks.

Show me the airline pilot who slows down for rain. At least I have a pilot (AA MD-82/83) that confirms that she flies through rain at crusing speed.

You guys are ignoring to topic which questions how 4-12 core columns magically get all of the remaining energy after destruction of the external columns, the plane and the floor. This is claimed by the famous MIT scientists which you guys seem incapable of questioning.

Talk about ignoring details. You guys are ignoring the most significant detail that most the remaining energy cannot possibly hit the core columns because they are only 12" wide (according to Wierzbicki) and have a gap of more than 20 ft between them. That's it. Your MIT guys failed you.

What will we do now? Who can we trust? Bush, Cheney, anyone with authority, please tell us some lies to make us feel better.



Yawn. Wake us up when you've concluded (Pssst! You already have.) that a vast, mathematically-impossible conspiracy surmounted insurmountable logistical problems and brought down the towers with explosives.

[rwguinn]

Show me the water jet cutter that severs W14 A36 steel I-beams with a 500 mph stream and no abrasive in 0.1 seconds. Water jets cut slowly. Without abrasive they are good for cutting fishsticks.
you have already ignored the aluminum, titanium, and silica particulates that came in with the aid of the cdollision, along with all the other abrasive materials inherent in the collision. And the paper give a momentum, not cutting solution to the problem, anyway. You know what they calkl the result of slowing down a flow of air/liquid stream? Pressure! PressureXarea=force.

Show me the airline pilot who slows down for rain. At least I have a pilot (AA MD-82/83) that confirms that she flies through rain at crusing speed.
which airline, so I won't fly that one.

You guys are ignoring to topic which questions how 4-12 core columns magically get all of the remaining energy after destruction of the external columns, the plane and the floor. This is claimed by the famous MIT scientists which you guys seem incapable of questioning.

Talk about ignoring details. You guys are ignoring the most significant detail that most the remaining energy cannot possibly hit the core columns because they are only 12" wide (according to Wierzbicki) and have a gap of more than 20 ft between them. That's it. Your MIT guys failed you.

What will we do now? Who can we trust? Bush, Cheney, anyone with authority, please tell us some lies to make us feel better.

ad populum.
"Most people cannot understand what this is all about, therefore it is wrong."

[jaydeehess]

they are only 12" wide (according to Wierzbicki) and have a gap of more than 20 ft between them. That's it.


Small point;
If the plane hit perpendicular to the face of the building and was travelling directly along that perpendicular vector then the columns were indeed 20 feet apart in the direction the debris was travelling. At a 45 degree angle to the side of the building, columns would be 14.1 feet apart in a plane perpendicular to the line of travel. At greater angles it gets wider until it gets to perpendicular and 20 feet between columns. The plane that hit the south tower indeed was turning into the tower and did not hit perpendicular at all.

So you have a mass of liquid hitting the core columns directly (not a force directed against the perimeter frame) imparting a shear force on them , followed closely by solid debris travelling at various velocities and consisting of materials of various densities including wheel assemblies and engine cores. This occurs on several different floors and some aircraft parts indeed hit floor pans while others hit only perimeter columns or just window glass, then interior office furnishings.

[Furcifer]

Whoah, getting heated in here. Seems like some are taking this as an afront to their beliefs rather than a purely acedemic exercise. I for one like it because it gives me a chance to exercise my brain which has been going soft from lack of use [insert joke]

That being said, something doesn't add up here. I think I was looking at the impact as an inelastic collision instead of a series of elestic ones. A possible over simplification, but we should be able to determine the degree of error we are assuming here. If we consider the first impact with the plane and the exterior we have a loss of KE that goes into severing/deforming the exterior. The process of deformation partially atomizes the plane and the fuel. I would contend that this where a mojority of the fuel is atomized as the wings severed the exterior. At almost the same instant the overpressure from the wake would be travelling faster than the fuel, and further accelerate the atomization. We must also consider a certain amount of sway imparted into the building during this initial collision. I think this would be small due to the velocity of the plane and how little resistence the exterior presented. The next collision is the plane with the floor. A large section of the floor would have been driven directly into the core, causing substantial damage to several core columns as the floor/truss system crumpled. The CM of the plane is still travelling towards the core at this point, allbeit spread over a much larger area at this point. None the less, all of the debris is still travelling towards the core, the only loss so far is the KE in deforming the exterior, floor and two very small amounts into mechanical atomization of the fuel and the sway. The next stage of impact would be the core. I have assumed that the initial collision with the exterior imparted a small amount of sway but the floor and core collision none. This is of course not correct but I'm assuming most of the sway would have been imparted when the debris hit the core. I'm not sure if I missed anyhting but I still don't see where there is a considerable loss of KE not accounted for by Wierzbicki? Does assuming the fireball happening after the debris impact with the core have any positive or negative results? Does a small amount of damage over a large core area have a considerably different effect than a large amount of damage over a small area? Doesn't the way it failed suggest the former of these two?

[Corsair 115]

Common, as in more common than slowing down for rain.Note that I never said they slow down for rain; I said most often they fly through rain when moving relatively slowly, which is to say, on approach for landing.

[GregoryUrich]

Maybe she doesnt slow down for rain, but she should slow down for the 250 kt speed limit below 10,000'. Cruising speeds aren't reached until at least 15,000 ~ 20,000' or so and rain at that altitude is rare.

Perhaps your pilot friend simply said she doesnt slow down for rain?

Note that I never said they slow down for rain; I said most often they fly through rain when moving relatively slowly, which is to say, on approach for landing.

Convective and frontal rain falls from cumulonimbus and altostratus clouds respectively. Cumulosnimbus clouds are found at altitudes between 6,500 ft and 50,000 feet. Altostratus clouds are found between 8,000 to 20,000 ft.

My pilot friend says she flies through rain at cruising speed. She's been at American Airlines for 10 years. Perhaps she actually does.

[GregoryUrich]

Small point;
If the plane hit perpendicular to the face of the building and was travelling directly along that perpendicular vector then the columns were indeed 20 feet apart in the direction the debris was travelling. At a 45 degree angle to the side of the building, columns would be 14.1 feet apart in a plane perpendicular to the line of travel. At greater angles it gets wider until it gets to perpendicular and 20 feet between columns. The plane that hit the south tower indeed was turning into the tower and did not hit perpendicular at all.

So you have a mass of liquid hitting the core columns directly (not a force directed against the perimeter frame) imparting a shear force on them , followed closely by solid debris travelling at various velocities and consisting of materials of various densities including wheel assemblies and engine cores. This occurs on several different floors and some aircraft parts indeed hit floor pans while others hit only perimeter columns or just window glass, then interior office furnishings.

AA 11 hit WTC1 perpendicular to the side of the building. UAL 175 hit WTC2 at 13% from perpendicular.

Regarding whatever hit the core please see this (http://forums.randi.org/showthread.php?postid=2739589#post2739589) and this (http://forums.randi.org/showthread.php?postid=2739981#post2739981).

[tsig]

Convective and frontal rain falls from cumulonimbus and altostratus clouds respectively. Cumulosnimbus clouds are found at altitudes between 6,500 ft and 50,000 feet. Altostratus clouds are found between 8,000 to 20,000 ft.

My pilot friend says she flies through rain at cruising speed. She's been at American Airlines for 10 years. Perhaps she actually does.

You would not know the truth if it bit you in the butt.

[beachnut]

Show me the water jet cutter that severs W14 A36 steel I-beams with a 500 mph stream and no abrasive in 0.1 seconds. Water jets cut slowly. Without abrasive they are good for cutting fishsticks.

Show me the airline pilot who slows down for rain. At least I have a pilot (AA MD-82/83) that confirms that she flies through rain at crusing speed.

You guys are ignoring to topic which questions how 4-12 core columns magically get all of the remaining energy after destruction of the external columns, the plane and the floor. This is claimed by the famous MIT scientists which you guys seem incapable of questioning.

Talk about ignoring details. You guys are ignoring the most significant detail that most the remaining energy cannot possibly hit the core columns because they are only 12" wide (according to Wierzbicki) and have a gap of more than 20 ft between them. That's it. Your MIT guys failed you.

What will we do now? Who can we trust? Bush, Cheney, anyone with authority, please tell us some lies to make us feel better.
I have not known one pilot who has flown at 470 mph though 50,000 pounds of water and lived. ZERO

When will you put together your momentum junk to support your truther stand on 9/11. Tiny rain drops are not very a factor to a jet which flies through rain. But heavy rain will flame out all the jet engines in any plane at any speed. FACT. Look it up. I always avoid heavy rain, some dead pilots have not! Look it up.

What the heck is this rain crap about? But you need to warn your pilot friend, there are certain rainstorms she will not want to go through, and if she does you have warned her. When you fail to find the pilots who have crashed I may help you out, but I am sorry I cannot spoon feed a truther who seems unable to use his engineering training to make rational conclusions on 9/11.

[Apollo20]

Gregory:

Did you know there is a JREFer with a BS in Mechanical Engineering who posts on this thread who apparently has never heard of IMPACT VAPORIZATION?

Perhaps he/she should read about experiments by N. Sugi et al. which show that for water ice targets impacted by metal objects moving at velocities in the range 100 - 180 m/s, up to 26 % is VAPORIZED via shear banding at the Hugoniot elastic limit.

And by the way, the jet fuel entering the Twin Towers was moving at ~ 220 m/s and interestingly the mean molecular velocity of iso-octane vapor at 300 K is 224 m/s!

[T.A.M.]

tsk tsk tsk...

here we go again.

TAM:mad:

[T.A.M.]

Show me the water jet cutter that severs W14 A36 steel I-beams with a 500 mph stream and no abrasive in 0.1 seconds. Water jets cut slowly. Without abrasive they are good for cutting fishsticks.

Show me the airline pilot who slows down for rain. At least I have a pilot (AA MD-82/83) that confirms that she flies through rain at crusing speed.

You guys are ignoring to topic which questions how 4-12 core columns magically get all of the remaining energy after destruction of the external columns, the plane and the floor. This is claimed by the famous MIT scientists which you guys seem incapable of questioning.

Talk about ignoring details. You guys are ignoring the most significant detail that most the remaining energy cannot possibly hit the core columns because they are only 12" wide (according to Wierzbicki) and have a gap of more than 20 ft between them. That's it. Your MIT guys failed you.

What will we do now? Who can we trust? Bush, Cheney, anyone with authority, please tell us some lies to make us feel better.


I know lets trust a bunch of no-name, government hating, agenda filled architects and would be scientists who are more concerned with finding the incorrect minutia in a paper, rather than the overwhelming correctness of the paper as a whole.

Lets trust a Theologian and a Philosophy Professor, as well as a wingnut Mechanical Engineer who believe beams from outer space brought down the towers.

Lets believe a couple of twenty something highschool grads who set out to make a fictional film, but figured out there might be a better market in the documentary area for their material.

Anyone else????

oh wait, how about a B-rated songwriter who thinks nothing hit the towers that day, or a twenty something hack investigator who thinks the plane at the pentagon flew over it, not hitting it, with NO WITNESSES or EVIDENCE to prove it.

And yes, I deserve a tsk tsk tsk, for the above, and I will take it, but sometimes this Fickwuts get on my nerves...to the extreme.

TAM:)

[Apollo20]

TAM:

Why no "tsk, tsk, tsk", for the BS Mech Eng poster who disparages Chemists?

Here we go again indeed!

[Dave Rogers]

Perhaps he/she should read about experiments by N. Sugi et al. which show that for water ice targets impacted by metal objects moving at velocities in the range 100 - 180 m/s, up to 26 % is VAPORIZED via shear banding at the Hugoniot elastic limit.

That's not exactly what the abstract says - it's saying that 18-26% of the impact kinetic energy is partitioned into vaporization. I presume it's the ice target that's being vaporized rather than the metal object, and that the ice target is very much larger than the metal object i.e. effectively immovable (I don't have access to the full paper), so the momentum transfer would be very different to the impact of an airliner into a WTC tower. While it's perfectly reasonable to assume that some of the kinetic energy of the airliner could have been transferred into latent heat of vaporization, momentum conservation will limit the amount of energy transfer more in this case than in Sugi et al, where the collision dynamics are much simpler.

Dave

[T.A.M.]

TAM:

Why no "tsk, tsk, tsk", for the BS Mech Eng poster who disparages Chemists?

Here we go again indeed!

you are correct. I believe if was Rwguinn (I apologize if it wasnt). tsk tsk tsk...

Actually I was going to comment on it, and should of, but usually he is quite civil, so it was an oddity to see, though I notice between you two seems to be a little antagonism.

I stand corrected of a double standard. Maybe, everyone should keep the ad homs down...including me, as if you read just above, I let a little lace of them go, albeit, not to anyone directly on this forum.

TAM:)

[rwguinn]

you are correct. I believe if was Rwguinn (I apologize if it wasnt). tsk tsk tsk...

Actually I was going to comment on it, and should of, but usually he is quite civil, so it was an oddity to see, though I notice between you two seems to be a little antagonism.

I stand corrected of a double standard. Maybe, everyone should keep the ad homs down...including me, as if you read just above, I let a little lace of them go, albeit, not to anyone directly on this forum.

TAM:)
:p
I do tend not to suffer foolishness gladly.
To Apollo20:
I never said that some of the KE did not reduce to heat (the final resting place of all energy) and actually vaporize some of the fuel.
What I did say was that equating the heat of vaporization to the purely mechanical process of atomization was foolish, at least. The atomization process is much more energy efficient, and presents huge surface areas, so that vaporization is more efficient when the self-sustaining reaction of rapid oxidation is initiated from a heat source, such as friction between a fast moving aircraft and a stationary building. That vaporization and subsequent reaction is the release of chemical, not mechanical, energy. Your attempt to rewrite the technical dictionaries of the world to your liking is rejected.
If you wish to change the definition of terms and technical issues,please tell us the definition you wish to use, first. However, just in translating Spanish to English, do not attempt to tell us that "rojo" is roll, just because it sounds similar to a word you know. Do not assume that widely used, perfectly appropriate and universally understood terms mean what you wish them to, regardless of the understanding of the rest of the world. The translation is up to you, not us. We are not mind-readers--Mr. Randi still has the $1.0e6 as proof of that.

[GregoryUrich]

I know lets trust a bunch of no-name, government hating, agenda filled architects and would be scientists who are more concerned with finding the incorrect minutia in a paper, rather than the overwhelming correctness of the paper as a whole.

Lets trust a Theologian and a Philosophy Professor, as well as a wingnut Mechanical Engineer who believe beams from outer space brought down the towers.

Lets believe a couple of twenty something highschool grads who set out to make a fictional film, but figured out there might be a better market in the documentary area for their material.

Anyone else????

oh wait, how about a B-rated songwriter who thinks nothing hit the towers that day, or a twenty something hack investigator who thinks the plane at the pentagon flew over it, not hitting it, with NO WITNESSES or EVIDENCE to prove it.

And yes, I deserve a tsk tsk tsk, for the above, and I will take it, but sometimes this Fickwuts get on my nerves...to the extreme.

TAM:)

Totally lame TAM. You provide no substantial argument and the issue is major. Core damage is incorrectly calculated. NIST uses these numbers to support their model.

Their are not a bunch of people criticizing this paper, only me. I have never suppested that people should trust anyone. I encourage critical thinking even regarding the conclusions of experts.

All too often here, I am painted as a government hating liar with an agenda. If you know so much about me, what is my agenda then? Since you are sure I hate the government, why do I hate the government?

Let's not make statements you can't back up.

[rwguinn]

Bolding mine...
Totally lame TAM. You provide no substantial argument and the issue is major. Core damage is incorrectly calculated. NIST uses these numbers to support their model.

Their are not a bunch of people criticizing this paper, only me. I have never suppested that people should trust anyone. I encourage critical thinking even regarding the conclusions of experts.

All too often here, I am painted as a government hating liar with an agenda. If you know so much about me, what is my agenda then? Since you are sure I hate the government, why do I hate the government?

Let's not make statements you can't back up.[/
:dl: :dl:

Mr. Pot, meet Ms. Kettle....

[GregoryUrich]

I have not known one pilot who has flown at 470 mph though 50,000 pounds of water and lived. ZERO

When will you put together your momentum junk to support your truther stand on 9/11. Tiny rain drops are not very a factor to a jet which flies through rain. But heavy rain will flame out all the jet engines in any plane at any speed. FACT. Look it up. I always avoid heavy rain, some dead pilots have not! Look it up.

What the heck is this rain crap about? But you need to warn your pilot friend, there are certain rainstorms she will not want to go through, and if she does you have warned her. When you fail to find the pilots who have crashed I may help you out, but I am sorry I cannot spoon feed a truther who seems unable to use his engineering training to make rational conclusions on 9/11.

I agree this rain crap is nuts. It wasn't me that brought it up. Someone else was trying rather ineffectually to show that liquid at 500 mph could cut steel.

After 10 years at American, I'm sure she's aware of the flameout issue and avoids heavy rain.

[GregoryUrich]

Mr. Pot, meet Ms. Kettle....

I used to think you were capable of substantial arguments.

[Myriad]

I agree this rain crap is nuts. It wasn't me that brought it up. Someone else was trying rather ineffectually to show that liquid at 500 mph could cut steel.

Yeah, I share your frustration, Gregory. People are always trying ineffectually to tell me that rocks thrown at 15mph can injure people. I know they're wrong because on windy days at the beach, grains of sand hit me at that veolocity all the time, and it doesn't hurt. If only people would think more logically!

Respectfully,
Myriad

[GregoryUrich]

Yawn. Wake us up when you've concluded (Pssst! You already have.) that a vast, mathematically-impossible conspiracy surmounted insurmountable logistical problems and brought down the towers with explosives.

Typical. No substantial argument.

[Newtons Bit]

I did a bit of research (goooo google!) on the rain and flying thang. The only thing I could find was engine problems with flying through heavy rains at high speeds. There were also warnings that flying through bad weather means a chance of hitting hail. Considering the damage my car took in a hail storm in 2004, I think a plane travelling at 500mph might want to avoid that kind of thing.

I found nothing about raindrops cutting into the plane. 500mph probably isn't going to be enough to do serious damage to steel, but it certainly will cause debris to strip fire-proofing off.

[Vincent Vega]

I see no specific mention of the two engines and three landing gear in the equations. The most mass/volume hence momentum retaining peices of equipment on the aircraft.

[GregoryUrich]

Yeah, I share your frustration, Gregory. People are always trying ineffectually to tell me that rocks thrown at 15mph can injure people. I know they're wrong because on windy days at the beach, grains of sand hit me at that veolocity all the time, and it doesn't hurt. If only people would think more logically!

Respectfully,
Myriad

I would say that you are comparing apples and oranges, but you are comparing water and rocks. Enough said.

Mr. Wierzbicki, the expert says that the impact is dominated by momentum transfer not cutting. Are you equally frustrated with him?

Further, the energy required to sever the columns in the worst case scenario (according to the experts) is more than twice the energy available from the impact on any one core column. This with the simplification in favor of damage that all fluid and debris impact on one floor in the middle 20% of the core.

The only sane response you guys have left is UNCLE!

[T.A.M.]

Show me the water jet cutter that severs W14 A36 steel I-beams with a 500 mph stream and no abrasive in 0.1 seconds. Water jets cut slowly. Without abrasive they are good for cutting fishsticks.

Show me the airline pilot who slows down for rain. At least I have a pilot (AA MD-82/83) that confirms that she flies through rain at crusing speed.

You guys are ignoring to topic which questions how 4-12 core columns magically get all of the remaining energy after destruction of the external columns, the plane and the floor. This is claimed by the famous MIT scientists which you guys seem incapable of questioning.

Talk about ignoring details. You guys are ignoring the most significant detail that most the remaining energy cannot possibly hit the core columns because they are only 12" wide (according to Wierzbicki) and have a gap of more than 20 ft between them. That's it. Your MIT guys failed you.

What will we do now? Who can we trust? Bush, Cheney, anyone with authority, please tell us some lies to make us feel better.

Gregory:

It was a rant, I admitted it, and if you feel it was lame...ok.

I bolded the words that spawned the rant, since you don't seem to get why I said what I did.

I wasn't attempting to debate or argue the facts, trust me. If I were, my points would be exact, backed up by facts, and I try not to talk outside my area of knowledge, unless I have a good source that has aided me to do so.

TAM:)

[GregoryUrich]

I see no specific mention of the two engines and three landing gear in the equations. The most mass/volume hence momentum retaining peices of equipment on the aircraft.

Those could cause some damage if they actually hit a core column.

The Wierzbicki article uses a simplified model which in all fairness was done very quickly after 9/11. I'm not trying to estimate actual damage but rather just pointing out a major problem with the article.

[T.A.M.]

I would say that you are comparing apples and oranges, but you are comparing water and rocks. Enough said.

Mr. Wierzbicki, the expert says that the impact is dominated by momentum transfer not cutting. Are you equally frustrated with him?

Further, the energy required to sever the columns in the worst case scenario (according to the experts) is more than twice the energy available from the impact on any one core column. This with the simplification in favor of damage that all fluid and debris impact on one floor in the middle 20% of the core.

The only sane response you guys have left is UNCLE!

No, the sane response is the one I used when I first posted on this, which is GET A REPLY FROM THE AUTHOR. Until I see a response to your accusations from the author, and then DO NOT BUY his explanations, your opinion is just that...an opinion, and one that likely (likely) has less training and education in the field than the original author.

TAM:)

[beachnut]

I agree this rain crap is nuts. It wasn't me that brought it up. Someone else was trying rather ineffectually to show that liquid at 500 mph could cut steel.

After 10 years at American, I'm sure she's aware of the flameout issue and avoids heavy rain.
Rain does damage aircraft. You can see the erosion. If the plane has some defect, rain can damage the aircraft skin. You cannot ignore momentum. Only an idiot would knowingly fly into heavy rain. Someone else was correct, planes rarely encounter rain or heavy rain at 35,000 feet; only above 27,500 feet do jets get to cruise speed, in the range from 450 to 550 mph (unless terrorist are breaking the limits)! Usually a plane in the rain is at 300 mph to 180 mph. If you need help, talk to your pilot friend. Even cars have problems with heavy rain, I saw over 20 cars wreck in heavy rain last week; not sure how many people were injured due to rain. I think you are having problems with energy, and by teaming up with a woo woo journal of woo, you are not doing your educational background justice. I suspect anyone who does not stand up and criticize those who make up lies about 9/11, is one who supports those who make up lies about 9/11.

Hi speed jets of water can cut just about anything. You still have to understand energy.

[Myriad]

I would say that you are comparing apples and oranges, but you are comparing water and rocks. Enough said.

No, I'm comparing rocks with grains of sand, and you're comparing a 30,000 kilogram fluid stream with raindrops.

Pretty silly on both our parts. But I was doing on purpose, to make a point about how silly it is.

By the way, I agree that momentum transfer is the relevant process, and I've never said otherwise. I did mention water-jet cutting, to make the more general point that momentum transfer (which is required even for "cutting") from fluid to a solid target cannot be assumed to be negligible due to the fluid merely "splashing" on the target as you had previously described. It was you who made that a topic of contention when you stated:

I can't imagine there is any research regarding cutting steel by splashing liquids on them with varying debris content and granularity at any velocity. I make the value judgement that it is not worth my time to look for article.

I also tried arguing a more substantive point concerning debris in the fluid stream, as an example of the pitfalls of making one "correction" to a simplified model (as you did for the limited cross-section of the core columns) without making all other relevant corrections at the same level of detail (such as for the entrained debris in the fluid stream). I noticed no response to that.

Respectfully,
Myriad

[Vincent Vega]

I wonder if Niagara Falls was dammed up, and a WTC steel core structure was constructed horizontally at the fall's base it would hold up if the dam was suddenly removed? I suspect the surface area the structure would play a significant role.

That said i think the main effect of the aircraft on the core was to strip away fireproofing and dry wall from the steel columns. If any were significantly damaged from impact it would have been from the engines or landing gear, and most of the rest of the airframe would have been disassociated by the perimeter wall.

[Corsair 115]

I agree this rain crap is nuts. It wasn't me that brought it up. Someone else was trying rather ineffectually to show that liquid at 500 mph could cut steel.The last sentence in the quote is faulty memory on your part.

In the interest of accuracy, here is the progression of the rain and aircraft theme:

It begins with this in post #45:
In a similar way, it's not a good idea from fly through a rainstorm at supersonic speeds:

http://www.time.com/time/magazine/article/0,9171,823522,00.html

Your reply in post #50:
Yes, but do commercial airliners slow down for rain?

Me, in post #54:
The main time commerical airliners fly through rain is on approach to the airport for landing, at which point they are moving relatively slowly. There's an enormous difference between that speed and flying supersonic.

You, in post #82:
I checked with an American Airlines (MD-82/83 cruising speed = 504 mph) pilot. It is common to fly through rain at cruising speed. I.e. they don't slow down for it. Since the speeds associated with the WTC impacts are in that range it is useless to talk about super-sonic effects.

Me, in post #103:
Considering that cruising speed is usually associated with cruising altitude (35,000 feet generally), I doubt it's that common to fly through rainstorms at that altitude. Sometimes, perhaps, but not common. Flights prefer to either fly around or over bad weather - headwinds slow the aircraft down causing delays in arrival time and more fuel being burned.

Your reply in post #108:
Common, as in more common than slowing down for rain. The point was that liquids at 500 knots don't wreck metal.

The relevant part of rwguinn's response in post #123:
Then, a guy who wants to ignore the details that don't fit, who has raindrops at 35000 feet MSL (Hint--clouds are composed of a much, MUCH finer droplet size than rain--that's why they are clouds and not rain), and apparently has never, ever, seen or heard of a waterjet cutter.

The relevant portion of your comments in post #125:
Show me the airline pilot who slows down for rain. At least I have a pilot (AA MD-82/83) that confirms that she flies through rain at crusing speed.

Apathoid, in post #129:
Maybe she doesnt slow down for rain, but she should slow down for the 250 kt speed limit below 10,000'. Cruising speeds aren't reached until at least 15,000 ~ 20,000' or so and rain at that altitude is rare.

Perhaps your pilot friend simply said she doesnt slow down for rain?

Me, in post #135:
Note that I never said they slow down for rain; I said most often they fly through rain when moving relatively slowly, which is to say, on approach for landing.

You, in post #136:
Convective and frontal rain falls from cumulonimbus and altostratus clouds respectively. Cumulosnimbus clouds are found at altitudes between 6,500 ft and 50,000 feet. Altostratus clouds are found between 8,000 to 20,000 ft.

My pilot friend says she flies through rain at cruising speed. She's been at American Airlines for 10 years. Perhaps she actually does.

Beachnut offers the following in post #139:
I have not known one pilot who has flown at 470 mph though 50,000 pounds of water and lived. ZERO.

When will you put together your momentum junk to support your truther stand on 9/11. Tiny rain drops are not very a factor to a jet which flies through rain. But heavy rain will flame out all the jet engines in any plane at any speed. FACT. Look it up. I always avoid heavy rain, some dead pilots have not! Look it up.

What the heck is this rain crap about? But you need to warn your pilot friend, there are certain rainstorms she will not want to go through, and if she does you have warned her. When you fail to find the pilots who have crashed I may help you out, but I am sorry I cannot spoon feed a truther who seems unable to use his engineering training to make rational conclusions on 9/11.

And here we are.

I will merely observe that the initial post spoke of supersonic speeds, to which you asked if airliners slow down for rain. A question which, it seems to me, does not fully appreciate the difference between supersonic and the speed at which a commerical jetliner would likely encounter rain.

[rwguinn]

The last sentence in the quote is faulty memory on your part.

In the interest of accuracy, here is the progression of the rain and aircraft theme:

It begins with this in post #45:


Your reply in post #50:


Me, in post #54:


You, in post #82:


Me, in post #103:


Your reply in post #108:


The relevant part of rwguinn's response in post #123:


The relevant portion of your comments in post #125:


Apathoid, in post #129:


Me, in post #135:


You, in post #136:


Beachnut offers the following in post #139:


And here we are.

I will merely observe that the initial post spoke of supersonic speeds, to which you asked if airliners slow down for rain. A question which, it seems to me, does not fully appreciate the difference between supersonic and the speed at which a commerical jetliner would likely encounter rain.

My apologies--I allowed a twoofer to derail me, in his search for a strawman that we would actually fall for--and apparently we all dislike appeals to unknown authorities very much....
The contention all along (here, and in NIST) is that damage to the structure from the collision included removal of insulation (the so-called "fire-proofing") from the steel structure in the vicinity of the impact. It was that loss, along with the exterior and floor structural damage, which when combined with the heat from the fires, caused loss of structural integrity.
Any physical damage to the core steel is actually irelevant.The thermal weakening due to local heating and loss of insulation is the main event--the sagging of floors, resultant buckling of the perimeter columns, and the fact that photographic evidence shows at least some of the central core structure remained vertical after the collapse had passed it adds evidence that core damage and collapse was not the biggest problem the building had that day.
Again, my ap[ologies for falling for the strawman. Back to business...

[HeyLeroy]

Gregory:

I like your surface area argument!

The photos of the towers with the sun setting in the background show that those buildings were far from solid! That's why some aircraft parts went all the way through....

(snip)

http://liveu-50.vo.llnwd.net/vidilife/image/2006/10/10/946639/1162750L.jpg

Common, as in more common than slowing down for rain. The point was that liquids at 500 knots don't wreck metal.

I had the mast torn off a sailboat I crewed on by a wave. I assure you the wave wasn't travelling at 500 kts.

[T.A.M.]

Well, looks like we don't need no stinkin experts anyways Gregory et al.

Fetzer has declared that Nick Irving...

Nick Irving (AM)

Audio Engineeer
Website Manager
Musician (singer, songwriter)

Nick Irving has proven the Purdue Study a Hoax. Go ahead, read the article by the WTC expert AUDIO ENGINEER (What is an audio engineer anyway), and how he debunks the purdue group of silly little scientists.

http://twilightpines.com//index.php?option=com_content&task=view&id=112&Itemid=67

Actual article by Irving here:

http://twilightpines.com/images/purduesimulation.doc

TAM:)

[T.A.M.]

In case you haven't read the paper I listed above, here are some UNREFERENCED claims the audio engineer makes just in one paragraph...

http://twilightpines.com/images/purduesimulation.doc
(full article)


Underwriters Laboratory certified the steel used in the towers to three to four hours at 2000F without weakening. A kerosene (jet fuel) based fire can reach a temperature of 1800F after 40 minutes only if it happens to be maintained for that interval of time in an oxygen-rich environment. When the plane hit the North Tower, most of the fuel was burned up in a big fireball. Any remaining fuel would have been completely exhausted within minutes.

The kerosene fuel source was therefore clearly not maintained, and the black smoke which the fires were producing was indicative of oxygen-starved, cool burning fires. With little oxygen and the kerosene exhausted after a few minutes, these fires did not achieve temperatures anywhere near the maximum for a jet fuel based fire. The Purdue simulation was therefore based upon a false premise.


Now boys and girls how many outright lies, or unsubstantiated, unreferenced errors can you point out in the above...

TAM:)

Edit: I figure since Urich et al are attacking an article without the Author defending himself/herself here, why not....two can play at that game.

[Furcifer]

Imparted momentum from liquid? I thought this was about a kitty car wash. :)

Liquids and gases can all impart momentum during collisions. I had this little rocket you filled half way up with water, then pumped up with air. It went about 30 feet in the air when it was launched. I tried using sand instead of water and it didn't work. Funny how sand didn't impart the same momentum as water in this case don't you agree? I mean sand is harder and more dense than water and yet doesn't quite deliver the same punch. Perhaps there are a bunch of other physical principles involved i never considered...

[Apollo20]

Yes, I think so: This is from my son's NEW ARTIST's HANDBOOK, page 310, on "Water Jet Profiling" by Ray Smith; 2003, DK Publishing Inc:

"In water-jet cutting, water is pressurized to around 55,000 psi... water comes through a nozzle at a speed of mach 3. Soft materials such as foam or rubber are cut with water alone. For harder materials, such as steel or stone, the stream of water is dosed with fine-powdered garnet. This abrasive powder is what does the cutting and the water is simply the vehicle for the abrasive."

[Cuddles]

Show me the airline pilot who slows down for rain.

avoids heavy rain.

Hmm?

[jaydeehess]

The whole rain doesn't-affect-aircraft argument can be solved, if anyone chooses to do so, by figuring the crossectional area of a Boeing, the density of the atomized fuel and thus the mass that an aircraft would encounter travelling through sucha fuel cloud and then determine whether or not any freakin rain storm would have an aircraft flying through and impacting that much mass of water.

At any rate, except for the small amount of debris that exited the towers, all of the momentum of the aircraft was transferred to the tower. The tower was designed to take some momentum transfer from the wind but only is imparted to the perimeter frame. The aircraft penetrated the perimeter and therefore imparted most of its momentum to interior components such as the core columns and floor pans neither of which were designed to take such abuse.

The momentum transfer would cause core columns to bend, bend them far enough under vertical load and they will fail or be significantly less effective in supporting a vertical load. Given that bridge supports can fail when dealing with water traveling at 40 MPH in a flood it would not be suprising to have less braced steel of the WTC core bend due to a 300-500 MPH flow of fuel and aircraft/ office debris at least an order of magnitude greater momentum transfer than that which a bridge support would be taking in a flood.

However, as has been pointed out, the initial damage did not by itself doom the towers. The heat of the fires ( which started immediatly on several floors and each of which was an immediate major fire and in areas in which the fire insulation had been degraded), the creep induced by that heat, the brittle fracture of steel that is cooling after the fire moves on, the inward pull of sagging floors combined with the initial damage gave rise to the collapse.

[rwguinn]

The whole rain doesn't-affect-aircraft argument can be solved, if anyone chooses to do so, by figuring the crossectional area of a Boeing, the density of the atomized fuel and thus the mass that an aircraft would encounter travelling through sucha fuel cloud and then determine whether or not any freakin rain storm would have an aircraft flying through and impacting that much mass of water.
here (http://www.super70s.com/Super70s/Tech/Aviation/Disasters/77-04-04(Southern).asp) is a link to the one crash I remember as a newly-minted Aero engineer...

At any rate, except for the small amount of debris that exited the towers, all of the momentum of the aircraft was transferred to the tower. The tower was designed to take some momentum transfer from the wind but only is imparted to the perimeter frame. The aircraft penetrated the perimeter and therefore imparted most of its momentum to interior components such as the core columns and floor pans neither of which were designed to take such abuse.
Momentum transfer form wind loading (AKA Pressure load) was also designed to be distributed evenly across 1 or 2 faces of the building, not localized to a single corner and a few floors...


The momentum transfer would cause core columns to bend, bend them far enough under vertical load and they will fail or be significantly less effective in supporting a vertical load. Given that bridge supports can fail when dealing with water traveling at 40 MPH in a flood it would not be suprising to have less braced steel of the WTC core bend due to a 300-500 MPH flow of fuel and aircraft/ office debris at least an order of magnitude greater momentum transfer than that which a bridge support would be taking in a flood.
actually, the core columns would experience fery little bending load under wind loading conditions. That entire load would be pretty much carried by the perimeter of the building


However, as has been pointed out, the initial damage did not by itself doom the towers. The heat of the fires ( which started immediatly on several floors and each of which was an immediate major fire and in areas in which the fire insulation had been degraded), the creep induced by that heat, the brittle fracture of steel that is cooling after the fire moves on, the inward pull of sagging floors combined with the initial damage gave rise to the collapse.
Not a bad description of the situation.

[jaydeehess]

here (http://www.super70s.com/Super70s/Tech/Aviation/Disasters/77-04-04(Southern).asp) is a link to the one crash I remember as a newly-minted Aero engineer...

That was a flame out though and it resulted from both the water choking the engine as well as the fan blades hitting the water and hail that was ingested. The collision of water/hail with a fan blade would be at speeds much greater than the forward velocity of the aircraft.

In MHO, engine damage is going to occur long before great physical damage is done to the airframe by water alone at sub-sonic speeds although if the paint is getting stripped off then you very well may be in great physical danger as well.:D


Momentum transfer form wind loading (AKA Pressure load) was also designed to be distributed evenly across 1 or 2 faces of the building, not localized to a single corner and a few floors...
actually, the core columns would experience very little bending load under wind loading conditions. That entire load would be pretty much carried by the perimeter of the building


A more succinct way of putting my point.
The momentum transfer on an entire building associated with a hurricance wind as seen in natural occurances, and focusing that same momentum transfer to be imparted on a 120 foot wide by 25 foot high portion of the building (and am I not being quite generous in that description?) are two very separate situations and never ceases to amaze me when CT says something along the line that the towers were designed to take a hurricane and that proves that the towers were little affected by the impact of the plane.

Although the collision did not doom the building, far from it, it still did what can only be termed as major damage to the structure. I suggest that those doubting this try removing 30% of one wall of their home and see just how well the structure looks like it is supporting the roof after that. It most likely will not fall down that day or even in a month but to say it is still almost as good as new would be a very great error. There is a good reason for doubling up the studs around a window opening in a typical frame house.

[jaydeehess]

However, as has been pointed out, the initial damage did not by itself doom the towers. The heat of the fires ( which started immediatly on several floors and each of which was an immediate major fire and in areas in which the fire insulation had been degraded), the creep induced by that heat, the brittle fracture of steel that is cooling after the fire moves on, the inward pull of sagging floors combined with the initial damage gave rise to the collapse.


Sorry Apollo20, I did forget to include possible (probable?) chemical erosion or catalyst aided reactions that could (would have?) also attacked the exposed steel in high heat and 'chemical soup' conditions. I also failed to mention probable oxygen generators (from the aircraft) that could have increased the heat output of the fires proximate to those generators.

In one corner (SW?) of the south tower it is quite obvious that the fire there is hotter than anywhere else and continues to be for quite some time.

[Apollo20]

Information available on U.S. FAA websites, and confirmed in the NIST NCSTAR 1-5 report, indicate that the Boeing 767 aircraft involved in the 9-11 impacts on the WTC Towers carried a number of oxygen cylinders and oxygen generators. A NASA report by T. L. Reynolds, (No. NASA/CR-2001-210903, issued in May 2001), discusses Onboard Oxygen Gas Generating Systems, or OBOGS, and other sources of breathable oxygen on aircraft:

“Oxygen systems, as they are currently designed for use on commercial transport aircraft, include passenger oxygen for use in the event of a sudden loss of cabin pressure (provided by either compressed oxygen or solid chemical oxygen generators) and gaseous oxygen for use by the flight deck crew. There is also portable gaseous oxygen available for medical use and for protective breathing equipment. The use of oxygen on commercial aircraft, required by FAA regulations, does pose a potential fire safety hazard because of the extremely high gas combustion temperatures that can be produced by combustible materials burning in either pure or oxygen-enriched air environments. This is true of any oxygen system in any environment.”

The standard oxygen cylinder carried on all U.S. commercial aircraft contains 3200 liters of O2 stored at 1850 psi when full. Details of the over-pressure relief of these cylinders are provided in a FAA report by T. R. Marker et al., (No. DOT/FAA/AR-TN98/29):

“Different types of pressure relief devices are used for storing breathable oxygen. There are two types of rupturing relief valves, a frangible disc that will fail under excessive pressure (typically 2500 psi) and a thermal disc that will fail when the temperature exceeds 165°F or 225°F, depending on the type. The rupture disc pressure relief device is the only type used on gaseous oxygen cylinders for crew and passenger breathing systems on commercial transport aircraft….. Ironically, the rupture disc type pressure relief devices pose a more serious concern in a fire environment because, with these relief devices, it is possible for the entire contents of the oxygen cylinder to be discharged at elevated temperatures.”


Marker’s report describes studies showing that rupture disc failure occurs within 15 minutes for cylinders exposed to temperatures as low as 200° C.

The standard chemical oxygen generator used in the OBOGS on commercial aircraft consists of a small metal canister equipped with a spring-loaded striker. When activated, a “candle” of sodium chlorate and additives such as barium peroxide undergoes spontaneous thermal decomposition releasing oxygen gas. The OBOGS units installed on most Boeing aircraft contain about 250 grams of NaClO3 per canister that generate about 50 liters of O2 in 12 minutes – an amount of oxygen considered sufficient to supply two passengers during an emergency descent.

NIST report that the Boeing 767s involved in the 9-11 impacts on the WTC Towers carried about 100 canisters per aircraft; each canister capable of 12-minute oxygen generation for a total of 5000 liters of O2 per aircraft; the canisters were located in compartments above the passenger seats. Researcher D. Blake, in a study of the response of aircraft oxygen generators to elevated temperatures, (See report No. DOT/FAA/AR-TN03/35), found that the lowest temperature for self-activation of a generator canister was 315° C. Other tests conducted by Blake showed that more than 80 % of generator canisters heated to 370° C activated during an hour of heating.

Based on the experimental data presented above it appears quite probable that a significant portion of the oxygen carried by the two aircraft that hit the Twin Towers was released prior to the collapse of these buildings. Experimental data also show that gas cylinders undergo acute release of oxygen at much lower temperatures than the chemical generators onboard the aircraft. Furthermore, the chemical generators release oxygen in 50-liter increments involving many locations in the aircraft cabin, while the bottled gas supply would be released in one 3200-liter pulse at the front-end of the aircraft fuselage where the cylinder is wall-mounted.

In one of the tests described by Marker, 600 liters of oxygen was released into a cargo container where a small fire had been deliberately set. The initial discharge of oxygen caused a very violent combustion reaction that ripped open, and subsequently destroyed, the container. Other data from fire tests in oxygen-enriched environments show that cellulose-based materials such as wood, cardboard and paper, burn almost four times faster in air enriched to 40 vol % O2. This increased combustion rate induces a comparable increase in the heat flux from the burning material and results in flame temperatures as much as 600° C higher than the flame for the same material burning in air – thus flame temperatures up to 1500° C are possible.

Based on the calculated trajectory of UA Flight 175 inside WTC 2, the forward cabin area of the aircraft ploughed into floors 80 to 82 of the northeast corner of the building. Thus the 3200-liter oxygen cylinder carried in the crew compartment of Flight 175 came to rest precisely in the area where the bright yellow glow was to later appear. As many videos show, about 50 minutes after impact, fires were well established in localized areas of the northeast corner of WTC 2 – these fires would have gradually heated the entire forward fuselage to temperatures in excess of 200° C. I would therefore suggest that the intense yellow glow seen moments before the collapse of WTC 2 was caused by the discharge of the onboard oxygen cylinder and the subsequent enhancement of the pre-existing fires.

[rwguinn]

Very interesting stuff, there, and it could definitely be a factor.
However, I do feel that you have left out a possible factor in reaching your conclusion.
The rupture disk on these canisters can also be activated by physical forces, such as high velocity collision, and subsequent impact with other materials. In fact, envisioning the rupture of the entire canister due to the collision of the aircraft with either tower is not much of a reach.
I would surmise that most, if not all, of the oxygen on-board was consumed within the first 1-5 minutes after the collision.

[jaydeehess]

Very interesting stuff, there, and it could definitely be a factor.
However, I do feel that you have left out a possible factor in reaching your conclusion.
The rupture disk on these canisters can also be activated by physical forces, such as high velocity collision, and subsequent impact with other materials. In fact, envisioning the rupture of the entire canister due to the collision of the aircraft with either tower is not much of a reach.
I would surmise that most, if not all, of the oxygen on-board was consumed within the first 1-5 minutes after the collision.


Which could explain why that intense fire in the corner is really the only one visible in either tower. It may well be fed by the only tank to survive the initial impact.
It is certainly one probable explanation for this particularily intense fire.

[T.A.M.]

Here are some questions regarding the O2 Cannisters.

1. What were the Cannisters made of?
2. Could the structure of the Cannisters have survived the initial plane impacts.
3. If they survived the impacts, what are the chances of the pressure valves remaining on them and intact?
4. Have you ever seen the results of an O2 cannister that has had its pressure valve "chopped off"?

TAM:)

[jaydeehess]

At any rate the O2 cannisters gave up their contents. If they did so during the initial fireball then that fireball was a much hotter proximate to the outgassing cannister and remained so until all its contents were released.

If a cannister survived the initial crash then it released it contents when the pressure relief valve did what it was designed to do and the heat output of the fire proximate to it went up dramatically. If this occured deep in the tower no one would see it, even the helicopter crews might have difficulty seeing such a flare up. The only place it would be more noticible would be if the cannister was near the perimeter of the tower when it released its contents into a fire.

I do also recall at least one instance of a witness on the street seeing what they thought was one of these cannisters hit the street after it was ejected with the debris from the initial crash(not that it was in pristine condition). If one could make it all the way through then one could also survive the initial crash and remain in the building. I would imagine they have some impact resistance built in.

[T.A.M.]

the ejected cannister example you give was what I had expected to hear, and was the reason for my previous post.

Essentially, the cannisters could have acted like enourmous steel (or what ever they were made of) projectiles travelling very fast through the buildings. I have heard stories of the cannisters blasting through walls after their valves were "knocked off" releasing all the pressure at once. I think it may or may not have had an impact on the overall damage done inside the WTC...hard to say, but may have been a factor.

TAM:)

[beachnut]

the ejected cannister example you give was what I had expected to hear, and was the reason for my previous post.

Essentially, the cannisters could have acted like enourmous steel (or what ever they were made of) projectiles travelling very fast through the buildings. I have heard stories of the cannisters blasting through walls after their valves were "knocked off" releasing all the pressure at once. I think it may or may not have had an impact on the overall damage done inside the WTC...hard to say, but may have been a factor.

TAM:)The generators burn in fires like this.
6i_l_ux3R-4
http://www.youtube.com/watch?v=6i_l_ux3R-4

[beachnut]

Aircraft Impact Damage
Tomasz Wierzbicki, Professor of Applied Mechanics, MIT
Liang Xue, Ph.D. Candidate of Ocean Engineering, MIT
Meg Hendry-Brogan, Undergraduate student of Ocean Engineering, MIT

http://web.mit.edu/civenv/wtc/PDFfiles/Chapter%20IV%20Aircraft%20Impact.pdf

http://public.gregjenkins.promessage.com/Ningen1.jpg
http://public.gregjenkins.promessage.com/Ningen2.jpg
http://public.gregjenkins.promessage.com/Ningen3.jpg

Wierzbicki et al.'s conclusion regarding core damage is based on flawed assumptions. They arrive at the amount of energy left to damage the core by subtracting Eplane + Eext_col + Efloor from Ekinetic. The Ekinetic is based on the total mass of the airplane which includes the fuel mass (roughly 32% of KE for 10,000 gal).

Once the fuel tanks disintegrate the fuel is incapable of damaging the steel core columns in the same manner as the wings cut the exterior columns. In fact the fuel mass can only reasonably be assumed to apply a general shear force to the entire structure which the structure is perfectly capable of absorbing.

So essentially there is an energy deficit before any damage can be done to the core columns.
But what is your conclusion, and what does it mean? Why are you just posting fluff about something you have no conclusion about? And you talk about rain, and planes, why? Do you have a thesis to prove or test? What is it? And how does Jones' thermite fit in? Not one of the many people who have used thermite would use if to destroy the WTC. Why?

What else do you have on this, and what does it mean? Conclusion?

[T.A.M.]

now now beachnut...they are only "asking questions"...lol

TAM;)

[beachnut]

now now beachnut...they are only "asking questions"...lol

TAM;)
I was hoping some truthers had conclusions, unlike the p4t. (pilots for 9/11 truth)

[Geedubya]

One aspect that may be somewhat overlooked in this discussion, although I certainly may have missed something, is the fact that in addition to some possible severing and cutting, certain interior columns may have simply been dislodged or broken apart at their splice points. They apparently were not connected with lateral strength/stability being a prime concern:

Figure 11(e) shows interior columns of the towers stacked on top of each other at recycling plant. Almost all interior column pieces that were inspected were intact and did not show failure of welds. As indicated earlier, these columns were gravity columns and their splices did not need to be designed for any amount of tension or bending. However, a minimal splice was provided for these columns presumably for secondary forces and the forces during construction. Obviously, such minimal splices did not have a chance during the collapse stage to keep the columns together and had fractured. Observing the fact that the interior column splices were not needed and were so minimal, it is not clear if when the attacking Boeing 767 airplanes entered the towers any of the interior column were actually dislodged and eliminated or bent due to failure of their splices.

http://www.nistreview.org/WTC-ASTANEH.pdf

[Apollo20]

Geedubya:

I have seen some folks claim that the column welds were very strong, and others say that they were "tack welds"....., so who is correct?

[rwguinn]

Geedubya:

I have seen some folks claim that the column welds were very strong, and others say that they were "tack welds"....., so who is correct?
Damn good question.
From my experience with welding (not buildings) warpage is so bad on the number of welds that I need to see some evidence to convince me that they actually welded much at all to make the verticals continuous..
Common procedure at one time was (I believe) since one never will see a tension load in the columns, a simple "Fishplate" would be tack-welded on either side of the column to hold it in place while they (the fish plates) were rivited to the upper and lower portions of the column. There should also be some sort of "socket" like set-up to hold things aligned for assembly.
There was much that was unconventional about the towers, however, and the above is simply a description of how I would probably do it. But then, I am not a designer--I am an analyst--which is probably for the best.

[jaydeehess]

Is there any common practice that would have made the connection between column sections as strong (laterally) as the solid sections themselves? If so would there ever have been a requirement for this?

Seems to me that the level at which column sections were joined was staggered so as to allow normally experienced lateral forces to be distributed evenly. Thus there would not be a great need for individual columns to have the inherent lateral resistance by virtue of their dimensions required to garner the compression strength required. In fact this is obvious since the columns at the 35th floor are themselves not as large as those at the 75th floor. Obviously the 50th floor requires greater compression strength while the 75th does not, but if they can both be assumed to have the same (or similar) lateral load under normal circumstances then the smaller columns at the 75th floor obvious sufficed.

In small home construction one can construct a cottage that sits on posts on concrete pads. The posts need not be attached to the cottage nor to the pads because the force due to gravity makes any lateral forces insufficient to move the post off the pad or out from under the cottage. (except in seismicly active areas of course)

So anyone want to calculate just the friction force that would be encountered by sliding two columns sections along each other at their joint at 1 cm per second (for eg.)

You'd need the gravity load on that joint, the coefficient of friction of rough steel on rough steel and the velocity of 1 cm/s. How does this compare to any normally experienced lateral loads that the joint would be expected to experience?

[rwguinn]

snip
So anyone want to calculate just the friction force that would be encountered by sliding two columns sections along each other at their joint at 1 cm per second (for eg.)

You'd need the gravity load on that joint, the coefficient of friction of rough steel on rough steel and the velocity of 1 cm/s. How does this compare to any normally experienced lateral loads that the joint would be expected to experience?


Coefficient of static friction is usually much greater than dynamic. Just getting it started would require much greater force than keeping it moving

[jaydeehess]

Coefficient of static friction is usually much greater than dynamic. Just getting it started would require much greater force than keeping it moving

Ok, the coeff. of static friction for mild steel on mild steel is 0.74 while the coeff. of kinetic friction is 0.57.

OK its been a long time. Let's see if I have this straight.

So, given that static friction = coeff X value of normal force , the lateral force required to start moving two sections of core column would be equal to about 75% of the value of the force due to gravity that is occuring at that joint.

One can stack steel columns on top of each other with no worries that they will slide apart as long as they remain vertical. Its if they tip or bend that one gets into trouble since now the force due to gravity is not perpendicular to the contacting surfaces. Thus part of the force due to gravity is acting to slide these surfaces. Using the above, if my take on this is correct and my trig is correct, then if those steel on steel surfaces are at 22 degrees from horizontal the force due to gravity will overcome the static friction and they will start to slide and when the do they will acellerate as they do because the static friction is 30% greater than the sliding friction.

If a lateral force is applied while the building is experiencing a tilt then less tilt would be required to overcome that static friction.

So, what would be a good figure on the force due to gravity on a single column? 12,000 N?

a 1000 Kg object moving at 220 m/s and impacting a column, staying in inelastic contact with it for 0.1 sec would impart a force of 22,000 N on the column. Easily twice the amount required to start moving two steel column sections.

[GregoryUrich]

Ok, the coeff. of static friction for mild steel on mild steel is 0.74 while the coeff. of kinetic friction is 0.57.

OK its been a long time. Let's see if I have this straight.

So, given that static friction = coeff X value of normal force , the lateral force required to start moving two sections of core column would be equal to about 75% of the value of the force due to gravity that is occuring at that joint.

One can stack steel columns on top of each other with no worries that they will slide apart as long as they remain vertical. Its if they tip or bend that one gets into trouble since now the force due to gravity is not perpendicular to the contacting surfaces. Thus part of the force due to gravity is acting to slide these surfaces. Using the above, if my take on this is correct and my trig is correct, then if those steel on steel surfaces are at 22 degrees from horizontal the force due to gravity will overcome the static friction and they will start to slide and when the do they will acellerate as they do because the static friction is 30% greater than the sliding friction.

If a lateral force is applied while the building is experiencing a tilt then less tilt would be required to overcome that static friction.

So, what would be a good figure on the force due to gravity on a single column? 12,000 N?

a 1000 Kg object moving at 220 m/s and impacting a column, staying in inelastic contact with it for 0.1 sec would impart a force of 22,000 N on the column. Easily twice the amount required to start moving two steel column sections.

Added***

First lets fix the force due to gravity.

Bazant et al. have the mass above the impact point (WTC1) as 58 x 10^6 Kg. Approx 50% of that acts on the core. Also at least 50% of the mass acting on the core acts on the core perimeter columns (24 columns). So:

((58 x 10^6 x 0.50 X 0.50)/24) x 9.8 = 5,9 x 10^6 N

***

I hate to return to the actual topic but what you are saying is related (except for the fact that the columns were actually welded and there were bolted or welded horizontal beams at each floor):

Now Wierzbicki uses a 12" wide core column. If you spread the entire fuel mass over the width of the core at 220 m/s you have < 280 Kg impacting each column which means you can't even overcome friction, let alone welds and horizontal members.

This is the problem with the Wierzbicki article that no one here (expect possibly Apollo) is willing to admit. Wierzbicki applies the entire energy associated with the fuel mass to the core columns when only a very small portion of that mass can actually impact a particular column.

[Apollo20]

Gregory:

Well, yes.... But I am also arguing that some of the fuel was vaporized on impact, consuming kinetic energy. I accept that some fuel was atomized too,(I still hate that term!). This means a lot of fuel was broken into fine droplets, a process that also consumes energy through the creation of more surface area.

I get the feeling that Wierzbicki, NIST and Perdue treat the impact effects of the fuel quite differently and therefore reach quite different conclusions.

[rwguinn]

Gregory:

Well, yes.... But I am also arguing that some of the fuel was vaporized on impact, consuming kinetic energy. I accept that some fuel was atomized too,(I still hate that term!). This means a lot of fuel was broken into fine droplets, a process that also consumes energy through the creation of more surface area.

I get the feeling that Wierzbicki, NIST and Perdue treat the impact effects of the fuel quite differently and therefore reach quite different conclusions.
Apollo20:
Would not a great deal of that energy consumed in atomizing (:D ) the fuel come from fuel impact with structure? The same thing would apply to vaporizing it--impact would yield energy, heat being the lowest form, and that would contribute to the vaporization as well.
So it didn't just disappear (or appear)--it had to be converted, and you have to admit that impacts were abundantly available...

[GregoryUrich]

Apollo20:
Would not a great deal of that energy consumed in atomizing (:D ) the fuel come from fuel impact with structure? The same thing would apply to vaporizing it--impact would yield energy, heat being the lowest form, and that would contribute to the vaporization as well.
So it didn't just disappear (or appear)--it had to be converted, and you have to admit that impacts were abundantly available...

I don't mean to answer for Apollo, but I don't think anyone on the thread has suggested that no impacts would occur. In fact, even I agree that some core damage must have occured due to impacts of fluid and other debris. My point is that the entire impact energy (after break up of the aircraft, the external columns and floor) cannot be neatly applied to a small number of core columns. This is the main problem with Wierzbicki's article.

I have shown by a large margin (here (http://forums.randi.org/showthread.php?postid=2739589#post2739589)) that in fact no columns will fail due to fluid only impacts.

[rwguinn]

I don't mean to answer for Apollo, but I don't think anyone on the thread has suggested that no impacts would occur. In fact, even I agree that some core damage must have occured due to impacts of fluid and other debris. My point is that the entire impact energy (after break up of the aircraft, the external columns and floor) cannot be neatly applied to a small number of core columns. This is the main problem with Wierzbicki's article.

I have shown by a large margin (here (http://forums.randi.org/showthread.php?postid=2739589#post2739589)) that in fact no columns will fail due to fluid only impacts.
No, you assert that it didn't happen that way, and reject combined loading.
You did not have "just" fluid, "just " airplane parts (of varying types)--you had combined impacts.
The whole da$n impact can be treated as being primarily inelastic, so the energy went somewhere--a very small %age exited the other side, so where did it go?

[GregoryUrich]

No, you assert that it didn't happen that way, and reject combined loading.
You did not have "just" fluid, "just " airplane parts (of varying types)--you had combined impacts.
The whole da$n impact can be treated as being primarily inelastic, so the energy went somewhere--a very small %age exited the other side, so where did it go?

I don't remember rejecting combined loading but let's try and keep this argument to whether Wierzbicki is correct or not.

Wierzbicki is the one who divides up the energy dissipation and has essentially somewhat less than the energy associated with the fluid mass left to damage the core. The simple fact is that the fluid mass can not damage the structure (columns or floors) in the same way as the airplane parts.

Just because we don't know where the energy went does not necessarily mean it gets applied to a minimum number of core columns. But this is exactly what Wierzbicki does. As you are surely aware, there is lot of stuff in the core including partitions, ducts, elevators, wiring, plumbing, machinery, restrooms, closets, storage, stairs, etc.

Then there is the fact that less than 50% of the fluid/debris has a free shot at the core. The lower 50% of an impacted floor probably has 50 workspaces at around 200-400 Kg / workspace. The upper 25 percent is the floor structure with 60 ft of truss matrix which essentially nothing will penetrate.

As I have said before, surely there was core damage. Some airplane parts or other debris must have the core columns. Even the fluid surely caused some damage. Nonetheless, no core columns were severed by fluid impact.

Wierzbicki drastically overestimates the core damage due to applying all fluid energy to a small number of core columns when 90% of the fluid can not even hit a core column.

[rwguinn]

I don't remember rejecting combined loading but let's try and keep this argument to whether Wierzbicki is correct or not.

Wierzbicki is the one who divides up the energy dissipation and has essentially somewhat less than the energy associated with the fluid mass left to damage the core. The simple fact is that the fluid mass can not damage the structure (columns or floors) in the same way as the airplane parts.

Just because we don't know where the energy went does not necessarily mean it gets applied to a minimum number of core columns. But this is exactly what Wierzbicki does. As you are surely aware, there is lot of stuff in the core including partitions, ducts, elevators, wiring, plumbing, machinery, restrooms, closets, storage, stairs, etc.

Then there is the fact that less than 50% of the fluid/debris has a free shot at the core. The lower 50% of an impacted floor probably has 50 workspaces at around 200-400 Kg / workspace. The upper 25 percent is the floor structure with 60 ft of truss matrix which essentially nothing will penetrate.

As I have said before, surely there was core damage. Some airplane parts or other debris must have the core columns. Even the fluid surely caused some damage. Nonetheless, no core columns were severed by fluid impact.

Wierzbicki drastically overestimates the core damage due to applying all fluid energy to a small number of core columns when 90% of the fluid can not even hit a core column.
Assertions are not evidence. I can assert that 93.21% of your statistics are made upon the spot. See? I used a number--a very precise number. Must be right, huh?
While it can never be shown that the core structure was or was not damaged by whatever, the overwhelming evidence is that it was. This is known by the term "inference"--where you take what evidence you have, and work out what had to have happened, based on physical possibilities.
The buildings came down, according to laws of physics that are very well known, and which are followed mathematically by every modeling program I know of. Given the boundary conditions that existed and are known, a number of modeling techniques predict that the building will come down, assuming various amounts of damage to the core.
They came down. The overwhelming scientific and engineering (informed) conclusion and opinion is that the core was damaged by those collisions.

[jaydeehess]

To summerize and add my own visualization;

By GU's account the max force on any one, by fuel impact alone, column(averaged out) would be about 1% of the force required to overcome static friction between column splice points. Only a fraction of the columns suffered any significant structural damage (ie. I do not include stripping of the insulation) and only a few of those were completely compromised ( severed or bent until a column splice failed or simply bent until the column can no longer be said to be supporting any vertical load)

Obviously then the fuel alone did not compromise these columns nor was the damage done equally to all columns. One could be safe in assuming that the force due to aerosolized (better that atomized? or does aerosolized have another connotation) fuel on individual columns was greater or lesser than that 22,000 N figure from my calculations above. It is unlikely (IMHO) though that it was greater than 10% or 20% of the force required to overcome the static friction on any of the 47 columns. This force was also likely applied for a longer time period than say, for the impact of an engine core.

Yes aerosolizing the fuel requires energy but believein that it 'consumes' energy would be a mistake that a first year physics prof would drill into his under grad students. Energy to aerosolize the fuel came from the kinetic energy of the fuel itself. When the fuel left the ruptured tanks it imparted some of that energy into the aerosolizing so where is that energy now? It did not disappear when the fuel became a dense mist. It now resides, does it not, in the surface tension of each droplet and in the elastic response of the objects that the fuel hit (aircraft wing pieces, office furnishings, perimeter columns, people) and many of those objects now carry that energy in the form of kinetic energy and they are mostly not liquids. Neither are the more solid parts of the aircraft, the wheel assemblies, engine cores, O22 cannisters all of which is travelling at some velocity less than the velocity of the aircraft as it hit the perimeter. NIST gives the average value of that velocity as about 100 MPH less than impact velocity.

Given that only some of the core columns failed we know that averaging the available energy over all columns is not valid and indeed we can expect that some streams of debris would be carrying more of that energy than at other areas of the entire debris stream.

We also know for a certainty that most of the momentum of the aircraft was transferred to the building since relatively little of the aircraft came out the other three sides(and anything coming out perpendicular to the line of travel would have to have imparted 1/2 of its momentum to something in order to do so). That momentum was transferred not to the core columns as a whole, averaged over 47 columns. It was transfered (or what remained after perimeter penetration) predominantly to the first line of columns and predominantly to any that were in line with the direction of travel of the more dense parts of the aircraft.

The high velocity fuel mist simply applied a long period (relatively) force to the columns that could do nothing but add to the force of impact of other, solid pieces of debris.

[Apollo20]

Gregory and rwguinn/jaydehess:

If you look at Wierzbicki's table of "Energy Loss" due to the aircraft impacts you'll see only four terms:

"airplane" - the energy to fragment the aircraft
"exterior" - the energy to fracture the exterior columns
"floors" - the energy to fracture the concrete and steel of the floors
"core columns" - the energy consumed in damaging the core columns

These four terms are supposed to add up to the impact kinetic energy. Wierzbicki calculates the first three terms and determines the fourth term by difference. This is where I have a problem because there is no term for energy dissipation by the fuel!

Wierzbicki is happy to allow for energy going into "shredding" the aircraft by fragmentation. Well, I'm sorry to say, the fuel was "fragmented" too! And this is NOT a trivial term, but is probably in the 200 MJ range.

Since the energy to damage the core is determined by Wierzbicki by difference, the fuel "atomization energy" must first be added to the "airplane", "exterior" and "floors" contributions making the "core column" term smaller by ~ 200 MJ.

Now if you apply Gregory's arguments as well, you wind up with so little energy left over to damage the core columns that I would have to say that NO core columns would have been damaged significantly by Wierzbicki's impact damage mechanism.

[rwguinn]

Gregory and rwguinn/jaydehess:

If you look at Wierzbicki's table of "Energy Loss" due to the aircraft impacts you'll see only four terms:

"airplane" - the energy to fragment the aircraft
"exterior" - the energy to fracture the exterior columns
"floors" - the energy to fracture the concrete and steel of the floors
"core columns" - the energy consumed in damaging the core columns

These four terms are supposed to add up to the impact kinetic energy. Wierzbicki calculates the first three terms and determines the fourth term by difference. This is where I have a problem because there is no term for energy dissipation by the fuel!

Wierzbicki is happy to allow for energy going into "shredding" the aircraft by fragmentation. Well, I'm sorry to say, the fuel was "fragmented" too! And this is NOT a trivial term, but is probably in the 200 MJ range.

Since the energy to damage the core is determined by Wierzbicki by difference, the fuel "atomization energy" must first be added to the "airplane", "exterior" and "floors" contributions making the "core column" term smaller by ~ 200 MJ.

Now if you apply Gregory's arguments as well, you wind up with so little energy left over to damage the core columns that I would have to say that NO core columns would have been damaged significantly by Wierzbicki's impact damage mechanism.
This is wghere I have to take issue:
I think everybody is looking at this fro their own perspective. The entire systeem is what counts.
You say "probably" in the 200mJ range. What is that "Probably" based on?
Remember that fluids have next to no shear and tensile strength, tearing big chunks of it apart is no big consumer of energy--and as I pointed out, that energy comes from impact--energy dissipation=work=Force X Distance. This means in order to break up into fine particles, the fluid applied a force to something, equal and opposite to what it took to break up. That force is as real as anything.
I also feel that you are dismissing the release of chemical energy in the combustion of the fluid, for reasons unbeknownst to me.
The initial spray of atomized fuel ignites, releasing: 1. Heat; and 2. sonic overpressure impulse (shock wave, big boom--whatever). Both of those products cause damage to structure, and further atomization and vaporization of the fuel, which leads to more heat, etc--in a "self-eating watermelon" type process.
Look at it as a system--not a bunch of individual happenings. It can, and does, make a difference.

[Furcifer]

rw is right, we are talking about balancing an energy equation here. The mechanical process of taking a large body of fluid and reducing it to smaller particles is only a transfer of energy from 1 big thing to many small things. This does not represent a sink in the energy equation, at least not an apreciable one.

When we consider the collision of two billiard balls, how much energy is lost as heat? as sound? drag? friction?

[Apollo20]

RWGUINN:

We are considering Wierzbicki's paper. He does not consider the combustion of the fuel so I am not considering it either. That came AFTER the momentum transfers as did the degradation of the impact energy into heat.

So please confine your arguments to isothermal energy transfers involving physical (not chemical) processes.

And please answer me this:

Wierzbicki does not have an energy term involving the fuel anywhere in his calculation. The fuel weighed about 30,000 kg. When the aircraft hit the towers, this fuel was dispersed.

The aircraft was also "dispersed" as was the concrete in the impacted floors. These were energy sinks, but the fuel dispersion was not?

And to say that all the aircraft KE was absorbed by the buildings is not true when a significant amount of fuel was ejected OUT of the towers....

[rwguinn]

RWGUINN:

We are considering Wierzbicki's paper. He does not consider the combustion of the fuel so I am not considering it either. That came AFTER the momentum transfers as did the degradation of the impact energy into heat.

So please confine your arguments to isothermal energy transfers involving physical (not chemical) processes.

And please answer me this:

Wierzbicki does not have an energy term involving the fuel anywhere in his calculation. The fuel weighed about 30,000 kg. When the aircraft hit the towers, this fuel was dispersed.

The aircraft was also "dispersed" as was the concrete in the impacted floors. These were energy sinks, but the fuel dispersion was not?

And to say that all the aircraft KE was absorbed by the buildings is not true when a significant amount of fuel was ejected OUT of the towers....

There are no energy "sinks" there- all the energy performed work, one way or the other.
You Can't have it both ways, Doc.
By your own assertion, the fuel ejected had already given up its energy as it was in a "Vaporous state"--either atomized or vaporized--your choice. (witness the Fireball) So, if it had given up its KE, it was not moving, therefore not producing work. It gave it all to the building--making for an inelastic collision.
Also, according to the reports, fairly large quanmtities of fuel "flowed" donw the elevator shafts and burned, causing deaths and explosions in elevator shafts, etc.
Nor can you dismiss the energy transferred to the structure (30000lb, you said?) by tearing the fuel into little bitty pieces as insignificant, while that of tearing the aircraft into little bitty pieces is considered "significant".

[GregoryUrich]

Assertions are not evidence. I can assert that 93.21% of your statistics are made upon the spot. See? I used a number--a very precise number. Must be right, huh?
While it can never be shown that the core structure was or was not damaged by whatever, the overwhelming evidence is that it was. This is known by the term "inference"--where you take what evidence you have, and work out what had to have happened, based on physical possibilities.
The buildings came down, according to laws of physics that are very well known, and which are followed mathematically by every modeling program I know of. Given the boundary conditions that existed and are known, a number of modeling techniques predict that the building will come down, assuming various amounts of damage to the core.
They came down. The overwhelming scientific and engineering (informed) conclusion and opinion is that the core was damaged by those collisions.

You have no evidence. I have demonstrated that at least one of the overwhelming scientific and engineering (informed) conlusions (based on inference) is incorrect. Why not just admit it?

My assertions are so called facts from from NIST, Wierzbicki and Bazant:

50% of gravity load on core
Floor thickness including trusses = 34"
Core column thickness = 12"
Mass of upper portion = 58,000 tonnes

That only a portion of the fluid/debris wave could hit the columns is an inference based on physical laws. So what's the problem? Why does every conclusion that supports gravity driven collapse need to be correct?

In this case, I think you are too busy fighting the twoofers and ending up a septic sceptic?

[Apollo20]

rwguinn:

Where did the energy to eject the fuel out of the tower come from?

P.S.
I am starting to think Gregory is correct about your time constraints!

[GregoryUrich]

There are no energy "sinks" there- all the energy performed work, one way or the other.
You Can't have it both ways, Doc.
By your own assertion, the fuel ejected had already given up its energy as it was in a "Vaporous state"--either atomized or vaporized--your choice. (witness the Fireball) So, if it had given up its KE, it was not moving, therefore not producing work. It gave it all to the building--making for an inelastic collision.
Also, according to the reports, fairly large quanmtities of fuel "flowed" donw the elevator shafts and burned, causing deaths and explosions in elevator shafts, etc.
Nor can you dismiss the energy transferred to the structure (30000lb, you said?) by tearing the fuel into little bitty pieces as insignificant, while that of tearing the aircraft into little bitty pieces is considered "significant".

The energy went into creating the vaporous state not into the building. You can't use the energy twice. The building broke the container, the fuel was torn into small bits in a number of ways:


Flowing out of the ruptured tanks
Wind resistance
Deflecting through the floor truss matrix
Splashing against office contents
Splashing against core contents
Impacting core columns


Some of the energy went into plastic deformation of the tanks, the office contents, core contents and possibly the floor and floor truss matrix. Some of the energy went into small-bitizing the the fuel. Some of the energy went into pushing air. Some of the energy went into elastic displacement which was dissipated as vibrational energy and eventually heat.

This does not change the fact that Wierzbicki was off by a long shot.

[GregoryUrich]

rwguinn:

Where did the energy to eject the fuel out of the tower come from?

P.S.
I am starting to think Gregory is correct about your time constraints!

Did I say something about time constraints?

Nevermind, I see what you mean.

[Furcifer]

Greg: This isn't about gravity driven collapse, we are back to initiating events. I still see very little to refute Dr.G's first paper on global failure here.

The fundamental principle of conservation of momentum is being bastardized here, as well as some thermodynamics unless someone defines what a "sink" is. A "sink" should only be referred to as a method of transmitting energy AWAY from the impact site, subtracting from the available to damage the core. I hate to say this but the two of you seem to have blinders on to this basic principle. If I am mistaken I apologize.

[Apollo20]

Gregory:

When rwguinn starts posting mumbo-jumbo like this:

"Nor can you dismiss the energy transferred to the structure (30000lb, you said?) by tearing the fuel into little bitty pieces as insignificant, while that of tearing the aircraft into little bitty pieces is considered "significant"."

I know you have won your argument with this man "fair and square".

Unfortunately, these guys will NEVER admit that an authority figure, such as an MIT Professor, could be wrong.

They will argue (as RGUWINN) and ARGUE and ARGUE and make sure they have the last say even when they KNOW they are wrong or don't even know what they are arguing about!

PITY I say...

PITY!

[rwguinn]

Gregory:

When rwguinn starts posting mumbo-jumbo like this:

"Nor can you dismiss the energy transferred to the structure (30000lb, you said?) by tearing the fuel into little bitty pieces as insignificant, while that of tearing the aircraft into little bitty pieces is considered "significant"."

I know you have won your argument with this man "fair and square".

Unfortunately, these guys will NEVER admit that an authority figure, such as an MIT Professor, could be wrong.

They will argue (as RGUWINN) and ARGUE and ARGUE and make sure they have the last say even when they KNOW they are wrong or don't even know what they are arguing about!

PITY I say...

PITY!
reported.
When you refer to the towers as a "sink", you are refusing to admit that energy was transferred. It did not go away. If the fluid was atomized, it traded KE for something else. The kinetic energy did not just disappear.
Was the energy state of the atomized fuel greater or less than the energy state of the liquid fuel at 570MPH?

[Dave Rogers]

Wierzbicki is happy to allow for energy going into "shredding" the aircraft by fragmentation. Well, I'm sorry to say, the fuel was "fragmented" too! And this is NOT a trivial term, but is probably in the 200 MJ range.

Several days ago, in this thread, I posted a comment that, based on the surface tension of kerosene and your own calculation from an incorrect value of that surface tension, the energy required to disperse the fuel entirely into 100 micron droplets was 250kJ. Now your estimate has gone up from 20MJ to 200MJ. Where did these additional orders of magnitude come from?

Dave

[Apollo20]

Dave Rogers:

I have never used surface tension to calculate the energy required to disperse the fuel... That was your suggestion I believe!

My starting point is that some fuel was FLASH-VAPORIZED by the impacts. Some was atomized too. And asuming only 100 micron particles were formed is not really valid. For example, an airblast atomizer produces about 50 % of droplets with diameters less than 75 microns. You should use something like a Rosin-Rammler distribution first and then estimate the total effective surface area....

As for the vaporized component of the fuel.... well unfortunately it is difficult to predict exactly how much fuel was vaporized when the wing tanks impacted with the towers but a figure ~ 200 gal would appear to be a reasonable estimate in line with values given by FEMA and NIST. This being the case, we have 530 kg of fuel requiring 175 MJ to be vaporized.

[Dave Rogers]

Dave Rogers:

I have never used surface tension to calculate the energy required to disperse the fuel... That was your suggestion I believe!

Not exactly. You made an estimate based on the surface energy per unit area, I just pointed out that that's the same thing as surface tension and that hence your estimate was a couple of orders of magnitude too high.

As for the vaporisation, is your estimate of the total amount of fuel vaporised, or for the amount vaporised on impact? My point is that the chemical energy liberated in the combustion of the fuel was also available to cause vaporisation once it had ignited, so if you only have the total amount vaporised you could easily be overestimating the impact energy required. Since the dispersal energy, from the surface tension argument, appears to have been at least a couple of orders of magnitude less than the vaporisation energy, I suspect that the latter is the only term we really need consider here.

Dave

[Apollo20]

Dave, I am assuming direct (near instantaneous) vaporization of the fuel, which I believe would happen at the impact velocities in question. Indeed I think it is quite possible that some of the aluminum may have vaporized too.

I also think that the fuel was dispersed into a continuous distribution of fragments from gaseous to sub-micron to micron sized particles. The energy to do this was drawn from the impact kinetic energy. This was not considered by Wierzbicki.... you say it's small.... I say it's not that small!

There appears to be a paucity of data on this type of fuel dispersal. There are some papers by S. R. Tieszen but they are in Sandia Reports that I are hard to obtain.

[jaydeehess]

rwguinn:

Where did the energy to eject the fuel out of the tower come from?

P.S.
I am starting to think Gregory is correct about your time constraints!

Was any fuel ejected before the fireball erupted? If so then what's the estimate of how much went all the way through the building? Any that was ejected out the sides of the building parallel to direction of travel must have given up some momentum to other objects inside the building in order to change their direction of travel. If none of the fuel was ejected prior to the fireball then the ejection of fuel cannot be shown to have any bearing on any arguement about what occured prior to the fireball. For all we know the fuel mist that managed to make it all the way through the building did not contain enough momentum to break the glass and in fact many of the windows opposite the impact side did remain unbroken immediatley after impact and before the fireball.
__________________

If by that you mean that GU is correct that the fuel alone could not have severed a core column then I agree. It would seem though that it did put a small force on some of them that could only add to that which some of them would experience when hit by more dense , solid objects.

[Furcifer]

Apollo: That's not really a fair observation, this has nothing to do with who said what and where their degree was conferred to them. Furthermore, this is all undergrad stuff, any advanced degrees hardly make someone any more of an authority in this area. Greg made an observation, he was given the reason why his observation was incorrect by this forum, and then the author himself confirmed the reason he was incorrect. What's so pitiful about that? This wouldn't be much of a forum if everyone just instantly agreed with whatever someone posted all the time.
Greg and yourself seem to be in denial about how to properly balance energy equations. You are insisting that the atomization of fuel removed energy from the available to damage the core. Greg is going further and saying the atomized fuel could not impart any energy to the core (or very little). All I am saying is if this is true, then where did the energy go? If we wish to disect this part of the impact we need to consider all of the variables.

[T.A.M.]

in general, the higher the degree, the more focused on a particular area one becomes. Generally, the basics of engineering or physics, or what have you would remain the same, their knowledge if anything decreasing through a lack of use of some elements of the basics within their discipline (ask me a biochem question right now and you'll get a funny look, but ask me about prostate issues, or pneumonia, and I'm your man).

So I agree, unless the PhD is directly related to the point of contention, than a Bachelors of the discipline is likely equally able and qualified to answer.

TAM:)

[jaydeehess]

Some of the energy went into pushing air. Some of the energy went into elastic displacement which was dissipated as vibrational energy and eventually heat.


That dissipation by vibration could have weakened truss seats. It was enough to cause cracks in concrete, visible in the lower stairwell areas if IIRC. Certainly other damage such as furniture that moved and light fixtures that fell out of the ceiling were reported to occur at the time of the aircraft impact. That damage near the bottom of the towers spurs CT's to the basement bomb conjectures.

I know we are not speaking to the effect of the fireball but your 'pushing air' comment makes me wonder about the effect of the overpressure on the floor above the explosion. Each floor would have had its own explosion but it would originate in a different area on each floor(ie fuel from right wing exploding on the floors the right wing hit while the fuel from the left wing exploding on the floors the left wing hit) Would it take much over pressure to cause a floor pan to lift? The floors after all are constructed to resist gravitational force which is acting in the opposite direction. Would the floor lift then drop back onto the truss seats? If so then there is also the possibility of the floor pan twisting and not coming back down precisly on the seats again and of damaging the truss seats.

[jaydeehess]

All I am saying is if this is true, then where did the energy go? If we wish to disect this part of the impact we need to consider all of the variables.

I am satified that a significant amount of the KE of that fuel was transferred to making the fuel into droplets. What was left would impart a small force on some of the columns. It seems that some here want to minimize the effect of the aerosolization and vaporation while some want to minimize the effect of the KE of the fuel mist.

Yes some fuel was vaporized or aerosolized but using that amount of detail and then still averaging the KE of the fuel mist over all 47 columns would seem to show a bias IMO. Granted that if one assumes that 80% of the fuel mist KE was imparted to other than the columns and that of the remaining 20% only 15 columns took the brunt of it one still has only a small force on the columns by fuel mist alone.

Can we now then move on and consider that of the other components of the aircraft that made it into the building that we can also not average that transfer of KE over all 47 columns? After all if the KE was evenly disperesed to all 47 columns then all 47 columns would have suffered the same amount of damage.

[Furcifer]

I don't know, I'm getting confused. Seems like a case of over analysis to me. I see the plane hitting, breaking up, mixing with the building debris, so you end up with a larger, less dense, shrapnel cloud. The CM of this cloud is still travelling in the same direction as the plane, towards the core. Some of this cloud is vapour, most of it is large pieces of metal, concrete and liquid fuel. The vapour is lagging slightly due to its relative density. But the 500 mph debris cloud strikes the core with less energy than it took to destroy the exterior columns and affected floors. The leading edge of this cloud is the most dense material (exterior steel, landing gear, engines etc.) It impacts the core and the trailing edge of the debris cloud "pushes" the more dense material into the core, stripping the walls, elevator doors and what not, in the process allowing some of the liquid fuel to enter into the core section and ultimately into the levator shafts. It's about this time that fuel ignites, while CM of the plane and debris is about the center of the building. Dense material that did not strike the core, continues through the building, almost unimpeded, until it hits the exit side and punches through.
The expansion of the fuel, as it atomizes, only serves to pick up more debris, and impart the KE over a larger area. The energy is just transferred, not destroyed.

What's wrong with this? Makes perfect sense to me.

[jaydeehess]

I don't know, I'm getting confused. Seems like a case of over analysis to me. I see the plane hitting, breaking up, mixing with the building debris, so you end up with a larger, less dense, shrapnel cloud. The CM of this cloud is still travelling in the same direction as the plane, towards the core. Some of this cloud is vapour, most of it is large pieces of metal, concrete and liquid fuel. The vapour is lagging slightly due to its relative density. But the 500 mph debris cloud strikes the core with less energy than it took to destroy the exterior columns and affected floors. The leading edge of this cloud is the most dense material (exterior steel, landing gear, engines etc.) It impacts the core and the trailing edge of the debris cloud "pushes" the more dense material into the core, stripping the walls, elevator doors and what not, in the process allowing some of the liquid fuel to enter into the core section and ultimately into the levator shafts. It's about this time that fuel ignites, while CM of the plane and debris is about the center of the building. Dense material that did not strike the core, continues through the building, almost unimpeded, until it hits the exit side and punches through.
The expansion of the fuel, as it atomizes, only serves to pick up more debris, and impart the KE over a larger area. The energy is just transferred, not destroyed.

What's wrong with this? Makes perfect sense to me.


In many chaotic situations there will be some order to be found. The resultant debris of the impact of a large, fast Boeing airliner with a steel framed skyscraper can certainly be described as a chaotic system. Some debris will no longer even be travelling parallel to the original line of travel having been deflected to one degree or another by impact with the perimeter columns and the floors. However, there will be a preferred direction which is of course the original line of travel. A very large percentage of the debris will still be moving in that direction.

The aircraft also was not a homogeneous object and so neither will be the debris as it breaks apart. The material that impacted only glass will separate from the material that hit perimeter columns, denser parts of the aircraft will slow less that less dense parts and if they also hit only glass then their velocity entering the building will be so much the greater.

What all simplifications do is attempt to break this chaos down and describe what is occuring by focusing on details and idealizing them. Although that is not a bad thing it must be realized that this is going to break down at some point in actually predicting the actual damage done.

IMHO, NIST did a good job of showing what occured inside the building at impact. They took the best estimates of trajectory of the aircraft as it hit the building and used FEA to predict what came next. They ran the FEA and changed the parameters around within the margin of error in determining the original trajectory and velocity and compared the results with as much empirical data as they could find. They then determined the best match between impact conditions and predicted damage.

If Gregory Urich chooses to believe that the impact could not have damaged the interior columns at all then he will have to supply at least as detailed an analysis as was done by NIST.

If all he wishes to do is state that the fuel mist alone could not have severely damaged a core columns then fine. However the point is a very small one. Whatever energy went into aerosolizing and vaporizing that fuel was also involved in breaking up the aircraft and imparting momentum to the perimeter columns. Throw a ballon full of water at a stop sign and the balloon breaks and the water flies in all directions(do it at enough velocity and some will vaporize, some will aerosolize) BUT the stop sign will also bend over(do it fast enough so as to have the water vaporize/aerosolize and the stop sign post will be bent over and the sign itself will cave in). So if the largest percentage of the KE of the fuel load was transfered to the perimeter columns and to the surface tension of trillions of small droplets that simply means that more of the KE of the solid bits-o-plane was transferred to the inside of the towers.

[Furcifer]

What all simplifications do is attempt to break this chaos down and describe what is occuring by focusing on details and idealizing them.
If Gregory Urich chooses to believe that the impact could not have damaged the interior columns at all then he will have to supply at least as detailed an analysis as was done by NIST.


Yep. I see this all too often where people seem to be taking these simplified things, point out some detail that was not included, and then saying the simplfied model is wrong. It just doesn't work that way. If you wish to get into the particulars then you need to dive in and consider everything, and I'm guessing this is why NCSTAR took as long as it did.

[jaydeehess]

What also strikes me is that the more aerosolized or vaporized the fuel is the greater the explosive nature of the fireball.

I certainly have no expertise on that matter but it would seem to be that the energy that went into aerosolization/vaporation would come back in spades by increasing the energy output (per second) of the explosion.

[Furcifer]

What also strikes me is that the more aerosolized or vaporized the fuel is the greater the explosive nature of the fireball.

I certainly have no expertise on that matter but it would seem to be that the energy that went into aerosolization/vaporation would come back in spades by increasing the energy output (per second) of the explosion.

But then they say the fires would have less fuel to burn later, so the steel woudln't have got as hot. But wait, you have to consider that the bigger fireball would have blown out more windows, allowing in more air, making the fires hotter. It's an energy juggling act. I think the smart guys went "Plane hit building, caused damage, fire burned, building fell down, what's for dinner?"

[GregoryUrich]

Apollo: That's not really a fair observation, this has nothing to do with who said what and where their degree was conferred to them. Furthermore, this is all undergrad stuff, any advanced degrees hardly make someone any more of an authority in this area. Greg made an observation, he was given the reason why his observation was incorrect by this forum, and then the author himself confirmed the reason he was incorrect. What's so pitiful about that? This wouldn't be much of a forum if everyone just instantly agreed with whatever someone posted all the time.
Greg and yourself seem to be in denial about how to properly balance energy equations. You are insisting that the atomization of fuel removed energy from the available to damage the core. Greg is going further and saying the atomized fuel could not impart any energy to the core (or very little). All I am saying is if this is true, then where did the energy go? If we wish to disect this part of the impact we need to consider all of the variables.

This is your lamest post to date. :mad: You incorrectly summarizing the thread and misquoting me at the same time.

The problem is my observation is correct and Wierzbicki hasn't dealt with the real issue yet.

I have never said that very little energy was imparted to the core. The core contents surely absorbed a good part of the remaining energy. However, the core columns cannot have absorbed enough energy to be severed unless hit by an engine.

You refuse to accept the basic fact that the vast majority of fuel/debris missed the core columns. It doesn't matter where the energy went (even though I have pointed out 5 sinks). The columns made up less than 10% of the impacted area. This isn't college stuff. My dog understands this.

Maybe the law of conservation of energy was amended since I was at school to read:

If an object misses impacting another object (due to any reason) it must go back and try again until impact is achieved in order for conservation of energy to be upheld.

[beachnut]

This is your lamest post to date. :mad: You incorrectly summarizing the thread and misquoting me at the same time.

The problem is my observation is correct and Wierzbicki hasn't dealt with the real issue yet.

I have never said that very little energy was imparted to the core. The core contents surely absorbed a good part of the remaining energy. However, the core columns cannot have absorbed enough energy to be severed unless hit by an engine.

You refuse to accept the basic fact that the vast majority of fuel/debris missed the core columns. It doesn't matter where the energy went (even though I have pointed out 5 sinks). The columns made up less than 10% of the impacted area. This isn't college stuff. My dog understands this.

Maybe the law of conservation of energy was amended since I was at school to read:

If an object misses impacting another object (due to any reason) it must go back and try again until impact is achieved in order for conservation of energy to be upheld.
This thread is about an idiot physics youtube message. You are posting about some paper you did which does not have an impact on 9/11. You seem to support 9/11 truth but have no stand on 9/11 ideas. I do not understand what you stand for. Are you supporting the thermite scholars, or do you think the OP physics points are valid? I think posting a paper or letter that tries to support the 9/11 truth misinformation idiots is not very engineering like. What do you think?

I have no idea what you think happened on 9/11. Why are you not able to say if you support the misinformation of 9/11 truth or not?

[T.A.M.]

This thread is about an idiot physics youtube message. You are posting about some paper you did which does not have an impact on 9/11. You seem to support 9/11 truth but have no stand on 9/11 ideas. I do not understand what you stand for. Are you supporting the thermite scholars, or do you think the OP physics points are valid? I think posting a paper or letter that tries to support the 9/11 truth misinformation idiots is not very engineering like. What do you think?

I have no idea what you think happened on 9/11. Why are you not able to say if you support the misinformation of 9/11 truth or not?

I am only speculating, but for many people who are secret truthers, but also have reputations to keep, they are torn between supporting the nuttery publicly, which would make them look nutty, like the rest, or supporting them in secret, by claiming to just have questions about the attacks, but really having a secret agenda, made clear in the subtext of their posts.

Then there are a scattered few who are legitimately neutral, with just a curiosity for the scientific oddities of that day. they are rare.

TAM:)

[GregoryUrich]

This thread is about an idiot physics youtube message. You are posting about some paper you did which does not have an impact on 9/11. You seem to support 9/11 truth but have no stand on 9/11 ideas. I do not understand what you stand for. Are you supporting the thermite scholars, or do you think the OP physics points are valid? I think posting a paper or letter that tries to support the 9/11 truth misinformation idiots is not very engineering like. What do you think?

I have no idea what you think happened on 9/11. Why are you not able to say if you support the misinformation of 9/11 truth or not?

Wrong thread dude. This one's about Wierzbicki's paper.

[Apollo20]

Gregory:

Wierzbicki's paper?

Is that the paper you have shown to be fraught with "difficulties"?

Way to "stump" the JREFers!

Perhaps Gravy and "Pomster" need to get a new team;

the present bunch isn't doing too well....

[pomeroo]

Gregory:

Wierzbicki's paper?

Is that the paper you have shown to be fraught with "difficulties"?

Way to "stump" the JREFers!

Perhaps Gravy and "Pomster" need to get a new team;

the present bunch isn't doing too well....



Perhaps we should become conspiracy liars?

[T.A.M.]

Gregory:

Wierzbicki's paper?

Is that the paper you have shown to be fraught with "difficulties"?

Way to "stump" the JREFers!

Perhaps Gravy and "Pomster" need to get a new team;

the present bunch isn't doing too well....

Now see. The GPSG (Greening Persona Study Group) can only remain puzzled as they continue to see the schizophrenic nature of posts that come from this Engima we know as Dr. Greening.

TAM:)

[Furcifer]

This isn't college stuff. My dog understands this.


Let me talk to the dog then.

[beachnut]

Wrong thread dude. This one's about Wierzbicki's paper.
Oh, you presented this paper as a debunking of the "physics by experts" thread, which was a thread about an idiot who does not understand physics like truther and scholars for truth do not understand 9/11. Now this makes sense. But you are still the one of 0.0067 percent engineers in the world who is sympathetic to the woo of 9/11. Thus the original thread where an idiots video of warped physics has another thread to debunk something about an idiot video or your own paper?

Truther stuff is confusing since it contains no facts and no logical conclusions based on facts. Why?

The OP mentioned paper does debunk the idiot physics video, good job.

[Furcifer]

This is your lamest post to date. :mad: You incorrectly summarizing the thread and misquoting me at the same time.

Sorry about the misquote, I'm working on a Stundie.


The problem is my observation is correct and Wierzbicki hasn't dealt with the real issue yet.

You should go teach his classes for him, that will give him time to properly address you. ;)

I have never said that very little energy was imparted to the core. The core contents surely absorbed a good part of the remaining energy. However, the core columns cannot have absorbed enough energy to be severed unless hit by an engine.


"I didn't punch her officer, I gave her an open hand slap"


You refuse to accept the basic fact that the vast majority of fuel/debris missed the core columns. It doesn't matter where the energy went (even though I have pointed out 5 sinks). The columns made up less than 10% of the impacted area. This isn't college stuff. My dog understands this.

All i saw here was "It doesn't matter where the energy went".

Maybe the law of conservation of energy was amended since I was at school to read:

If an object misses impacting another object (due to any reason) it must go back and try again until impact is achieved in order for conservation of energy to be upheld.

:) That was funny. I get your point. But you are wrong, had most of the debris not hit the core, there would have been a hole almost as big on the other side of the buidling and most of the plane would have been on the ground. Oh, and the buidling wouldn't have collapsed either.

[Furcifer]

I don't know if the other physics guys see it the same way as I do or not. But I was taught to see this as a point mass system. Once we have the center mass for the plane, we then determine the trajectory of the CM traveling with some momentum, or kinetic energy. This is how we arrive at the equation as per Weirzbicki. It would be considered a ballistic problem, and that's how we would solve it.
You guys want to consider more than just the CM system after impact with the exterior. You want to consider what happened to every single particle after the first collision. You now have to figure out what every single piece did. Once you add up all of these little equations, you will end up with the KE of the CM prior to impact. If you want to do this, then fine, I can understand why you would want to have a better understanding, it is after all the scientific way.
This does not change the fact that the simplified model is correct. It has to be, it is based in fundamental physics. And we all know the sum of the parts is not more or less than the whole.
And Greg, I know exactly what you are trying to say and it is a valid point. The thing is even if the energy imprted to the core was dispersed over a larger area, the net damage it does will be the same. If it was 20 severed colums, yes it could have been 40 columns reduced to 50% of their strength.

[GregoryUrich]

I don't know if the other physics guys see it the same way as I do or not. But I was taught to see this as a point mass system. Once we have the center mass for the plane, we then determine the trajectory of the CM traveling with some momentum, or kinetic energy. This is how we arrive at the equation as per Weirzbicki. It would be considered a ballistic problem, and that's how we would solve it.
You guys want to consider more than just the CM system after impact with the exterior. You want to consider what happened to every single particle after the first collision. You now have to figure out what every single piece did. Once you add up all of these little equations, you will end up with the KE of the CM prior to impact. If you want to do this, then fine, I can understand why you would want to have a better understanding, it is after all the scientific way.
This does not change the fact that the simplified model is correct. It has to be, it is based in fundamental physics. And we all know the sum of the parts is not more or less than the whole.
And Greg, I know exactly what you are trying to say and it is a valid point. The thing is even if the energy imprted to the core was dispersed over a larger area, the net damage it does will be the same. If it was 20 severed colums, yes it could have been 40 columns reduced to 50% of their strength.

The simplified model is deeply flawed, based on fundmental physics.

If the entire residual energy was implied directly to 12 columns in the worst case scenario, 12 columns would have failed according the Wierzbicki. Most of the energy however was applied directly to office and core contents resulting in plastic deformation of those contents (energy sink):

According to NIST:

Office contents in line with the core on both sides (stuff that made it through the core had roughly 65 tons of office contents on the other side to contend with) = 133 tons

Core Contents = 85 tons includes:


partitions
elevators or their tracks and cables
water pipes
sewer pipes
steam pipes
mechanical equipment
stored goods
restrooms
electrical cabling
stairs
air ducts


So the debris had 218 tons of rather strong stuff to impact. There was "probably a general shear" as the core contents were ripped from their mountings and from destroyed office debris getting pushed through the core column matrix. Don't forget 25% was still had to get through the floor truss matrix imparting resulting in a general shear on the entire building.

In summary we have:

Ecolumns = Ecore - Ecore contents - Eoffice contents - Efloor matrix - Evaporisation

We can not as Wierzbicki does apply this remaining energy to the smallest number of core columns. Even if it is distributed among at least 8 columns which results in ZERO severed columns.

Now NIST distributed the impact over 4 floors further reducing the damage of Wierzbicki's best case where only 4 columns were severed.

Given the above equation and the fact that less than 1% of Ecore could have been directly imparted on a core column (according to Wierzbicki's dimensions), we are down to zero severed columns and very few damaged.

I believe this will be my last statement on the subject.

[GregoryUrich]

Oh, you presented this paper as a debunking of the "physics by experts" thread, which was a thread about an idiot who does not understand physics like truther and scholars for truth do not understand 9/11. Now this makes sense. But you are still the one of 0.0067 percent engineers in the world who is sympathetic to the woo of 9/11. Thus the original thread where an idiots video of warped physics has another thread to debunk something about an idiot video or your own paper?

Truther stuff is confusing since it contains no facts and no logical conclusions based on facts. Why?

The OP mentioned paper does debunk the idiot physics video, good job.

No, this thread has essentially no relation to the "9/11 Physics by Non-Experts" started by Totovader.

The point of the OP is that we should be as critical of experts as we are of non-experts because even MIT professors get it wrong sometimes.

[Dave Rogers]

If the entire residual energy was implied directly to 12 columns in the worst case scenario, 12 columns would have failed according the Wierzbicki. Most of the energy however was applied directly to office and core contents resulting in plastic deformation of those contents (energy sink):

Given that a large proportion of the office contents were either not fixed in place or relatively loosely fixed in place, wouldn't a large proportion of the energy transfer to these be in the form of kinetic energy rather than plastic deformation? In that case, the kinetic energy of the office contents could then be transferred to the core columns via impacts with relatively small loss, causing fracture and plastic deformation. There would also be some kinetic energy transfer to debris from the perimeter columns knocked free by the initial impact, which could also transfer to the core columns via impact. The fractional cross-section for impacts of that type would be larger than the area fraction filled by the core columns because the office contents and debris would have significant size; in other words, there is a smaller probability of a large piece of debris passing right through the core without impact than of a fuel droplet doing the same thing. Have you considered these effects in your calculations? Whatever the significance, it cannot be correct to treat energy transferred to contents as a pure energy loss term; a very large proportion of this energy must still be available, as kinetic energy, to cause damage.

Dave

[jaydeehess]

Now NIST distributed the impact over 4 floors further reducing the damage of Wierzbicki's best case where only 4 columns were severed.

???

Many simplifications of the towers puts all damage on one floor which is of course untrue.

However if column 'A' is damaged on floor 'X' while column' B' is damaged on the adjacent floor 'Y' the effect on the ability of the structure to support a load is very similar to havin both columns 'A' and 'B' damaged on the same floor. If the damaged columns were on widely separated floors the redistribution of loads to all remaining columns would be more complete but if they are on adjacent floors that cannot happen as efficiently. The effect of the damage occuring over 4 adjacent floors rather than on one is not particularily significant IMHO.

Dave Rogers writes:

In that case, the kinetic energy of the office contents could then be transferred to the core columns via impacts with relatively small loss, causing fracture and plastic deformation.

I had noticed the GU seems to treat everything that gets hit as a stationary, fixed object.

[rwguinn]

???

Many simplifications of the towers puts all damage on one floor which is of course untrue.

However if column 'A' is damaged on floor 'X' while column' B' is damaged on the adjacent floor 'Y' the effect on the ability of the structure to support a load is very similar to havin both columns 'A' and 'B' damaged on the same floor. If the damaged columns were on widely separated floors the redistribution of loads to all remaining columns would be more complete but if they are on adjacent floors that cannot happen as efficiently. The effect of the damage occuring over 4 adjacent floors rather than on one is not particularily significant IMHO.



I had noticed the GU seems to treat everything that gets hit as a stationary, fixed object.
By concentrating on the Energy conservation, the Twoofers and their helpers can ignore the fact that impact results in a force. Even the "Energy sinks" that GU describes (plastic deformation of furniture, etc) absorb a force due to impact-a force that must be reacted, somewhere, somehow. If the furniture does not move, but is plasticly deformed, then the force is reacted by the floor, or whatever the piece is mountd to. These forces get reacted end-to-end, where they finally are reacted by the framework of the structure--core columns or perimeter columns. There is nowhere else for them to go.
By the very nature of Newtonian physics, the forces must ballance--which means that the energy did get imparted to the core (by loadpath analysis) in a way that the original designers did not anticipate.
Thus, the simplification to essentially free-body analysis is indeed valid, especially for a first cut prior to details being knowmn, as is pointed out in the abstract of the paper (http://web.mit.edu/civenv/wtc/PDFfiles/Chapter%20IV%20Aircraft%20Impact.pdf)

[beachnut]

No, this thread has essentially no relation to the "9/11 Physics by Non-Experts" started by Totovader.

The point of the OP is that we should be as critical of experts as we are of non-experts because even MIT professors get it wrong sometimes.
Actually, the MIT professor has the big picture right, the nitpicking trolls of 9/11 truth will never get anything right ever. Why is that? Since you never commented on the video physics idiot I assumed this thread was a carryon of your lack of comment.

But the big picture is correct, aircraft hit building, fire, collapse. Sorry there is not thermite planted, no bombs planted, no extra stuff needed for building to fail. It is sad your engineering degree has been compromised by your political biases on 9/11. You would have been a good Nazi. If you need help with this analogy I can point you to what happen to German Physicists in 1933. You may have failed to realize those who post to your posts are open minded logically thinkers. You should strive as I do to join them. But your posts continue to show the closed minded lock step with 9/11 truth, which misleads others to false information. How did they fool you?

[Minadin]

By concentrating on the Energy conservation, the Twoofers and their helpers can ignore the fact that impact results in a force. Even the "Energy sinks" that GU describes (plastic deformation of furniture, etc) absorb a force due to impact-a force that must be reacted, somewhere, somehow. If the furniture does not move, but is plasticly deformed, then the force is reacted by the floor, or whatever the piece is mountd to. These forces get reacted end-to-end, where they finally are reacted by the framework of the structure--core columns or perimeter columns. There is nowhere else for them to go.
By the very nature of Newtonian physics, the forces must ballance--which means that the energy did get imparted to the core (by loadpath analysis) in a way that the original designers did not anticipate.
Thus, the simplification to essentially free-body analysis is indeed valid, especially for a first cut prior to details being knowmn, as is pointed out in the abstract of the paper (http://web.mit.edu/civenv/wtc/PDFfiles/Chapter%20IV%20Aircraft%20Impact.pdf)

I was about to point this out as well, but you did a pretty good job if explaining it. It doesn't matter if the fuel / debris from the plane hits a sprinkler standpipe, a partition wall, or an actual column. The force has to be transferred to the structure at some point because all of those things are tied together in a building.

I would still be interested in hearing what you would expect to happen to your home / office / apartment building if it were to be hit by a 30,000 gallon water balloon travelling at 500 mph.

[rwguinn]

I was about to point this out as well, but you did a pretty good job if explaining it. It doesn't matter if the fuel / debris from the plane hits a sprinkler standpipe, a partition wall, or an actual column. The force has to be transferred to the structure at some point because all of those things are tied together in a building.

I would still be interested in hearing what you would expect to happen to your home / office / apartment building if it were to be hit by a 30,000 gallon water balloon travelling at 500 mph.
The fastest forced drowning on record?
Look at what happens to very stout buildings when they are hit by mere 200MPH moving air (http://www.spc.noaa.gov/faq/tornado/f-scale.html)

One additional note:
When I stated that forces must ballance, I was refering to a static equilibrium case. Obviously, the building moved somewhat, as will any structure when delt a blow. This movement was the result of work done by the incoming KE of the aircraft/fuel system, and was changed into Potential energy by Hooke's Law (http://webphysics.davidson.edu/applets/animator4/demo_hook.html) which was then released when the impulse was removed. This resulted in oscillation of the building (Free Vibration at sway resonant frequency) which died out eventually due to friction withing the structure (AKA Structural Damping).
Additionally--something ignored by everybody: What would happen if a fully-laden 757 was gently lowered onto the 78th floor of oneof the towers?
Remember, the aircraft had not only Kinetic energy, but the potential energy due it its position above ground level...

[Corsair 115]

I would note that so far there has been no attempt to determine the damage caused to the building structure from the explosion of the aircraft after impacting the buildings. Considering the enormous size of the explosions, I would think those must have also contributed at least some damage to the structure in some way. Is that a reasonable assumption?

[Furcifer]

Additionally--something ignored by everybody: What would happen if a fully-laden 757 was gently lowered onto the 78th floor of oneof the towers?
Remember, the aircraft had not only Kinetic energy, but the potential energy due it its position above ground level...


It would turn to vapour, and vapour has has no mass so it wouldn't do nothing.

HA! this is my lamest post yet! (Seriously is my bitterness showing now?)

Greg included it in his mass calculations, but not in his energy equations :). I have always treated it as though the plane retained this potential, due to the fact that most of the mass remained at or near the height of the point of impact. The delta h would be about 7.4M if you assume an even distribution over the estimated four floors that were destroyed.
So in calculating the effects of the conversion of PE due to impact, it is very small, i get about 7EE6 J. About the same amount of energy required to vapourize the fuel ;)

Things get overlooked when we start splitting hairs.


Corsair: Yes, that would be a reasonable assumption if you wished to consider the exogenic nature of the collision. This implies an ellastic collision and changes the whole gosh darn thing around. I'm guessing this is why Mr. Weirzbicki did not do so, he was working under the assumption it was inellastic.

[jaydeehess]

I would note that so far there has been no attempt to determine the damage caused to the building structure from the explosion of the aircraft after impacting the buildings. Considering the enormous size of the explosions, I would think those must have also contributed at least some damage to the structure in some way. Is that a reasonable assumption?


I brought this up earlier in that the explosion would lift the floor above the explosion and since the explosion originates at differing areas on adjacent floors that it would also twist the flooring. This certainly could damage the trusses and truss seats at the outset and again create a much different senario than a typical office fire would.

[Furcifer]

Actually in retrospect, the delta h would not be 7.4M, probably closer to 3.7M. So that's about 3.5EE6 J.

[rwguinn]

Actually in retrospect, the delta h would not be 7.4M, probably closer to 3.7M. So that's about 3.5EE6 J.

Actually, I was pointing out that after things stopped bouncing around, the building gained the mass of the loaded airplane at a distance of some 70-80 stories up, which would no doubt exceed the maximum floor loading--at least locally, even accounting for the spills and parts exiting the other side of the building. This favors collapse, quite strongly...

[Furcifer]

Actually, I was pointing out that after things stopped bouncing around, the building gained the mass of the loaded airplane at a distance of some 70-80 stories up, which would no doubt exceed the maximum floor loading--at least locally, even accounting for the spills and parts exiting the other side of the building. This favors collapse, quite strongly...


Yah, it works out to some 3ee8 J of PE localized to the impact site. Makes you wonder how they calculated where to put the thermite/thermate/thermonium dispensers.

I think it is also a reason the SE corner was a low spot in WTC2, allowing pools of possibly molten metal and hydrocarbon based plastics to form and leak out. Based on the trajectory of the plane this would be a point where much of the mass collected. I believe this is also pointed out in the NIST report.

[rwguinn]

Yah, it works out to some 3ee8 J of PE localized to the impact site. Makes you wonder how they calculated where to put the thermite/thermate/thermonium dispensers.

I thought thermonium was used to clean up Thermite/thermate residue and leave enigmatic spheroids of ferrite/aluminum/sulfur scattere....


Oh

Thermonium, not thermonia....
Never mind...

[Furcifer]

Thermonium is a new one (I think) that reacts sooper fast. People were having trouble explaining to me why the building suddenly collapsed, instead of just slowly as the thermite ate its way through the steel. If you have a lot of steel you need to get out of the way fast, and gravity alone just won't work, use thermonium.