PDA

View Full Version : A Fermi problem for C7: Iron spheres mean how much thermite?

Oystein
1st September 2010, 07:58 AM
The aim of this thread is to shed some light on a claim made by christopher7 (C7), formulate it as a hypothesis or theory, and make rough predictions from that theory. In particular, I want to formulate this as a Fermi problem (http://en.wikipedia.org/wiki/Fermi_problem) to arrive at a rough guess (order of magnitude) for the amount of thermite predicted by the theory.

C7's iron sphere theory to date

As far as I am aware, C7 claims
a) that about 6% (of the mass?) of the dust released in the WTC event of 9/11 consists of iron spheres
b) that such iron spheres could only be formed by extreme temperatures as are released in a thermite reaction, and not at temperatures known to exist in building fires or trash fires.

C7 concludes from this that
c) The presence of iron spheres in such abundance is indicative of the massive use of thermite (or derivatives)

To support a), christopher7 has linked the following paper a few times:

http://www.nyenvirolaw.org/WTC/130%20Liberty%20Street/Mike%20Davis%20LMDC%20130%20Liberty%20Documents/Signature%20of%20WTC%20dust/WTC%20Dust%20Signature.Composition%20and%20Morphol ogy.Final.pdf

In this paper, the RJ Lee Group Inc. analysed dust collected from a building near GZ to assess hazards.

Indeed, on page 24 of that paper (page 28 of the PDF), in Table 3, we find confirmation for a):
Fe Sphere 5.87%

I will, for the sake of this thread, accept assumption b) as true. I would, however, like to ask C7 to specify more clearly the chemical and/or physical process that would release iron spheres by using thermite.
C7, do the iron spheres result from the thermitic reaction itself (FeOx + Al -> Fe + AlyOz), or from the melting of structural steel? Or both?

The Fermi problem

If thermite is responsible for the bulk of the iron spheres, then a certain minimum amount of thermite must have burned to create the resulting amount of iron spheres. To estimate that amount, we need to estimate the following numbers:

1. How much dust was created in the event? This would be a portion of the mass of the collapsing buildings. Let's deonte this mass as md
2. What is the overall percentage of iron spheres in all of the dust? Is it ok to go with the 6% from the Lee report? Let's denote this number as pfe
From 1. and 2., the total mass of iron spheres would be estimates as mfe = md*pfe
3. How much thermite is needed to create 1g of iron spheres? Let's denote this proportion as pt.
From 1.-3. it follows that the minimum amount of thermite in use would be mt = md*pfe*pt

So the problem boils down to estimating
- md = The total amount of dust
- pt = the amount of thermite needed to create one unit of iron spheres

So christopher, and whoever wants to join in: Bang away with your best estimates!

Oystein
1st September 2010, 08:06 AM
Oh I should add: It is a bit in the nature of Fermi problems that we don't have to insist too heavily on sources and measurements. If we can source something, great, but if we can't, that need not stop us. Just employ common sense and make some effort to justify your assumptions. The key is really to clearly define your assumptions.

Sabretooth
1st September 2010, 09:23 AM
The aim of this thread is to shed some light on a claim made by christopher7 (C7), formulate it as a hypothesis or theory, and make rough predictions from that theory. In particular, I want to formulate this as a Fermi problem (http://en.wikipedia.org/wiki/Fermi_problem) to arrive at a rough guess (order of magnitude) for the amount of thermite predicted by the theory.

C7's iron sphere theory to date

As far as I am aware, C7 claims
a) that about 6% (of the mass?) of the dust released in the WTC event of 9/11 consists of iron spheres
b) that such iron spheres could only be formed by extreme temperatures as are released in a thermite reaction, and not at temperatures known to exist in building fires or trash fires.

C7 concludes from this that
c) The presence of iron spheres in such abundance is indicative of the massive use of thermite (or derivatives)

To support a), christopher7 has linked the following paper a few times:

http://www.nyenvirolaw.org/WTC/130%20Liberty%20Street/Mike%20Davis%20LMDC%20130%20Liberty%20Documents/Signature%20of%20WTC%20dust/WTC%20Dust%20Signature.Composition%20and%20Morphol ogy.Final.pdf

In this paper, the RJ Lee Group Inc. analysed dust collected from a building near GZ to assess hazards.

Indeed, on page 24 of that paper (page 28 of the PDF), in Table 3, we find confirmation for a):

I will, for the sake of this thread, accept assumption b) as true. I would, however, like to ask C7 to specify more clearly the chemical and/or physical process that would release iron spheres by using thermite.
C7, do the iron spheres result from the thermitic reaction itself (FeOx + Al -> Fe + AlyOz), or from the melting of structural steel? Or both?

The Fermi problem

If thermite is responsible for the bulk of the iron spheres, then a certain minimum amount of thermite must have burned to create the resulting amount of iron spheres. To estimate that amount, we need to estimate the following numbers:

1. How much dust was created in the event? This would be a portion of the mass of the collapsing buildings. Let's deonte this mass as md
2. What is the overall percentage of iron spheres in all of the dust? Is it ok to go with the 6% from the Lee report? Let's denote this number as pfe
From 1. and 2., the total mass of iron spheres would be estimates as mfe = md*pfe
3. How much thermite is needed to create 1g of iron spheres? Let's denote this proportion as pt.
From 1.-3. it follows that the minimum amount of thermite in use would be mt = md*pfe*pt

So the problem boils down to estimating
- md = The total amount of dust
- pt = the amount of thermite needed to create one unit of iron spheres

So christopher, and whoever wants to join in: Bang away with your best estimates!

My brain hurts today and I don’t feel like doing math…but I can’t help but find this question intriguing.

So we are just estimating? I mean, I don’t even know where to begin figuring the weight of the dust/mass of the WTC7 wreckage.

But let’s say I take a wild estimate and say 1 million tons (2 million lbs).

6% of 2 million lbs = 120,000 lbs.

So…120,000 lbs…of nothing but slag from thermite…from what is probably a gross underestimate of the weight of WTC7…

I’ve hit kind of a brain-blank here, Oystein. How do I translate waste/slag into an amount of thermite needed?

Regardless, I opted to post anyway, because we are venturing into the territory of tens, maybe hundreds, of thousands of pounds of thermite…

Oystein
1st September 2010, 09:35 AM
sabretooth,

thanks for chiming in.
How did you arrive at your numbers? Wild guess? I think we should do better than that.

We can find upper bounds and lower bounds, I think.
Upper bound would be the mass of the 3 principal buildings taken together. We should be able to find estimates for that in the literature.
A percentage of that mass would have been turned into dust. More than 5%, less than 50%, I would say.
Lower bound ... hmmm I think in the Lee Group report, we can find quotes about how thick the WTC dust was in and on buildings in the immediate vicinity; we can estimate the total area of that vicinity, multiply with thickness and specific weight, and that would give us a lower bound.

The proportion of thermite:iron can also be estimated, One way would be to use figures such as energy density of thermite, the energy needed to melt iron. Another could be looking at the chemical formula for the thermite reaction, and taking into account atomic weights. These two methods would give us lower bounds for melting of steel and iron resulting as reaction product.

R.Mackey
1st September 2010, 10:19 AM
Something to think about is that an efficient thermite attack would generate relatively little in the way of iron microspheres. Such spheres indicate that the reacted iron was exposed to atmosphere -- while still liquid -- rather than in contact with structural members. It also suggests that heat was wasted in boiling off the surface layers and through convection to the atmosphere rather than being directed anywhere useful.

I've run calculations like this on my own before, and the numbers I get are alarmingly large. You can also eyeball it using known thermite experiments, such as this epic from The Mythbusters:

PPAYZMzGMwQ

Oystein
1st September 2010, 10:33 AM
Some data to work with:

1. Thermite reaction

See http://en.wikipedia.org/wiki/Thermite_reaction

Chemical reaction:
Fe2O3 + 2Al → 2Fe + Al2O3 + heat

Atomic weights in g/mol: (rounded to full number)
Iron: 56
Aluminium: 27
Oxygen: 16

The reaction above contains, by weight, 112 parts Fe, 54 parts Al and 48 parts O, for a total of 214 parts.

So we need 1,91 parts of thermite to produce 1 part iron.

Heat produced:

Source: http://www.ilpi.com/genchem/demo/thermite/index.html
1 mol Fe2O3 + 2mol Al -> 847.6 kJ

Standard thermite releases 847.6 kJ/214g = 3,96 kJ per gram of thermite.

Other thermite or thermate mixtures may have a somewhat lower or higher energy density. Nano-thermate will have a lower energy density. Reason: Nano-sized particles of Al have a higher surface-to-volume ration than larger particles; the surface of Al will always oxidise before use. The Al-oxides add to the mass of the mixture, but not to its energy release.

9/11 Chewy Defense
1st September 2010, 10:42 AM
My question to C7 is this: "What the hell does rust (iron oxide) have to do with you proving that thermite was used?"

Rust is rust, does that mean every car/truck that has rust on them carry the "highly explosive" thermite on them?

Oystein
1st September 2010, 10:43 AM
Something to think about is that an efficient thermite attack would generate relatively little in the way of iron microspheres. Such spheres indicate that the reacted iron was exposed to atmosphere -- while still liquid -- rather than in contact with structural members. It also suggests that heat was wasted in boiling off the surface layers and through convection to the atmosphere rather than being directed anywhere useful.

I've run calculations like this on my own before, and the numbers I get are alarmingly large.

I know you've done it before. But the best excercises are those you do yourself. I hope, christopher 7 will tag along for the educational ride!

You can also eyeball it using known thermite experiments, such as this epic from The Mythbusters:

PPAYZMzGMwQ

So.
More than 1000lb of thermite
Took quite a while.
Didn't even cut straight down through the roof of the car.

Should be pretty hard to apply it to large steel columns and make it burn through horizontally within a tightly controlled time frame for a "Controlled" demolition.

But that's not even the point I am going at. Just want to know the bare minimum - and more importantly: Lead christopher7 to spell out and test his theory about iron spheres.

Oystein
1st September 2010, 10:45 AM
My question to C7 is this: "What the hell does rust (iron oxide) have to do with you proving that thermite was used?"

Rust is rust, does that mean every car/truck that has rust on them carry the "highly explosive" thermite on them?

Please Chewy, not here. this thread is about the theory, that explains iron spheres in dust with use of thermite. Got nothing to do with anyone finding rust anywhere. I think.

R.Mackey
1st September 2010, 10:47 AM
I know you've done it before. But the best excercises are those you do yourself. I hope, christopher 7 will tag along for the educational ride!

Agreed -- it's a great exercise and you've framed it well. I just wanted to add a little extra to think about for the more methodical readers.

The funny thing about the efficiency issue is that either way it inflates your final thermite estimate. If it was an efficient thermite attack, then we find a very small fraction in the form of microspheres, so given the amount we did find the amount must have been much higher. On the other hand, if it wasn't an efficient attack, first of all "why bother," but that implies much more thermite was needed to cause structural failure.

Unless, of course, there was no thermite attack in the first place. I know it's a radical idea but it's worth considering. :D Carry on.

Disbelief
1st September 2010, 10:48 AM
So.
More than 1000lb of thermite
Took quite a while.
Didn't even cut straight down through the roof of the car.

That was probably 1.2 mm thick. If you add in the reinforcements in the front and rear, that would add 2-3 mm more.

9/11 Chewy Defense
1st September 2010, 10:55 AM
Please Chewy, not here. this thread is about the theory, that explains iron spheres in dust with use of thermite. Got nothing to do with anyone finding rust anywhere. I think.

I said it just in case C7 does come here, if he ever does! :D

We know that thermite works best if there's a right mixture of aluminum & iron oxide particules. But it would be impossible to bring down a building with the stuff, since it liquifies and burns out within minutes of ignition.

Oystein
1st September 2010, 11:00 AM
Agreed -- it's a great exercise and you've framed it well. I just wanted to add a little extra to think about for the more methodical readers.

The funny thing about the efficiency issue is that either way it inflates your final thermite estimate. If it was an efficient thermite attack, then we find a very small fraction in the form of microspheres, so given the amount we did find the amount must have been much higher. On the other hand, if it wasn't an efficient attack, first of all "why bother," but that implies much more thermite was needed to cause structural failure.

Unless, of course, there was no thermite attack in the first place. I know it's a radical idea but it's worth considering. :D Carry on.

Ah yes, of course, I forgot to acknowledge that efficiency issue. Thank you! So far, I am only looking for the amount of thermite needed to melt the total amount of iron spheres. Yes, of course we then need to add thermite for every chunk of steel that was melted but not turned to dust, and for all the energy that was lost due to such things as radiation, convection, kinetic whatever etc. etc.

Maybe, for starters, we can guess that between an optimistic 5% and a super-optimistic 50% of the thermitik heat actually goes into melting the spheres - to keep this within one order of magnitude

Oystein
1st September 2010, 11:49 AM
Some more data to work with

2. Mass of the Twin Towers

See http://www.journalof911studies.com/volume/200703/GUrich/MassAndPeWtc.pdf

The Journal of 9/11 Studies is, as we know, the journal run be the thermite champions Steven Jones and Kevin Ryan.

Gregory H. Urich estimates the mass of one of the twin towers to be
288,100 metric tons
or
2.881 x 1011g

Two Towers then have a mass of
5.762 x 1011g

3. Mass of WTC7

Ok I have not found a quote for the mass of WTC7 after a quick search. Acknowledging that it shares basic properties of the twin towers (tube in tube design, steel frame), a first estimate might compare volumes:

Volume of a twin tower is 415x63x63 m3 = 1.65 x 106 m3

WTC7's long sides are 247ft and 329ft, respectively, that's an average of 288ft = 87.78m
It's 140ft = 42,67m deep and 186m tall
Volume of WTC7 is 87.78 x 42.67 x 186 m3 = 6.96709 x 105 m3 or 42% of the volume of WTC1

Let's assume further that WTC7, on account of being smaller, would be 25% lighter per volume unit that the larger towers.

That gives a mass for WTC7 of
2.881 x 1011g x 42% x 75% = 9 x 1010g

Total mass of the 3 collapsing towers is approximately
6,6 x 1011g

(I'll ignore the other buildings that were destroyed; shouldn't affect the order of magnitude too much.)

alienentity
1st September 2010, 12:04 PM
Estimates will assume that thermite was present in all the affected buildings - is there any reason to exclude WTC5 and 6, for example?

Or for that matter any way to exclude either WTC 1, 2 or 7?

Oystein
1st September 2010, 12:23 PM
Even more data to work with

4. Energy needed to melt iron

Let's take the values from Wikipedia:
http://en.wikipedia.org/wiki/Iron
(For the sake of simplification, I'll consider pure iron. The properties of steel vary. For example, the melting point may be higher or lower. But for the sake of estimating values of a Fermi problem, I think looking at pure iron will not yield results that are vastly off-target. If anybody better verses in metallurgy begs to differ, please do so).

The physical properties we need are
Standard atomic weight: 55.845(2) g/mol
Melting point: 1538 °C
Heat of fusion (http://en.wikipedia.org/wiki/Enthalpy_of_fusion): 13.81 kJ/mol
Specific heat capacity (http://en.wikipedia.org/wiki/Specific_heat_capacity#Specific_heat_capacity) at 25 °C: 25.10 J/(mol K)

The following is probably pretty bad material physics, but hey...

To heat one mol (56g) of iron from ambient temperature to melting point, you need approximately
25.1J * (1538-18) = 38.152kJ
In addition, to transition that mol to liquid phase, you need 13.81kJ for a total of 52kJ.
Actually, for droplets of that iron to stay liquid long enough to break free from a larger mass, we would have to heat it to somewhat above melting point. So let's say, to melt iron from which to form iron spheres, we need to expend

56kJ/mol = 1kJ/g

Oystein
1st September 2010, 12:27 PM
Estimates will assume that thermite was present in all the affected buildings - is there any reason to exclude WTC5 and 6, for example?

Or for that matter any way to exclude either WTC 1, 2 or 7?

You are right. I am excluding 5 or 6, which means I am excluding both their contribution to the dust amount and to the thermite needed. 5 and 6 are only a few percent of the mass of 1, 2, 7, so they are not significant. Our estimates are much too rough for that.

You are right, the amount of thermite that we compute might have been distributed among the 3 buildings. But then we can break down that amount and estimate how much thermite they might have used on each single building.

Oystein
1st September 2010, 01:14 PM
Data to work with, continued

5. How much dust was airborne?

The RJ Lee Group sampled dust from WTC that had settled in and on the Deutsche Bank building at 130 Liberty Street (see Google Maps (http://maps.google.com/maps?f=q&source=s_q&hl=de&geocode=&q=130+Liberty+Plaza,+New+York,+NY,+United+States&sll=37.0625,-95.677068&sspn=48.909425,114.169922&ie=UTF8&hq=&hnear=130+Liberty+St,+New+York,+10006&ll=40.709442,-74.013079&spn=0.002879,0.006968&t=h&z=18))

This building had 1500 of its windows broken (Lee report, page page 1). Inside, they found on average 8.62g/m2 of dust.
The building has 42 stories, each having an area of approximately 2500m2, so total amount of dust would be
42 x 2500m2 x 8,62 g/m2 = 9 x 105g of dust inside that one building

130 Liberty Street was about 200m away from the "center of gravity" of the WTC collapses (south tower much closer, north tower farthe, WTC7 even farther). A circle of radius 200m has a circumference of 1256m. The Facade of 130 Liberty Street had at most a total width of 50m of windows facing the WTC, that is 4% of that perimeter. If we estimate that a great amount of dust never made it to that 200m perimeter, or blew above the height of the building, or did not enter the building, I am fairly confident that at most 1% of all the WTC dust landed inside 130 Liberty Street to be found there months later by the Lee group.

Hence, a lower bound of the mass of airborne dust from WTC is 100 x 9 x 105g = 9 x 107g

Mikemcc
1st September 2010, 01:58 PM
Some more data to work with

2. Mass of the Twin Towers

See http://www.journalof911studies.com/volume/200703/GUrich/MassAndPeWtc.pdf

The Journal of 9/11 Studies is, as we know, the journal run be the thermite champions Steven Jones and Kevin Ryan.

Gregory H. Urich estimates the mass of one of the twin towers to be
288,100 metric tons
or
2.881 x 1011g

Two Towers then have a mass of
5.762 x 1011g

3. Mass of WTC7

Ok I have not found a quote for the mass of WTC7 after a quick search. Acknowledging that it shares basic properties of the twin towers (tube in tube design, steel frame), a first estimate might compare volumes:

Volume of a twin tower is 415x63x63 m3 = 1.65 x 106 m3

WTC7's long sides are 247ft and 329ft, respectively, that's an average of 288ft = 87.78m
It's 140ft = 42,67m deep and 186m tall
Volume of WTC7 is 87.78 x 42.67 x 186 m3 = 6.96709 x 105 m3 or 42% of the volume of WTC1

Let's assume further that WTC7, on account of being smaller, would be 25% lighter per volume unit that the larger towers.

That gives a mass for WTC7 of
2.881 x 1011g x 42% x 75% = 9 x 1010g

Total mass of the 3 collapsing towers is approximately
6,6 x 1011g

(I'll ignore the other buildings that were destroyed; shouldn't affect the order of magnitude too much.)According to this source 185,101 tons(I'm assuming that means ye olde worlde Imperial/standard measurement) of steel was removed from the site:

http://911research.wtc7.net/wtc/groundzero/cleanup.html

That works out at 907185g/ton, so 1.68E11 g of steel removed from the site.

Now this site guesstimates the mass of steel in WTC1 and 2 to be 9.6E10g per tower, giving 1.92E11 g for both WTC1 & 2. Assuming your 42% ratio is correct then total steel mass will be 2.42/2 * 1.68E11 = 2.03E11 g.

http://www.physforum.com/What-was-the-weight-of-a-WTC-Tower_4299.html

Therefore the 'missing steel' is 3.53E10g (only 35kt of steel there folks!)

This would mean that 1760t of steel ended up as this 'dust'.

Anybody that's ever seen a thermite reaction will attest that most of the product ends up as a slag, rather than a dispersed dust (that's why it's used to weld railway joints). So a thermite reaction is extremely inefficient at generating this 'dust', probably only a few percentage points. I'll take a probable over-estimate (WAG) of 10% of the reaction producing these dust particles, that gives an effective end result of 17600t of steel undergoing a thermite reaction.

Next problem - thermite assumes a finely ground iron oxide / aluminium mix - not solid steel objects. I don't know how this affects the reaction.

femr2
1st September 2010, 02:12 PM
Don't think there is much value in the thread, but...
Something to think about is that an efficient thermite attack...
Mythbusters need to work on their efficiency I reckon...
8a2OeWS3G-A

1000lbs/Plant pot.

Oystein
1st September 2010, 02:26 PM
Thanks, Mikemcc!

You are definitely zeroing in on the target!

A couple of questions:

1.
http://911research.wtc7.net/wtc/groundzero/cleanup.html
You quote "Some 185,101 tons of structural steel"
However, there is also the number "According to FEMA, more than 350,000 tons of steel were extracted from Ground Zero and barged or trucked to salvage yards where it was cut up for recycling."
Which number should we go with?

2.
http://www.physforum.com/What-was-the-weight-of-a-WTC-Tower_4299.html
That thread runs from january to september 2006 - with a late last post by Gregory Urich from may 2007 - the same Urich who I relied on for estimate of total mass.
I think from that early guesstimate of 9.6E10g per tower we should not subtract estimates of hauled away steel - the errors of guessing will multiply wildly!

3.
You say "Therefore the 'missing steel' is 3.53E10g (only 35kt of steel there folks!) This would mean that 1760t of steel ended up as this 'dust'."
I don't get that. The 1760t of dust are 5% of 3.53E10g. What's the reasoning there?

GlennB
1st September 2010, 02:27 PM
Don't think there is much value in the thread, but...

Mythbusters need to work on their efficiency I reckon...

1000lbs/Plant pot.

Nope. Couple of pounds / plant pot. Hole in safe. Safe mostly untouched.

Had the safe weighed 1000 tons but of the same thickness metal then the result would be the same.

You really have no shame do you?

Oystein
1st September 2010, 02:28 PM
Don't think there is much value in the thread...

Why do you think so? Maybe I can explain?

beachnut
1st September 2010, 02:36 PM
Don't think there is much value in the thread, but...

... value?
Like your work, with no goal you are proud of.

You post a safe being hit by thermite. Wow, already posted years ago, but the army did it in Iraq. Not too smart if you want the money inside.

Now where are your delusional flower pots used to destroy the WTC, and how do you get the pots to gravity flow sideways? lol

You are an on the fence no-planer with thermite and CD delusions saying there is no value in a thread? You can't figure out how many flt 175s there were, no wonder you can't find value when you have no idea what happen on 911.

Oystein
1st September 2010, 02:50 PM
...
Mythbusters need to work on their efficiency I reckon...
8a2OeWS3G-A

1000lbs/Plant pot.

Okay, here we see about 2l of thermite - let that be somewhere close to 7kg to 8kg.

And 2" steel, or 5cm thick steel.

let's say they melted a circle 10cm across or 78.5cm2.
That's 392.53 of steel melted.
And then some more inside.

Maybe a total of 550cm3

With steel having a density close to 8g/cm3, that's 4.3kg steel melted by 7.5kg of thermite, or a ratio of 1:1.75:

1.75 mass units of thermite can melt 1 mass unit of iron

Thanks, femr, for contributing to this thread! :)

ETA: I think the Mythbusters teach us that efficiency is not easy to achieve. The car was an uneven surface. Maybe that was part of the problem. It is apparently easy to nelt through horizontal sheet metal, but it gets much harder as soon as your target is of a different shape or alignment.

femr2
1st September 2010, 03:06 PM
1.75 mass units of thermite can melt 1 mass unit of iron

Thanks, femr, for contributing to this thread! :)

You're very welcome ;)

Then instead of looking at the mass of the building, why not work out the cross-sectional area of the core columns around floor, say, 98, then the volume of about, what, 6 inches ? a foot ? vertically.

Oystein
1st September 2010, 03:21 PM
Ok here is a first estimate for a lower bound on the amount of thermite to account for 6% iron spheres in airborne dust:

Assumptions
1. Thermite was applied in a maximally efficient way to melt all the steel it melted, and nothing beyond that
2. All steel that melted went into airborne dust
3. No further energy was lost by that process of dustification
4. The melted and then cooled iron spheres mixed uniformly with the other airborne dust to constitute 6% of the dust's mass
5. The thermite itself does not result in iron spheres

Step 1: In post 18, I estimated a lower bound of the mass of airborne dust:
9 x 107g

Step 2: Assuming that 6% of the dust is formerly melted iron, that gives us
9 x 107g * 6% = 5.4 x 106g of melted iron

Step 3: In post 25, I estimated that we need 1.75g of thermite to melt 1g of iron. That gives us
5.4 x 106g x 1,75 = 9,45 x 106g of thermite, or about 10 metric tons.

If we assume that the thermite itself contributes all of its iron molecules to the iron spheres in the dust, less thermite is needed:
1.75g of thermite result 0,915g of iron, which are added to the 1g of melted iron from the steel.
So 1,75g of thermite can produce 1,915g of iron spheres. That's a ratio of
0.914:1

To produce 5.4 x 106g of melted iron, we need 4.93 x 106g of thermite
Or roughly 5 metric tons.
That's assuming a lot.

Assumption 2. should probably be modified to allow for a factor of 20 (only 5% or less of the melted iron went into airborne dust)
Assumption 3. should probably be modified to allow for a factor of at least 2 (half of the energy used to melt the steel is lost on dustification, kinetic energy, increased heat loss du to larger surface etc.

Which gives us a more realistic lower bound of 5t x 2 x 20 = 200 metric tons of thermite to account for the dust spheres.

Oystein
1st September 2010, 03:23 PM
You're very welcome ;)

Then instead of looking at the mass of the building, why not work out the cross-sectional area of the core columns around floor, say, 98, then the volume of about, what, 6 inches ? a foot ? vertically.

Look at the OP!

Christopher7 has argued several times that the iron-rich spheres found in WTC dust near GZ, which account for 6% of the mass of that dust, could only have been formed by thermite.

The goal of this thread is to evaluate christopher's claim.

R.Mackey
1st September 2010, 03:28 PM
Okay, here we see about 2l of thermite - let that be somewhere close to 7kg to 8kg.

And 2" steel, or 5cm thick steel.

No way that safe was 2" thick solid steel. A typical safe that size and difficulty rating has double walls, typically about 3/8" outer plate and 16 gauge inner. You can even see the double wall construction in the hole in the bottom after they open the door.

What any of this has to do with the OP, however, I have no idea. Typical Truther tactics: Rather than answer the question, answer a question that nobody asked, and answer it wrong anyway... :rolleyes:

femr2
1st September 2010, 03:30 PM
Look at the OP!

Christopher7 has argued several times that the iron-rich spheres found in WTC dust near GZ, which account for 6% of the mass of that dust, could only have been formed by thermite.

The goal of this thread is to evaluate christopher's claim.

Yes, as I said, I don't see much value in the thread. It's clearly a ridiculous premise, that he'll ignore any way.

The result always going to be a ridiculous number followed by asking how the team of supersekrit ninjas hauled it all in there.

I, surprise surprise, don't really give supernanothermiate much value, but I think you'd get a more manageable output value if you looked at the cross-sectional area of the core, for about a foot, instead.

But whatever...

Mikemcc
1st September 2010, 03:36 PM
Thanks, Mikemcc!

You are definitely zeroing in on the target!

A couple of questions:

1.
http://911research.wtc7.net/wtc/groundzero/cleanup.html
You quote "Some 185,101 tons of structural steel"
However, there is also the number "According to FEMA, more than 350,000 tons of steel were extracted from Ground Zero and barged or trucked to salvage yards where it was cut up for recycling."
Which number should we go with?

2.
http://www.physforum.com/What-was-the-weight-of-a-WTC-Tower_4299.html
That thread runs from january to september 2006 - with a late last post by Gregory Urich from may 2007 - the same Urich who I relied on for estimate of total mass.
I think from that early guesstimate of 9.6E10g per tower we should not subtract estimates of hauled away steel - the errors of guessing will multiply wildly!

3.
You say "Therefore the 'missing steel' is 3.53E10g (only 35kt of steel there folks!) This would mean that 1760t of steel ended up as this 'dust'."
I don't get that. The 1760t of dust are 5% of 3.53E10g. What's the reasoning there?They were just the first results from my searches (life's too short to get too worried about this!)

The 5% figure was from the OP saying that 5% of the dust was from iron particulates - having just typed this, does that figure mean metallic iron, or all compounds containing iron, which would further reduce the useful amount?

We will always need to subtract the hauled steel so that we are left with considering the 'missing steel', that's the only part that could possibly contribute to this dust.

Another factor - how does the angle of attack influence the result - vertical action is easy with thermite, horizontal action is much less efficient, it requires a structure that can withstand the temperatures of a thermite reaction long enough to produce a cutting jet. The largest that I've ever seen (only in pictural form is approx 2" in diameter.

beachnut
1st September 2010, 03:39 PM
Yes, as I said, I don't see much value in the thread. It's clearly a ridiculous premise, that he'll ignore any way.

The result always going to be a ridiculous number followed by asking how the team of supersekrit ninjas hauled it all in there.

I, surprise surprise, don't really give supernanothermiate much value, but I think you'd get a more manageable output value if you looked at the cross-sectional area of the core, for about a foot, instead.

But whatever... What value does your 175 study have? It had value to show you lacked knowledge in flying topic, FAA, and more. What value does you claim you don't know if there were real planes used on 911? It shows you can't logically process evidence and make a sound conclusion.

The value here is to show the nut case idea the iron spheres are from thermite used to bring down the WTC complex is insane. With your goals not even stated for your video opinion study, how can you make the value statement? right, you typed it. oops

You see no value because it debunks 911 truth thermite? Or the fact thermite was made up out of insane claims by Jones?

Your are right, there is no value in using thermite or super-nano-thermite as something used on 911 to destroy the WTC complex.

Your work on the video is meaning less and free of value, it has no goal and no tie to 911 truth claims of CD.

I see your point, I find no value to any of your efforts on 911; example, the apple falling at 17 seconds, no value!

How much thermite was needed to make all the extrapolated iron dust? I find this stuff in my backyard, was there thermite here? Do you want to check their math? Help out? Debunk thermite?

Mikemcc
1st September 2010, 03:44 PM
Ok here is a first estimate for a lower bound on the amount of thermite to account for 6% iron spheres in airborne dust:

Assumptions
1. Thermite was applied in a maximally efficient way to melt all the steel it melted, and nothing beyond that
2. All steel that melted went into airborne dust
3. No further energy was lost by that process of dustification
4. The melted and then cooled iron spheres mixed uniformly with the other airborne dust to constitute 6% of the dust's mass
5. The thermite itself does not result in iron spheres

Step 1: In post 18, I estimated a lower bound of the mass of airborne dust:
9 x 107g

Step 2: Assuming that 6% of the dust is formerly melted iron, that gives us
9 x 107g * 6% = 5.4 x 106g of melted iron

Step 3: In post 25, I estimated that we need 1.75g of thermite to melt 1g of iron. That gives us
5.4 x 106g x 1,75 = 9,45 x 106g of thermite, or about 10 metric tons.

If we assume that the thermite itself contributes all of its iron molecules to the iron spheres in the dust, less thermite is needed:
1.75g of thermite result 0,915g of iron, which are added to the 1g of melted iron from the steel.
So 1,75g of thermite can produce 1,915g of iron spheres. That's a ratio of
0.914:1

To produce 5.4 x 106g of melted iron, we need 4.93 x 106g of thermite
Or roughly 5 metric tons.
That's assuming a lot.

Assumption 2. should probably be modified to allow for a factor of 20 (only 5% or less of the melted iron went into airborne dust)
Assumption 3. should probably be modified to allow for a factor of at least 2 (half of the energy used to melt the steel is lost on dustification, kinetic energy, increased heat loss du to larger surface etc.

Which gives us a more realistic lower bound of 5t x 2 x 20 = 200 metric tons of thermite to account for the dust spheres.Your estimate assumes ideal reactions - this isn't true since the reaction is acting against solid steel rather than fines and you can't easily cut sideways in steel using thermite. Even then, you can only cut for a short distance, not sufficient to cut through structural steel columns in buildings as massive as WTC7, never mind WTC1 or 2.

femr2
1st September 2010, 03:45 PM
What value does your 175 study have?
Oooh. Loads. Shows that the NIST impact orientation and trajectory was quite severely wrong, thus bringing the initial damage assessment into serious doubt, thus...

What value does you claim you don't know if there were real planes used on 911?
You have me (deliberately) mistaken for a no-planer. lol.

With your goals not even stated for your video opinion study, how can you make the value statement?
There's loads of observational value once the methods have been pored over.

Getting increasingly disturbing there beachnut.

Anyway, back to the massive thermite volume calc...

Oystein
1st September 2010, 03:46 PM
Yes, as I said, I don't see much value in the thread. It's clearly a ridiculous premise, that he'll ignore any way.

The result always going to be a ridiculous number followed by asking how the team of supersekrit ninjas hauled it all in there.

I, surprise surprise, don't really give supernanothermiate much value, but I think you'd get a more manageable output value if you looked at the cross-sectional area of the core, for about a foot, instead.

But whatever...

Oh sure he'll ignore it.
But next time he repeats his idea about that Lee-dust-iron-sphere nonsense, I can point him to this thread and say "hey, if you can't work out the implications of your own claim - stop making it".

Besides, I am compiling some data an links here that might come in handy next time someone muses about thermites.

And lastly, I excercise. Brain sport. ;)

Oystein
1st September 2010, 03:56 PM
...
The 5% figure was from the OP saying that 5% of the dust was from iron particulates

Uhm 5% (actually 6%) of the dust is iron-rich spheres. That does not mean that 6% of the mass of the WTC steel was turned to dust. Could be that all the "missing" steel was thus dustified, could be only 1% - we'd have to find reasons for such assumptions.
The 6% means: When you collect 100g of dust, you find, say, 50g silicates, 10g organic compounds, 2g rust, 0.1g asbestos, etc etc etc, 6g iron spheres....

- having just typed this, does that figure mean metallic iron, or all compounds containing iron, which would further reduce the useful amount?

Yes, that means (mainly) elemental iron. If they contain 20% contaminants, I'd not worry too much.

We will always need to subtract the hauled steel so that we are left with considering the 'missing steel', that's the only part that could possibly contribute to this dust.

That's correct, but still, subtracting one number from another without looking at how both numbers were derived at invites gross mistakes.

Another factor - how does the angle of attack influence the result - vertical action is easy with thermite, horizontal action is much less efficient, it requires a structure that can withstand the temperatures of a thermite reaction long enough to produce a cutting jet. The largest that I've ever seen (only in pictural form is approx 2" in diameter.

No doubt any thermite proponent would have to show that this horizontal action is at all feasibly, and at what grade of efficiency. For a lower bound, we can assume the same efficiency as for vertical action, and be sure the "real" amount must be higher. By what factor? Speculate away!

DaveThomasNMSR
1st September 2010, 09:52 PM
...

I've run calculations like this on my own before, and the numbers I get are alarmingly large. You can also eyeball it using known thermite experiments, such as this epic from The Mythbusters:

PPAYZMzGMwQ

We whipped up some thermite a couple of weeks ago. Here's my YouTube:
KYBaWw6XMFA
I was impressed by the large spheres (lots of mm-sized droplets). Haven't seen any reports of those! :D

Chuck Guiteau
1st September 2010, 10:19 PM
It occurs to me that before the amount of thermite becomes relevant in any way, a technically viable method of employment must be put forth, much the same way prison guards don't concern themselves over nuclear bombs because no one has developed a method for "keistering" one yet.
Why argue over how many micro-spheres can fit in an angels a55 until the CT'ers at least demonstrate the existence of the angel?

Oystein
1st September 2010, 11:59 PM
We whipped up some thermite a couple of weeks ago. Here's my YouTube:
KYBaWw6XMFA
I was impressed by the large spheres (lots of mm-sized droplets). Haven't seen any reports of those! :D

You fool!! You forgot to nanonize your thermite and thisaway endow it with magical properties! Duh'!

Oystein
2nd September 2010, 12:03 AM
It occurs to me that before the amount of thermite becomes relevant in any way, a technically viable method of employment must be put forth, much the same way prison guards don't concern themselves over nuclear bombs because no one has developed a method for "keistering" one yet.
Why argue over how many micro-spheres can fit in an angels a55 until the CT'ers at least demonstrate the existence of the angel?

It occurred to me that if we can convince them that all the reasons they have to suspect thermite in the first place, mathematically result in ridiculous mass requirements, then we would not have to go into nitty-gritty engineering details of where to put how much in what way to do what exactly. :D

alienentity
2nd September 2010, 12:04 AM
We whipped up some thermite a couple of weeks ago. Here's my YouTube:
KYBaWw6XMFA
I was impressed by the large spheres (lots of mm-sized droplets). Haven't seen any reports of those! :D

Nice work Dave, but your friggin' titles are way too fast to read properly. Not everyone has the metabolism of a squirrel, y'know.;)

Chuck Guiteau
2nd September 2010, 12:15 AM
It occurred to me that if we can convince them that all the reasons they have to suspect thermite in the first place, mathematically result in ridiculous mass requirements, then we would not have to go into nitty-gritty engineering details of where to put how much in what way to do what exactly. :D

Fair enough, but inasmuch as the CT'ers here have shown a marked inability to compose simple sentences, access an on-line dictionary, or even find the spell-check button on their own computers, expecting them to be able to comprehend mathematical concepts that extend beyond "naught times one is naught" might be a bit optimistic.

ozeco41
2nd September 2010, 04:04 AM
It occurs to me that before the amount of thermite becomes relevant in any way, a technically viable method of employment must be put forth, much the same way prison guards don't concern themselves over nuclear bombs because no one has developed a method for "keistering" one yet.
Why argue over how many micro-spheres can fit in an angels a55 until the CT'ers at least demonstrate the existence of the angel?
You are in the same school as me Chuck.

There is no way that thermxte in any form could have contributed to the collapses of any of the WTC towers without being discovered. And it is nearly as certain that there is no conceivable way thermxte could have been used even if everyone turned a blind eye to evidence.

For the twin towers one conceivable use would have been to cut multiple lower cords on floor joists thereby mimicking the observed inwards pulling of the outer tube columns.

The only minor problems being knowing in advance where the planes would strike AND proofing the thermxte and firing circuitry against thje "blast effects" of the plane crashing through PLUS fireproofing till needed.

So, given the impossibility of all those aspects why waste time proving or disproving thermxte on site. There could have been 20 tonnes on site. It wasn't used. It couldn't have been used. End of story.

Oystein
2nd September 2010, 04:54 AM
...
There is no way that thermxte in any form could have contributed to the collapses of any of the WTC towers without being discovered.

C7 claims that proof of the use of thermite was discovered. That is what this thread is about: If C7 were right, what would be the implications?

And it is nearly as certain that there is no conceivable way thermxte could have been used even if everyone turned a blind eye to evidence.

If you are honest, you are here arguing from incredulity or lack of imagination. Smarter man than you have argued before that there is a no conceivable way an object that's heavier than air could sustain flight. That man obviously underestimated the ingenuity of other men.

For the twin towers one conceivable use would have been to cut multiple lower cords on floor joists thereby mimicking the observed inwards pulling of the outer tube columns.

The only minor problems being knowing in advance where the planes would strike AND proofing the thermxte and firing circuitry against thje "blast effects" of the plane crashing through PLUS fireproofing till needed.

See? So you can conceive of at least a partial solution. Maybe someone else can help you where your engineering creativity fails you?

So, given the impossibility of all those aspects why waste time proving or disproving thermxte on site. There could have been 20 tonnes on site. It wasn't used. It couldn't have been used. End of story.

So far, I think I have established that, if C7 is right and his observation is best explained by the use of thermite, then 20 tons would not nearly suffice, it would have to be at least 200 tons (and quite probably a LOT more).
This still is not totally impossible to conceive, but I am sure we can make additional predictions from that theory that raise the odds of C7's theory to be true even further.

At any rate, what you and Chuck and I agree on is: The truthers who argue against such odds have to proof a lot more than they already think they did.

Sabretooth
2nd September 2010, 05:57 AM
Ok here is a first estimate for a lower bound on the amount of thermite to account for 6% iron spheres in airborne dust:

Assumptions
1. Thermite was applied in a maximally efficient way to melt all the steel it melted, and nothing beyond that
2. All steel that melted went into airborne dust
3. No further energy was lost by that process of dustification
4. The melted and then cooled iron spheres mixed uniformly with the other airborne dust to constitute 6% of the dust's mass
5. The thermite itself does not result in iron spheres

Step 1: In post 18, I estimated a lower bound of the mass of airborne dust:
9 x 107g

Step 2: Assuming that 6% of the dust is formerly melted iron, that gives us
9 x 107g * 6% = 5.4 x 106g of melted iron

Step 3: In post 25, I estimated that we need 1.75g of thermite to melt 1g of iron. That gives us
5.4 x 106g x 1,75 = 9,45 x 106g of thermite, or about 10 metric tons.

If we assume that the thermite itself contributes all of its iron molecules to the iron spheres in the dust, less thermite is needed:
1.75g of thermite result 0,915g of iron, which are added to the 1g of melted iron from the steel.
So 1,75g of thermite can produce 1,915g of iron spheres. That's a ratio of
0.914:1

To produce 5.4 x 106g of melted iron, we need 4.93 x 106g of thermite
Or roughly 5 metric tons.
That's assuming a lot.

Assumption 2. should probably be modified to allow for a factor of 20 (only 5% or less of the melted iron went into airborne dust)
Assumption 3. should probably be modified to allow for a factor of at least 2 (half of the energy used to melt the steel is lost on dustification, kinetic energy, increased heat loss du to larger surface etc.

Which gives us a more realistic lower bound of 5t x 2 x 20 = 200 metric tons of thermite to account for the dust spheres.

Just for clarity...and an attempt to bring this test into a simpler form:

Based on your estimates, we would need either 5, 10, or 200 metric tons of thermite to match the Lee report of 6% metal spheres in the WTC7 dust?

If this is the case, even at the low end, we're talking about A LOT of thermite that had to react perfectly and cut the steel with near 100% efficiency...right?

And this just for one building. The shear magnitude of this "Thermite Black-Ops Project"TM is astounding...but I guess we already knew that.

But I fear that the work you guys are doing isn't going to convince the unconvincable. This is great work, none-the-less.

:thanks

Oystein
2nd September 2010, 06:18 AM
Just for clarity...and an attempt to bring this test into a simpler form:

Based on your estimates, we would need either 5, 10, or 200 metric tons of thermite to match the Lee report of 6% metal spheres in the WTC7 dust?

If this is the case, even at the low end, we're talking about A LOT of thermite that had to react perfectly and cut the steel with near 100% efficiency...right?

And this just for one building. The shear magnitude of this "Thermite Black-Ops Project"TM is astounding...but I guess we already knew that.

But I fear that the work you guys are doing isn't going to convince the unconvincable. This is great work, none-the-less.

:thanks

Okay I realize that my posts reads a little like that scene from the Monty Python "Spanish Inquisition!" sketch:
"Our chief weapon is surprise...surprise and fear...fear and surprise.... Our two weapons are fear and surprise...and ruthless efficiency.... Our three weapons are fear, surprise, and ruthless efficiency...and an almost fanatical devotion to the Pope.... Our four...no... Amongst our weapons.... Amongst our weaponry...are such elements as fear, surprise.... I'll come in again."

10, 5 and 200 are results of three different sets of assumptions. The most simple yields 10, and the simplest that goes deepest into truther-friendls territory yields 5 tons.
These two sets of assumptions are totally unrealistic however.

The first set of assumptions that approach realistic territory yields 200 tons.

DaveThomasNMSR
2nd September 2010, 07:02 AM
Nice work Dave, but your friggin' titles are way too fast to read properly. Not everyone has the metabolism of a squirrel, y'know.;)

So I've learned. The next batch will be better! I was under the gun to get several YouTubes posted, and only finished 'em minutes before the big Debate, and didn't have a lot of review/polish time.

I'm also gonna dump the zooming of titles next time around.

Thanks! Dave

GlennB
2nd September 2010, 08:57 AM
....

The first set of assumptions that approach realistic territory yields 200 tons.

A few years back Twoofers were wetting their pants getting excited about a patent for a commercial thermite cutting tool. There was a patent. This was Jones' dream. Unfortunately it was massive relative to the volume of thermite it could contain :

http://i250.photobucket.com/albums/gg274/sap-guy/thermitecutter.jpg

and would be really hard to attach to a column in gangs. Even harder - read impossible - to conceal.

I was about to say that thermite theory is insane. But it all is really. Thank FSM that the daytime thermometer has dropped below 33°c for the first time in months and I can start working on the house and garden instead of jabbering about 9/11 in the only a/c part of our house ;)

alienentity
2nd September 2010, 09:13 AM
I spoze you could also make the argument that some of the evidence of thermite would have been pulverized along with lots of other material, during the collapses.
However this wouldn't be the case with WTC 7, but no definitive evidence of therm*te was found there either.
In either case one would expect obvious melting or cutting of steel to be observed - none of which happened.

I wonder how far the mm-sized droplets described by Dave would have dispersed, had they existed..

Oystein
2nd September 2010, 09:27 AM
I spoze you could also make the argument that some of the evidence of thermite would have been pulverized along with lots of other material, during the collapses.
However this wouldn't be the case with WTC 7, but no definitive evidence of therm*te was found there either.
In either case one would expect obvious melting or cutting of steel to be observed - none of which happened.

I wonder how far the mm-sized droplets described by Dave would have dispersed, had they existed..

What evidence would that be? I don't think that there is any mechanical mechanism (collapse) that would "dustify" a serious proportion of solid steel or metal. Some scraping, but the bulk of metal, even if ot was molten for a while, would be left in larger pieces.
Oh abd by the way, where are the tons of Al2O3 that result from the thermite reaction? There should be 100 tons of it around.

duMbunker
3rd September 2010, 03:33 AM
i hate to point out small careless mistakes but you meant to type 1 million tons = 2 billion lbs. 6% of 2 billion lbs is 360 million

So…360,000,000 lbs…of nothing but slag from thermite…from what is probably a gross underestimate of the weight of WTC7…

Oystein
3rd September 2010, 04:42 AM
?? duMbunker, what post are you referring to?

Sabretooth
3rd September 2010, 07:48 AM
i hate to point out small careless mistakes but you meant to type 1 million tons = 2 billion lbs. 6% of 2 billion lbs is 360 million

So…360,000,000 lbs…of nothing but slag from thermite…from what is probably a gross underestimate of the weight of WTC7…

I'm guessing that's from my post in #2.

You're correct. Miscalculation on my part. I said 1M tons is 2M pounds.

Either way, my post is useless because of another oversight on my part...I was taking 6% of the total weight of WTC7, not the total weight of the dust.

My failed attempt at doing math early in the morning. :blush:

Oystein
13th September 2010, 02:59 PM
Some data to work with:

1. Thermite reaction

See http://en.wikipedia.org/wiki/Thermite_reaction

Chemical reaction:
Fe2O3 + 2Al → 2Fe + Al2O3 + heat

Atomic weights in g/mol: (rounded to full number)
Iron: 56
Aluminium: 27
Oxygen: 16

The reaction above contains, by weight, 112 parts Fe, 54 parts Al and 48 parts O, for a total of 214 parts.

So we need 1,91 parts of thermite to produce 1 part iron.

Heat produced:

Source: http://www.ilpi.com/genchem/demo/thermite/index.html
1 mol Fe2O3 + 2mol Al -> 847.6 kJ

Standard thermite releases 847.6 kJ/214g = 3,96 kJ per gram of thermite.

Other thermite or thermate mixtures may have a somewhat lower or higher energy density. Nano-thermate will have a lower energy density. Reason: Nano-sized particles of Al have a higher surface-to-volume ration than larger particles; the surface of Al will always oxidise before use. The Al-oxides add to the mass of the mixture, but not to its energy release.

Density of thermite:

Fe2O3 has a density of 5.242 g/cm3
Al has a density of 2.70 g/cm3
(both from Wikipedia)

For 214g of thermite, we need to mix
160g Fe3O2 = 30,523cm3
54g Al = 20,000cm3

So thermite, perfectly mixed with no air in between, would have a density of
214g/(30,523+20)cm3 = 4,236g/cm3

Accounting for air in the mix, I think we are on the safe side if we go with a value of

Density of standard thermite is 4,2g/cm3

Density of steel is near the density of iron: 7.874 g/cm3

Steel is thus about 87% denser than thermite, or thermite has 53% the density of steel.

We found earlier that, experimentally, we need 1,75g of thermite to melt 1g of iron. That would translate to:
We need 3.2cm3 of thermite to melt 1cm3 of iron.

(In "4. Energy needed to melt iron" I estimated that we need 1kJ of energy to melt 1g of iron to somewhat above melting point. This would assume 100% efficient heat transfer.
1kJ is contained in 0.253g of thermite. The experimental value of 1,75g implies 14.4% efficiency. Not unrealistic, I'd say, but that is just my layman's intuition.)

Oystein
14th September 2010, 05:39 AM
Even more data to work with

4. Energy needed to melt iron
...
The following is probably pretty bad material physics, but hey...

To heat one mol (56g) of iron from ambient temperature to melting point, you need approximately
25.1J * (1538-18) = 38.152kJ
In addition, to transition that mol to liquid phase, you need 13.81kJ for a total of 52kJ.
Actually, for droplets of that iron to stay liquid long enough to break free from a larger mass, we would have to heat it to somewhat above melting point. So let's say, to melt iron from which to form iron spheres, we need to expend

56kJ/mol = 1kJ/g

I have to correct myself here after finding Appendix A of this paper:
http://www.journalof911studies.com/volume/200704/JLobdillThermiteChemistryWTC.pdf
On page 12, it lists the heat necessary to heat iron to melting point: 235cal/g = 56.2J/g
plus my 13.81kJ for transition to liquid -> 70J/g

I forgot that the heat will first melt the thermite and its reaction products first, and then the iron it touches. That paper finds that, assuming 100% efficency, 1g of thermite can melt these amounts of external iron, by end temperature:
T, deg C H/g, Fe H/g, Al2O3 H,/g Thermite H for column steel g Fe from column
1540°C: 2.02g
1600°C: 1.90g
1700°C: 1.73g
1800°C: 1.56g
2000°C: 1.27g

(And not, as I implied, about 4g)

Oystein
14th September 2010, 05:43 AM
...
(In "4. Energy needed to melt iron" I estimated that we need 1kJ of energy to melt 1g of iron to somewhat above melting point. This would assume 100% efficient heat transfer.
1kJ is contained in 0.253g of thermite. The experimental value of 1,75g implies 14.4% efficiency. Not unrealistic, I'd say, but that is just my layman's intuition.)

Have to correct that, too:
At 100% efficendy, we'd need about (1/1.9)g = 0.53 of thermite to melt iron and heat it to 1600°C.
Experimental value is estimated 1.75g
That would imply 30% efficiency. Too good to be true, says my layman's intuition ;)

jaydeehess
14th September 2010, 08:29 PM
.

For the twin towers one conceivable use would have been to cut multiple lower cords on floor joists thereby mimicking the observed inwards pulling of the outer tube columns.

.

Ohh, I've tried that tact with those who believe in 911 conspiracies before. I have pointed out that their pet material, explosives or thermite could have been used to, for example, sever the girder attached to col 79 in WTC 7 thus mimicing the initiating event of this girder coming off its column seat by thermal expansion of the floor beams. The rest of the collapse would then follow as per the NIST computer modeling.

Problem with that, in the mind of the 911 conspiracy believers, is that it requires giving NIST some credibility and in those circles such a thing must be avoided at all costs.