Subsonic 'explosions' as cause of pulverization

[metamars]

The thread is split off from

Jones New Paper: Microspheres and Temperatures (http://forums.randi.org/showthread.php?p=3394684#post3394684)

Basically, I had suggested a low velocity blast of less than 100 mph, from a tempered thermobaric, as source of the pulverisation. Some people on that thread keep missing the point that I am not positing this as a source of the columns' destruction, but rather pulverization of most of the other stuff. Besides the visuals of the buildings as they were coming down, recall reports of not finding a piece of a phone bigger than the touchpad, or the scarcity of photos that show even a squashed computer screen or shard of glass.

There was some back and forth on this, which you can read in the other thread. Mr. Mackey's last post to me on the subject is:

:eye-poppi Hokey smokes!!

You're going to get Stundied for that one. I'm not going to do it, and I don't participate in teh Stundies, I'm just warning you.

Either you're playing dumb to gain some leverage off my sense of charity (not a bad strategy) or you're even more confused than I could have imagined. But I'll try to help. We have to go back to Square One for this.

There is, by definition, no possible explosive of any kind with such a low blast front speed. Remember what we're talking about, here. The "blast front" you are describing is a pressure wave. In the case of a high explosive, like TNT or RDX, the "blast front" is a shock wave, and is therefore supersonic. The speed depends on a lot of things but will exceed 340 m/s, or 770 MPH to use your choice of units. A low explosive, like black powder, does not generate a shock wave, instead generating a possibly large in amplitude, but not sharp, pressure wave. This wave moves at the speed of sound, 770 MPH.

The sound speed is the minimum speed of the "blast front." There is no explosive, not of any kind, that will go a mere 100 MPH.

To get such a slow speed, you're not talking about explosives any more, nor a "blast front." That kind of speed, being at Mach numbers of < 0.15, is definitely in the regime known as "incompressible flow." Since we're not setting off this strange device in a sealed chamber, the static air pressure remains constant. The only forces are kinetic, i.e. what "pressure" you feel is strictly due to the air's velocity. Your device will simulate the effect of a 100 MPH gust of wind.

Because the force is purely kinetic, we can calculate the actual felt pressure directly -- it only depends on speed in this case. Using the Bernoulli equation (http://en.wikipedia.org/wiki/Bernoulli%27s_equation), the felt pressure is equal to ρ v2 / 2, where ρ is the density of air, and v is the speed of the air at infinity.

In your case, the speed is your mandated 100 MPH (about 45 m/s), and air density is about 1.2 kg / m3. The felt pressure then works out to about 1200 kg m2 / (s2 m3), or 1.2 kPa. In archaic units, this is 0.17 PSI.

That's it. Not even enough to break windows. Abandon this hypothesis now.

The only way you can reconcile such a slow airflow speed with structural damage is if your mystery device is in mechanical contact with the structure -- rather than transmit a "blast wave," it just pushes on the columns. That, of course, can be done as slow as you wish.

So rather than focus on hyperbaric explosives, you should instead start looking into hypotheses involving, for instance, expanding foam, or (dare I say) collapse of the upper structure.

If you need still further help, as I imagine you do, please start another thread. This is long overdue.

My answer, on this brand spanking new thread, is:

Well, .17 psi overpressure isn't going to pulverize much of anything. It's not entirely clear to me, though, whether the .17 psi represents the effect of a single plane wave, or a continuous train of waves. Do you know which it is? And if the latter, how dense can these wave fronts be, and will the effects be additive, in some sense?

Thanks to your post, I spent time - too much, it seems, yet still not enough - googling around for info on deflagrations, thermite, solid propellants, etc. Basically, I am trying to get a sense of whether or not 'mild' controlled explosions can 'shoot' ferrous by-products subsonically at hundreds of mph, yet still not create a purely gaseous pressure wave that exceeds 170 mph. (170 mph limit for a WTC window is guesstimated from http://www.litchfield-group.co.uk/sheerframe/news/walling-index.asp?story=20060413 ) I assume this would not be from a thermobaric, since dispersing the reactants first would make for more of a mismatch between a blast wave containing ferrous molecules ( about 3,000x as dense as air molecules ), and a concomittant gaseous pressure wave. We either want an air pressure wave which never exceeds 170 mph (or whatever the correct limit is for the WTC windows), or else one which does, but the trailing particle front is close enough, and moving fast enough, so that we can't distinguish it as a separate event. I think this argues for point sources, not dispersed ones. (Hence, again, we're not talking about thermobarics.)

Now, consider:
(caveat emptor-I haven't done much double checking of my calculations. However, the Giants are going to beat the Patriots, and the game is starting in only 20 minutes. First things first!)


A .22 Long rifle takes a 40 grain bullet, with muzzle velocity 1255 ft/s, or 2.6 gram and 382 m/s, giving a momentum of roughly .99 kg-m/s

So, 10,000 bullets would give us a momentum of 9900 kg-m/s

a mole of Fe203 + 2 moles of Al will weigh 210 grams, and have a heat energy of 853 kJ

If .5% of this can be utilized to impart kinetic energy to the reactants (via rapid heating of gases), then we can compute the speed from

.005 * 853,000 = .5 * .21 * v^^2

v = sqrt ( 853,000 )


201 m/s = 449 mph < 770 mph = speed of sound in air


This would represent a momentum of .21 kg * 201 m/s = 42.21 kg-m/s.


To get the equivalent momentum of 10K bullets, you would need (9900 / 42.21) * .21 kg, or about 50 kg of 'exploding thermite'.


This calculation is suggestive, at best. I've not made any attempt to rigorously determine what gas speeds would be associated with a thermite explosion with a .5% conversion efficiency to KE. I also have no idea how quickly the thermite would heat up. Presumably, you want it to heat up quickly, so that it can pulverize via burning through, not just kinetic energy. Perhaps we need a sophisticated nano-thermite, not regular thermite.

Recall that the red-gray chips have a red side (that Professor Jones believes is thermite) of thickness 40 microns. This is about equal to the radius the "preferred" sized aluminum particle in a solid fueled rocket engine, if I read the following correctly: http://dspace.dsto.defence.gov.au/dspace/bitstream/1947/3835/1/DSTO-GD-0344%20PR.pdf


Generally the aluminium content will vary between 5 and 25 wt% with 15 wt% being common. The particle size of the aluminium affects the plateau burning behaviour. A large particle size from 80 - 120 micrometer is preferred.


Counter-arguments that readily come to mind are: 1) I would expect liquid metal droplets to get deformed as they slam into any solids. Thus, I would expect most of them not to be spherical. 2) I would think that there would be ubiquitous mottling. Just like I don't believe that a column punching through a floor element will cause it to disintegrate far from it's impact area, I also wouldn't expect a tiny piece of metal traveling at, say, 250 mph to destroy a structure many times it's surface area. Of course, if you had millions of them, that might be another story.

Hmmm. I was going to sign off, but this is too tempting.

Well, I recently came across the density of rust. It is 4 g / cm3. If we pretend that one of Professor Jones' chip (red side) has a similar density, then know that there would be ~ (10^^-6 m^^3/ .004 kg) / {(.001 m)^^2 * 4x10^^-5 m} chips, or about 6 million.

At 44,000 sq ft per floor in a WTC tower, this works out to about 136 thermite chip-projectiles per square foot.

[Loss Leader]

Basically, I had suggested a low velocity blast of less than 100 mph, from a tempered thermobaric, as source of the pulverisation.


Um ... large passenger jets hit the buildings.

[beachnut]

Nope, redo

[Gravy]

Basically, I had suggested a low velocity blast of less than 100 mph, from a tempered thermobaric, as source of the pulverisation.This just in: concrete pulverized by moderately strong wind from impossible weapon, not by thousands of tons of collapsing building. Stay tuned for more at 11..............


I assume this would not be from a thermobaric, Hey, that's progress! Know why? Because a thermobaric weapon is an EXPLOSIVE.

I think this argues for point sources, not dispersed ones. I got yer "point source" right here:
http://911stories.googlepages.com/WTCBeforeWFC.jpg/WTCBeforeWFC-full.jpg


Now consider: [babbling deleted]Now consider this, metamars: the quarter-mile high buildings collapsed and crushed their contents. I know reality sucks, but you can either live with it or keep drifting farther and farther from the shore.

Which will it be?

[Gravy]

At 44,000 sq ft per floor in a WTC tower, this works out to about 136 thermite chip-projectiles per square foot.Paint chips, you mean.

Welcome to Christopheraville.

[boloboffin]

Chip Projectiles. Isn't that the Green Arrow's new sidekick?

[R.Mackey]

Sweet merciful crap, this is still going on.

But I thank you for starting a new thread.

The 0.17 PSI estimate I made is neither a "wave" nor a "Train of waves." That thinking is ludicrous. The minimum speed of a wave in atmosphere is the speed of sound. I can't believe I have to tell you this again, but there we are. No matter how faint, how slight, approx. 770 MPH is the minimum speed for any pressure disturbance to propagate in the atmosphere near sea level. The output of any explosive is a pressure wave. That means, to a fixed observer, the pressure measured as a function of time rapidly increases, then decays as the wave passes. There is no "train of waves," though there can be multiple reflecting waves. There is no "interference," these waves simply add or subtract. You cannot have significant additive effects unless you have rigid reflectors, i.e. something strong enough to stand up to your explosive and direct the blast elsewhere. Shaped charges do this, of course. But not at low speed. Supersonic only.

If you want slower, you're not sending a pressure wave. You're moving the air itself. Like turning on a fan, for instance. You'll hear the fan turn on much sooner than the breeze gets to you. That breeze, as shown before, is in the sub-PSI range and won't "explode" anything.

Yes, you could devise something that lobbed projectiles at 100 MPH, for instance, and pushed the columns around that way. This device is not an "Explosive." This device is a "gun."

You bring up the example of a .22LR round. Most .22LR's are supersonic, but there are plenty of subsonic guns, e.g. .45ACP, muzzle-loaders, or large mortars. You've forgotten, however, that the .22LR round also makes noise! Even a subsonic gun has muzzle blast, and that does indeed travel at the speed of sound (or faster).

A whomping great low-velocity cannon like you would be forced to propose, big enough to damage the WTC structure, would issue a thunderous report, and this would probably even be visible in the smoke, even if no muzzle flash was issued.

So now you need a silencer. Perhaps, instead of the perfectly reasonable gravity-driven collapse, there were enormous, whomping cannons just below the fire and impact floors, lobbing multiton projectiles against the structure, all fitted with silencers the size of garbage trucks. Sure, it's physically possible.

It's also completely nuts.

[BigAl]

Besides the visuals of the buildings as they were coming down, recall reports of not finding a piece of a phone bigger than the touchpad, or the scarcity of photos that show even a squashed computer screen or shard of glass.



If the "Truth Movement" people ever learn to recognize metaphor and simile when used, the movement will self-dustify and disappear in a pyroclastic cloud like a freight train.

The "phone pad" quote is from the Naudet film. It is said by a fireman in an after-the fact interview while footage of the building debris is shown. It wasn't literally accurate. Who knows why he said it.
http://video.google.com/videoplay?docid=6371069744838112957&q=Naudet

[leftysergeant]

The "phone pad" quote is from the Naudet film. It is said by a fireman in an after-the fact interview while footage of the building debris is shown. It wasn't literally accurate. Who knows why he said it.
http://video.google.com/videoplay?docid=6371069744838112957&q=Naudet

The fact that that was the largest piece he found may have something to do with where on the pile he was searching. At the perimeter, I would expect to find nothing larger. Under the steel beams in the middle of the footprint, I should expect more and larger objects, such as the meteor.

Fire fighters would probably be assigned specific sectors by unit, just like a military operation. It helps maintain accountability in a hazardous environment.

[gumboot]

The "phone pad" quote is from the Naudet film. It is said by a fireman in an after-the fact interview while footage of the building debris is shown. It wasn't literally accurate. Who knows why he said it.
http://video.google.com/videoplay?docid=6371069744838112957&q=Naudet


Aside from the fact that the comment was from immediately after the day (well before most of the debris was sorted), about 40,000 people worked on the debris pile. I'd be quite surprised if anyone handled every single piece of debris.

[metamars]

I talked to my solid state physics prof after class tonight about this. I asked about whether it would be possible to have a subsonic, non-explosive 'explosion', which could destroy things by virtue of it's momentum, pointing out that a pressure wave of 100 mph will only exert an overpressure of .17 psi. I mentioned that, e.g., the model rockets I used to shoot off made a 'whooshing' sound, not a bang, so I am thinking of something like a solid rocket fuel, but with mass deriving from metallic components. I mentioned aluminotherics could explode, and that metallic constituents of the chemical reactants would be far more massive than air molecules. (I didn't explicitly mention thermite, or ferrous constituents.)

He told me to check out magneto waves, Magnetic Hydro-Dynamics, and Alfven (waves?). He said he thought that keeping subsonic should be doable if you control the burn rate. He wasn't too sure about who to best ask regarding the destructiveness, but he seemed to agree that a chemical engineer would be a good person to ask.

He said that the magneto waves in dielectrics are sound waves, but of a sort that travel much slower than regular sound waves. I asked him what sort of dielectrics one could use, and he said "rocket fuel".

Any miscommunication between my professor and myself is probably my fault!

-----------------------------------------

On a related note:
From http://pdf.aiaa.org/preview/CDReadyMASM03_582/PV2003_241.pdf


In another study, Aumann et al. (1995) examined the oxidation behavior of aluminum nanopowders. They suggest that Al powder mixtures with average particle sizes of 20-50 nm can react 1000 times faster than conventional powdered thermites..

[Gravy]

Good luck with your hypothesis that the Twin Towers were pushed around by little rocket chips. You'll find that this is a viable source of Alfven waves:

http://forums.randi.org/imagehosting/879047a92c6745729.jpg
Be sure to let us know when you get back to Earth, and remember to change your foil weekly.

[R.Mackey]

I talked to my solid state physics prof after class tonight about this. I asked about whether it would be possible to have a subsonic, non-explosive 'explosion', which could destroy things by virtue of it's momentum, pointing out that a pressure wave of 100 mph will only exert an overpressure of .17 psi. I mentioned that, e.g., the model rockets I used to shoot off made a 'whooshing' sound, not a bang, so I am thinking of something like a solid rocket fuel, but with mass deriving from metallic components. I mentioned aluminotherics could explode, and that metallic constituents of the chemical reactants would be far more massive than air molecules. (I didn't explicitly mention thermite, or ferrous constituents.)

I give you full credit for talking to a physics professor. This is good practice.

Yes, solid rockets go "whoosh," not "bang." There's a reason for this. Rockets -- if properly built -- are not explosives. Instead, the rocket situation is referred to as a gas generator. It does not propel the rocket by creating pressure waves, as these tend to reflect inside the rocket motor and destroy it. In solid rockets, including the small Estes type you describe, a common failure mode is for a piece of the solid rocket to become dislodged and choke the nozzle. When this happens, flow rebounds off the obstruction, creating a pressure wave that reflects up the rocket core, and can split the casing. This happened not too long ago on Mythbusters (http://mythbusters-wiki.discovery.com/page/Episode+90:+Supersize+Special?t=anon), for instance.

The "whoosh" you hear from a rocket motor is due to reaction gases accelerating. In simple terms, the rocket motor consists of a combustion chamber, with the "burning" propellant at one end generating a volume of gas; and a nozzle, which accelerates the gas. But there is no pressure wave, or at least there had better not be. The gas generation is essentially a static phenomenon which raises the pressure in the combustion chamber. The nozzle allows some of the gas to escape, often supersonically (see Laval nozzle) and produce thrust.

With a gas generator and a nozzle, you can direct gas flow to create a locally strong gust of wind. But this is still awfully inefficient compared to an explosive and its pressure pulse. In the very largest rockets, the force of the backblast is easier to shield against than the heat and even the sound, which exceeds 170 dB SPL in the case of the Space Shuttle. The Shuttle launchpad expends over a quarter million gallons of water (http://www.nasa.gov/missions/shuttle/f_watertest.html) during liftoff as sound absorbers, without which the sound would actually destroy the spacecraft!

What does this prove? This proves that the "gust of wind" created by any gas generator, no matter how enormous or efficient, is trivial in terms of destructive force compared to the other possible effects.


He told me to check out magneto waves, Magnetic Hydro-Dynamics, and Alfven (waves?). He said he thought that keeping subsonic should be doable if you control the burn rate. He wasn't too sure about who to best ask regarding the destructiveness, but he seemed to agree that a chemical engineer would be a good person to ask.

He said that the magneto waves in dielectrics are sound waves, but of a sort that travel much slower than regular sound waves. I asked him what sort of dielectrics one could use, and he said "rocket fuel".

Any miscommunication between my professor and myself is probably my fault!


I don't know about "Magneto Waves," but I know about magnetosonic waves (Alfven waves (http://en.wikipedia.org/wiki/Alfv%C3%A9n_wave), in the limit of low temperature). These also travel at the local "speed of sound," although since you're in a highly specialized medium, that sound speed can be slower than Mach 1. In general, though, that sound speed is in fact comparable to the speed of light...

Unless you can think of a way to fill the WTC Towers with a low-temperature ionic or electron gas, and permeate it with a strong magnetic field, I don't think this is going to be viable.

[HeyLeroy]

metamars, I'd just like to make two brief points.

Debris from higher floors impacted the ground at speeds over 100 mph just from the accelleration imparted by gravity.

Second, how many 10,000-round volleys of .22 long do you think it would take to deliver the energy equivalent to pulverize 220 acres of four-inch-thick concrete? That's a lot of shootin'.

[beachnut]

Was he talking about thrust setting up standing waves that rip up your guts; like an engine run for a J-58/SR-71 engine; engine in full burner, diamonds patterns, close enough to feel like someone was inside you moving things around.

[leftysergeant]

There are no explosives that I know of that would propogate more slowly than an air/fuel bomb. We know three of those were used, jerry-rigged out of air liners.

They did not pulverise the concrete. To pulverize concrete requires a fast-propogating explosive like dynamite, and a great deal of it. You can't do it quitely.

An old hard-rock miner friend of mine once explained to me that for hard rock mining, they use dynamite because it shatters the rock and makes it easy to scoop out.

For quarrying, where they want the stone in the largest pieces they can manage, they use prells or ANFO, ammonium nitrate charges, because they propogate slowly and push the gases relatively gently into the cracks and crevices of the rock and push it apart.

So no, the idea of using a slow-propogating explosive to bust up concrete does not even make sense.

[Dave Rogers]

Basically, I had suggested a low velocity blast of less than 100 mph, from a tempered thermobaric, as source of the pulverisation. Some people on that thread keep missing the point that I am not positing this as a source of the columns' destruction, but rather pulverization of most of the other stuff. Besides the visuals of the buildings as they were coming down, recall reports of not finding a piece of a phone bigger than the touchpad, or the scarcity of photos that show even a squashed computer screen or shard of glass.

Just when I though the truth movement couldn't come up with a more absurd premise, they prove me wrong. The argument here is as follows:

The conspirators developed a completely unknown and logically contradictory type of explosive. They then placed charges formed from this explosive in the Twin Towers prior to the 9-11 attacks. These novel charges then exploded very, very slowly, pulverising concrete over an enormous area but did not break any windows or expel any debris from the buildings because their maximum gas expansion velocity was within the range of weather-related velocities that the towers were designed to withstand. The purpose of these unheard-of explosives was not to initiate or to accelerate the collapse of the towers, as they could not have had any possible effect on the support columns, but to pulverise telephones, computer screens and glass panels, none of which would in any case have survived the building collapses.

Despite being an atheist, there are times when I find the language of atheism to be inadequate.

In the name of God, why?????

Back in 1987, southern England was hit by a hurricane, with winds gusting well over 100mph. Surprisingly, these winds, which are in the range of speeds Metamars is proposing here, did not cause extensive pulverisation of concrete, despite the exposure to these winds of large area concrete structures in... well, just about everywhere. My house remained standing, despite being made of soft brick - far easier to pulverise than concrete. Plastic toys in my garden were also not pulverised by the 100+mph blast. Just how fragile are your American telephones and computer monitors anyway?

Metamars, if you can take this stuff seriously, you need help.

Dave

[Cl1mh4224rd]

Back in 1987, southern England was hit by a hurricane, with winds gusting well over 100mph. Surprisingly, these winds, which are in the range of speeds Metamars is proposing here, did not cause extensive pulverisation of concrete, despite the exposure to these winds of large area concrete structures in... well, just about everywhere. My house remained standing, despite being made of soft brick - far easier to pulverise than concrete. Plastic toys in my garden were also not pulverised by the 100+mph blast. Just how fragile are your American telephones and computer monitors anyway?

Metamars, if you can take this stuff seriously, you need help.


I'm glad someone brought this up. I'm having trouble finding a confirmation, but this page (http://www.tms.org/pubs/journals/JOM/0112/Eagar/Eagar-0112.html) says, "The building is a huge sail that must resist a 225 km/h hurricane."

That's about 140mph.

Granted that's a lateral load, but it's also a Category 4 hurricane. metamars' maximum estimate of 100mph is equivalent to a Category 2 hurricane.

If you've seen video of a Category 2 hurricane, you'll know that metamars' theory is pure bunk.

[SpitfireIX]

This just in: concrete pulverized by moderately strong wind from impossible weapon, not by thousands of tons of collapsing building. Stay tuned for more at 11..............


"Video (on YouTube) at 11." :D

[twinstead]

I think we must have a record for the most inane theories being discussed at one time in multiple threads in the CT forum.

[PhantomWolf]

I think we must have a record for the most inane theories being discussed at one time in multiple threads in the CT forum.

for some strange reason I read this as "insane"

[twinstead]

for some strange reason I read this as "insane"

Same difference, I suppose ;)

[metamars]

Fast Reaction of Nano-Aluminum: A Study on Fluorination Versus Oxidation


At: http://etd.lib.ttu.edu/theses/available/etd-06012007-132204/unrestricted/Watson_Kyle_Thesis.pdf



Table 8 (truncated): Mach number calculations for the flame speed of the reactions

Al Size Composition Ma in gas medium at reaction temp

50 nm Al/Teflon 1.18
50 nm Al/MoO3/Teflon 0.90
50 nm Al/MoO3 0.87

1-3 micron Al/Teflon 0.49
1-3 micron Al/MoO3/Teflon 0.15
1-3 micron Al/MoO3 0.22


Initially looking at the flame speeds, the reactions appear to approach Mach 3 as shown by the Mach number calculation at room temperature shown in Table 8. If this was the case acoustical effects may play a huge role and detonation in the reaction would be imminent. However, considering the reaction occurs in air at the reaction temperature yields Mach numbers on the subsonic regime and would be more consistent with a deflagration. The actual Mach numbers will most likely be somewhere in between and may be best represented by the Mach number calculation in the gas byproduct medium at the reaction temperature. The number is probably slightly high as the gas will not be at the adiabatic flame temperature but it will be much higher than that of room temperature. These Mach numbers are on the order of Mach 1 and would suggest a reaction that is still a deflagration but may be nearing detonation. This is consistent with the comparison of the optical and acoustical propagation rates from above.


(emphasis mine)

[Gravy]

That's great, metamars. Too bad you couldn't read the comments above before making a further fool of yourself.

Be sure to keep your nano-aluminum beanie away from magnesium sparks.

Take a photo of Neptune while you're up there. Neptune's cool.

[metamars]

Again from Fast Reaction of Nano-Aluminum: A Study on Fluorination Versus Oxidation


http://etd.lib.ttu.edu/theses/available/etd-06012007-132204/unrestricted/Watson_Kyle_Thesis.pdf


The pressure wave propagation will tell how fast the pressure is moving through the confined space. This can be used to determine if the reaction reaches the point of detonation or if it is a deflagration. If the pressure wave proceeds equal or faster than that of the optical propagation wave the reaction can be considered to have reached detonation. If the pressure wave propagates slower than the optical wave the reaction will be a deflagration.

The optical propagation rate, or flame speed, is deduced from the high-speed camera data. It is primarily used as a quantification for the speed of the reaction, but can also give indication of detonation when compared to the pressure wave propagation rate as described above. Another interesting characteristic derived from the optical propagatioin rate is the Mach number achieved by the reaction. In many MIC reactions, flame speeds can approach and exceed 1000 m/s, which would be in excess of Ma 3 if the surroundings were considered to be air at room temperature. The achieving of such Mach numbers could mean that there are significant acoustic effects in the reaction. However, reaction proceeds within the flame zone assumed to be at the adiabatic flame temperature for the reaction. This extreme temperature environment reduces the Ma number calculation significantly.

.
.

Peak flame speeds of 4.249 m/s, 410.636 m/s, and 456.559 m/s were obtained for the nano Al samples of Al/Teflon, Al/MoO3/Teflon, and Al/MoO3 composites, respectively.


Note: the flame propagation rate varied enormously as a percentage of aluminum. For example, from Figure 11, which plots flame propagation rate vs. % Al for Al/MoO3/Teflon, there are not only supersonic flame rates of about 410 m/s and 360 m/s, there are also flame rates of ~ 230, 80, 10 and 10 m/s.

In other words, we can get both supersonic and subsonic flame rates, the speed of sound in air being 344 m/s.

I'm not sure if this holds for rapid, yet subsonic flame rate regimes, but for the case of 50 nm Al burns of 40% Al, we can see from Table 5 that supersonic, optical propagation rate exceeds the pressure propagation rate for all of the species being studied. Perhaps the same will be true, for example, for a 230 m/s flame propagation rate, but I haven't seen the data for that.

[cludgie]

So in conclusion it seems the claim is the WTC was pulverised by effectively a big gust of wind? Brilliant. Perhaps we should call it the 'Three Little Pigs Theory'?

[R.Mackey]

And in something like, for instance, the wood in your fireplace, the flame rate is in mm/minute.

You can get rates of reaction to be anything you like, up to about Mach 8 for violent fluourine chemistry and down to near zero if you restrict the oxidizer. None of this has any effect on the way pressure waves move in air. No reaction rate will support your hypothesis.

[dudalb]

I think we must have a record for the most inane theories being discussed at one time in multiple threads in the CT forum.


I am beginning to wonder if Marvel and DC comics are not the Twoofers main source of Scientific Information.

[Gravy]

My money's on the destructive power of the Pistol Shrimp (http://scienceblogs.com/zooillogix/2008/02/the_pistol_shrimp_sonic_weapon.php).

[rwguinn]

Again from Fast Reaction of Nano-Aluminum: A Study on Fluorination Versus Oxidation


http://etd.lib.ttu.edu/theses/available/etd-06012007-132204/unrestricted/Watson_Kyle_Thesis.pdf


.
.


Note: the flame propagation rate varied enormously as a percentage of aluminum. For example, from Figure 11, which plots flame propagation rate vs. % Al for Al/MoO3/Teflon, there are not only supersonic flame rates of about 410 m/s and 360 m/s, there are also flame rates of ~ 230, 80, 10 and 10 m/s.

In other words, we can get both supersonic and subsonic flame rates, the speed of sound in air being 344 m/s.

I'm not sure if this holds for rapid, yet subsonic flame rate regimes, but for the case of 50 nm Al burns of 40% Al, we can see from Table 5 that supersonic, optical propagation rate exceeds the pressure propagation rate for all of the species being studied. Perhaps the same will be true, for example, for a 230 m/s flame propagation rate, but I haven't seen the data for that.

And flame propagation rate is related to shock wave propagation how?

(I see RMackey beat me to it...
He's just too quick...)

[metamars]

And in something like, for instance, the wood in your fireplace, the flame rate is in mm/minute.

You can get rates of reaction to be anything you like, up to about Mach 8 for violent fluourine chemistry and down to near zero if you restrict the oxidizer. None of this has any effect on the way pressure waves move in air. No reaction rate will support your hypothesis.

Table 16 shows avg. results for Al/Fl 1-3 microns, with peak pressure of 606 psi and propagation rate of 186 m/s. Do you think this will create an explosive shock wave, or not? And what do you think will happen to office materials exposed to a 606 psi pressure, at God knows what temperature? I haven't finished studying the report (not sure I will), so I don't even know if the author discusses the drop-off behavior of the peak pressure with distance.

Unfortunately, the author seems to have only presented the most energetic, supersonic cases for 50 nm Al. I am most interested in the subsonic, 50 nm Al case....

[Gravy]

Table 16 shows avg. results for Al/Fl 1-3 microns, with peak pressure of 606 psi and propagation rate of 186 m/s. Do you think this will create an explosive shock wave, or not? And what do you think will happen to office materials exposed to a 606 psi pressure, at God knows what temperature? Hell, you could blow the whole building apart with 15 psi at ambient air temperature. Try to think about what you're missing here, metamars.

[R.Mackey]

Table 16 shows avg. results for Al/Fl 1-3 microns, with peak pressure of 606 psi and propagation rate of 186 m/s. Do you think this will create an explosive shock wave, or not? And what do you think will happen to office materials exposed to a 606 psi pressure, at God knows what temperature? I haven't finished studying the report (not sure I will), so I don't even know if the author discusses the drop-off behavior of the peak pressure with distance.

Unfortunately, the author seems to have only presented the most energetic, supersonic cases for 50 nm Al. I am most interested in the subsonic, 50 nm Al case....

Sigh.

If you create a pressure wave of 606 PSI, this wave propagates at the speed of sound. Or more, depending on its continuity.

The burning rate ("propagation" as you have it here) is something totally different. This determines how long this pressure is sustained, by describing how long it takes to exhaust your reactants. It has nothing to do with how fast the pressure wave travels.

Temperature is a totally different phenomenon. You started this on a quest for "pulverization" at low speed, remember?

[Jonnyclueless]

Anyone who has been to Taco Bell knows very well there are mere 100mph explosives.

[metamars]

And flame propagation rate is related to shock wave propagation how?

(I see RMackey beat me to it...
He's just too quick...)


'everything subsonic scenario'
---------------------------------
if
pressure propagation rate < flame rate
and if
flame rate < speed of sound

then

pressure propagation rate < speed of sound

In other words, all relevant speeds are subsonic.


From the paper, we can see that there are cases where
pressure propagation rate < flame rate
and
flame rate > speed of sound

Unfortunately, from what I've seen to far of the paper, he doesn't present data for us to know if the 'everything subsonic scenario' exists for the species the studies, or not. Do you agree with this statement?

[R.Mackey]

'everything subsonic scenario'
---------------------------------
if
pressure propagation rate < flame rate
and if
flame rate < speed of sound


This is false!

Pressure propagation rate => speed of sound.

Always.

Period.

It's the bloody definition of pressure. If you're a condensed matter physics guy, pressure is transmitted at the phonon speed, unless mechanical motion exceeds it. If you're a fluid dynamicist, you can solve for pressure as a function of location and time using Navier-Stokes. This is true for any and all phenomena that affect pressure.

That's all there is to it. Don't think about anything else until you grasp this fact.

[Furcifer]

This thread is becoming the CT equivalent of the search for the Brown note (http://en.wikipedia.org/wiki/Brown_note)

[metamars]

Sigh.

If you create a pressure wave of 606 PSI, this wave propagates at the speed of sound. Or more, depending on its continuity.

The burning rate ("propagation" as you have it here) is something totally different. This determines how long this pressure is sustained, by describing how long it takes to exhaust your reactants. It has nothing to do with how fast the pressure wave travels.

Temperature is a totally different phenomenon. You started this on a quest for "pulverization" at low speed, remember?

There some kind of disconnect between what the author says (or what I think he's saying), and what you are saying (or what I think you are saying.)

If you look on page 73, table 16, in the AVG row you will see the figures I have quoted. My interpretation of 606 psi is that this is the total peak pressure from all sources, which includes gaseous pressure waves as well as solid, incompletely combusted particles, which will also impart kinetic energy. Since, as you pointed out, the overpressure due to a 100 mph wind is only .17 psi, I expect almost all of the 606 psi pressure to be due to the kinetic energy of the aluminothermic powder, and not due to gas pressure.

Actually, the 186 m/s propagation rate is a (also) a bit nebulous, as it's not clear whether he is talking about 1) just the pressure wave, 2) the flame propagation, or 3) whichever comes first. (I suppose, in the unlikely event that they impact the sensor at the same velocity, it could also mean 4) the combined pressure/flame front.)

In short, I don't think the author is claiming a "pressure wave of 606 psi".

[Gravy]

It's the bloody definition of pressure.I'm dyin' over here!

[Gravy]

There some kind of disconnect between what the author says (or what I think he's saying), and what you are saying (or what I think you are saying.)Focus on the highlighted parts.

Actually, the 186 m/s propagation rate is a (also) a bit nebulous, as it's not clear whether he is talking about 1) just the pressure wave, NO!

[rwguinn]

I'm dyin' over here!
Relax, have a corn dog, break out the popcorn, and pop open a homebrew.
It's Class Time!

[R.Mackey]

There some kind of disconnect between what the author says (or what I think he's saying), and what you are saying (or what I think you are saying.)

I'd bet on the parenthetical version, personally.

If you look on page 73, table 16, in the AVG row you will see the figures I have quoted. My interpretation of 606 psi is that this is the total peak pressure from all sources, which includes gaseous pressure waves as well as solid, incompletely combusted particles, which will also impart kinetic energy. Since, as you pointed out, the overpressure due to a 100 mph wind is only .17 psi, I expect almost all of the 606 psi pressure to be due to the kinetic energy of the aluminothermic powder, and not due to gas pressure.

I haven't looked at the paper, and I don't need to at the resolution of this discussion. Whether the 606 PSI (probably a reference pressure at the surface) is a true pressure wave or a kinetic equivalent, it will be in contact with surrounding air. This will transmit a pressure wave of some, probably greatly diminished strength. That wave will travel at the speed of sound.

Actually, the 186 m/s propagation rate is a (also) a bit nebulous, as it's not clear whether he is talking about 1) just the pressure wave, 2) the flame propagation, or 3) whichever comes first. (I suppose, in the unlikely event that they impact the sensor at the same velocity, it could also mean 4) the combined pressure/flame front.)

It's extremely likely he's talking about the reaction front within the material.

It's faintly possible he's talking about the speed of ejected fragments following reaction.

Either of these could plausibly be at 186 m/s, about 0.5 Mach. Neither of these has anything to do with the pressure wave speed, which again, universally, is equal to or greater than Mach 1.

There is no "combined pressure/flame front." The pressure wave will outrun the flame front. Just like any other deflagration.

[johnny karate]

This thread is becoming the CT equivalent of the search for the Brown note (http://en.wikipedia.org/wiki/Brown_note)

Having never heard of "the brown note", thank you so much for introducing me to the concept. My band finally has a name.

[R.Mackey]

Maybe this will help. This is video of the PEPCON disaster, the largest and best-filmed rapid chemical reaction -- i.e., explosion -- I'm aware of.

HJVOUgCm5Jk

When the main blasts let go, you can see the pressure front sweeping across the desert. This pressure front is actually not a shock wave, just a very, very loud noise, because the explosion is a deflagration rather than a detonation. The sound on the microphone proves this.

You will also note that the pressure front outruns the speed of debris. Right at the moment of explosion there are some reactants that are swept up with the blast, propagating the reaction front at speeds comparable to the pressure front, but in general the "flame propagation speed" is less than the speed of sound.

That's why the debris ejected doesn't go fast or far. Heck, the primary kinetic force is due to the thermal plume, as demonstrated by convection effects in the resulting mushroom cloud.

If I'm a building, and the pressure front doesn't destroy me, then the mere wind motion of what follows won't bother me at all. In your hypothetical situation, you are insisting that the pressure front is inconsequential. Therefore, there is no possible significant gas effect in anything you propose, no matter how it's generated.

Again, you could propose a "gun" scenario where much slower gas phenomena in sealed vessels launch large masses of material at low speed, and these damage the structure, but such a proposal is inherently ludicrous, I trust you'll agree.

[metamars]

My interpretation of 606 psi is that this is the total peak pressure from all sources, which includes gaseous pressure waves as well as solid, incompletely combusted particles, which will also impart kinetic energy. Since, as you pointed out, the overpressure due to a 100 mph wind is only .17 psi, I expect almost all of the 606 psi pressure to be due to the kinetic energy of the aluminothermic powder, and not due to gas pressure.



The oxidation mechanism of an aluminum nanopowder is described on p. 57. The author supports the "melt dispersion mechanism proposed by Levitas, Asay, Son, and Pantoya". Basically, you need Al powder particles slamming into each other with enough velocity in order to rupture the oxide layer. I thus have assumed that spallated Al particles are a necessity in order to have a flame front which can exceed a pressure front. These particles, being solid, will be far more dense than any gasses present.

Being more massive, and moving at a faster velocity than ambient gasses, there contribution to net pressure should easily swamp that of a (gaseous) pressure wave.

[R.Mackey]

The oxidation mechanism of an aluminum nanopowder is described on p. 57. The author supports the "melt dispersion mechanism proposed by Levitas, Asay, Son, and Pantoya". Basically, you need Al powder particles slamming into each other with enough velocity in order to rupture the oxide layer. I thus have assumed that spallated Al particles are a necessity in order to have a flame front which can exceed a pressure front. These particles, being solid, will be far more dense than any gasses present.

Being more massive, and moving at a faster velocity than ambient gasses, there contribution to net pressure should easily swamp that of a (gaseous) pressure wave.

oh, my god. :notm

After they react, they become gaseous. But that doesn't even matter.

The density of the "expanding gas" will never appreciably increase that of the air. Air masses about 1.2 kg / m3. You're only going to slightly contaminate this with reactants, unless you're talking about a stupendous mass of those reactants.

See, it isn't density you should be looking at now. You need to look at total impulse. Your magic thermite cocktail is not going to generate an expanding, burning ring of solid material at uniform density. Mass will be conserved!

To get a low-speed, and hence low-pressure, but high-density "gust" of ejecta, you need a mass of "ejecta" that is comparable to the objects being hit. Conservation of momentum requires this.

So now your mythical not-explosives weigh hundreds of tons, most of which is essentially ballast.

This theory gets stupider every time I try to bottle it. I think it's time to quit.

[Furcifer]

metamars: perhaps a better course of action is to suggest a destructive resonance frequency in the gypsum (one of these babies should work) (http://www.freepatentsonline.com/5004166.html),that also disturbs brainwave activity, resulting in temporary memory loss in the listening range. If the resonance frequency were below the human auditory range (<20Hz)...

[metamars]

The oxidation mechanism of an aluminum nanopowder is described on p. 57. The author supports the "melt dispersion mechanism proposed by Levitas, Asay, Son, and Pantoya". Basically, you need Al powder particles slamming into each other with enough velocity in order to rupture the oxide layer. I thus have assumed that spallated Al particles are a necessity in order to have a flame front which can exceed a pressure front. These particles, being solid, will be far more dense than any gasses present.

Being more massive, and moving at a faster velocity than ambient gasses, there contribution to net pressure should easily swamp that of a (gaseous) pressure wave.

Oops. By the time the oxide layer ruptures, the Al interior is liquid, not solid.

[metamars]

Maybe this will help. This is video of the PEPCON disaster, the largest and best-filmed rapid chemical reaction -- i.e., explosion -- I'm aware of.

HJVOUgCm5Jk



Cool video. Unfortunately (or fortunately), I have to do some real work. I expect to reply further this weekend.

However, for now, one last comment re your subsequent post, wherein you say


After they react, they become gaseous.


As search through the paper will show numerous references to "incomplete combustion". While nanopowders generally help overcome this, I don't assume they do so with 100% efficiency, especially in an open configuration.

Furthermore, in a dynamic situation, a deflagrating nanopowder may have already burned/pulverized a substantial amount of material before giving up the gaseous ghost, so to speak.

More likely, though, is that if the goal is pulverization, you would not want complete combustion to a gas phase, anyway. That might be accomplished by, e.g., spiking your nanopowder with a micron powder. Bi-modal nano and micron Al powder studies are mentioned on pp. 6-7.

By the time the micron particles are combusting, the reactants may be so rarified that complete combustion is impossible. Then too, are you sure that the Ferrous reaction products in a thermite reaction should be gaseous? I don't recall reading anything like that.

[Gravy]

Furthermore, in a dynamic situation, a deflagrating nanopowder may have already burned/pulverized a substantial amount of material before giving up the gaseous ghost, so to speak.No.

More likely, though, is that if the goal is pulverization, you would not want complete combustion to a gas phase, anyway. That might be accomplished by, e.g., spiking your nanopowder with a micron powder. Bi-modal nano and micron Al powder studies are mentioned on pp. 6-7.No.

[Totovader]

Perfect example of where Occham can save you so much trouble...

[pomeroo]

Perfect example of where Occham can save you so much trouble...


Ah, but Fetzer* is more fun.


*Fetzer's Razor: Entities are to be multiplied until they resemble clowns tumbling out of a tiny car.

[R.Mackey]

By the time the micron particles are combusting, the reactants may be so rarified that complete combustion is impossible. Then too, are you sure that the Ferrous reaction products in a thermite reaction should be gaseous? I don't recall reading anything like that.

Your basic thermite reaction merely liquefies, and it also doesn't generate any 600+ PSI. Just heat. That unusual metal reaction you were talking about must generate gas -- pressure comes about through a volumetric change in the reactants, and solid to solid or solid to liquid won't do much if any of that. Solid to gas is the usual way, along with heating which expands that gas much more than it would expand a solid or liquid.

You may have some solid products, though, but they will be diffuse, essentially suspended droplets or dust.

But as before, this is hardly going to pulverize anything. You simply can't pulverize concrete rapidly without sending a pressure wave, and you can't send a pressure wave without leaving visible evidence of it in the smoke.

[jaydeehess]

Besides the visuals of the buildings as they were coming down, recall reports of not finding a piece of a phone bigger than the touchpad, or the scarcity of photos that show even a squashed computer screen or shard of glass

Tell that to the few people who were removed from the debris pile alive. Several of them were firemen and every fireman I have ever seen or met is quite a bit larger than the average telephone keypad.

[metamars]

I read a few more pages of Fast Reaction of Nano-Aluminum: A Study on Fluorination Versus Oxidation during lunch. In the open configuration, the nanopowder is placed in a longish groove, reminiscent of a cigarette. Ignition occurs as one end.

The flame front is caused by ignition of nanopowder that, for the most part, is already there, not by nanopowder that was 'shoved' there, by the force of the process.

Not sure what the situation is for reacted and unreacted matter that does get ejected, outside of the groove. Of course, that is what I'm interested in. :(

As for reactants all turning to gasses, Figure 13 p. 36 says otherwise.
For 50 nm Al, 50% Al, the Al/MoO3/C2F4 composite yields less than 30% gas, as a percentage of reactant weight.

[jaydeehess]

So, if you are trying to pulverise concrete with such a powder what would be the momentum of the particles being ejected and how much of this stuff would have to be present in order to create the effect you want it to? Furthermore is it the ejected particles or a pressure front that you are supposing will be crushing the concrete?

R.M. has already shown you that pressure waves must , by definition, move at or above the velocity of sound in the medium in question.

BTW, R.Mackey, I read an article last year in Sci-American about using supersonic fluid flow in a Laval nozzle as an analog to a black hole. Took several readings before I believeed I had a grasp of the concept. Your reference to the Laval nozzle is the first I have seen anywhere since then.

[Gravy]

I read a few more pages of Fast Reaction of Nano-Aluminum: A Study on Fluorination Versus Oxidation during lunch. In the open configuration, the nanopowder is placed in a longish groove, reminiscent of a cigarette. Ignition occurs as one end.

The flame front is caused by ignition of nanopowder that, for the most part, is already there, not by nanopowder that was 'shoved' there, by the force of the process.

Not sure what the situation is for reacted and unreacted matter that does get ejected, outside of the groove. Of course, that is what I'm interested in. :(

As for reactants all turning to gasses, Figure 13 p. 36 says otherwise.
For 50 nm Al, 50% Al, the Al/MoO3/C2F4 composite yields less than 30% gas, as a percentage of reactant weight.metamars, I am but a lowly tour guide, but I say this with absolute confidence: the tree you are barking up will never produce a raccoon.

[R.Mackey]

As for reactants all turning to gasses, Figure 13 p. 36 says otherwise.
For 50 nm Al, 50% Al, the Al/MoO3/C2F4 composite yields less than 30% gas, as a percentage of reactant weight.

Since gases typically are five to six orders of magnitude less dense than their solid or liquid equivalents, turning 30% of the mass into gas is a quite significant amount of gas generation. This is totally different from an ordinary thermite reaction. Everything I posted above applies here in full.

BTW, R.Mackey, I read an article last year in Sci-American about using supersonic fluid flow in a Laval nozzle as an analog to a black hole. Took several readings before I believeed I had a grasp of the concept. Your reference to the Laval nozzle is the first I have seen anywhere since then.

I also mentioned it in the WTC collapse context, trying to visualize how the BLBG paper predicts transsonic flow at late stages of collapse, leading to unusually loud booms. However, unless you're a rocket or supersonic jet engine designer, or a fluid dynamicist working on supersonic wind tunnels, it's an obscure term.

Not sure how it relates to a black hole, however, except with respect to flow of information. This is relevant to metamars's continued confusion...

In the black hole case (and any relativistic situation), the limit of information is the speed of light. There will be an "event horizon" near the black hole from which no light (and no information) can return, thus infalling material will cross from being able to "see" each other to suddenly being totally out of contact. Think of two spaceships sending each other radio messages. They can talk to each other, with increasing distortion, right up until one of them crosses the event horizon. After that, nothing.

In the fluid situation, "information" is pressure, and it travels at the speed of sound. Pressure is that scalar quantity that defines how energy is concentrated at any one place, in a static sense. Gases try to equalize their pressure, but can only do so at the speed of sound. This is why subsonic flow is said to be "incompressible," because it can equalize its pressure upstream or downstream. But supersonic flow is "compressible," because pressure equalization can no longer flow upstream

The Laval nozzle, a concept essential to rocketry, exploits this fact. (The Wikipedia page (http://en.wikipedia.org/wiki/Rocket_nozzle) is actually pretty good on this subject.) It's not fancy, just a constricting aperture that opens on the other size. What happens is that the combustion chamber builds up pressure, and this starts gas flowing through the opening, but slowly. As the gas is constricted, it goes faster -- because the gas is incompressible, conservation of mass requires that the narrower passage has to flow faster to get out of the way of gas behind it.

Somewhere in the nozzle, ideally at the narrowest part, the gas accelerates so much that it becomes sonic. This places a static shock in the nozzle throat. The shock is the boundary between subsonic, incompressible flow inside the combustion chamber, and supersonic, compressible flow outside.

Here's why we do this: Outside the nozzle, the gas continues to accelerate. In subsonic flow, the pressure is held constant, but that is no longer true in supersonic flow. The pressure can't equalize, because the pressure "signal" can't move upstream! The gas is already going too fast.

Inside the combustion chamber, the gas all "talks" with each other, so the gas is getting pushed along by its neighbors. That push is pressure. Outside the nozzle, once supersonic, the gas is moving faster than its neighbors can "push," so it is basically unrestrained. The gas accelerates until it runs out of heat energy, or gets mixed with the freestream outside your rocket. In this way the gas that started from rest can be accelerated to several times the speed of sound, provided it's hot enough.

You don't need a Laval nozzle to work a rocket, as you know if you've ever let go of an inflated balloon or applied a bicycle pump to a water bottle. You can get propulsion without the gas ever reaching sonic speeds. But in this case, the thrust is basically limited to the chamber pressure, and the pressure at the nozzle is the same as the pressure in the chamber. In a more sophisticated rocket, the supersonic flow means that your thrust is limited by temperature, not the burst pressure of your combustion chamber, which can now be held to a more reasonable level. Furthermore, instabilities in the rocket plume cannot propagate past the shock, since pressure can't flow upstream faster than Mach 1. This means your rocket is at much less risk of destruction due to turbulence in its own wake, or due to reflection of pressure waves inside the combustion chamber. Once those pressure disturbances pass through the normal shock, they're gone forever, as far as the rocket is concerned.

Another good treatment on the subject is this discussion of Mach diamonds (http://www.aerospaceweb.org/question/propulsion/q0224.shtml), describing what happens to the flow after it leaves the Laval nozzle. You kids these days have it easy, with so much good information just waiting out there to be linked. :D

[metamars]

from http://www.noahshachtman.com/archives/002434.html



DIME is used in the Low Collateral Damage version of the Small Diameter Bomb currently under development. This has a carbon fiber casing which turns into dust rather than creating dangerous fragments. The bomb is filled with explosive mixed with tungsten powder, which becomes micro-shrapnel. The small-sized tungsten particles drag to a halt at about 40 charge diameters. In the case of the SDB, that gives a destructive radius of about 25 feet.

The result is an incredibly destructive blast in a small area, what the Air Force Term "Focused Lethality." The AFRL Munitions Directorate provided this picture of a DIME test, but were unable to discuss the topic. However, I talked to others who have worked in this area. They were consistently awed by the destructive power of the mixture, which causes far more damage than pure explosive within the near field. The impact of the micro-shrapnel seems to cause a similar but more powerful effect than a shockwave.


(emphasis mine)



Because there are no large fragments, Focused Lethality Munitions should not cause a hazard at any great distance. The standard Small Diameter Bomb is claimed to be lethal out to 2,000 feet or more, the Focused Lethality version will have a smaller but deadlier footprint - a 12-gauge compared to a rifle.

Little has been released on the exact effects of DIME explosives, but it's interesting that a presentation on future munitions illustrates focused lethality with a tank which had been turned on its side by blast. Aimed accurately, it looks like it would be capable of destroying a building completely without damaging the rest of the neighborhood.


Metal powders -- typically aluminum -- have been added to explosives for many years. But those are reactive metals, making the blast even stronger. Tungsten, on the other hand, is inert. So it remains in metallic form and absorbs some of the energy of the explosion. DIME originated in work to increase the density of the explosive mixture, improving the penetrating power of bunker busting bombs. But the bonus effect of the micro-shrapnel proved to be more significant than the increased density.


However, a comment was posted that disputed some of the report:

If you go and check out the google cache (below or click on my name) of that PPT that's been converted to PDF and most certainly EDITED and probaby REDACTED prior to posting... you will see
what has been blacked out is the words "MULTIMODE WARHEAD SHOT" (see slide 18).

The full photo as well shows some kind of test stand - which you've cropped out in the photo you've posted. Why'd you do that? Hmm?

Stop jumping to conclusions and making assumptions on very thin evidence (about the tank).

The "MUNITION TECHNOLOGY DRIVERS" preseentation does not say one d*mn thing about DIME.

Stop futzing up your otherwise good website with crappy reporting and blatent speculation.

It makes you look like bumbling amateurs.

http://72.14.203.104/search?q=cache:Vh0wtam0ucsJ:www.dtic.mil/ndia/2001munitions/masiello.pdf+%22MUNITION+TECHNOLOGY%22+Masiello&hl=en&gl=us&ct=clnk&cd=1


I do think one thing seems clear - micro-shrapnel can do a lot of damage 'independently' of a shockwave. Whether you can propel the micro-shrapnel with sufficient velocity to do significant damage to building materials, without a shockwave, I don't know.

[defaultdotxbe]

from http://www.noahshachtman.com/archives/002434.html

(emphasis mine)

However, a comment was posted that disputed some of the report:

I do think one thing seems clear - micro-shrapnel can do a lot of damage 'independently' of a shockwave. Whether you can propel the micro-shrapnel with sufficient velocity to do significant damage to building materials, without a shockwave, I don't know.
too bad development on that weapon didnt even begin until after 9/11

[R.Mackey]

I do think one thing seems clear - micro-shrapnel can do a lot of damage 'independently' of a shockwave. Whether you can propel the micro-shrapnel with sufficient velocity to do significant damage to building materials, without a shockwave, I don't know.

You cannot. Small size means inconsequential KE of any given fragment, unless velocity is increased. This is why my 125 grain .270 Win is about equally effective as a 300 grain .450 Minie ball -- it's much faster. But if you reduce a bullet's size and speed, you get nothing. Your carbon-vapor microshrapnel device basically adds density to the existing shockwave, and does so with particles so small that they rapidly dissipate through mixing rather than propagating as a pure pressure wave.

In terms of shrapnel, the most accessible example of this is a "lemon grenade." Mythbusters exploded a number of these under controlled conditions, demonstrating the extremely small size of its shrapnel, comparable to about #8 shot in size and mass. These are, however, propelled at absurdly high speed, about 2000 m/s initially, which makes them quite lethal. The small size and high speed also means a low ballistic coefficient and high drag, which is why grenades have a limited area of effect -- a feature, not a bug. Once the "microshrapnel" slows to below sonic speed, they are not particularly dangerous to even exposed personnel, and certainly would not threaten a structure's integrity.

---

It's not my intent to encourage further attempts to rescue a dead hypothesis, but I have thought of another relevant situation. You can create a locally very strong "gust of wind," moving slower than sonic speeds, if you create a vortex ring. Vortex rings are apparently being studied for less-lethal antipersonnel uses (http://www.defense-update.com/products/v/vortex-ring.htm), and allegedly the Axis studied this as an anti-aircraft weapon before abandoning the idea.

I question whether a vortex ring strong enough to cause meaningful structural damage is possible, however, without greatly heating or compressing (or both) the acting fluid. There are also practical issues -- it requires a large and complicated apparatus, vortex rings behave unpredictably close to solid objects, and the noise will still travel at the speed of sound. There are no silent vortex generators of any meaningful strength. The stronger ones (http://srl.org/machines/shockwave/) are generally powered by explosives, and make an incredible amount of noise.

[metamars]

You cannot. Small size means inconsequential KE of any given fragment, unless velocity is increased. This is why my 125 grain .270 Win is about equally effective as a 300 grain .450 Minie ball -- it's much faster. But if you reduce a bullet's size and speed, you get nothing. Your carbon-vapor microshrapnel device basically adds density to the existing shockwave, and does so with particles so small that they rapidly dissipate through mixing rather than propagating as a pure pressure wave.

In terms of shrapnel, the most accessible example of this is a "lemon grenade." Mythbusters exploded a number of these under controlled conditions, demonstrating the extremely small size of its shrapnel, comparable to about #8 shot in size and mass. These are, however, propelled at absurdly high speed, about 2000 m/s initially, which makes them quite lethal. The small size and high speed also means a low ballistic coefficient and high drag, which is why grenades have a limited area of effect -- a feature, not a bug. Once the "microshrapnel" slows to below sonic speed, they are not particularly dangerous to even exposed personnel, and certainly would not threaten a structure's integrity.



Well, I'm pushing this line of inquiry to try and determine the plausibility of CD-like causes of pulverization. The energy needed to accomplish this may be orders of magnitude less than what's needed to "threaten a structure's integrity", if that means blowing apart columns.


---

It's not my intent to encourage further attempts to rescue a dead hypothesis, but I have thought of another relevant situation. You can create a locally very strong "gust of wind," moving slower than sonic speeds, if you create a vortex ring. Vortex rings are apparently being studied for less-lethal antipersonnel uses (http://www.defense-update.com/products/v/vortex-ring.htm), and allegedly the Axis studied this as an anti-aircraft weapon before abandoning the idea.

I question whether a vortex ring strong enough to cause meaningful structural damage is possible, however, without greatly heating or compressing (or both) the acting fluid. There are also practical issues -- it requires a large and complicated apparatus, vortex rings behave unpredictably close to solid objects, and the noise will still travel at the speed of sound. There are no silent vortex generators of any meaningful strength. The stronger ones (http://srl.org/machines/shockwave/) are generally powered by explosives, and make an incredible amount of noise.

Wow, this seems too wild even for me to look into. :) However, Max Photon may be just the man for the job!


Meanwhile, back at the subsonic ranch:

There is such a thing as subsonic ammunition. From

http://www.alphecca.com/mt_alphecca_archives/001756.html


It's mostly for shooting rats that the cat has cornered in the oak tree.

Out of a six-inch High Standard Supermatic and inside the fenced yard that's about 100 feet from the anal neighbor it sounds like somebody politely clapped their hands.(emphasis mine)
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People who used suppressed .22 pistols in urban environments (can you say Mossad? or KGB?) found that the subsonic loads penetrated almost as deeply as a standard load yet were very quiet.




Also, surrounding a blast with tungsten powder should muffle it, to some degree or another. This web page (http://query.nytimes.com/gst/abstract.html?res=9E00E0DF1439EF3ABC4E53DFB3668389 639EDE) brings up a NY Times article from 1922 which describes how safe blowers muffled their explosion with bags of sugar. Sweet!

[X]

Well, I'm pushing this line of inquiry to try and determine the plausibility of CD-like causes of pulverization.

The building collapsed.
What more do you need?

[uk_dave]

;3457330']The building collapsed.
What more do you need?

Attention

[R.Mackey]

Well, I'm pushing this line of inquiry to try and determine the plausibility of CD-like causes of pulverization. The energy needed to accomplish this may be orders of magnitude less than what's needed to "threaten a structure's integrity", if that means blowing apart columns.

This appears to be a paradox. How can you pulverize vast quantities of structural materials, yet be "orders of magnitude" below a threat to the structural integrity? Remember, the pulverization and collapse requirements are handily met by the gravitational energy present, so say several independent published results.


Meanwhile, back at the subsonic ranch:

There is such a thing as subsonic ammunition.

Yes, I know. If you look further up this thread, you will see where I describe several types of subsonic ammunition. It's really quite easy to make a slower bullet; making them faster is what takes work.

The subsonic ammunition you're talking about is caliber .22 Long Rifle, which is really only remarkable in that .22 LR is commonly loaded in both supersonic and subsonic forms. Most ammunition is either one or the other. .22 is really a family of cartridge, from the anemic CB cap originally intended for indoor shooting at paper targets a few feet away, to the deceptive and surprisingly hot .22 WMR.

I happen to have a couple of boxes of CCI .22 LR subsonic in the safe. You can buy the stuff anywhere, it's not new or exotic. It is also, as you note, relatively quiet. You can clap louder than the report. The advantage of subsonic .22 LR is that you can fire it without irritating your neighbors too much, and so you can pop rats and things without having to go buy a pellet gun.

But just because .22 LR subsonic is quiet does not mean that all subsonic ammo is quiet. The other well-known example I already told you about is .45 ACP (Colt Automatic Pistol). If you're unfamiliar with firearms, this is the cartridge of the legendary 1911 service automatic, and the Thompson submachine gun. It is also subsonic, firing a fat slug about six times the mass of a .22 LR. But it sure isn't quiet. Where you can almost get away without ear protection firing even supersonic .22 LR, a few strings of .45 ACP will leave your head ringing in no time. If we scale up to the size of a "gun" that could actually pulverize an estimable amount of concrete, it'll be thunderous.

For a practical but very quiet projectile thrower, take a look at my avatar -- paintball. Carefully regulated driver gas, carefully calibrated projectile speeds, and barrels tuned to match can produce virtually zero excess expansion at the muzzle. Paintballs carry about half the momentum of .22 LR rounds, and if well tuned are not much louder than footsteps on a hardwood floor. Of course, scaling this up to WTC destroying dimensions will put this safely in the realm of complete stupidity.

Incidentally, subsonic .22 LR is sometimes annoying to use. Its lower recoil means less reliable functioning in autoloaders, such as the Hi-Standard Supermatic in your quote, and my Marlin Model 70 rifle. Also, any shooter is trained to recognize the signs of malfunction -- the subsonic .22 LR is so quiet, it sounds just like a "squib" (this is proper usage of the term, unlike the Truth Movement application to demolitions), viz. an underloaded shot that can leave the bullet lodged somewhere in the barrel, which is very dangerous. Every single person I've ever seen fire .22 LR subsonic fires, immediately stops, and checks to make sure it wasn't a "squib." I did it too. It takes getting used to.

A subsonic .22 LR is a halfway decent assassination weapon -- see Ronald Reagan if you don't believe .22's can hurt you in a big way -- but their effective range is quite low and stopping power is minimal. No expert will recommend .22's for personal defense; the lower limit is about .380 ACP, another marginally subsonic load.


Also, surrounding a blast with tungsten powder should muffle it, to some degree or another. This web page (http://query.nytimes.com/gst/abstract.html?res=9E00E0DF1439EF3ABC4E53DFB3668389 639EDE) brings up a NY Times article from 1922 which describes how safe blowers muffled their explosion with bags of sugar. Sweet!

Yes, but how are you going to pulverize large amounts of concrete and muffle it? Are you planning to cover the entire floor or encase the whole building with sound absorbing material? This isn't any better than the earlier "slow motion explosive" proposal, it's replacing one absurdity with another.

The sugar sacks or whatever are not mixed in with the charge, nor are they a driver material. They're just sound insulation outside the blast. Totally different.