Kinematic production of molten steel and its cooling rate

[letrec]

Hi everyone,

As we all know jet fuel can't melt steel beams. Of course melting steel
beams is unnecessary to explain the collapse of WTC 1 or 2. But then
truthers will point to the various witness statements talking of "molten
steel" or "molten metal" in the WTC basements. This topic has been
discussed in this thread.

Various explanations has been provided. I think everyone agrees that there have
been long-burning fires in the WTC rubble. That being said, it is being also
agreed that uncontrolled hydrocarbon fires can hardly exceed 1300 K, the
melting point of steels being around 1600 K.

The WTC was full of metals having melting points below 1300 K and this includes
common metals like aluminum, zinc, lead. Therefore large quantities of these
metals may have melted because of the actions of the underground fires,
and these may have been reported by the witnesses inaccurately as being molten
steel, especially if glowing steel elements were dipping in pools of molten
aluminum.

Forum member Jazzy was suggesting that molten steel may have been produced as a
result of the kinetic energy of the collapsing towers being partially
transferred to some of the steel elements, causing them to melt. I had thought
of this (relatively obvious) possibility too and I found Jazzy's posts by
searching this forum. (There is also some material at JREF/IS but the
discussions there are lost in self-congratulatory noise.)

A quick estimate of the gravitational potential energy of the towers is 500-1000
GJ per tower. An enthalpy of fusion of 270 kJ/kg and a specific heat of 460
J/kg seems reasonable for steel. Starting from an ambient temperature of 300 K
one therefore needs 868 kJ/kg to melt steel, leaving it at the melting
temperature. Thus the maximum amount of steel that could conceivably be molten
by the gravitational potential energy of each tower would be 576 to 1152 tons.

Of course a portion of that energy will be expended in endothermic processes,
and a portion will be lost to the environment in the form of dust clouds, etc.
It is difficult to estimate what portion of that energy could perform work on
steel.

Also, energy would have to be concentrated on steel beams.

I would simply argue that to someone with a general scientific education it does
not seem implausible that a small percentage of the total available energy would
produce molten steel.

In other words, one could expect from basic arguments that from 10 to 30 tons of
molten steel would be produced in the collapse.

Note that the collapse duration was 15 to 25 seconds according to NIST; this
means that the power release was 20 to 67 GW. A small percentage of this would
be 0.2 to 2 GW. If this acts on 10 to 30 tons, it would take 4 to 130 seconds.

Now 10 to 30 tons is only 1.25 to 3.75 cubic meters. The characteristic
dimension (assuming a sphere) would be 0.7 to 1 meters, for a surface of
6.2 to 12.6 square meters.

The incoming power density would be something like 16 to 320 MW/m^2.
If the steel is at 1600 K, with the given surfaces, up to 2.3 to 4.7 MW could be
lost by radiative cooling. This is one to two orders of magnitude below the
incoming power density.

Therefore it is not implausible, based on energy and power density
considerations, that some limited amount of molten steel could be produced in
the collapse.

In my next post I will show the results of a simple spherical cooling
simulation that shows that molten steel could stay in a molten state for many
weeks.

 

[Mick West]

Therefore it is not implausible, based on energy and power density
considerations, that some limited amount of molten steel could be produced in
the collapse.

Two points:

1) There's no need to explain what was not there. There's simply no evidence of molten steel. None was ever reported as found, and the eyewitness accounts could quite easily refer to small amounts of molten aluminum or lead.

2) dropping a girder from the top of the WTC onto unyielding ground would only raise the temperature a few degrees. How then is the energy concentrated in one spot? @Jazzy suggests something like the mechanism of a Newton's cradle, where the impulses all travel to the bottom of the pile. But this seems backwards to me.

 

[letrec]

Two points:

1) There's no need to explain what was not there. There's simply no evidence of molten steel. None was ever reported as found, and the eyewitness accounts could quite easily refer to small amounts of molten aluminum or lead.

I agree that for reasonable people there isn't sufficient evidence of molten steel to warrant anything other than a yawn. But when I was a truther, molten steel was a core pillar of my belief.

There are a number of anecdotal reports of molten steel. CTs use those to support their claims. I could make a list, but if you hang on Reddit in /r/911truth or /r/conspiracy you may be see them for yourself.

That the witnesses could have been mistakenly referring to molten metals other than steel is a good point, but that's not good enough for a CT. Why?

Because some of the reports are early and some of them are published in non-media outlets such as professional bulletins. In the conspiracy theorist's mind such reports are more likely to tell the truth, because (a) the powers that be didn't have enough time to tie the loose ends and (b) they don't have control over small publications.

It's basically "what the underdog says must be true" bias.

(That's also why they're all in love with the BBC WTC7 cock-up.)

2) dropping a girder from the top of the WTC onto unyielding ground would only raise the temperature a few degrees. How then is the energy concentrated in one spot? @Jazzy suggests something like the mechanism of a Newton's cradle, where the impulses all travel to the bottom of the pile. But this seems backwards to me.

I don't have a mechanism for that. I don't know how one could answer that question without a very detailed simulation OR really advanced arguments (something from statistical physics) and that's beyond my reach. So I can't exclude it. But I don't think anyone has an analysis to exclude that. Which means CT's can't exclude it either.

But CT's cling to the "thermite hypothesis" because they believe there was unreacted thermite in the rubble that kept reacting intermittently producing molten metal over all these weeks.

I want to present an alternative hypothesis where molten steel, produced kinematically during the collapse (exact mechanism admittedly unknown, however it is energetically plausible), can still be in a molten state weeks later.

 

[letrec]

Part II

It is assumed that a spherical blob of molten steel of radius R has been produced by some undetermined mechanism converting kinetic energy to thermal energy during the collapse of a WTC tower. The aim is to determine under what conditions such a blob could still be in a molten state three weeks after the collapse using a simple numerical simulation, and to compare the energy necessary for the formation of such a blob to the gravitational potential energy contained in each tower.

Parametrization

Time t=0 is taken immediately after the collapse initiation and blob formation. The initial temperature of the blob is assumed to be a uniform T0, which is supposed to be above the melting point Tf of steel. The blob is assumed to be encased in sea of debris, which has a uniform initial temperature T1.

Physical parameters that are supposed to be known include the densities, specific heats and thermal conductivities for the two materials (steel and debris), as well as the temperature and enthalpy of fusion of steel. These are also assumed to be constant (which is inaccurate, as conductivities have a known temperature-dependence.)

Evolution of the system

As the blob cools, the surrounding sea of debris warms up. At some point in time, the outer surface of the blob reaches the melting point of steel and the blob starts solidifying; at that point a blob of molten metal is enclosed in a shell of solid steel, which itself is encased in a sea of debris. The blob of molten metal shrinks while the shell grows, the total blob of metal keeping its initial dimensions.

Finally the blob is completely solidified at time t1 and this is where the analysis stops.

Numerical simulation

The system has been modeled as m concentric spherical shells whose radii have a constant increment of dr and a numerical solution computed using the simplest method (Euler's finite difference method.) Different time-step and radius increments have been tested to ensure that the results are numerically robust. A radius increment of 2.5 cm and a time increment of 50 s have been found to yield satisfactory results.
Parameter selection

Parameters maximizing the solidification time but judged to be plausible were selected. The debris temperature was set at 1366 K based on an OHSA report of continuous underground fires reaching that temperature. The initial temperature of the steel was taken as 3135 K, which is the boiling point of iron.

Initially, the debris material was assumed to be cinder concrete (k = 0.76 W/m/K, rho = 2100 kg/m^3, cp = 880 J/kg/K).

This was then changed to Portland cement (k = 0.29 W/m/K, rho = 1500 kg/m^3, c = 1550 J/kg/K.)

The radius was then set to R=0.6 m so that the initial thermal energy (above a background temperature of 300 K) is 1% of the high estimate of the gravitational potential energy of 1000 GJ.

When the initial temperature of the debris is 1366 K, the solidification time was found to be 10.9 days in concrete and 51.4 days in cement. If the initial temperature of the debris is reduced to 300 K, the solidification time drops to 1.9 days in concrete and 7.3 days in cement.

If the initial temperature of the cement is reduced to 1650 K with the debris at 300 K, the solidification time is 0.5 days in concrete and 1.4 days in cement.

The following plot shows the temperature of the center of the blob with respect to time for the two scenarios, with a debris temperature of 1366 K.

Discussion and conclusion

Given an initial mechanical formation mechanism, this analysis indicates that a 0.6 m radius, 7.2 ton blob of molten steel, encased in a homogeneous mass of debris will fully solidify in 0.5 to 50 days.

The possibility of observing, weeks after the collapse, molten steel formed during the collapse as a result of the conversion of mechanical energy is therefore not excluded.

 

[Oystein]

Not excluded, but chance atronomically slim.

The potenrtial energy is distributed throughout the entire mass. As the mass falls, each fraction of the tower has its potential energy converted first to kinetic energy, then later to "other", some of that other being heat. Now, as Mick already pointed out: 1 kg of mass falling from the greatest height (excluding the antenna) of 415 m has a potential energy of m g h = 1 kg * 9.8 m/s^2 * 415 m = 4067 J. One could say, specific potential energy of the mass at roof level is 4067 J/kg.
Iron has a specific heat capacity of 449 J/kg/K. If all the potential energy is fully converted into heat and equally distributed, iron will warm by (4067/449) K = 9 K. That is merely 1/166 of the temperature differential you need to get from ambient temp to the melting point of iron - at which point you need to expend an additional 247 J/kg (heat of fusion), or 27 times the available energy, to make it liquid.

That's not going to happen. Not nearly! At most, expect sparks (tiny chips of iron that heat enough to ignite, which is still far below melting point). Friction does that: If impact of a relatively heavy object with another along a relatively small surface reduced the velocity of the large object to zero, much of the energy is concentrated on that surface and heats the surrounding (relatively small) volume. I don't know how to model this thermodynamic situation of a tumbling tower and cannot make exact calculations there, but I can approximate a best case scenario:

You can only hope for this "deceleration by concentrate friction" mechanism for solid pieces of steel, not for assemblies. Candidates might be the biggest core columns or the wall panels (three columns of 11+ meters quite solidly connected by spandrels). The theoretical optimal scenario would then be for that piece of steel to fall freely from the roof to the ground, impact on its end and come to a grinding halt (literally) with all the kinetic energy passing into 1/200 of the piece's mass as heat.
I have been told that wall panels near the top weighed 6-7.5 tons. I don't know if there were any core columns, or pieces of the hat truss that were much heavier. Let's go with an estimated 10 tons as the heaviest bit of dsteel from near the top, just for startes. The fall of such could heat 1/200 of that mass = 50 kg enough to melt. That's a volume of 6.4 l. A sphere of 6.4 l has a diameter of 0.23 m.
How long till that cools to solid?

Of course you'll never get to concentrate the heat this tightly - thermodynamics is your enemy every way you look.

And of course the assumption of any molten steel being enclosed in a sphere is laughably unrealistic. Remember, truther like to quote mine the "rivers" of molten iron, flowing "like lava" - i.o.w. steel stretched out along a considerable length. If your 6.4 l of molten iron form a river only 1 m long, shaped as a rectangular box, it's down to 8x8 cm, with one face unenclosed and radiating heat freely. That will solidify in a matter of minutes.

 

[Oystein]

Ohhhh and you have two more totally unrealistic assumptions!
"debris temperature was set at 1366 K based on an OHSA report of continuous underground fires reaching that temperature"
This temperature was a maximum small spot reading a short while after the collapses, after underground fires had indeed already burned. But the hypothetical steel melted upon collapse impact would have been immersed in cool debris!

"The initial temperature of the steel was taken as 3135 K, which is the boiling point of iron"
Impossible. The moment a small volume of the steel melts, it separates from the piece of solid steel whose impact/friction was heating it, effectively cutting the drop off of any more heat input.
Plus, with an additional 1300+ K to go, you multiply the factor of concentration. I don't have the heat capacity of liquid iron handy. Assuming it is the same as for solid, you are now down to something like 1/350 of any steel element melting from its own potential energy, or less than 30 kg for the biggest pieces.

 

[Mick West]

Forum member Jazzy was suggesting that molten steel may have been produced as a
result of the kinetic energy of the collapsing towers being partially
transferred to some of the steel elements, causing them to melt. I had thought
of this (relatively obvious) possibility too and I found Jazzy's posts by
searching this forum

I'm not sure Jazzy ever suggest this would melt tons of steel (or any steel at all), as I remember it he rather argued it as a source of retained heat that would create and sustain fires, and create steam.

Much of the buildings' kinetic energies remained as the wreckage hit the deck. Much of that was transferred by direct metal-to-metal contact (a la Newton's Cradle) to Gzero itself, where probably a hundred to a thousand tons of steel (a small proportion of the building masses) was the beneficiary - and reached high temperatures.

The world's original method of manufacturing HYDROGEN GAS was by passing steam through heated iron pipes.
This is HISTORY. It amazes me that our society never learns its history.

Nobody should have been surprised when the wreckage burst into flames after being dowsed with water. Especially not the firemen, and you (out there) should have known it too.

[...]

My point is that the temperature of the steel would necessarily PEAK the very moment the final piece of steel had come to rest. The mechanism was by ELASTIC KINETIC ENERGY TRANSFER, the very same that is demonstrated by Newton's Cradle, or, for that matter, a game of pool.

From there on in, the heat was retained by the insulation of the wreckage - the top of it being pulverized lightweight insulation material.

 

[drommelsboef]

Weren't there genuine measurements of the surface temperature? I'm not sure what the official explanation for that temperature is. If it is "too hot" what can we conclude from this? If it is to be expected as a result of the collapses then it should also be a normal result for controlled demolitions or fire induced collapses.

 

[letrec]

Thanks for the comments.

Let me just repeat that I'm not really convinced that the collapse could produce molten steel, however I think it's an interesting thought and I don't see a bullet-proof way of excluding it.

You can only hope for this "deceleration by concentrate friction" mechanism for solid pieces of steel, not for assemblies. Candidates might be the biggest core columns or the wall panels (three columns of 11+ meters quite solidly connected by spandrels).

I'm not sure I understand what you mean by that.

A large chunk of steel falling from great height certainly won't do the job. If I was to speculate I would maybe think of something like the following. You have some steel structure (e.g. assembly) at the bottom of a shaft (think elevator shaft), and a large amount of debris is falling on top of that structure, causing it to be crushed. It undergoes plastic deformation, which is exothermic, and melts.

Is that plausible? Meh. But I'd buy that rather than thermite.

Now I agree that I should have spent some proper time surveying the witness claims and collecting them, however I was more in a number-crunching mood yesterday.

Ohhhh and you have two more totally unrealistic assumptions!

Well that's a bit under the belt, they are min/max values, I provided the cooling times for different combinations of debris
and initial temperature.

A sphere of 6.4 l has a diameter of 0.23 m.
How long till that cools to solid?

Re-running the simulation gives 0.1 ("realistic"; concrete with starting temperatures for debris at 300 K and metal at 1650 K) to 1.5 days ("unrealistic"; cement, 1366/3135 K).

PS. Looks like someone installed a suspicious contraption as my profile picture, do I need to call an EOD team?

 

[Mick West]

PS. Looks like someone installed a suspicious contraption as my profile picture, do I need to call an EOD team?

See: http://commons.wikimedia.org/wiki/File:Joule's_Apparatus_(Harper's_Scan).png

 

[letrec]

See: http://commons.wikimedia.org/wiki/File:Joule's_Apparatus_(Harper's_Scan).png

Very appropriate.

While researching specific sources for the molten metal claims, I stumbled onto
this person's suggestion that the rubble pile formed natural cupola furnaces.

I don't know if this is plausible so any input would be appreciated. If it is plausible then it provides a nice, conventional explanation for the molten metal.

 

[Oystein]

Do you mean "molten metal" or "molten steel"?

 

[letrec]

I meant molten steel, sorry. (There is no problem of course explaining molten aluminum, etc. with the underground fires.)

 

[Oystein]

Ok. Just throwing a few thoughts out here.

1. We have no direct evidence of there actually having been bulk amounts of molten steel. Eye witness reports are unreliable for various reasons, many no doubt are quote-mined (the speaker did not intend to claim, literally, that they saw "steel" that was actually "molten"). The physical evidence is elusive, and there is no hope today to recover any.

2. Such coke-fired furnaces depend on a conflation of several circumstances to actually be able to melt steel:
a) Some amount of a suitable fuel. Coke will do, but doing it with wood, paper, a number of other of the more plentiful hydrocarbons found in office towers is going to be much more difficult, if at all possible. There is a reason why the iron age started some 2,000 yeaes after the bronze age: producing the required temperatures is difficult technologxy. Charcoal will do, though.
b) A sufficient concentration of said fuek. If you have 10% fuels mixed with 90% inert debris, chances are your kiln fire won't burn well enough to get really hot
c) A sufficient supply of oxygen, which requires a brisk flow of air through the furnace chamber.
d) An amount of iron in suitable proportion to the fuel and airflow
e) A stable casing that encloses the heat while not suffocating the fire
f) And finally a path for the molten metal to escape such that it can be seen by the eyewitnesses.

3. Remember that molten steel is a liquid which, like water, tries to run down where gravity pulls it, seeping down in the debris. It would thus take, as an additional requirement, that the resulting molten steel drips on some "water-proof" surface where it can pool, perhaps flow. Any contact with any such surface will instantly cool the melt, of course. It therefore seems reasonable to assume that such a "furnace" would exist and be active close to, and above, the places where molten steel was reportedly seen.

All this leads me to believe that such a "natural furnace" giving rise to bulk amounts of molten steel that could be observed pooling or running is extremely unlikely.

It is hugely more likely that the reports of "molten steel" are simply in error.

 

[letrec]

Ok. Just throwing a few thoughts out here.

1. We have no direct evidence of there actually having been bulk amounts of molten steel. Eye witness reports are unreliable for various reasons, many no doubt are quote-mined (the speaker did not intend to claim, literally, that they saw "steel" that was actually "molten"). The physical evidence is elusive, and there is no hope today to recover any.

There are indeed no available pictures or videos. I'm reviewing the claims for molten steel based on truther compilations, I'll post something when I'm done (it's too nice outside to finish that today.) So far it doesn't look good for the molten steel hypothesis.

So far the only possibly significant witness report I've seen is that one supposed quote & video segment from Leslie Robertson where he supposedly talks of "rivers of molten steel". Apparently he denied ever saying that. Maybe it's a truther fabrication. If not then it could be credible since he is the WTC structural engineer and when he says steel one could assume that he means it (although this could be debated).

2. Such coke-fired furnaces depend on a conflation of several circumstances to actually be able to melt steel:
a) Some amount of a suitable fuel. Coke will do, but doing it with wood, paper, a number of other of the more plentiful hydrocarbons found in office towers is going to be much more difficult, if at all possible. There is a reason why the iron age started some 2,000 yeaes after the bronze age: producing the required temperatures is difficult technologxy. Charcoal will do, though.

What about gasoline or diesel? These were certainly present in the basement levels.

b) A sufficient concentration of said fuek. If you have 10% fuels mixed with 90% inert debris, chances are your kiln fire won't burn well enough to get really hot

Could vehicle fuel mixed with paper or wood do the job?

c) A sufficient supply of oxygen, which requires a brisk flow of air through the furnace chamber.

I can imagine drafts in the WTC basement due to shafts etc. After all, there were underground fires, so there was some oxygen coming in.

d) An amount of iron in suitable proportion to the fuel and airflow

There was steel in all kinds of sizes and shapes so this would be the least problem for the molten steel hypothesis.

e) A stable casing that encloses the heat while not suffocating the fire

I think that's the most problematic point. Even if we assume that a furnace is accidentally formed, it seems unlikely that it would remain stable long enough to continuously produce quantities of molten steel large enough to form "little rivers."

f) And finally a path for the molten metal to escape such that it can be seen by the eyewitnesses.

That could be explained by excavation work puncturing a pocket of molten steel.

3. Remember that molten steel is a liquid which, like water, tries to run down where gravity pulls it, seeping down in the debris. It would thus take, as an additional requirement, that the resulting molten steel drips on some "water-proof" surface where it can pool, perhaps flow. Any contact with any such surface will instantly cool the melt, of course. It therefore seems reasonable to assume that such a "furnace" would exist and be active close to, and above, the places where molten steel was reportedly seen.

All this leads me to believe that such a "natural furnace" giving rise to bulk amounts of molten steel that could be observed pooling or running is extremely unlikely.

Agreed, but I'm still interested in a quantitative argument.

It is hugely more likely that the reports of "molten steel" are simply in error.

The evidence for molten steel does not meet any kind of threshold, and the postulated steel melting mechanisms are implausible at best.

 

[Jazzy]

Of course you'll never get to concentrate the heat this tightly - thermodynamics is your enemy every way you look.

But one CAN concentrate the kinetic energy tightly.

Newton's Cradle does it every time. Turn it on its side, remember beams and columns aren't spherical, and envisage a mostly one-way and semi-efficient process, where most/half of the energy arriving at the top leaves at the bottom (to make heat - coherent kinetic energy becoming incoherent).

Oh, and steel demonstrates its propensity to do this every time it is struck. Clang.

Thanks, @letrec, for running with the ball. Those figures came rushing back. AE911T initiated that idea, realised it worked against them (after having started with a very stupid preconception or two) - and buried it.

 

[Mick West]

Newton's Cradle does it every time. Turn it on its side, remember beams and columns aren't spherical

So if a Newtons Cradle requires spheres, how can you apply the same mechanism to a chaotic pile of non-spheres?

 

[Jazzy]

So if a Newtons Cradle requires spheres, how can you apply the same mechanism to a chaotic pile of non-spheres?

Not too difficult. Any blow is predominantly downward by the time an item has fallen six hundred feet. The kinetic transfer will then take place predominantly downward.
It cannot NOT take place. The other wreckage is significantly (three times) less massive than the steel items, and doesn't participate to any great extent.
It's a Newton's Cradle. Just less efficient, with half a million tons to make transactions with.

 

[Mick West]

Maybe instead of the one-dimensional analogy of Newton's Cradle, a less constrained 2D example like pool balls might be better?

Energy is diffused in all directions, even with just a few balls.

Of course some energy is going to find its way to the bottom of the pile with each impact. But very little, and when it gets there, then there is no reason for the energy to stop at the bottom. If it were really like a Newton's cradle, then the energy would just bound right back up to the top, and a girder would fly off the top off the pile.

You can try this with a Newtons Cradle, or a simulation. Just put the last ball against some rock.

 

[Jazzy]

Maybe instead of the one-dimensional analogy of Newton's Cradle, a less constrained 2D example like pool balls might be better? Energy is diffused in all directions, even with just a few balls.
Of course some energy is going to find its way to the bottom of the pile with each impact. But very little, and when it gets there, then there is no reason for the energy to stop at the bottom. If it were really like a Newton's cradle, then the energy would just bound right back up to the top, and a girder would fly off the top off the pile.
You can try this with a Newtons Cradle, or a simulation. Just put the last ball against some rock.

Three things wrong with your argument, but I liked the pretty pictures...
1) The wreckage fragments were NOT spherical, so didn't have such a wide range of possible contact points or trajectories. So the predominant direction would be DOWN.
2) The wreckage wasn't a PILE of spheres either, and would have resisted/diverted upward transmission. It would have dealt differently with forces transferred in an upward direction.
3) Nor was the contact face an unyielding surface. It deflected downward, and returned the energy as best it could at a very much lower speed.
Kinetic energy is a function of the square of the speed, and the wreckage pile acted like a diode to the KE input. There is some analogy to be found in the way the Earth returns solar illumination at lower frequencies, and the atmosphere acts in the manner of a diode there, too, retaining heat.
I know you have always resisted this idea. You shouldn't. It's basic energetics.

 

[Mick West]

I know you have always resisted this idea. You shouldn't. It's basic energetics.

Perhaps then you could show an example of the "heating the bottom of the pile" elsewhere in reality? Or even in some contrived example?

 

[Jazzy]

Perhaps then you could show an example of the "heating the bottom of the pile" elsewhere in reality? Or even in some contrived example?

Not really, because it is a scale effect which wouldn't be noticeable at the cube root, so-to-speak, of a model. There would be more ways to lose energy more quickly.
More to the point, that is where the remaining kinetic energy HAD to go, otherwise the tower would have bounced up again. And all the relevant reactants were insulated. As I said before, it's the way the kinetic energy (an energy which cannot ever be lost) transforms from a coherent state (an object in motion) to an incoherent state (motionless heated object). It's just that in this case the "object" had borrowed the kinetic energy from above, and by heating and deforming, was never to pass it on.
Dampers do the same job on a car, and as they do so, they get hot.
When hot forging large steel billets with a high energy press, the billets gain as much heat from the forging process as they lose by radiation.
That's all I've got.
P.S. It isn't possible to melt steel by forging pressures, because it will have become too plastic to accept the energy input. The approach to melt will be asymptotic, never to be reached. This, of course, wouldn't apply if the "iron" was some meteorite doing five miles per second. LOL.

 

[Mick West]

More to the point, that is where the kinetic energy HAD to go, otherwise the tower would have bounced up again.

The only way that makes any kind of sense is if the ground was heating up, and not the steel.

Consider, you are positing the KE travels down to the ground through a series of contacts, via multiple pathways. This is problematic in itself, ignoring concrete, smaller metal objects, rotation and bending. This is not a pile of rigid objects in solid contact with each other.

but leave that for now.

For this to work, the effect has to be elastic, meaning the objects (the beams) on the way down return to their original form after "passing on" the KE.

Now the last layer of beams is on the ground. According to your theory, then some of the KE stops at this point, causing the bottom steel to heat up (correct me if I misinterpret).

Impact will only make things heat up via internal friction - i.e. an inelastic collision that causes the object to permanently deform. So why would the bottom beam deform, but the beam above it not deform?

If the steel beam at the bottom heats up because of inelastic collision, then why would the beam above it (which is essentially part of the same object) not also heat up?

The only reason there would be heat is if the bottom of the pile is being driven into the ground and the deformation of the ground is what is being converted into heat. i.e. for the bottom of a pile to heat up, it needs to be made of a material that is less elastic than that the material above it. And then only that will heat up.

 

[Oystein]

...
So far the only possibly significant witness report I've seen is that one supposed quote & video segment from Leslie Robertson where he supposedly talks of "rivers of molten steel". Apparently he denied ever saying that. Maybe it's a truther fabrication. If not then it could be credible since he is the WTC structural engineer and when he says steel one could assume that he means it (although this could be debated).

I remember having seen a video of Robertson making a presentation where indeed he relays this "molten steel in the basement" lore (I don't think he spoke of "rivers", but I can easily be mistaken). If I recall correctly, he attributed this to workers telling him they saw molten steel. So if I am right, this is a) a second-hand account, and b) it is not clear whether Robertson meant to convince the audience that "molten steel", literally, is what they saw, or just a dramatic description of the circumstances in which they worked.
This would then fall in the broad category "eyewitnesses are not reliable". You can usually not identify the metal species of a melt by eyesight alone (and even the properties "metal" and "molten" can easily be in doubt).

What about gasoline or diesel? These were certainly present in the basement levels. Could vehicle fuel mixed with paper or wood do the job?

Correct. Problem is to keep a suitable amount of fuel in the chamber. I guess there are reasons why metallurgists from antiquity till today almost always use solid fuels to smelter and melt iron. These liquids vaporize at low temperatures, making them even more difficult to contain. Fuel vapors explode much more easily than charcoal or coke especially when mixed with a suitable amount of oxygen/air.

Bottom line is: I don't know, but diesel and gasoline pose additional problems.

I basically agree with your other points, so no need to quote.
Can't help you much to quantify the odds.

 

[Oystein]

...
For this to work, the effect has to be elastic, meaning the objects (the beams) on the way down return to their original form after "passing on" the KE.
...

Yes, I think this is key!

The only way that I see to concentrate the potential energy of the [steel + other, much less elastic stuff] structure on a small amount of the total mass by way of falling if the same column passes many repeated blows (falling mass impacting said column) elastically to its foundation, which, if inelastic, swallows the energy; THEN the column has to bounce back elastically to about original shape so it can pass on ther next hammer blow.
Trouble is the actuall predominant collapse mechanism of the twin towers: Most of the falling mass bypassed the columns. What certainly did not happen to any significant degree was column impacting column. Most of the mass impacted floors and cross-beams, much of the rest fell outside of the perimeter. Impacted floors and beams could only pass a small proportion to the columns before beam/joist-to-column connections failed. Thus, only a small proportion of the total potential energy could have propagated elastically down to the foundations.
And then, as Mick points out, much of that energy would go into the ground, not the steel.

And then, Jazzy, would the softening of the steel make it swallow less and less energy the closer it gets to melting? I am not sure I understand why, but ... ok. Won't happen anyway ^^

 

[letrec]

Thinking about this Newton's cradle business, I thought of the following model that may possibly produce molten steel.

Remember the "spire" that stood up? (You know, the one that was being dustified by directed energy weapons from space...)

OK now imagine the spire just before collapse. It is attached to n floors below the impact region (for example n=80). It ends at the foundation of the tower, in concrete or something.

Now when the top segment falls, it collides with the horizontal structure (sorry my structural vocabulary is limited) around the spire at each one of the n remaining floors, pulling the spire downwards then releasing it.

The spire transmits that downwards impulse from each of the n collisions between the top segment and the corresponding floor down to the bottom.

I'm not sure what law the speed of the falling segment follows. I think the speed must have been increasing. It can be assumed that the mass was linearly increasing with each added floor.

Dynamic load on a spring is proportional to the square root of the mass times the speed of the falling section. Therefore the dynamic load increased at each collision.

Starting from the i-th collision, the load of the impulses exceeds the yield strength of some portion of the spire, causing plastic deformation. For lack of a better idea, I'll assume that this happens at the bottom of the spire, at the foundation.

From that point, each impact causes extra plastic deformation and thus extra heat in that plasticized segment.

The plasticized segment absorbs a good chunk of the impact energy at each floor, protecting the remaining upper portion of the spire, which remains elastic.

It ends up melting, but is now surrounded by debris and dust, which acts as thermal insulation, and stays in a molten state for a few weeks (see previous
analysis.)

Note that I don't have a background in mechanical engineering, so I have to do some reading and thinking before I can provide some reasonable numbers.

If it's easy for anyone to provide numbers, please do.

 

[Mick West]

Dynamic load on a spring is proportional to the square root of the mass times the speed of the falling section. Therefore the dynamic load increased at each collision.

Starting from the i-th collision, the load of the impulses exceeds the yield strength of some portion of the spire, causing plastic deformation. For lack of a better idea, I'll assume that this happens at the bottom of the spire, at the foundation.

The load applied to the core is same on each collision, it's the resistance of the floor supports, and is unrelated to the weight of the falling mass (assuming it's enough to break the supports).

Since the core columns are vastly strong than the floor support, there's nothing to suggest you'd get plastic deformation. Nor is there any mechanism by which this would only happen at the bottom - in fact it's more likely to happen at the top.

You are verging into the pointless here. Vague theories to explain something that did almost certainly not happen.

 

[letrec]

The load applied to the core is same on each collision, it's the resistance of the floor supports, and is unrelated to the weight of the falling mass (assuming it's enough to break the supports).

That's a good point. The dynamic load increases but each floor can transfer only a limited quantity.

But while there is no reason for the resistance of the floor supports to increase from top to bottom, the horizontal supports of the core itself are being broken; I don't know if these get thicker.

(Reordering your response.)

Nor is there any mechanism by which this would only happen at the bottom - in fact it's more likely to happen at the top.

There is, the height at which each pressure pulse is applied decreases with each floor, so the lower a segment is, the more pressure pulses it sees.

The cross-section of the columns also increases, but rubble also accumulates at the bottom, providing thermal insulation.

Since the core columns are vastly stronger than the floor support, there's nothing to suggest you'd get plastic deformation.

I'm not sure about that.

The bottommost segment sees a series of pressure pulses. Even if each pulse stays in the elastic region, there will be some temperature increase due to non-idealities, and a corresponding decrease in yield strength. How do we know if we can reach a point where molten is produced without running numbers?

You are verging into the pointless here. Vague theories to explain something that did almost certainly not happen.

I think the theory is getting more precise, and it's useful to have some plausible theory that to explain any molten steel that a truther insists exists. Also it's Sunday Science entertainment.

 

[MikeC]

The load applied to the core is same on each collision, it's the resistance of the floor supports, and is unrelated to the weight of the falling mass (assuming it's enough to break the supports).

The load is the same - but if I recall my mechanical engineering roughly accurately (it's up for discussion!) the time taken for the limit to be reached will decrease as the falling mass increases - so more power* is being applied on each floor in succession, so more heat generated?

Power = integral of work - the rate work is done - the more work done in a given time, or the shorter time for a given amount of work means more power means more heat.

 

[Jazzy]

The only way that makes any kind of sense is if the ground was heating up, and not the steel.

No.

Consider, you are positing the KE travels down to the ground through a series of contacts, via multiple pathways. This is problematic in itself, ignoring concrete, smaller metal objects, rotation and bending. This is not a pile of rigid objects in solid contact with each other.

It IS at the point where any steel/steel kinetic transaction takes place. That is the point.

For this to work, the effect has to be elastic, meaning the objects (the beams) on the way down return to their original form after "passing on" the KE.

Yes.

Now the last layer of beams is on the ground. According to your theory, then some of the KE stops at this point, causing the bottom steel to heat up (correct me if I misinterpret).

Yes. WHEN the steel deforms.

Impact will only make things heat up via internal friction - i.e. an inelastic collision that causes the object to permanently deform. So why would the bottom beam deform, but the beam above it not deform?

Because the beam above it has just handed its energy down. If that energy had been too much for the beam above it would have deformed and robbed some of that energy. Any "spare" would have been handed down.

If the steel beam at the bottom heats up because of inelastic collision, then why would the beam above it (which is essentially part of the same object) not also heat up?

See above.

The only reason there would be heat is if the bottom of the pile is being driven into the ground and the deformation of the ground is what is being converted into heat. i.e. for the bottom of a pile to heat up, it needs to be made of a material that is less elastic than that the material above it. And then only that will heat up.

I am not arguing that deformation of the ground didn't take place, and that the ground wasn't heated.

Deforming steel IS "less elastic" than the non-deforming steel above it. It is handling more energy than it too, er, by definition.

The "ground" was arguably MORE elastic than the steel.

For a man with some magnificent crush videos under his belt...

 

[Jazzy]

Impacted floors and beams could only pass a small proportion to the columns before beam/joist-to-column connections failed. Thus, only a small proportion of the total potential energy could have propagated elastically down to the foundations.

I heartily disagree.

The floors, compacted, had a free ride to the basement. They weren't a "small proportion" of the potential energy at all.

The floors carried THE LOAD. The steelwork of the columns amounted to only 40% of the total potential energy.

And then, Jazzy, would the softening of the steel make it swallow less and less energy the closer it gets to melting? I am not sure I understand why, but ... ok. Won't happen anyway ^^

That's right. It's hard to bend a liquid.

 

[Jazzy]

the horizontal supports of the core itself are being broken; I don't know if these get thicker.

They don't have to. All the floors are similar.

 

[Mick West]

The "ground" was arguably MORE elastic than the steel.

So why would the KE impulse stop at the bottom piece of steel? Why would it not travel back up into the pile?

 

[MikeC]

My understanding is that the KE will "bounce around" as shock waves between changes in phase until it all dissipates as heat.

 

[Jazzy]

So why would the KE impulse stop at the bottom piece of steel? Why would it not travel back up into the pile?

Because KE is STILL arriving from above, and the bottom piece is STILL likely to be the most stressed item around, AND WILL DEFORM, absorbing the most KE THERE, in THAT position. And there's your HEAT.

My understanding is that the KE will "bounce around" as shock waves between changes in phase until it all dissipates as heat.

Yes it will. Steel will be deformed wherever it meets forces strong enough to deform it. But the majority of these forces occur against the ground. So that's where most of the heat occurs (or where much of the kinetic energy ends up).
While the KE whistles around (at 25,000 f.p.s.) it cannot heat anything, but when it meets steel it CAN deform, it does so and changes its state to incoherent kinetic energy, or HEAT.
The clang that steel makes when it is struck is witness to the KE input of say, a hammer. Buried and damped by rubble, the remaining KE MUST result in vibration and sound, to be absorbed by the rubble and causing it to WARM slightly.

The violence of these processes is familiar to anyone with intensive military training.

I still find it difficult to comprehend a working Newton's Cradle. Personally I prefer Euler. Long live Private Eye...

 

[Oystein]

I heartily disagree.

The floors, compacted, had a free ride to the basement. They weren't a "small proportion" of the potential energy at all.

The floors carried THE LOAD. The steelwork of the columns amounted to only 40% of the total potential energy.

The scenario I tried to describe was an attempt to concentrate the potential energy of mass spread out over a larger area and volume onto a very small area and volume, namely the base of a column, through repeated kinetic impacts on that column, transfering energy from the floors onto said columns.
So you agree this did not happen enough to heat the columns foot and/or foundation very much?

The floors then, you claim there would be wonderfully elastic collisions when, say, floor 77 drops onto the pile of floors 1-76? Or perhaps more precisely when, say, floor 1 impacts the ground with floors 2-110 pushing it down?
I don't believe a word of it. Lots and lots of concrete crushing eats much of that energy, even while collapse is under way. The rubble block may be severely compacted, but it is MUCH less elastic than a steel column!
Plus, you hit the ground over the full area of the towers and more.

Try to build a Newton's cradle witj layers of reinforced light-weight concrete. Compare with a regular steel cradle. Report what you find.

That's right. It's hard to bend a liquid.

Ah yes, no problem once its liquid. I was wondering if or why steel would swallow less energy through bending when it gets hotter and loses strength - bit before it goes liquid. It appears to me that hot steel bends more easily than cool steel (is less elastic).

 

[Mick West]

Because KE is STILL arriving from above, and the bottom piece is STILL likely to be the most stressed item around, AND WILL DEFORM, absorbing the most KE THERE, in THAT position. And there's your HEAT.

Surely the KE would be reflected before the next collision arrives? If it is actually like Newton's cradle, then it moved across the steel at the speed of sound in steel, about 5900 m/s

Perhaps you could describe what you think is happening to this bottom piece at the actual real world molecular level, rather than in abstractions?

 

[MikeC]

I don't think we are being mathematically precise enough to determine the exact travel of shockwaves and their heating effects.......IMO it is sufficient to generalise that the KE mostly gets turned into heat by the time the movement has ceased.

 

[Mick West]

I don't think we are being mathematically precise enough to determine the exact travel of shockwaves and their heating effects.......IMO it is sufficient to generalise that the KE mostly gets turned into heat by the time the movement has ceased.

Sufficient for what? We know it turns into heat, the question is where, and is it possible for that KE to be concentrated enough to make steel hot enough to melt, or at least start a fire.

 

[MikeC]

Sufficient to know anything precise - such as whether a shockwave is reflected before "the next collision arrives", or whether there is enough heat generated to melt steel.

Such calculations require accurate knowledge of starting conditions and subsequent events, and I suspect would be a challenge for a team of professional engineers let alone a bunch of amateurs