Wednesday, July 26, 2006

9/11 probe ignored 'free fall' issue

All three World Trade Center buildings fell at near the rate of free fall, which is the maximum that can occur without resistance. In other words, both structural resistance and air resistance were negligible.

It is well known that buidlings felled by controlled demolition tend to fall near the free-fall rate because lower supports are blown out and so there is little structural resistance. The rates of fall is something that set off alarm bells in some quarters.

Considering the enormous potential energy in the top sections of the twin towers, a fall rate near free fall might be plausible. In fact, I once did a back-of-the-envelope differential equation, whereby I estimated the structural resistance based on steel-to-air ratio and found that the results, for both buildings, were near the free fall rate. But, my calculation was no substitute for a computer model.

BUT, the National Institutes of Standards and Technology simply ignored the issue. The NIST computer models only reached the point where "global collapse" was triggered. The scientists ran no computer model of the actual fall, meaning that the collapse rate was not faced. Yet, the government knew that the rate-of-fall question was high in the minds of a number of experts.

And, they published no other data or expert opinion concerning the rates of fall.

In addition, the NIST's report on the twin towers went to press without a report on the day's seismic activity, which was squelched without explanation. (See my trade center links.)

NIST officials have tried to cope with WTC7's free-fall puzzle by supposing that the building collapse began at a low floor, but that probe is still under way. The contractor designated to generate a computer model of the WTC7 collapse, based solely on NIST input values, does not have authority to do a simulation that includes rate of fall.

Now it is possible that the simulation of the lead-up to collapse could not include the events of collapse. But there is no word as to why separate simulations covering the actual
collapses weren't feasible. Nor is there any opinion presented as to the probabilities of such rates.

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