by David Chandler source: 9/11 Blogger Sep 26, 2011
I have uploaded to YouTube (http://www.youtube.com/watch?v=xvw0_i1rGns) an analysis of the acceleration of a projectile that races ahead of the surrounding falling debris. I had discussed this object before but due to the difficulty caused by a moving camera I had not previously measured the motion directly.
The object (apparently a perimeter wall unit) raced ahead of its neighboring debris, but its acceleration was about 1/3 of gravity. This is an indication that it was kicked downward initially by an explosion, after which the air resistance partially canceled the effect of gravity as it approached terminal velocity. As it fell, however, there was an outburst of white smoke, at which point the projectile changed directions, slightly, and accelerated downward for about a half second at 1.5 times gravity. It then fell back to continued acceleration a little under 1 g.
The acceleration of the projectile is unambiguous proof that very energetic material was applied to the wall unit. What I found particularly surprising is that the ignition of the material in an unconfined space where it was free to expand three dimensionally would provide sufficient thrust due to expanding gasses alone to cause what was probably a 4-ton wall unit to accelerate 50% faster than gravity. The fact that the unit continued to accelerate close to freefall thereafter is an indication of an ongoing thrust capable of largely canceling the effect of air resistance.