No, that's hand-waving Mr. Mackey. Most of the people here accept hand waving from "knowledgable experts". I don't.
The majority of the inital momentum (vertical approach angle = 10.6 degrees) was lateral the rest was downward so only deflections could have caused ceiling impacts on the south side.
- Debris with a mean lateral trajectory were displaced downward by gravity by more than the depth of the truss assembly.
- This also is true for debris with a mean trajectory that was even slightly downward.
- Debris that was not deflected even with a mean upward trajectory could not impact the trusses at more than a glancing blow (> 60% to perpendicular). Even at the laboratory energy levels (equivalent to debris approaching the core), an impact at 60 degrees did not remove fireproofing. Also, most of this debris would be stopped by the core floor beams.
All that is left is deflected debris or debris that suddenly got lift 18' from the south edge of the core. So let's look at deflected debris.
Deflected debris would have to bounce upward at > 30% measured relative to the floor less than 18' from the south edge of the core otherwise it hits the core floor beams or has an impact angle > 60% from perpendicular to the truss. The debris has three cases for deflection. Impacting the floor, impacting core or office contents, or a combination of these.
- Deflection from the floor: Assuming an elastic collision (in favor of truss impact), the debris would need to impact the floor at at least 30% within 18' of the south edge of the core. The only way this can happen is if the debris is previously deflected downward at least 30%. Now in order for that to happen the debris must be deflected previously upward (again at least 30%). If this deflection is by core or office contents we are in case three. If one continues along this line we have the debris component deflecting no less than 6 times! Of course the rebounds are not anywhere near elastic so this can't even happen.
- Deflection by core components or office components: Here we have the problem that impact with any vertical surface can not give an upward deflection. Horizontal surfaces have the ability to deflect upward and downward for that matter. The question arises, how much of the impact area is of a horizontal nature? I can think of desk tops and chairs and anything else with a "top" such as a file cabinet. Nonetheless, the vast majority of the impact area is vertical (i.e. columns, core floor beams, partitions, pipes, ducts, elevator cables and tracks, sides of desks, office dividers, etc.). From viewing the architectural drawing it is easy to conclude that there are very few "tops" within the core. Of the small portion of material impacting a "top" a little less than half will be deflected upward. Then there is the question, what is the nature of these collisions? NIST has stated that the dominant effect in these collisions is momentum transfer which further reduces the momentum of the impacting debris. Keep in mind that a desktop deflection, in this case, can only occur on the south side outside the core. On the south side of the core the energy has already been reduced to 3% of that when approaching the core. This energy is further reduced by the deflection impact.
- Combination of floor impact and content impacts: This case is essentially the same as the content only impact except there is further energy loss due to a prior floor impact.
Mr. Mackey is conveniently ignoring the energy requirements based on laboratory tests. He is conveniently ignoring that, even at the laboratory energy levels, an impact at 60 degrees did not remove fireproofing. He is conveniently ignoring that at 70 mph fireproofing was not damaged in tests. He is conveniently ignoring that the average debris velocity was 43.4 mph upon leaving the core. He is conveniently ignoring that the truss system on the south side was mostly blocked from lateral trajectories by core beams at each column row. He is conveniently ignoring that half the mass in the core was left out of the analysis. He is conveniently ignoring the probability of any debris actually impacting the floor trusses on the south side.
Mr. Mackey will probably bring up rotational aspects, lift, and the Froude number. To which I will reply, poppy-cock. NIST has given no indication how these were handled.
Mr. Mackey will probably again bring up that no one could explain the flight 93 crater to my satisfaction. To which I will reply that his assertions regarding live-loads in the towers were easily contradicted by numerous sources including NIST. Not that either of these issues has anything to do with this thread. The point being that no one is infallible.
Not your best work Mr. Mackey!
