The 9/11 Forum

femr2 · by **femr2** on Fri Jun 05, 2009 3:41 am

Various estimates have been proposed for the "Collapse Time" of WTC 1 & 2.

I have seen little discussion of what the number actually means, and what it actually refers to.

Does it mean:

a) The time the first descending debris within the footprint reaches ground level ?
b) The time the last descending debris within the footprint reaches ground level ?
c) The time an obscured visualised 'crushing front' reaches ground level ?
d) Any of the above with ground level replaced by the level of the top of the rubble 'pile' ?
e) The time the top of the dense dust cloud reaches ground level ?
f) Something else... ?

May I suggest that all definitions can be valid for their own purposes, that the result is a minimum/maximum with known meaning of both, and that any agreed minimum should be treated as a serious point of focus when deciding whether each descent was 'too quick' ?

newton · by **newton** on Fri Jun 05, 2009 6:48 pm

i know what i would LIKE it to mean.
i would like it to mean when the uppermost floor hits the ground.
for science's sake, though, i would say only the visible collapse should be analysed in great detail. once the dust cloud obscures the crushing front, there is no telling what happened exactly.
witness the "spire"in the second collapse. there was complete arrest of that phase of the collapse, and then the spire "magically" went into freefall.
for deciding whether things fell "too fast", i would say that events like the penthouse sinking, or the core in the big towers going first, do not "count" too much concerning debris which is supposedly falling and crushing itself.
granted, if the cores fail first, it allows the perimeter to fall faster, but i still think the perimeters fell too quickly even for a "normal" demo. i mean, the landmark took over twenty seconds for the top to hit the ground after the first blast at the bast, and that tower was like one quarter the size of "nelson" or "david", three fifths the size of wtc7.

femr2 · by **femr2** on Fri Jun 05, 2009 7:19 pm

newton wrote:i would like it to mean when the uppermost floor hits the ground.

Are you sure ? To me that would be the maximum time. What about the minimum ?

http://femr2.ucoz.com/photo/3-0-55

The photo shows that ejecta from the tower is level with the lowest free-falling debris at the point that the descending debris is level with the first mechanical floor region.

I'll post an extrapolation of the tower ejecta timings when I've finished putting it together, but do you not think that it would be 'very informative' to determine the time that the 'wave of destruction' reached ground level ?

psikeyhackr · by **psikeyhackr** on Sat Jun 06, 2009 6:17 am

It would be nice to have a graph of the percentage of material hitting the ground over time so it could taper down for hours or days with all of the stuff that was dustified. But since there doesn't seem to be any dispute that the collapses registered seismically and that would have to be caused bay a large percentage of the solid mass I think that makes the most sense to go with.

But I usually just say less than 18 seconds because there are so many people that want to argue about the time. Since I don't think the buildings could possibly have collapsed without energy sources other than planes and fire the precision of the time is irrelevant to me.

psik

Major_Tom · by **Major_Tom** on Sat Jun 06, 2009 3:48 pm

femr2, from where did you get that picture 2 posts ago?

Good question about collapse time. I believe many people view measurable WTC1 collapse progression motion only by using:

1) The first data from the initial descent of the "upper block".

2) Seismic data

But you introduce a third way, by watching the floor by floor ejections progress down the building when they are visible.

On some sides we see the initial ejections leaving individual floors at definite times progressing downward. Our view becomes blocked when the large objects falling at freefall leave a dust trail (smoke screen) which covers these floor by floor ejections.

(Lastly, along at least 6 of the 8 sides (WTC1 W, N, E and WTC2 S, W, N) we see large perimeter sheets emerging from the obscuring dust. These sheets are most interesting to record as they appear to be huge, interconnected, most always unbuckled, identifiable objects which pop off the building during the earliest moments of collapse initiation and go into freefall and leading all other objects in their descent.)

femr2, I haven't seen anyone including the data on the downward progression of visible ejections when matching theory to observables.

Thank the good lord that you notice this can be very useful data and is silly to ignore when discussing collapse progression theories and data plots.

There are good views floor by floor ejecta along WTC1 NW corner and W face,

Excellent views of WTC2 E face and the crazy way in which the S and N faces eject debris floor by floor along their east sides far, far before their west sides.

I'd love to see some introductory study on these ejecta progressions (which are very visible) compared to theory.

T_Szamboti · by **T_Szamboti** on Sat Jun 06, 2009 4:28 pm

Major_Tom wrote:femr2, from where did you get that picture 2 posts ago?

Good question about collapse time. I believe many people view measurable WTC1 collapse progression motion only by using:

1) The first data from the initial descent of the "upper block".

2) Seismic data

But you introduce a third way, by watching the floor by floor ejections progress down the building when they are visible.

On some sides we see the initial ejections leaving individual floors at definite times progressing downward. Our view becomes blocked when the large objects falling at freefall leave a dust trail (smoke screen) which covers these floor by floor ejections.

(Lastly, along at least 6 of the 8 sides (WTC1 W, N, E and WTC2 S, W, N) we see large perimeter sheets emerging from the obscuring dust. These sheets are most interesting to record as they appear to be huge, interconnected, most always unbuckled, identifiable objects which pop off the building during the earliest moments of collapse initiation and go into freefall and leading all other objects in their descent.)

femr2, I haven't seen anyone including the data on the downward progression of visible ejections when matching theory to observables.

Thank the good lord that you notice this can be very useful data and is silly to ignore when discussing collapse progression theories and data plots.

There are good views floor by floor ejecta along WTC1 NW corner and W face,

Excellent views of WTC2 E face and the crazy way in which the S and N faces eject debris floor by floor along their east sides far, far before their west sides.

I'd love to see some introductory study on these ejecta progressions (which are very visible) compared to theory.

Theory without observational confirmation is a waste. Observation on it's own does have some merit.

However, when trying to scientifically prove something, the indisputable combination is theory which matches and explains the observation, allowing for repeatability.

femr2 · by **femr2** on Sat Jun 06, 2009 4:38 pm

Major_Tom wrote:femr2, from where did you get that picture 2 posts ago?

YouTube
South Tower
North Tower
Annotated

Good question about collapse time. I believe many people view measurable WTC1 collapse progression motion only by using:

1) The first data from the initial descent of the "upper block".
2) Seismic data

I'm hoping we can all compile all forms of measurement together, to try and come to more analytical conclusions. I've seen good focussed use of math/physics and extrapolation on this forum, and think applying the member skillset to the 'timing' factor is a good call.

One element of seismic data that is overlooked IMO is that much of the descent is not 'ground linked' and so will not produce a direct seismic signature, but I imagine I'll need to go into more detail to get the point across. In contrast, the lack of ground linkage also highlights other issues with the seismic data, such as early peaks.

But you introduce a third way, by watching the floor by floor ejections progress down the building when they are visible.

This video is quite useful on that aspect:
Linear Rate Wave of Destruction

On some sides we see the initial ejections leaving individual floors at definite times progressing downward. Our view becomes blocked when the large objects falling at freefall leave a dust trail (smoke screen) which covers these floor by floor ejections.

From studies here it seems acceptable to apply extrapolation techniques (and curve fitting), so I think that taking measurements from observable processes and extrapolating beyond what is 'visible' will also be met with acceptance, which is a good thing.

(Lastly, along at least 6 of the 8 sides (WTC1 W, N, E and WTC2 S, W, N) we see large perimeter sheets emerging from the obscuring dust. These sheets are most interesting to record as they appear to be huge, interconnected, most always unbuckled, identifiable objects which pop off the building during the earliest moments of collapse initiation and go into freefall and leading all other objects in their descent.)

From your studies into the peeling behaviour, do you think you could produce data specifying the timing of each floor external panel detachment ? (Including extrapolation for obscured portions)

femr2, I haven't seen anyone including the data on the downward progression of visible ejections when matching theory to observables.
Thank the good lord that you notice this can be very useful data and is silly to ignore when discussing collapse progression theories and data plots.
There are good views floor by floor ejecta along WTC1 NW corner and W face,
Excellent views of WTC2 E face and the crazy way in which the S and N faces eject debris floor by floor along their east sides far, far before their west sides.
I'd love to see some introductory study on these ejecta progressions (which are very visible) compared to theory.

I'm currently in progress synchronising a number of different views of each descent, in order to be able to extract the data from as many points along the descent timeline as possible...no one video includes all of the available data, so synchronising them will help enourmously. (Sorting out the various timebase creep between video's is taking time to sort out)

I think I have most/all of the good quality video of each descent, but I'm very open to suggestion...

newton · by **newton** on Sat Jun 06, 2009 5:20 pm

faster than freefall is too fast for the inside of the tower. i brought this up in 2006...

http://www.abovetopsecret.com/forum/thread201098/pg1

and was going to use the exact same video for some more frame extraction, but lost track of the video until i found your version, femr2:

http://www.abovetopsecret.com/forum/single/6321064.html

that's what i mean about "science" (heisenberg screwed it up for everyone, lol). extrapolation is good for theories, but only direct measurements are 'rock solid'. i think that one video is proof enough that the towers were blown. the freefalling debris (including the huge, still-connected spandrel trees that popped off at collapse initiation; very massive and dense and therefore not even subject to much air resistance) which has fallen several tens of stories is outpaced by the ejections from inside the tower. that means the tower not only offered less resistance than air, but also that it had more gravity force than outside the tower. people who worked in the towers must have had sore feet from all the extra weight they had to deal with daily. i'm guessing there must have been AT LEAST 2 or 3 G's in there for the insides to be able to crush themselves faster than gravity can push something earthward through air.

is it possible to model that? have different gravity inside the tower for a little ad absurdum illustration?

has anyone guesstimated what the percentage of mass is represented by the external steel columns? i think the mass shedding arguments might be a little shy at 20%, considering steel is the densest building material used, and ALL of the perimeter steel fell outside the footprint. it's clear that there's a lot of concrete going (exploding) over the edge, too.

femr2 · by **femr2** on Sat Jun 06, 2009 5:51 pm

newton wrote:faster than freefall is too fast for the inside of the tower. i brought this up in 2006...
http://www.abovetopsecret.com/forum/thread201098/pg1

Indeed, though it should be made as clear as possible that the tower ejecta traverses essentially at a linear rate, so it's only 'ahead' of free-fall for 2/3 of the tower height, until the free-falling debris catches up and subsequently passes it. I noticed this image being used in that thread:

Odd that the poster did not identify the very clear and significant ejecta from the right hand side of the tower, nor far behind the free-falling debris.
I'll be gathering photographic evidence of the ejecta also, so if anyone has specific images...

http://www.abovetopsecret.com/forum/single/6321064.html
i think that one video is proof enough that the towers were blown.

I think it best to gather lots of data, then present all the conclusions in one go, but the question is very valid: How can destruction within the tower initially outpace free-falling debris, and given that the rate of ejecta progression is linear, how long does it take to reach the ground ? I suggest the question is answered a little later.

is it possible to model that? have different gravity inside the tower for a little ad absurdum illustration?

Of course. If you grab my spreadsheet, simply change the gravity parameter. (All within the limits of a crush-down model, but...)

has anyone guesstimated what the percentage of mass is represented by the external steel columns?

Approximately 15%

i think the mass shedding arguments might be a little shy at 20%, considering steel is the densest building material used, and ALL of the perimeter steel fell outside the footprint. it's clear that there's a lot of concrete going (exploding) over the edge, too.

Always going to be a contested question. If there are studies of ground zero debris distribution kicking around, a link would be useful. An extimation of the mass of the dust outside the footprint would be very useful. Did Jones et al quantify the percentage of the dust that was concrete, rather than wallboard, ...?

femr2 · by **femr2** on Sun Jun 07, 2009 12:19 am

psikeyhackr wrote:It would be nice to have a graph of the percentage of material hitting the ground over time so it could taper down for hours or days with all of the stuff that was dustified.

An interesting proposition. Noted

But since there doesn't seem to be any dispute that the collapses registered seismically and that would have to be caused bay a large percentage of the solid mass I think that makes the most sense to go with.

Seismic spikes could have been caused by more than simply debris hitting the ground.

But I usually just say less than 18 seconds because there are so many people that want to argue about the time.

If more accurate timings can be determined through a combination of observational and calculated data, and the various timing each given a specific meaning, then the arguments can be settled either fully, or to a greater extent than without supporting data.

Since I don't think the buildings could possibly have collapsed without energy sources other than planes and fire the precision of the time is irrelevant to me.

Whilst there are scenarios whereby 'physics' informs us that global 'collapse' is 'possible', it is our unfortunate task, given that the discussion is still on the table 8 years later, to reduce the number of unknowns to the point whereby there is a more definitive answer which none can refute any further. I am sure that answer will prove you right, and show that the actual events were exactly as they appeared to be, incredibly well prepared and superbly executed deliberate destruction, performed by a group of people with a great understanding of exactly what they were doing.

einsteen · by **einsteen** on Mon Jun 08, 2009 12:34 pm

It's indeed a matter of definition. But I think the interesting one is is the crush-down time, in other words, when the demolition wave hits ground zero minus t0. The discrete collapse model has a lower limit (when E1=0) but also a upper limit for a complete collapse. For an arrested collapse other times are possible but not relevant for a complete crush-down. It becomes more difficult if material is ejected.

femr2 · by **femr2** on Tue Jun 09, 2009 6:31 pm

einsteen wrote:It's indeed a matter of definition. But I think the interesting one is is the crush-down time, in other words, when the demolition wave hits ground zero minus t0. The discrete collapse model has a lower limit (when E1=0) but also a upper limit for a complete collapse. For an arrested collapse other times are possible but not relevant for a complete crush-down. It becomes more difficult if material is ejected.

My intention is for all defined timing types to be determined from study of the actual events, with supplemental calculations being used to predict and extrapolate timings for portions which are obscured in photo or video evidence. Seismic data can only provide minimal additional detail IMO.

To clarify, the ejecta from the tower can be seen in video until at least the first (lower) mechanical floor region, which is far beyond the point at which the roofline becomes obscured. Calculation of a lower-bound 'collapse time' (when 'crush front' reaches the ground) can be determined with inclusion of such specific time and displacement of video and photographic evidence. Traversal rate at such a low point in the tower can then be validly extrapolated to ground based on trend behaviour of the preceeding visually confirmed points.

Generation of timing purely from models is a totally separate exercise.
I assume you are aware of my own 'crush-down' model ? It's very easy to set parameters to simulate collapse arrest. Well worth having a play around with it if you haven't already.

psikeyhackr · by **psikeyhackr** on Tue Jul 21, 2009 7:33 pm

This might be relevant:

http://www.journalof911studies.com/volu ... hShake.pdf

psik

femr2 · by **femr2** on Fri Nov 06, 2009 6:13 pm

Given recent discussion of the linear/terminal velocity ejecta mentioned earlier in this thread, does anyone have a problem with me extrapolating a descent time from the data we have on it ?

Major_Tom · by **Major_Tom** on Fri Nov 06, 2009 7:02 pm

The OOS sw portion leads all others so it is the natural choice to define collapse time.

OOS mechanics is interesting in that the frictional force should be predictable (it is just office flooring which has a very consistent pattern governed by floor type.

Mass build-up is predictable, frictional force is predictable...

Movement should be relatively smooth with the exception of special flooring.

The uneven movement of ejections seen along the OOS sw region make no sense. Accelerations and decelerations? How? DId flooring change? Did driving mass change? Then how?

I'd be very interested in seeing a descent time guessed based on sw corner ejections.

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