The 9/11 Forum

femr2 · by **femr2** on Thu Nov 05, 2009 9:15 am

Trippy wrote:I was under the impression that those were large pieces of debris?

Indeed some of the descending debris is enourmous (MT's sheet peeling posts are very relevant).

What I think you are *seeing* is the dust trail being blown by the wind making it *appear* that the falling debris is not going straight down, when it is...

As I said it's worth tracking some debris to make sure (new thread :wink:

), but my gut feeling is wind (almost a pun there)

femr2 · by **femr2** on Thu Nov 05, 2009 9:25 am

Heiwa wrote:According DBB (and BLGB?) ejecta shall be 20% of "crushed" materials/elements. Remaining 80% shall form a compressed, high density (5X the original density of the structure) rubble layer, B, inside the foot print of the structure that is supposed to form a 4000m² large 'crush front'.
Are there any methods to verify this when checking the ejecta velocity?

Can't think of a way to determine *crush front* surface area from ejecta velocity to be honest. Perhaps OWE or DBB have some thoughts...?

I think it's clear that there was no such 4000m² *piston* though.

femr2 · by **femr2** on Thu Nov 05, 2009 9:50 am

Have uploaded a colour levelled copy of the BBC footage for reference:

http://www.megaupload.com/?d=CVDEAAJL

http://femr2.ucoz.com/photo/6-0-225-3 (960x720px/86.9Kb)

Added annotation to the still to highlight the distance between upper and lower front.

I'd estimate around the 35m mark.

Heiwa · by **Heiwa** on Thu Nov 05, 2009 2:09 pm

It should be noted that the thickness of the alleged rubble layer inside the foot print of the structure, i.e. distance between lower/front and upper/tail ends of the 'crush front' increases by abt. 0.92 meter per floor crushed according BLGB! At end of crush down of 95 floors and 5 basement levels (original uniform (sic) density 0.2), the rubble layer is 92 meters thick (density abt. 1- with the 53 m tall top part C still on the tail) as per below figure of BLGB with colors by me. The lower/front end of the 'crush front' has reached ground at bottom of basement, while the tail of the crush front is 92 m behind!

At end of crush up (part C is destroyed) the rubble layer is 42 m with 20 m above ground (density abt 2!).
Ejecta apparently takes place both from the rubble layer and just before the front.

femr2 · by **femr2** on Thu Nov 05, 2009 4:49 pm

Heiwa wrote:Ejecta apparently takes place both from the rubble layer and just before the front.

I'm a little unclear on the purpose of your post, though I'm certainly not an advocate of the over-simplified BLGB model.

To clarify my previous post, there are two *crush fronts* highlighted. The upper being from the Northerly half of the West face and the lower being from the Southerly half of the West face.

Heiwa · by **Heiwa** on Thu Nov 05, 2009 5:25 pm

femr2 wrote:
Heiwa wrote:Ejecta apparently takes place both from the rubble layer and just before the front.

I'm a little unclear on the purpose of your post, though I'm certainly not an advocate of the over-simplified BLGB model.

To clarify my previous post, there are two *crush fronts* highlighted. The upper being from the Northerly half of the West face and the lower being from the Southerly half of the West face.

I must have misunderstood your post! I thought it was about the front and tail of one, BLGB, 'crush front' and not the fronts of two (?) separate crush fronts within the same structure, the latter I cannot grasp! Where would they meet inside the structure?
Maybe DDB or Dr. G can clarify what they mean with the BLGB crush front and this B rubble layer part?

femr2 · by **femr2** on Thu Nov 05, 2009 5:46 pm

Heiwa wrote:I thought it was about the front and tail of one, BLGB, 'crush front' and not the fronts of two (?) separate crush fronts within the same structure, the latter I cannot grasp! Where would they meet inside the structure?

Watching the referenced video carefully should help clarify:
http://www.megaupload.com/?d=CVDEAAJL

I'm not sure if they ever meet up lower in the descent (Traversal seems very similar rates), but it's quite possible IMO that the separate *crush fronts* reached ground zero at different times.

(I'd also add that there was probably more than two separate *crush fronts*, leading us into the zoning discussed by MT a short while ago)

David B. Benson · by **David B. Benson** on Thu Nov 05, 2009 6:09 pm

Trippy ---- The various ejecta give the illusion of following one another in an indward or outward path. In fact, each was ejected by a different specific impulse, so traveled further or less far horizontally. The breeze was too small to have a large effect early on.
Also, BLGB considers the resistance due to moving the air out of the structure.

Heiwa --- The 20% mass ejection is the estimate from BLGB, taken from B&V, I think. The actual value is not critical.

femr2 --- I don't see two crushing fronts. The position you mark as "lower front" is about 2 floors below the crushing front, IMO. Above that is simply the continued horizontal movement of the dirty air expelled from the structure.

femr2 · by **femr2** on Thu Nov 05, 2009 6:39 pm

David B. Benson wrote:Trippy ---- The various ejecta give the illusion of following one another in an indward or outward path. In fact, each was ejected by a different specific impulse, so traveled further or less far horizontally. The breeze was too small to have a large effect early on.
Also, BLGB considers the resistance due to moving the air out of the structure.

If the wind did not have a significant effect on the dust plume, then something else did, as it's lateral shift is very pronounced (As you would see if you viewed the previously referenced video. Perhaps I'll include an inline animation to clarify.) I'll perform tracking on some debris in relation to dust cloud movement if required.

David B. Benson wrote:Heiwa --- The 20% mass ejection is the estimate from BLGB, taken from B&V, I think. The actual value is not critical.

That makes no sense at all. Try 50% mass loss, or 75% and see what difference it makes.

David B. Benson wrote:femr2 --- I don't see two crushing fronts. The position you mark as "lower front" is about 2 floors below the crushing front, IMO. Above that is simply the continued horizontal movement of the dirty air expelled from the structure.

No, it is the *crush front* as identified by almost every other observer. Again, video is very handy. I'll yet again go to the additional effort to place video in front of you on this forum.

Major_Tom · by **Major_Tom** on Thu Nov 05, 2009 6:54 pm

OWE and all, the ejections down the NW corner west face (OOS w, sw) are not isolated events.

The thread linked shows ejections racing way ahead of freefalling perimeter pieces on the east face.

http://the911forum.freeforums.org/wtc-1-diagonal-slice-t193.html#p4057

Great thread that didn't get the attention it deserved.

Remember how the entire north east corner just "popped" away from the building, unbuckled and cut along a straight line along it's lower edge and went into freefall? (You can see it clearly in the phot about 6 posts before this one.) We can see how much farther ahead the OOS e ejections are relative to the falling corner assembly. Pretty amazing.

That piece is a good reference object to use in all videos. A talented video editor can show us how the OOS w, sw and OOS e ejections traverse the building relative to each other by using reference objects like that in both videos.

My original guess is the OOS e ejections are faster than the OOS w, sw ejection rate under discussion.

David B. Benson · by **David B. Benson** on Thu Nov 05, 2009 6:59 pm

femr2 wrote:If the wind did not have a significant effect on the dust plume, then something else did, as it's lateral shift is very pronounced.

Yes, horizontally away from the structure face. Anything orthogonal to that would be the breeze, I suppose.

That makes no sense at all.

In my context, yes it does. The ratio of zone C mass to zone A mass, less mass loss in forming zone B only changes the parameters a bit. Recall that I always produce best fit to OneWhiteEye's measurements. The B&V crush-down ODE contains to surprises, isn't stiff, etc.

No, it is the *crush front* as identified by almost every other observer.

Alas, not very thoughtful of them, is it? Read what BLGB has to say about the difficulty of locating the actual crushing front as opposed to dirty air being expelled in advance of it.

Again, video is very handy.

Misleading for this question; need to think it through (although that has been done for you in BLGB.)

I'll yet again go to the additional effort to place video in front of you on this forum.

Thank you.

As for the "upper crushing front", assuming vaf is correct then one mght expect to see the effects throughout the entire zone B. That might include addtional expulsion of dirty air and entrained materials.

femr2 · by **femr2** on Thu Nov 05, 2009 7:16 pm

Trippy wrote:Why does the debris cloud (the falling debris) look like it has a lean on it.

This video may be of interest:
http://www.youtube.com/watch?v=94cMcFjzKhU

Heiwa · by **Heiwa** on Thu Nov 05, 2009 7:45 pm

David B. Benson wrote:Heiwa --- The 20% mass ejection is the estimate from BLGB, taken from B&V, I think. The actual value is not critical.

It is! 0% ejection means that nothing of A or C or B is ejected = a clean hammer C (very weak) hitting nail A (a little stronger) by gravity only with/w/o any rubble B inside footprint being produced situation = your funny theory.

Where in BLGB do you consider 20% mass ejection? What can produce it?

And how can little C produce both rubble B and x% ejection? Yours or Bazant's diff. equations do not consider them.

David B. Benson · by **David B. Benson** on Thu Nov 05, 2009 7:51 pm

Heiwa wrote:0% ejection means that nothing of A or C or B is ejected ...

Yes. I computed this case. Hardly different that 20% mass ejection.

Bazant's diff. equations do not consider them.

It is Bazant & Verdure's ODE and if you bothered to read the paper you will see that mass ejection (or even injection, for that matter) is indeed considered.

peterene1 · by **peterene1** on Thu Nov 05, 2009 8:22 pm

So, femr2, can you offer the speed of the LR ejecta and a comparison with the freefalling debris?

The 9/11 Forum

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Re: WTC1 Debris Ejecta Traversal Rate (Linear/Terminal Velocity)

Re: WTC1 Debris Ejecta Traversal Rate (Linear/Terminal Velocity)

Re: WTC1 Debris Ejecta Traversal Rate (Linear/Terminal Velocity)

Re: WTC1 Debris Ejecta Traversal Rate (Linear/Terminal Velocity)

Re: WTC1 Debris Ejecta Traversal Rate (Linear/Terminal Velocity)

Re: WTC1 Debris Ejecta Traversal Rate (Linear/Terminal Velocity)

Re: WTC1 Debris Ejecta Traversal Rate (Linear/Terminal Velocity)

Re: WTC1 Debris Ejecta Traversal Rate (Linear/Terminal Velocity)

Re: WTC1 Debris Ejecta Traversal Rate (Linear/Terminal Velocity)

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