Hardfire: Physics of 9/11

[R.Mackey]

Robertson's design point of a 707 at 180 mph matches, and you could figure out a plane can be resisted at 180 mph back in the 60s when the WTC was built; Robertson did that.

Bingo. This compares extremely well with our estimate that the threshold for wing penetration is at 185 MPH. That's not an accident.

The fuselage would still penetrate even at much lower speed, of course, but the destruction would be much less widespread.

Quite good.(technical side aside )
Several things:
1)For international audinece,could there be version of presentation with SI units? Thanks.
2)You were smiling upon mention of Heiwa!

Final rating:Excellent.Can be used for overview of part of physics.(Some more things + thermodynamics and you covered it all)

Glad you liked it, one more to go. I do apologize for using Imperial units, which I abhor, but I had to in order to get through it all in time. Ron would have been asking me to phrase it in "familiar" units.

This talk was aimed at people with interest but not much education in science, and I didn't want to bury the intent of the talk with measurements in kPa and N-s and so on. Fortunately the equations are all there, so you can go back and insert whatever units you like.

One other point, responding to a post in another discussion, but relevant to comments earlier here:

I just repeat myself. A part C of a structure* A (C 1/10th of A) cannot crush down A, when dropping by gravity on A. C will be locally damaged as A (C may even bounce) and no crush down will take place. Quite basic! [...] It is simply because equal type structures produce equal local damages on one another at collision contact (by gravity or horizontally by other forces - it does not matter). Therefore little C cannot crush big A.

(Bolding in original)

The bolded statement is utterly wrong. This is exactly the kind of abuse of Newton's Laws I alluded to in the first show.

What Newton's Third Law states is that at the point of contact, the forces are equal and opposite. It says absolutely nothing about damage. Damage can easily be different between the two entities, simply because damage is not well defined.

Example, consider firing a lead bullet at a large lead sheet. Think of the bullet as a lead cylinder (wadcutter type) with some radius, and some length. Basically, what Mr. Bjorkman's claim above would mean is that this bullet could never penetrate a lead sheet thicker than the bullet was long. No matter how fast the bullet was going. This is obviously preposterous. If you crank up the bullet speed enough, it will go through any thickness. It'll get melted, vaporized, ionized, compacted to neutronium, whatever, but in theory it can carry as much momentum as you want, and eventually it will have enough to smash/burn/radiate/tunnel through the lead sheet.

Similarly, if you collide two dissimilar objects, and the (equal and opposite) force is below the plastic limit of one but above the plastic limit of the other, you can damage one of them without doing hardly anything to the other. Very, very, very simple.

This is the kind of idiocy that "Truth Movement science" is founded upon. It's just plain wrong. There can be no debate on this subject at all. May as well claim 1 + 1 = 4.

 

[Baylor]

Bingo. This compares extremely well with our estimate that the threshold for wing penetration is at 185 MPH. That's not an accident.

The fuselage would still penetrate even at much lower speed, of course, but the destruction would be much less widespread.

Other estimates put it higher. The paper Gregory Urich cited and partly reproduced by me says the minimum impact velocity for the plane to penetrate the exterior columns would be 130 m/s or 291 mph.

 

[A W Smith]

I liked the second segment as well. cant wait for the third. One question.

How come Ron's hardfire Stein isn't full of pencils and pens? He certainly ain't drinking from it.

 

[R.Mackey]

Other estimates put it higher. The paper Gregory Urich cited and partly reproduced by me says the minimum impact velocity for the plane to penetrate the exterior columns would be 130 m/s or 291 mph.

Yup, there's some spread in the results. Dr. Astaneh-Asl came up with a similar estimate of thickness required to make the perimeter columns survivable as well. I forget where the Purdue estimate was, but it's somewhere in the middle. Obviously their models are much more detailed than mine. The speed required is also a function of which part of the wing we're talking about -- closer to the wing root, the fuel tanks are larger, so there's a bigger hit on the column.

The simple first-principles approach I walk through here, however, is similar to what the designers would have done in the 60's. No LS-DYNA available. So I'm not surprised that my more conservative figure came closer to the original spec, though it could just be coincidence.

 

[Doctor Evil]

Second show is up! http://video.google.com/videoplay?docid=8184528465256118271

Happy viewing.

Oh thanks. Will try to watch this later tonight.

 

[Heiwa]

Originally Posted by Heiwa
"I just repeat myself. A part C of a structure* A (C 1/10th of A) cannot crush down A, when dropping by gravity on A. C will be locally damaged as A (C may even bounce) and no crush down will take place. Quite basic! [...] It is simply because equal type structures produce equal local damages on one another at collision contact (by gravity or horizontally by other forces - it does not matter). Therefore little C cannot crush big A."

The bolded statement is utterly wrong. This is exactly the kind of abuse of Newton's Laws I alluded to in the first show.

What Newton's Third Law states is that at the point of contact, the forces are equal and opposite. It says absolutely nothing about damage. Damage can easily be different between the two entities, simply because damage is not well defined.

Example, consider firing a lead bullet at a large lead sheet. Think of the bullet as a lead cylinder (wadcutter type) with some radius, and some length. Basically, what Mr. Bjorkman's claim above would mean is that this bullet could never penetrate a lead sheet thicker than the bullet was long. No matter how fast the bullet was going. This is obviously preposterous. If you crank up the bullet speed enough, it will go through any thickness. It'll get melted, vaporized, ionized, compacted to neutronium, whatever, but in theory it can carry as much momentum as you want, and eventually it will have enough to smash/burn/radiate/tunnel through the lead sheet.

Similarly, if you collide two dissimilar objects, and the (equal and opposite) force is below the plastic limit of one but above the plastic limit of the other, you can damage one of them without doing hardly anything to the other. Very, very, very simple.

This is the kind of idiocy that "Truth Movement science" is founded upon. It's just plain wrong. There can be no debate on this subject at all. May as well claim 1 + 1 = 4.

Who has said that Newton's laws are about damages?

And evidently a bullet of lead is not the same structure as a lead sheet. Same material, yes, but there the comparison ends.
Drop a bullet of lead C on another bullet of lead A ... and C bounces.
Drop a lead sheet C on another lead sheet A ... and well, lead sheet A doesn't globally collapse.

Objects of dissimilar material. Yes, the rubber ball bounces on the wood floor, etc, etc. Very, very, very simple.

Sorry, I am plain right and I look forward to your appearance next week on Hardfire where we are told you will debunk above statement.

 

[Klimax]

Glad you liked it, one more to go. I do apologize for using Imperial units, which I abhor, but I had to in order to get through it all in time. Ron would have been asking me to phrase it in "familiar" units.

This talk was aimed at people with interest but not much education in science, and I didn't want to bury the intent of the talk with measurements in kPa and N-s and so on. Fortunately the equations are all there, so you can go back and insert whatever units you like.

Yes,that's why it wasn't that suprising,just wondered about presentation on website.(Maybe put SI into brackets for internation audience? - for last part)

Not that I trust myself not to do nice number of numerical errors... But will see if I can convert them and replace in presentation.

And than one isn't suprised when some probes are lost on entry in atmosphere of Mars.

 

[Niclas]

Next, we reason that the first column to yield will be the one at the top of the stack, almost without exception. This is for two reasons. First, the columns grow progressively stronger as you move down the structure, since their static loads are higher. Second, the columns on top are the least supported, having lost their bracing as the upper floors are damaged and have come loose.

Would it matter whether the columns further down are stronger or not,
when nothing or little of the stress waves is transmitted to the structure below?

 

[Heiwa]

Next, we reason that the first column to yield will be the one at the top of the stack, almost without exception. This is for two reasons. First, the columns grow progressively stronger as you move down the structure, since their static loads are higher. Second, the columns on top are the least supported, having lost their bracing as the upper floors are damaged and have come loose.

But isn't the columns in the upper, dropping part weaker and not supported at all, as they are also loose at ther fractured ends? Wouldn't they, according Newton, be subject to the same contact load/force ... and get damaged? Or do you suggest that the floors in the upper, dropping part keeps the columns there together?

 

[A W Smith]

Answered in another thread already. accelerating part "c" has more destructive energy

But isn't the columns in the upper, dropping part weaker and not supported at all, as they are also loose at ther fractured ends? Wouldn't they, according Newton, be subject to the same contact load/force ... and get damaged? Or do you suggest that the floors in the upper, dropping part keeps the columns there together?

Relax Anders, or start a new thread. your epic fail is coming to hardfire in a week. wait for it.

 

[Heiwa]

Relax Anders, or start a new thread. your epic fail is coming to hardfire in a week. wait for it.

But this is the Hardfire thread, A W Smith. Ryan Mackey is going to explain (or already has) at Hardfire that part C - upper 13 floors part of WTC 1 - can crush down the remainder 97 floors structure just assisted by a little drop + gravity and at 0.7 free fall speed, i.e. that this normal, happens every time, &c, and in accordance with recognized physics ... as further clarified by prof. Bazant two days after 9/11. Many persons have explained that this is wrong, i.e. a small part C of a structure A cannot crush down structure A, and so have I lately, using ship collisions as an example. And, it seems that Hardfire will focus on my explanations in their next show as my name was mentioned in the last show. Why not?
Ryan Mackey seems to have gotten my explanations wrong; he compares ship collisions with a lead bullet being shot through a lead sheet ????

It seems more like naval warfare (even if ships are generally built in steel ... and some yachts in wood, aluminium, GRP, &c.).

Actually a ship structure is quite similar to WTC from collision aspect! WTC has primary support elements columns on which the secondary structure floors are connected.

Ships have primary support horizontal/vertical stringers on which secondary structure shell plates and stiffeners are connected.

At collision contact always the secondary structure elements are destroyed first by the primary structure elements that remain less damaged. Reason for this basic physics and a little structural analysis. I can show you 100's of examples of that. Same would happen at WTC 9/11.

But no! On 9/11 weaker structural, secondary elements, like floors, are supposed to destroy stronger, primary structure, like columns ... and that only in one part - part A - the lower structure, you are told. So part A collapses! Has never happened before for any structure but you believe it is possible.

Sorry, you are manipped, as we say in French. Hope you understand? Manipped!! And also Ryan Mackey is manipped! I look forward to the Hardfire show.

 

[240-185]

Sorry, you are manipped, as we say in French. Hope you understand? Manipped!! And also Ryan Mackey is manipped!

I'd rather say "You are manipulated".
By the way, your french isn't very good.

 

[Gravy]

Many persons have explained that this is wrong, i.e. a small part C of a structure A cannot crush down structure A

Many persons are inside your head? You should really get that checked out.

 

[twinstead]

I'd rather say "You are manipulated".
By the way, your french isn't very good.

Hey. Be carerful; you're talking to the future most famous engineer in the world there mister...

 

[twinstead]

"many persons" must be Danish for "only me"

 

[Toke]

"many persons" must be Danish for "only me"

He is swedish, not danish.

Besides going from ships to buildings is a bad idea.
The accomodation of a ship is intended to be rolled through 30-45 degrees plus some serius shaking, without effect. Try that with a building ashore. They are not build to the same specifications.

I fail to see how Heiwa can be an engineer and not understand the problems in scaling.

It´s 3.32 am and I have just come home to a real internet connection, will wacht Makey´s show tomorrow.

 

[Niclas]

But isn't the columns in the upper, dropping part weaker and not supported at all, as they are also loose at ther fractured ends? Wouldn't they, according Newton, be subject to the same contact load/force ... and get damaged? Or do you suggest that the floors in the upper, dropping part keeps the columns there together?

I might be mistaken, but did not somebody on this forum suggest that the upper block is taking a ride down to the ground on a "pillow" of debree?

According to that theory,the upper block is not crushing the structure below,
instead we got rubble creating rubble...?

 

[Heiwa]

Besides going from ships to buildings is a bad idea.
The accomodation of a ship is intended to be rolled through 30-45 degrees plus some serius shaking, without effect. Try that with a building ashore. They are not build to the same specifications.

I fail to see how Heiwa can be an engineer and not understand the problems in scaling.

Well, WTC 1 was designed to withstand a hurrican wind and would deflect a lot doing so. All explained in my paper.

Re scale effects a Mr Froude had some bright ideas a long time ago. You see the resistance of a ship when propulsed through water consists generally of two parts; friction and form (generally waves being produced).
So when you measure resistance in model scale in a test tank at model speed you have to divide that resistance in the two parts and then apply different scaling factors for full scale and full scale speed. Then you add up the the two parts again and you have full scale resistance.
Nowadays there are also full scale simulation methods calculating the friction and form resistance full scale, that tally pretty well with model tests/methods. Mr Froud established a good relation between model and full scale speeds &c.

So when a ship is propulsed through water there is always equilibrium! The propulsive force equals the friction/form forces ... at any speed. But you have to watch out! Avoid collisions! At collisions the structures of both ships are affected. NIST & Bazant & Co should learn from that.

 

[beachnut]

Somewhere out there someone has no clue what Mackey was talking about and he can’t spell Mackey which is indicative of his failed flying knowledge, which now included drag, along with DME, FDRs, feet in a nautical mile, math, physics, 11.2G special physics just for p4t experts, and the type of electromagnetic radiation a RADAR altimeter uses. You always can find ignoreace3, but someplace practice making ignorance on flying and 911 their goal, their job, and package that ignorance on DVD for 16 bucks.

You can’t make this stuff up. But p4t experts can.

p4t -
Mackey is a complete joke. Pilots reading this, if you do nothing else, i encourage you to review the video at 23:37 when Mackety attempts to explain "Parasite drag" (actually defined as Parasitic Drag). Mackety claims Partasitic drag is "just regular aerodynamic drag". Obviously the kid doesnt know the difference between drag induced by aerodynamics and physical structures penetrating the air.

Hilarious!

Hilarious? Yes this standard 11.2G junk from p4t.

Why do expert pilots at p4t failed to understand drag and why Mackey was talking about parasite drag for the high airspeed case?

It is perfect when we now have someone fail at critiquing Mackey and use the term “partasitic” drag. Classic p4t; we had p4t math, now p4t aero.

I can work with parasite drag, and I could live with parasitic drag too. But partasitic drag…


P4t use ad hominem when they have no clue on a subject, like drag, and they threaten to bring those who oppose them using facts and real science to justice when their delusions come true.

From the diagram, parasite drag is directly proportional to dynamic pressure, and induced drag is inversely proportional to it. We thus have aerodynamic drag.

Mackey can teach this stuff, what happen to the p4t experts?

 

[Niclas]

"science demands repeatability". Quote from the Hardfire presentation.

Ryan, you told me earlier(#132) that it´s possible to make a physical model
where the vertical structure is progressively failing from top to bottom.

Now, assuming that the outcome of this experiment is positive, would this be the first
experiment in history to demonstrate this phenomena, to your knowledge?