Hardfire: Physics of 9/11

[Minadin]

All three are done. Enjoy. To recap:

First Show: Intro to the Scientific Method, quantification, applying to WTC impacts

Second Show: Part II, finishing WTC impacts, Q&A on AA 175

Third Show: Explaining how and why to model, simple model of WTC collapses, scaling

Again, an annotated and extended version of the slides can be found here and here.

Thank you Mr. Mackey for subjecting yourself to this sort of public display; I found all of the shows entertaining and intellectually stimulating. Your comments on the various scaling issues in building a model were not dissimilar to my own thoughts, and I'm glad that you were able to use the water-balloon analogy in Episode 2, because it is one of my favorites.

Making science accessible to the lay-people is one of the best ways to keep everyone informed, interested, and curious; and I think that it promotes critical thinking in a way that would make the JREF proud.

Good job.

 

[Heiwa]

Thank you Mr. Mackey for subjecting yourself to this sort of public display; I found all of the shows entertaining and intellectually stimulating. Your comments on the various scaling issues in building a model were not dissimilar to my own thoughts, and I'm glad that you were able to use the water-balloon analogy in Episode 2, because it is one of my favorites.

Making science accessible to the lay-people is one of the best ways to keep everyone informed, interested, and curious; and I think that it promotes critical thinking in a way that would make the JREF proud.

Good job.

Only error in Mackey's presentation is that it is assumed that, when M=km contacts m in the model and no elastic impact takes place (M bounces on m), that M=km fuses with m and becomes M=(k+1)m and that local failures (columns break) occur somewhere else in the structure remote from contact interface. It is a solid mechanics simplification, which has nothing to with real structural damage analysis!

Actually, the pressure to fuse M=km with m is so great that it is M and m that fail before anything else can happen away from the contact area, e.g. columns fail below m.

So M=km can never become M=(k+1)m.

Actually M<km after first and only impact and the difference is rubble of M that cannot damage any structure below.

Sorry, Minadin! The Mackey show has little to do with reality. It is just NWO nonsense to cover up the real cause of the WTC 9/11 destructions.

 

[bill smith]

Only error in Mackey's presentation is that it is assumed that, when M=km contacts m in the model and no elastic impact takes place (M bounces on m), that M=km fuses with m and becomes M=(k+1)m and that local failures (columns break) occur somewhere else in the structure remote from contact interface. It is a solid mechanics simplification, which has nothing to with real structural damage analysis!

Actually, the pressure to fuse M=km with m is so great that it is M and m that fail before anything else can happen away from the contact area, e.g. columns fail below m.

So M=km can never become M=(k+1)m.

Actually M<km after first and only impact and the difference is rubble of M that cannot damage any structure below.

Sorry, Minadin! The Mackey show has little to do with reality. It is just NWO nonsense to cover up the real cause of the WTC 9/11 destructions.

Heiwa In a post to RM I said:-

''Scale is interesting but plays no part in the argument as we are dealing with the known size and properties of a structure. The scale thing only applies to making a smaller model and is therefore somewhat irrelevent ''

and RM replied:-

''Regarding scale, you and Heiwa are wrong. The third show contains a simple model specifically to demonstrate that scale does matter. It does. The only way scale would not matter is if the equations of collapse are scale invariant. Since my equations are greatly simplified compared to the real thing, and they are not scale invariant -- indeed, they scale in several different ways to the point that a nondimensionalization is not even possible -- this proves, scientifically, that Heiwa is wrong, and you who follow him are wrong as well.''


Is RM saying that what what I said is wrong and that scale HAS relevence in the collapse of the full size Tower or is he still talking about modelling ?

 

[alex04]

Only error in Mackey's presentation is that it is assumed that, when M=km contacts m in the model and no elastic impact takes place (M bounces on m), that M=km fuses with m and becomes M=(k+1)m and that local failures (columns break) occur somewhere else in the structure remote from contact interface. It is a solid mechanics simplification, which has nothing to with real structural damage analysis!

Actually, the pressure to fuse M=km with m is so great that it is M and m that fail before anything else can happen away from the contact area, e.g. columns fail below m.

So M=km can never become M=(k+1)m.

Actually M<km after first and only impact and the difference is rubble of M that cannot damage any structure below.

Sorry, Minadin! The Mackey show has little to do with reality. It is just NWO nonsense to cover up the real cause of the WTC 9/11 destructions.

NWO nonsense? So Ryan Mackey's in on the conspiracy now? Is that what you're saying?

 

[metamars]

Case 1. Imagine an isotropic steel structure A 1 m high with cross area 1 m² (it is thus a steel cube that weighs abt 7800 kgs) and an upper part C 0.1 m high with same cross area (that weighs 780 kgs). Drop C on A and C bounces.

Case 2. Imagine an isotropic steel structure A 10 m high with cross area 100 m² (it is a 10 times bigger steel cube but weighs 1000 more) and an upper part C 1 m high with same cross area. Drop C on A and there is still a bounce.

(emphasis mine)

For a non-ideal, non-axial impact, it doesn't make sense to me to think of the word "isotropic" in terms of only 3 orthogonal axes. Rather, you should also think of, say, a representative set of 1,000 vertical axes, with 236 + 47 through columns (or only column ends, if you're considering the top to be tilted, at t = 0 of the collision) and the rest, not. "Isotropic", then, goes right out the window, as the stress through a WTC top column vertical axis is vastly different than the stress through adjacent WTC top non-column axis.

Even for an ideal, axial impact, you are posing the problem too simply. We all know the columns become thinner the higher we go up. (Maybe the mechanical floor columns are exceptions.) So, the WTC building is not isotropic in this sense, either. Certainly, the floor elements did not become thinner going in any horizontal direction.

( Now that I think about it a little more, just considering the set of all axes through the center of mass, why on earth would the strength through an axis which ends at a column end be the same as one that ends in thin air, or in a floor element, at the same vertical distance?)

 

[metamars]

( Now that I think about it a little more, just considering the set of all axes through the center of mass, why on earth would the strength through an axis which ends at a column end be the same as one that ends in thin air, or in a floor element, at the same vertical distance?)

In other words, even for an ideal collision, which is axial and has no tilt, neither the WTC top nor bottom will be "isotropic". I think that you are only thinking of 3 orthogonal axes - x, y and z. However, the definition of "isotropic" is " equal physical properties along all axes". There are infinitely many axes, through the center of mass.

 

[metamars]

Rather, you should also think of, say, a representative set of 1,000 vertical axes, with 236 + 47 through columns (or only column ends, if you're considering the top to be tilted, at t = 0 of the collision) and the rest, not. "Isotropic", then, goes right out the window, as the stress through a WTC top column vertical axis is vastly different than the stress through adjacent WTC top non-column axis.

I should have written :

as the strength through a WTC top column vertical axis is vastly different than the strength through adjacent WTC top non-column axis.

 

[Heiwa]

Heiwa In a post to RM I said:-

''Scale is interesting but plays no part in the argument as we are dealing with the known size and properties of a structure. The scale thing only applies to making a smaller model and is therefore somewhat irrelevent ''

and RM replied:-

''Regarding scale, you and Heiwa are wrong. The third show contains a simple model specifically to demonstrate that scale does matter. It does. The only way scale would not matter is if the equations of collapse are scale invariant. Since my equations are greatly simplified compared to the real thing, and they are not scale invariant -- indeed, they scale in several different ways to the point that a nondimensionalization is not even possible -- this proves, scientifically, that Heiwa is wrong, and you who follow him are wrong as well.''


Is RM saying that what what I said is wrong and that scale HAS relevence in the collapse of the full size Tower or is he still talking about modelling ?

RM mixes the two! An impact in any scale is an impact but the contact forces/pressures differs. What happens remote from the impact - above and below - is another thing. They differ too.
The only thing that is important is that - regardless of scale - the impact forces/pressures on the two objects in contact are the same on both objects that I call C and A. Scale cannot change that. So you are right.

best regards

Heiwa

 

[twinstead]

LOL. Heiwa I'm looking forward to your peer-reviewed paper. You know, the one that shuts up all those "experts" who contributed to the NIST report.

 

[Heiwa]

NWO nonsense? So Ryan Mackey's in on the conspiracy now? Is that what you're saying?

No! I just say that the RM model presentation in the show is wrong. I don't know RM but his presentation is bad. Let's discuss the latter.

 

[Heiwa]

(emphasis mine)

For a non-ideal, non-axial impact, it doesn't make sense to me to think of the word "isotropic" in terms of only 3 orthogonal axes. Rather, you should also think of, say, a representative set of 1,000 vertical axes, with 236 + 47 through columns (or only column ends, if you're considering the top to be tilted, at t = 0 of the collision) and the rest, not. "Isotropic", then, goes right out the window, as the stress through a WTC top column vertical axis is vastly different than the stress through adjacent WTC top non-column axis.

Even for an ideal, axial impact, you are posing the problem too simply. We all know the columns become thinner the higher we go up. (Maybe the mechanical floor columns are exceptions.) So, the WTC building is not isotropic in this sense, either. Certainly, the floor elements did not become thinner going in any horizontal direction.

( Now that I think about it a little more, just considering the set of all axes through the center of mass, why on earth would the strength through an axis which ends at a column end be the same as one that ends in thin air, or in a floor element, at the same vertical distance?)

Somebody suggested I should change monolithic to isotropic structure in my axiom with some good reasons, which I did. We are still discussing. He will report next week!
However, columns are not part of such structures - then we are talking about composite structures, like ships, to which the axiom should also apply.
When two similar, composite structures collide (like ships) of different masses (one structure is bigger but the local structure is the same), plenty of various elements of different types get in contact. The combined effect is either a 'bounce' or local failures of elements of both objects (no bounce).
And, as long as the structure of the two objects is the same, the smaller object is relatively more affected than the bigger; the smaller object will be destroyed before the bigger one.

In an isotropic structure you can imagine a great number of small, similar elements (columns!) all connected to one another some way or another. Even if a sponge is not really isotropic, it is quite similar. And when sponges collide, they deform a lot, internal sponge structure elements may get severly deformed locally (more close to contact!), plenty of internal friction between the elements but mainly elastic deformation, &c. But they do not collapse because one arbitrary element is overstressed.

In other words, an isotropic structure is in principle a composite structure. And a part C of such structure A cannot ever crush A, when C is dropped on A.

 

[tfk]

toke

I am not too sure about the drag either.

One of them is air resistance from the plane in general and the other is the effect of the lift of the wings?

Why bother.
If an airplane dives it can go alot faster than the manufacturer intended.
When leveling out it will be slowed by the difference between engine output and air resistance, but it will take some time.

It ain't that hard.

The Parasitic Drag is the one that is intuitively obvious. The faster you go, the higher the drag. It actually goes as the square of velocity.

The Induced Drag is the one that is less obvious.

Go here: http://en.wikipedia.org/wiki/Induced_drag Don't worry about all the math.

It results from the fact that basic drag measurements are taken with the airplane maintaining a constant altitude. (There is a word for a plane that does not maintain altitude for too long a time: "wreckage".)

It turns out that, in order to maintain altitude at low speeds, the plane has to increase its "angle of attack", i.e., it has to raise its nose. The slower you go, the higher you have to pitch the nose. (Until you raise it too far, stall, and the plane goes down. But that's another problem.)

Now look at the top image on that web page. The "Lift vector" is always perpendicular to the wing. As you tilt the nose (& wing) upwards as the speed gets lower, then the lift vector starts tilting backwards from the vertical. Now the Horizontal component of the lift vector starts pointing backwards from the direction of motion of the plane. This rearward HORIZONTAL COMPONENT of the wing's lift is "induced drag".

Again, it gets bigger at lower speeds because you have to increase the AoA at lower speeds.

Easy, no?

Now, to make sure you've got it, figure this one out. What happens to Induced Drag at low speed if the plane is NOT maintaining altitude, but is descending ? How about ascending?

tom

 

[Toke]

Easy, no?

Now, to make sure you've got it, figure this one out. What happens to Induced Drag at low speed if the plane is NOT maintaining altitude, but is descending ? How about ascending?

tom

Looks simple enough, the angle of lift gets tilted backwards at low speed.
And at a constant low speed AoA the induced drag will be a constant proportion of the lift vector. Wing lift can be split into a drag vector and a plane lift vector.

So descending with an constant AoA mean you have less lift vector and less induced drag vector.

A plane comming out of a long dive at a speed exceding intended max speed will still not slow down instantly. Even if some truther try use induced/parasitic drag as magic words.

 

[tfk]

Looks simple enough, the angle of lift gets tilted backwards at low speed.
And at a constant low speed AoA the induced drag will be a constant proportion of the lift vector. Wing lift can be split into a drag vector and a plane lift vector.

So descending with an constant AoA mean you have less lift vector and less induced drag vector.

A plane comming out of a long dive at a speed exceding intended max speed will still not slow down instantly. Even if some truther try use induced/parasitic drag as magic words.

Piece o' cake. You got it.

You descend whenever you decrease the VERTICAL component of the lift vector.

You can do this in two ways:

As you said, keep the AoA the same and decrease your speed. The direction of the lift vector stays the same, and the magnitude decreases. This drops the Induced drag.

Or keep the speed the same & decrease the AoA. This decreases both the angle and magnitude of the lift vector, and also decreases the induced drag. Even more so than the first way.

Regardless, you got it.

Re: Max speed of jetliners. A "Q" tire with rated to 100 mph. Does anyone think that it is gonna fall apart at 105 mph? 110 mph? 115 mph? At some point, you go from a no to a yes. It ain't at 105 mph. And there is a broad range between "absolutely no" & "absolutely yes". Expecially if it is made by a first rate company? Boeing is a first rate airplane manufacturer.

tom

 

[tsig]

NWO nonsense? So Ryan Mackey's in on the conspiracy now? Is that what you're saying?

I'm in so many conspiracies now that I can't keep track.

Funny i can't remember joining any of them. And they never offer discounts.

 

[bill smith]

I've always felt that the image of the USS Hinsdale illustrates this point very nicely.

I think this model is very informative.
http://www.youtube.com/watch?v=z0kUICwO93Q

 

[Toke]

I think this model is very informative.
http://www.youtube.com/watch?v=z0kUICwO93Q

I don´t.

One kind of building is damaged by nuklear blast from right above.
Another collapses from damage from airplane impact and fire.
So.

Then he spend some time explaining that mass and its distribution effect the swing frequency of a building.
I know that, it affects the stability, and thereby roll frequency, of a ship too.
Look up pendulum for the teory behind it.

Could you sum up the point of the video?

 

[twinstead]

Could you sum up the point of the video?

Frankly, even if he could (and he can't) he wouldn't, because it's not the truth that's important; it's about sticking it to The Man^tm, and in this case it is we who are The Man^tm.

 

[bill smith]

I don´t.

One kind of building is damaged by nuklear blast from right above.
Another collapses from damage from airplane impact and fire.
So.

Then he spend some time explaining that mass and its distribution effect the swing frequency of a building.
I know that, it affects the stability, and thereby roll frequency, of a ship too.
Look up pendulum for the teory behind it.

Could you sum up the point of the video?

For me it gives some idea of the oscillation of such a building after a short sharp blow. Then I think of how the plane entered the buildng almost seamlessly without any visible building oscillation worth talking about and I wonder how that could be possible. There must have been SOME force of impact surely ?

 

[Toke]

Frankly, even if he could (and he can't) he wouldn't, because it's not the truth that's important; it's about sticking it to The Man^tm, and in this case it is we who are The Man^tm.

It must be frustrating having only such blunt objects to stick with.