I have a few questions that stem from this article http://www.cnn.com/2001/US/10/05/inv.attacks.steel/index.html
“Astaneh-Asl drew that conclusion after coming across clues like a steel support 1.5 inches thick from around the elevator shaft in the center of one of the towers.
A semi-circular chunk of the support is gone. “It looks like a big bullet passed through here,” he said.
Judging by the curve of the chunk, that bullet, he said, was most likely the nose of a Boeing 767.”
I don’t really understand the physics of it.
1)How can 1 1/2 inch steel be sheered off by an object that is so much weaker?
2)If the weaker object, (ex.)the nose of a jet plane, is disintegrated at impact, how can it make such a cut through the steel beam?
A fast moving aircraft that’s got a goodly amount of mass behind it can push through quite a bit of stuff.
The example they used in the article “like a bullet” is a good analogy. A bullet is pretty darned small, mass wise. Push it fast enough, and it will go through concrete walls. Just scale it up to 767 size.
Good question. This troubles me, too. I’ve read a few more detailed explanations and analyses that I think are wrong.
I think the nose of a big jet, which is made from many lightweight parts, does most of the deforming when it is forced into concrete and heavy steel construction. It may damage the concrete and steel, but you can imagine if you threw a balloon full of water at the ground at ten thousand mph that it too would leave a crater. The projectile in either case may get completely disintigrated, and the damage it causes might not preserve the shape of the projectile.
The source you quote makes it sound as if there is a jet-shaped hole punched through these heavy parts. I think that isn’t true - it’s just implausible to me. Neither of us was there, and we can’t go look, but it just sounds impossible.
But on a related note, you can get a pretty good look at the Pennsylvania hijacking crash site, where the plane ploughed into the ground. I think that very oblique crater looks more like it was created by a crumpling wad of compressed airframe, than like it was neatly punched out by a specific profile of the plane. In fact, I think it looks like a fast water balloon could have caused it too.
Well, there are some very heavy, high-strength steel parts in the front of a 767: the nose landing gear. It’s gotta weigh more than a thousand pounds. Striking at several hundred miles per hour (sorry, I don’t know how fast the plane was going when it hit), it would do ferocious damage to the relatively weaker structural steel of a building. Perhaps that’s what the possibly mis-quoted person meant.
Napier’s explanation also sounds pretty good to me.
I’ve seen the pictures of the ‘bite’, and it looks to me like one of the engines went though it. If you watch the footage of the crash, you’ll see two grey ‘streaks’ come out the other side of the building. I believe those are the engines coming through the building. They are the densest parts of the airplane, and most likely to stay intact as they go through things.
Thanks for the information and insight. Like Napier, I also thought of occasions where planes have crashed to the ground, leaving no tell-tale imprint of the plane. To me, ground soil would be more likely to yield to the plane structure than steel.
On a related note, I once saw a program where the military or FAA ran crash tests on a plane. If I remember correctly, they ran a commercial craft into a wall at high speed. When viewed from the side in slow motion, the plane appeared to literally dissappear into the wall. Nothing permeated the other side. I’m almost certain the wall was made of steel, but I don’t remember the thickness.