Yes — An airplane hit the Pentagon.
Years ago, I worked with a man who was on a crew that made and tested secure enclosures. One of the things they found was that concrete is a lousy wall. They were only allowed to use materials that would be reasonably available to construction and demolition, and everything had to fit in the back of a pickup truck. They had 5 minutes to get in and get out with the target in the center of the vault. Six men were allowed in the truck.
They tested concrete and rebar enclosures over and over, because the designers were sure it would work. Designers put in more rebar. They made the walls thicker. The last enclosure tested was two walls, one inside the other, with a 3 foot space in between. Both walls were 3 feet thick.
The break-in crew drove up with their truck, and a manhole cover that had dynamite duct-taped to the back. Two guys put that up against the wall. Then they threw sandbags up against that, and buried it. Drove off 50 yards, and blew the hole. Zipped back over. The manhole cover was a little deformed, but had started to make a dent in the second wall. They formed a conveyor line, duct taped the charge to the back of the manhole cover again, threw sandbags through the hole, piled them up, scrambled back through the hole, took cover along the wall, and blew it off. Two guys went in for the target and got it. They were on their way in under 4 minutes. And that was the end of trying to make strong enough concrete walls.
Take a look at those walls again in that photo. They aren’t 3 feet thick. They aren’t even concrete. Even simple paper will cut your skin right through. Why? pounds per square inch concentrated in a small area. So let’s calculate how many pounds per square inch would the fuselage of a loaded jet airliner exert on the wall of the pentagon?
A 757–223 airliner has a max weight of 127.5 tons. so let’s figure it at a conservative 110 tons when it hit the wall. The outer diameter of the fuselage is 140 inches, or 11.6 feet. (Note that this is well within the diameter of that hole.)
The cylinder is aircraft aluminum, which is very strong, and a cylinder is the strongest geometry. it hit at around 250 miles per hour, which is equal to 366 feet per second. Force = mass times acceleration. So, 110 tons x 366 feet per second decelerated to zero in 2 seconds = 20,150 foot-tons per second per second.
The aircraft fuselage averages 0.9 millimeters thick. Circumference is 36.65 feet around. So, that edge is 0.035433071 inch thick, by 439.82 inches = 15.584278577 square inches.
0,150 foot-tons per second per second / 15.584278577 = 2588 foot tons per square inch. So let’s scale that. A fully loaded tractor trailer heavy-weight 3 axle truck will weigh 65,000 lbs fully loaded. Thats 32.5 tons. It would take 16.5 of those fully loaded trucks to equal the force on one square inch of the rim of the aircraft when it hit. Imagine a rod one inch square, that weighs what 16 and a half logging trucks full load, that is one inch in diameter, falling out of the sky end on at 250 miles per hour. What would that go through? Damn near anything. That is what hit the wall of the Pentagon.
Usually, we talk about foot pounds, not foot tons. Foot tons are bomb and missile level forces.
Yes, that would cut through concrete like a razor through butter. Better than that. Through mostly brick? It’s laughable.
Now let’s add fire.
Aluminum burns at a temperature of at least 3,320 F. That will destroy concrete. That will vaporize a human. The friction and impact of hitting the wall generates heat, and not just a little bit. Rub your hands together. That’s a tiny amount of force by comparison, a few inch-ounces, but it created a bit of heat. The aluminum skin would ignite similarly to thermite. Thermite is an aluminum compound that when it burns goes through steel.
There is fuel in the wings of the aircraft. But the wings of the aircraft will hit side-edge on. That’s like the fuselage getting hit from the side. It’s not strong in that direction. The wings will deform and be engulfed in the fireball that the front end of the airplane has become.
The momentum of the fuel means it has to go through the hole made by the aircraft. All of that is on fire. There is plastic inside the plane which also vaporizes and burns. Everything would be gone except a few things that didn’t make it through the wall.
If you look to the side of this photo, you will see piles of what look like struts. That’s all you would expect to find. That is EXACTLY what you would expect to find.
Oh, right. The floor! the floor! It’s not destroyed! The floor is not hit directly, and it’s parallel to the aircraft folks. If the plane was flown straight down, then, sure. The floor would have a hole punched in it. Bippety-bappity-boo. But, wasn’t.
