5 ms·

My dad told me that when he studied construction engineering in the late 70s at TU Munich one of their assignments was to calculate if the Isar nuclear reactors

by ascar 5y ago

My dad told me that when he studied construction engineering in the late 70s at TU Munich one of their assignments was to calculate if the Isar nuclear reactors are built strong enough to hold off a Mach 2.2 impact of a Phantom II. If I recall correctly the correct answer was that they were quite a bit stronger than necessary for that. However, I always wondered if a large civilian plane like a 747 with a speed close to Mach 1 creates more or less impact. The 747 is ~12 times heavier, but it's also less than half the speed and spreads the impact across a much larger area.

slapfrog 5y ago
This video shows an F-4 Phantom being slammed into a concrete wall using a rocket sled: https://www.youtube.com/watch?v=U4wDqSnBJ-k https://www.youtube.com/watch?v=U4wDqSnBJ-k At about 2 minutes in they show the aftermath. The plane is just gone, while the wall is a bit discolored...
- worik 5y ago
  Unconvinced. That concrete block was not ridged. It moved when the plane hit it. So the strongest aspect of concrete, compression, was tested. But the weakest, flexion, was untested. What fun though.
  - slapfrog 5y ago
    To test it as you suggest, you'd have to build the full containment building, which are built as domes. That dome structure should lend itself to exploiting concrete's compressive strength and minimize tensile forces. They are also specifically reinforced to increase their tensile strength, since they are primarily designed to contain explosions from within. I have little doubt that one of those domes could shrug off a Phantom crashing into them. More generally, in order to be successful a traditional armor piercing projectile needs two traits in particular: it needs to be harder than the target, and the projectile needs to be robust enough to not disintegrate on impact. Airplanes are neither of these; they're built out of soft aluminum and are built light to maximize payload, not to be robust. Consequently I would not expect an airplane striking a reinforced concrete building to ever behave as an armor penetrating projectile would. The part that I'm a bit skeptical of is the suggestion that shrugging off a Phantom is equivalent to shrugging off a 747, which is more than an order of magnitude heavier. Throwing an airplane at a concrete building is like throwing a wet ball of modeling clay at a glass window. Likely to splat, like that phantom did, but if your ball of clay is big enough it might go through. A large enough plane might even knock the building off its foundation, rather than penetrate the concrete.

by ascar 5y ago

slapfrog 5y ago

This video shows an F-4 Phantom being slammed into a concrete wall using a rocket sled: https://www.youtube.com/watch?v=U4wDqSnBJ-k https://www.youtube.com/watch?v=U4wDqSnBJ-k At about 2 minutes in they show the aftermath. The plane is just gone, while the wall is a bit discolored...

worik 5y ago
Unconvinced. That concrete block was not ridged. It moved when the plane hit it. So the strongest aspect of concrete, compression, was tested. But the weakest, flexion, was untested. What fun though.
- slapfrog 5y ago
  To test it as you suggest, you'd have to build the full containment building, which are built as domes. That dome structure should lend itself to exploiting concrete's compressive strength and minimize tensile forces. They are also specifically reinforced to increase their tensile strength, since they are primarily designed to contain explosions from within. I have little doubt that one of those domes could shrug off a Phantom crashing into them. More generally, in order to be successful a traditional armor piercing projectile needs two traits in particular: it needs to be harder than the target, and the projectile needs to be robust enough to not disintegrate on impact. Airplanes are neither of these; they're built out of soft aluminum and are built light to maximize payload, not to be robust. Consequently I would not expect an airplane striking a reinforced concrete building to ever behave as an armor penetrating projectile would. The part that I'm a bit skeptical of is the suggestion that shrugging off a Phantom is equivalent to shrugging off a 747, which is more than an order of magnitude heavier. Throwing an airplane at a concrete building is like throwing a wet ball of modeling clay at a glass window. Likely to splat, like that phantom did, but if your ball of clay is big enough it might go through. A large enough plane might even knock the building off its foundation, rather than penetrate the concrete.