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Dave has a rail gun, it weighs 20 pounds and is rougly the size of an AK 47 it shoots a projectile that is 5.5mm x 45mm and pointed like a modern bullet. The rail gun fires the projectiles at mach 10

he has 5 different kinds of rounds

#1 is a super hard metal weighs same as steel but millions of times stronger

#2 is depleted uranium

#3 is tungsten

#4 is cast iron

#5 is a hardwood slug with a metal base

he fires these into several targets

Target A WW2 Sherman tank fully crewed, shot is directed at the front of the tank at the thickest part of the armor. right down the center axis what happens ?

Target B A guy in a suit that has 2 inches of steel in the front, 1 inch in the back. shot is directed at the targets left shoulder. Does it past straight thru like a modern bullet punching through cardboard ? or does he go flying back 200 feet? Or does it vaporize or goo the rest of him ?

Target C. is an Elm tree. 3 feet thick at its thickest point

Target D Is a concrete wall 4 feet thick and reinforced with Rebar. like a german ww2 bunker

Target E: is an ancient fortress wall 2 feet of solid stone followed by 10feet of loose stones followed by another 2 feet of stone

Target F: is a ww2 era fighter. zero to be specific. what happens when it gets hit

Target G: is a vampire Bear (hence the wood projectile)

Also does Dave fly back 50 feet when he shoots because of recoil or prettymuch just sit there unaffected ?

Please don't feel the need to answer every possible outcome, but if you could give me a general idea of what would happen, I would appreciate it.


closed as too broad by Aify, Hohmannfan, JDługosz, Thucydides, Bellerophon Oct 9 '16 at 21:56

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  • $\begingroup$ Sorry forgot to mention , targets are all 50 meters away. $\endgroup$ – Hobgoblin Oct 8 '16 at 20:07

What happens to Dave is the simplest, since the projectile is 20 lb. (9.07 kg) and the speed is mach 10 (10 times the speed of sound, which is 343 meter / second at 1 atm). Momentum is conserved, so the kickback of the railgun imparts a momentum of 31,140 kg m/s backward. If the gun is firmly attached to the ground, Dave is safe. If he's holding the gun and weighs 90 kg, then the total mass of 99.07 kg flies backward at a speed of 314 m/s (just under mach 1).

What happens to the target mostly depends on how much the air resistance slows the projectile down before impact. At any reasonable distance (say under 1 mile), the resistance will be very small for a bullet-sized object. However, at mach 10, the bullet may very well flatten or vaporize from air resistance. Assuming it does not (and is still traveling above mach 1 at impact), then it is very likely that it will travel straight through all the targets listed. There was a scene showing a railgun punching through the hull of the MCRN Donnager in Syfy's "The Expanse". However, there is no air in space.

  • $\begingroup$ Its not the projectile that is 20lb it is the gun. Projectiles are roughly same as regular projectiles sans the gun powder. $\endgroup$ – Cem Kalyoncu Oct 8 '16 at 20:00

Dave will experience roughly 3-4 times the kickback of a regular gun. I guess someone can be trained to handle that. Mach 10 is not fast enough to do extreme damage. I assume rounds are similar to 7.62. I also ignore #1 bullet.

So Target A: nothing, Target B: no more shoulder for him. C, D, E: Nothing significant (5-10 times more damage compared to regular rifle). F: probably two large holes and a nice push. G: I guess it would break apart the body of the bear similar to getting hit by a cow catcher.


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