Guns in space!

[tedrick79]

Ok very simply. Would a firearm fire in space?

By firearm I would like to use the most widely known weapon on all the planet. The AK-47. Built for its rugged bile pocket making abilities. Would it function as advertised in the hard vacuum of space?




I tend to think it would. It is a gas operated weapon - the gas is contained in the gunpowder/cordite in the casing. The casing is sealed and requires no external oxygen - it will fire underwater although it might not recoil and reload properly due to water dragging on the internal parts.

Does anyone imagine that a firearm would not function in space? If so why not?

[Boerseun]

Firearms should fire perfectly well in space.

The oxidant required is included in the chemical mix in the shell casing, and the firing pin is a spring-loaded operation.

The only problem I can see is if half the weapon is in sunlight and the other half in the shade. The thermal difference might make the mechanism unpredictable, and the barrel might taper unevenly due to thermal expansion/contraction. If the tip of the barrel is in the shade (way below the freezing point of water) and the firing mechanism is in sunlight (way above 0 Celcius), the bullet might jam in the barrel. The bullets in the magazine might even go off due to heat. Simple preventative measures like a shiny reflective gold foil covering might prevent thermal stresses, but the vacuum of space will have no influence that I can foresee.

On second thought, you might also have lubrication issues, which is imperative for the smooth operation of any gun. It might fire once or twice and then just jam solid because the oil in the mechanism have boiled away in the vacuum. But then again, you are talking of an AK, which is famous for firing like a charm after having been shoved up a dead elephant's butt that drowned in a crocodile-infested swamp for thirty years.

[modest]

Some of the most reliable things used in space are explosive bolts and cable cutters. I would suspect bullets would perform equally well. Even with explosives which are not vacuum safe (e.g. RDX sublimates in a vacuum) the bullet itself should be vacuum safe so it would probably still work fine if it had RDX in the primer for example.

The mechanics of the gun on the other hand—I agree with Boerseun. First and foremost: the oil in the gun would most certainly freeze so if you're taking your firearm into space I'd recommend wiping it clean of oil first.

~modest

[Moontanman]

I think the barrel on a gun such as the AK-47 would over heat and fail since there would be no air to cool it. Other than that i see no reason it wouldn't work. The recoil would make the operator spin so some action would be necessary to avoid that.

[modest]

Moony, I, for some reason, am assuming you know this. How much force is required to remove the bullet from the shell? If you hung 2.2 lbs on the bullet (of, say, a .45) holding the shell static would the bullet come out?

If that amount of force is not enough to remove the bullet from the shell then a hard vacuum should not be a problem for the bullet itself. The difference in pressure (of inside the shell to outside the shell) should not be enough to force the bullet from the shell. But, I've never done such a thing and a quick search doesn't turn up anything.

~modest

[Racoon]

What interests me most about this topic is the fired bullet!

How long/far/fast would the bullet travel at its original velocity? (assuming it doesn't intersect with an asteroid or satellite, and avoids any major gravitational pull from celestial bodies)
If there is no resisitance from atmosphere, conceivably the bullet would travel perpetually across the galaxy and universe.

Since even a floating paint chip from space debris is said to be a "dangerous projectile" traveling at extreme rates of speed,and the impact would be that of a gun-shot, I can only imagine an actual fired bullet

[Moontanman]

Originally Posted by Racoon

What interests me most about this topic is the fired bullet!

How long/far/fast would the bullet travel at its original velocity? (assuming it doesn't intersect with an asteroid or satellite, and avoids any major gravitational pull from celestial bodies)
If there is no resisitance from atmosphere, conceivably the bullet would travel perpetually across the galaxy and universe.

Since even a floating paint chip from space debris is said to be a "dangerous projectile" traveling at extreme rates of speed,and the impact would be that of a gun-shot, I can only imagine an actual fired bullet

Actually the speed of the bullet as fired would be small compared to it's orbital velocity. a bullet fired in orbit would simply go into orbit around the body it was fired near. if you encountered that bullet in the same orbit it was in and in the same direction it wouldn't be any different than being hit by the bullet on the earth, But if you were in a different orbit and encountered the bullet at it's orbital velocity you would be in trouble for sure. a bullet is much bigger than a fleck of paint and would have tremendous energy on impact.

Fire all of your guns at once and
Explode into space!

[CraigD]

Originally Posted by Racoon

How long/far/fast would the bullet travel at its original velocity? (assuming it doesn't intersect with an asteroid or satellite, and avoids any major gravitational pull from celestial bodies)
If there is no resisitance from atmosphere, conceivably the bullet would travel perpetually across the galaxy and universe.

Solar escape speed from the Earth is about 42100 m/s. A typical assault rifle’s initial projectile speed is about 1000 m/s. The greatest chemical-powered projectile speeds are about double that. Earth’s orbital speed is about 30000 m/s. 30000 + 1000 to 2000 is less that 42100, so, no matter which way you fire it, you won’t be able to shoot a bullet free of the solar system.

Escape speed from a typical low Earth orbit is about 11000 m/s. A typical LEO orbital speed is about 8000 m/s. 8000 + 1000 to 2000 is less than 11000, so you won’t be able to shoot a bullet free of the Earth from LEO, either.

Starting with the formulae for orbital and escape speed, you can calculate the distance from its primary an orbiting body must be for a projectile shot from it to escape. The formula’s
, where , the primary’s standard gravitational parameter.

Working this out for a 1000 m/s projectile, Earth escape is possible at r= 68389024 m, about 62000000 m altitude, about 26000000 m above geostationary orbit, about 20% of the way to the Moon. For a 1000 m/s projectile escaping the Solar System, we get 22769854915837 m , about 152 AU, nearly 50 AU further out than Voyager 1. For a 2000 m/s projectile escaping the Solar System, it’s only about 38 AU, about the orbit of Pluto.

So, a really good tank gun in Pluto’s orbit (not actually on Pluto, but say, on one of it’s tiny icy neighbors) could shoot a projectile out of the solar system!

[modest]

Ok. I've figured a problem in our pirates-of-the-inner-solar-system plan. A typical .45 has a diameter of ~104mm. The pressure inside the cartridge is presumably 1 ATM which is 0.01033 kg/mm². This means there will be a force of ~1 kg (9.8 Newtons or 2.2 lbs) trying to force the bullet out of the shell in a hard vacuum.

I think a fair number of bullets placed in a hard vacuum would separate. The bullet would be forced from the shell before it is ever fired. I'm basing this on a youtube demonstration of a bullet remover where it seems very little force is required to remove a bullet from its shell:

YouTube - How To Use A Kinetic Bullet Puller

Yeah, I think if you put a bullet in a hard vacuum there would be a good chance the bullet would pop right out of the shell. Of course, this depends on how much gas there is inside a cartridge. Hummm....

~modest

[CraigD]

Originally Posted by modest

Ok. I've figured a problem in our pirates-of-the-inner-solar-system plan. A typical .45 has a diameter of ~10[.]4mm. The pressure inside the cartridge is presumably 1 ATM which is 0.01033 kg/mm². This means there will be a force of ~1 kg (9.8 Newtons or 2.2 lbs) trying to force the bullet out of the shell in a hard vacuum.

I think a fair number of bullets placed in a hard vacuum would separate. The bullet would be forced from the shell before it is ever fired.

You might be right, modest. Though I never measured it directly, I’ve reloaded thousands of cartridges of various rifle and pistol types, and on a few occasions had to pull the bullets from a batch of crimped cartridges after making a mistake in the powder load or bullet. I had a handy little tool for this, a kind of complicated pliers, so never directly pulled on a bullet, but would guess the force needed to be in the 2 to 10 N (1 kgf, 2 lb.) range.

1 atmosphere = 101325 N/m², so the force exerted by this pressure on a 0.009 m (9 mm) diameter bullet is , which might be enough to pop the bullet out of its case. The change in pressure would need to be fairly sudden, though, and the cartridge not in a magazine that would prevent the bullet from expanding much – though all the cartridges in a mag lock themselves in it with more force than the mag’s spring could overcome could be as dramatic a problem for our space-pirates as contending with a mess of lose bullet and powder.

It wouldn’t be a hard problem to overcome, though – just crimp your cases or notch your bullets a little bit to make a channel to assure the pressure inside and out are always equal. A bullet doesn’t depend on the tightness of its seal with its cartridge other than to keep water out and the powder in, so the worst this would do make your ammunition non-waterproof, which wise folk already assume to be the case.