Is it possible for shotguns or other firing mechanisms to fire effectively in a vacuum or outer space, assuming there is no oxygen present? Has anybody ever tested this? The reason I ask is to settle an argument with my dad after watching the film “Outland”, where a shotgun is fired normally from outside a space station. Wouldnt it need oxygen to ignite the gunpowder? Furthermore, if this is possible, would the bullet carry on at a constant speed in a vacuum after reaching its terminal velocity until it hit something, without air pressure to slow it?
thanks,
Paulberserker
Welcome to SDMB.
Guns should work fine in vacuum. Gunpowder does not need oxygen in the air, because it contains oxydizer. All the chemicals needed for the reaction is already in the shell. You can’t cause an explosion using oxygen in the air - not enough oxygen can get to the reaction site quickly enough.
If you fire a gun in vacuum, after the bullet exits the gun there are no forces acting on it - no friction, no acceleration. The bullet continues at the muzzle velocity. (Well, except for effects of gravity.)
Yes, As scr4 said, a shotgun would work just fine in space. A wrinkle to your question is what would happen to you?
Conservation of momentum dictates that you and the shot would separate at speeds commensurate with your relative masses. Scale this up a few million times and you have Project Orion – the atomic-bomb fueled rocket.
Your gun would fire under water too. Same principal.
But the bullet(s) would slow down more quickly than in air.
As long as we’re on the subject (heh heh), what effect would extreme cold have on firing?
Peace,
mangeorge
Same principal.
One could also say “same principle”. 
Peace,
mangeorge
Welcome, paulberserker, I am glad that someone asked this question. In the '60s a rocket scientist invented a gun called the gyro jet that used solid rocket fuel to propel to projectile. It had little recoil and the bullet could be stopped with your hand after it came out of the barrel. The rocket fuel fully kicked in and acellerated to full speed at 50 m. Military planners thought this was a great idea because it could be used in space. Am I right in thinking that it is because of the small recoil?
Yeah, the only real advantage of that would be the lesser recoil, but the recoil from a more conventional firearm would not be THAT much…couldn’t you figure out how fast you would be pushed back by dividing your weight by the weight of the bullet, then dividing the muzzle velocity by what you got? One could build up a good amount of velocity by repeatedly firing a gun, but I think if we were to send fighting men into space (there are a few scenarios where it might be necessary) they would probably not be shooting much while spacewalking, and would have some kind of reaction jets on them that would be more than enough to counter weapon recoil if they did.
The problem with the recoil most likely isn’t the overall speed, but the fact that it’s probably not lined up with your centre of mass. If so, you’d end up rotating out of control.
The biggest problem I see with the 60’s rocket gun is one of extended flight time reducing hit potential on moving targets, assuming an unguided projectile of course.
If it exits the barrel moving slow enough to stop it with your hand, it’s going to take a while to reach 50 meters, then the motor ignites, then it takes time to accelerate until the fuel runs out, than there’s the flight time to target. With a conventional firearm, acceleration is complete by the time the bullet leaves the barrel. Of course, there’s also the question of “what if the target is 10 feet away?” One solution is to use a shorter fuse, igniting the rocket within inches of the muzzle, but you still have to wait for acceleration. The beauty of the standard closed breach firearm is that the sealed chamber behind the bullet allows you to immediately begin massive acceleration, and recoil is the price we pay for it.
A more logical “space gun” would fire small, high velocity, armor piercing bullets. A high velocity shotgun load of sewing needles could be quite effective, until a self-sealing suit was developed. Then you just go to projectiles that leave holes too big to patch quickly. Why worry about killing someone with a bullet? You only need to let the air out of their suit, and space will kill them for you.
“Guns don’t kill people, vacuums kill people.”
dear SDMB members,
Thanks for the informative replies and welcomes etc. Its a hell of a lot better than I’ve received off of other message/bulletin boards (albeit for different subjects)
problem cleared, normality resumed
cheers
Paulberserk
Things need some kind of air resistance to have a terminal velocity. The bullets in space would leave the gun at about 1100 fps (depending on the round) and keep going at that speed forever. It would not take time to reach this speed. It would be instantanious.
One caveat, I suppose, is that you probably don’t want to use shells that were loaded in an atmosphere and then sealed. If there’s enough pressure within the cartridge to deform the shotgun shell significantly (or if some component of the primer outgasses), you might find yourself firing a gun with a blocked barrel.
If it’s extremely cold, you might also get differential thermal contraction of the barrel and the shell with similar results.
I’ve done some reading on the Gyrojet pistol ever since I heard of it when I was in high school. It doesn’t work quite the way you seem to understand it. The round is fired by a hammer that smacks the “bullet” on the nose, pushing the round back against the firing pin. As the round travels down the barrel, it pushes the hammer out of the way, re-cocking it. Here’s an article that tells a little more about the weapon: MBA Gyrojet. I also understand they made a carbine version of this weapon that used the same ammunition. The Gyrojet was an answer to a question nobody asked. It was an amazing technological achievement, but wasn’t that much better than a regular old pistol.
~~Baloo
My father helped build a three-stage projectile that is conventionally fired like a bullet, but the burn-time of the traditional second charge then burns its way into a solid-propellant stage that ignites like a rocket once the projectile is out of the barrel. I would imagine the caliber is quite large, and primarily designed for penetrating heavy armor.
An ideal gun for use in vacuum might use the same principles: low-reaction ejection from a rifled barrel (with, perhaps, a reciprocating exhaust) to aim the projectile, followed by a kick-in propellant to accellerate it to lethal speeds.
Robert Heinlein was one of the first to point out that a rifle on the moon should work much better than on Earth. With no atmosphere for which to compensate, a sight need only compensate for the slight gravity, omitting such Earth-important trivialities such as oil in the barrel and “windage.” However, I agree with Finangle’s observation that a shotgun shell might deform. Your first shot might be the only one you get, so aim true.
If anything, it sounds like a carbine version would be more effective. The article mentions a couple of disturbing characteristics. First, they talk about the range being limited, like any other pistol, but it sounds like it is for the same reasons. A pistol is less stable than a shoulder fired weapon, but it also suffers from a short sight radius. At least a carbine would spread the sights enough to allow the shooter to aim more precisely at longer ranges. The other problem (for a pistol) was that it takes a couple of yards to reach sufficient velocity for penetration. If you’re rushed by multiple targets and one gets within 6 feet, you’re just going to amuse him.
A multi-stage hybrid would be a better option. Give it enough muzzle velocity for penetration as soon as it clears the barrel, and then the rocket motor let’s you penetrate harder targets at a greater distance.
I’d never heard of the Gyrojet before. Sounds like it would be ideal as the next generation of military weapons. Put a heatseeker or laserseeker on the nose of the bullet, pop out guidance fins on the tail, and you’ve got a bullet that’s a guided missile. Cool, but also kinda scary in its implications, which I’ll omit…
Fortunately even if the technology existed to make guidance hardware that small, the expense would probably make it unreasonable.
First some accountant would have to weigh the cost of weapons & ammo against the cost of replacing soldiers if they have to be exposed to enemy fire while using a conventional weapon.
The gyrojet was mentioned on “The History of the Gun” recently, one of the reasons that it was not particularly useful was that it was wildly inaccurate, with a very low “muzzle velocity” its attitude when it finally picked up speed was more or less random.
I’ll just add something I saw in a movie.
In the classic Abbott and Costello Go to Mars, while they are in outer space, Costello fires a gun at one of the bad guys who have stowed away in the rocket ship. The bullet simply drops to the floor, “because they have moved away from Earth’s gravity,” IIRC.
If you think that’s goofy, the title is really crazy. They visit New Orleans and Venus, but never Mars.
THAT’S CRAZY!!!