The idea of taking guns into space has a long and scientifically…um…questionable history. It hasn’t been done much in real life (the pictured Soviet TP-82 is a rare exception) but literature abounds with fictitious examples. We’ve been speculating about heat rays, Phasers, and Imperial Laser Blasters for ages, but where does science take you when you start thinking about shooting real guns in space?
Live Science posted a fascinating article about shooting in space, but it offers little practical advice for the Armed Interplanetary Intelligentsia. With that in mind, I thought I’d add some more completely useless space shooting tips of my own.
Yes, guns will fire in space.
Combustion as we know it on Earth is nothing but the rapid oxidation of chemical compounds (typically with atmospheric oxygen) giving off heat and chemical byproducts. There can be no combustion without oxygen in the vacuum of space, but gunpowder and primers contain their own oxidizing agents so they’ll still ignite and propel the bullet out of the barrel.
The muzzle velocity for bullets fired in space could be slightly higher than the muzzle velocity for the same gun and cartridge fired in the Earth’s atmosphere, because the bullet will not have to push the atmosphere out of its way as it speeds down the barrel and out ofthe muzzle. This effect will only show itself if you keep the gun and cartridge at room temperature up until the time of firing, which leads us to the next tip.
Keep your powder warm, or wait for Hodgdon’s ‘Zero K’ space gunpowder.
Some propellants like Cordite are very temperature-sensitive, and were known to produce dangerously high pressures when Professional Hunters left their .477 Nitro Express ammo sitting in the Kenyan sun for too long. At the other end of the thermometer, really cold gunpowder (at 2.7 degrees above absolute zero) doesn’t burn as efficiently as room-temperature gunpowder, and a lot of it might not burn at all.
Proper ammunition handling can avoid this problem. If you keep your gun and cartridges at room temperature (say, inside your spacecraft) and only take them out the airlock briefly to fire them, they should still remain at nearly room temperature for some time and provide optimum ballistic performance.
If firearms in space become a viable market niche (never gonna happen) I’m sure SAAMI would test and certify certain propellants and primers for proper functioning at space temperatures.
Keep your guns cool.
Combustion is, well, hot, and that heat builds up in guns and has to go somewhere. Earthbound guns can cool off relatively quickly, because they benefit from conductive and convective cooling. A hot AR sheds its heat (conduction) to cooler surrounding air molecules, which becomes less dense and rises (convection) and makes room for heavier cooler air, which heats and becomes less dense and rises, etc.
Conduction and convection are why your smoking-hot AR barrel is safe to touch after ten minutes’ rest with the bolt held open. In space, none of this occurs: guns might start out very cold, but they heat up quickly and stay hot for a long time. How long? Black-body radiative cooling is governed by the Stefan-Boltzmann equation, which you’ll have to work out for yourself since I dropped out of college physics:
However the numbers crunch out, I’d bet a box of Barnes Bullets that after a few 30-round mag dumps, your AR’s cooling time will be measured in hours, or even days.
And keep them slightly rusty.
At low temperatures, uncoated metal can adhere strongly to the same uncoated metal. It’s called cold-welding, and it almost never happens on Earth because our oxygen-abundant atmosphere instantly attacks uncoated metals and leaves them coated with a thin layer of oxidation.
One solution to this problem is to make sure your metal gun parts are slightly oxidized, and this is easily accomplished by keeping them with you inside your hypothetical spacecraft. Keep in mind that excessive wear (between the bolt and barrel, or slide and frame) can scrape off the thin oxide layer and allow the parts to cold-weld themselves together forever.
Another solution is to use dissimilar metals in gun construction, to make sure that steel never touches a similar blend of steel anywhere in the gun. Either way, your all-steel 1911 is a good gun to leave Earthside.
Forget everything you thought you knew about ballistics.
As Einstein noted, everything is relative, so once the bullet leaves the barrel it’s only meaningful to speak of impact velocity, the speed of the projectile relative to the velocity of the intended target. This metric, and not muzzle velocity, determines how much damage you’ll do downrange.
Everything in space is moving relative to you. Some are moving toward you and some away from you, and most of them are doing it really quickly. Your AR bullet (which left your gun at 1,000 m/s) can either smash into them at many kilometers a second with the force of a 20mm cannon, or never catch up to them at all.
And projectiles in a microgravity vacuum don’t follow the external ballistics tables in the Speer Reloading Manual. They follow Newton’s First Law Of Motion: an object in uniform motion remains in motion until an external force is applied to it. This means that at 100 meters, or 100 kilometers, or 100,00o, or beyond the disk of the Milky Way galaxy, your bullet will still be traveling at exactly muzzle velocity unless it has hit something or encountered another force (read: gravity) to speed it up or slow it down, relative to the muzzle.
When your bullets don’t suffer any appreciable loss of velocity even at ranges of dozens of kilometers, you might be tempted to mount a 100x scope and take some pretty long shots. Don’t do it: everything in space is moving relative to you, and at ranges of dozens or hundreds of kilometers you’ll have to lead your target by an unknowable amount while compensating for orbital and gravitational perturbations. As the Live Science article points out, you could even end up shooting yourself in the back if you’re in orbit.
Choose your shooting stance carefully.
Newton’s Third Law states that for every action, there is an equal and opposite reaction. All shooters understand this law instinctively, since we’re subjected to recoil every time we drop the hammer. As unsettling as the recoil from your .50 Beowulf is on Earth, it gets much, much worse in microgravity because there’s nothing for you to brace against.
Planetside, we manage recoil by absorbing the force with our muscles, and transmitting some of that absorbed force into the ground through our feet. In microgravity, only the tiniest recoil impulses could be completely absorbed by our muscles, and the recoil from a firearm would send the shooter cartwheeling slowly backwards unless they’d firmly attached themselves to a massive firing platform like their spacecraft.
Firearms meant for use in space could be designed to produce nearly zero recoil impulse, using the principle of the recoilless rifle. Just like a recoilless rifle or RPG, these designs would create a massive blast area behind the shooter.
Conclusion: Why bother?
Only the Russians have ever thought to arm their cosmonauts, and the three-barreled pistol shown above was designed primarily for signaling and fending off wolves in the event of an off-target Soyuz landing. These still occur with remarkable frequency, but Russia has reportedly retired these now-elderly guns and now includes a regular service pistol in their Soyuz survival kits.
NASA never saw a need to send firearms into space; they sent machetes instead. Space is demilitarized by treaty, it’s the ultimate low-crime neighborhood (zero humans=zero crime) and it’s a rotten place to go hunting. Guns in space are as useful as chariots on an aircraft carrier.