Many of the world’s greatest science fiction films depict massive battles in outer space between starships and even the actors themselves, and while much of this takes place in the form of laser blasters or cannons as opposed older black powder muskets or modern semiautomatic pistols and rifles, it still begs the question about what would happen if someone tried to fire a modern-day gun in outer space.
It’s true that modern firearms operate via a combustion-based process, and it’s also true that outer space is essentially an airless vacuum, and so many would be quick to assume that such a gun wouldn’t fire. But quite the contrary – gunpowder contains its own oxidizer that enables guns to fire in airless environments, such as underwater, and perhaps even outer space.
What is worth noting, however, is that the gunshot will not be heard because there isn’t any air for the sound waves to travel through. Moreover, the smoke leaving the barrel of said gun would actually coalesce into a sphere at the end of the barrel, much like how water forms into orbs for astronauts on the International Space Station; this is due to how gravity forces the matter together.
But what of the projectile? If shooting an ordinary gun, the bullet wouldn’t have any air resisting its travel, and it would theoretically just continue moving through space at a constant rate of speed without ever slowing down until it slammed into something.
It’s also worth noting that the firearm’s recoil would have an impact on the shooter as well. The force emitted by the projectile igniting and leaving the barrel would push that person in the opposite direction, causing them to rotate slowly in the vacuum of space.
Obviously, this is all hypothetical, and it would be reckless to fire any type of gun in outer space. But it goes to show just how unrealistic some of those science fiction guns and cannons truly are in the face of real-world physics and the dangers they would present in space-based shootouts.