A couple weeks ago I took a look at railguns, how they work, and how the ones depicted in Starcraft 2 don’t look much like the real thing. This week I’d like to look at another favorite exotic gun in sci-fi video games: the gauss rifle. In Starcraft, the marines carry gauss rifles that act much like real-world assault rifles. In other games, like Fallout 3 and the Mechwarrior series, gauss rifles are a sniper weapon, used to do lots of damage at a distance with a single shot. So, what is a gauss rifle, really? And is it anything like those depicted in the games?
A gauss rifle (also known as a gauss gun or a coil gun) is actually much simpler than the railguns that I talked about before, but it also is based on electromagnetic forces. In a gauss gun, the barrel is a solenoid: essentially a big coil of wire. If you send a current through a coil of wire, it creates a magnetic field in the middle of the coil. We can use the right hand rule to prove this to ourselves: just point your thumb in the direction of the flowing current, and your fingers will curl in the direction of the magnetic field. Make your thumb follow an imaginary coil and you’ll notice your fingers always point the same way!
In a gauss rifle, this magnetic field is used to accelerate a magnetic projectile, essentially pulling it along the barrel of the gun. If you were to leave the current on, you’d just get the bullet stuck in the magnetic field, oscillating back and forth, but by carefully timing the current so that it turns off at the right time, the projectile will go flying out the end of the gun. In some cases, several coils in a row are used to accelerate the bullet to very high speeds.
The advantage of a gauss gun is that it is pretty simple, and doesn’t really have many moving parts. The difficulty is in getting the coils to turn on and off at just the right time, and in pumping enough current through the wires to accelerate the projectile without destroying the coils with the heat generated by their electrical resistance. If you’re dealing with a sci-fi setting, you can say that the coils are high temperature superconductors, which gets you around that particular problem.
I don’t know of any actual military uses of rail guns, but there are hobbyists who make them, and based on the videos I’ve found on YouTube, they are at least strong enough to blast holes in various household objects.
As you can see in the video, these aren’t exactly machine guns. It takes a while for the capacitors to store up enough energy to fire the gun, so I don’t know if a gauss rifle would ever work like a machine gun, as they are depicted in Starcraft. I think the sniper rifle role, as seen in Fallout and Mechwarrior is probably more plausible, though I’m not sure there would be any advantage over traditional guns.
My biggest problem with the gauss rifles shown in Starcraft is not the rate of fire. It’s the shell casings. In every cinematic, we see marines blasting away with their guns, casings flying all over the place. Heck, in one of the videos in Starcraft 2, we see a closeup of the casings piling up on the ground as the terrans try to hold off advancing zerg forces. It’s a nice cinematic touch, but why would a gauss rifle have casings? Those are there to hold the gunpowder behind the bullet! If you don’t have any gunpowder, there’s really no need for a casing, is there? I think this is another case where the “cool factor” was most important. The guns carried by marines are called gauss rifles because it sounds cool, not because they’re actually based on real gauss rifles.