"Enough of this. Bring up the Railguns, let's finish this and go home."
-Theresa Yao-A Rail Gun is a powerful ship-to-ship weapon used by the United Nations Navy, the Martian Congressional Republic Navy, and Protogen Corporation for space combat.
Railguns are large, powerful mass drivers, cannons that use electroconductive rails and the Lorentz Effect to accelerate a dense metal slug at very high speeds, relying on mass and sheer speed to punch clean through ships rather than warheads like with torpedoes. These weapons require significant power (presumably supplied by a fusion power-plant) to fire and must charge briefly before firing.
Rail guns are typically spinal weapons that require the ship to turn and face the target to aim the weapon. This is the case with Protogen's stealth ships. Donnager-class Battleships, however, carry at least a pair of Railgun turrets, allowing them to more easily engage targets without having to rotate the ship.
Railgun shots are powerful and accurate, capable of shooting clean through even large ships and doing critical damage, shown as they take down a Stealth Ship with one shot. However, if the shot does not hit critical components, it will over-penetrate through cleanly, leaving clean holes that can be plugged relatively easily.
Railguns are used almost exclusively in CQB (close quarter battles) because while the round is quite fast it is unguided and can be dodged fairly easily at longer ranges. Because of their short-range lethality, it was considered as suicidal to attack a Donnager-class battleship at close range.
"But here they were, firing the ship's big cannons, which meant that the range was sufficiently short that a nonguided weapon was viable. Hundreds or even dozens of kilometers, not thousands."
*Possible Spoiler Alert*Rail guns first enter the stage on the MCRN Donnager, a Martian battleship, in a CQB battle against an attacking squadron of Protogen Stealth craft, taking out the attackers with single hits. The "bandits" then reveal their own rail guns, putting shots clean through even the larger Donnager's hull. One shot penetrated so far into the Donnager that it decapitated Shed Garvey on its way through.
At the Battle of Thoth Station, a Protogen Stealth ship brings her integral Railgun to bear against Rocinante at point blank, scoring a hit on the Corvette's hull. The shot, however, hit nothing vital.
Rocinante later acquires a spinal railgun of her own to further enhance her combat capabilities.
- A rail gun uses the Lorentz Force, as in it will move perpendicularly or at a right angle with respect to the direction of the current path and magnetic field, to accelerate projectiles. The effect is initiated when a pair of electrically charged rails is bridged with an electroconductive material, like Tungsten for example.
- Current US Navy testing of Railguns employ Tungsten projectiles. Should the weapons be deployed, they will use Tungsten or Depleted Uranium projectiles.
- In the Expanse series, Railguns are sometimes referred to as Gauss guns. This is a contradiction, as Gauss guns are coilguns, which use magnetic coils to propel the projectile instead conductive rails. The name "Gauss" comes from Carl Friedrich Gauss, an 18th-century German mathematician, who formulated mathematical descriptions of the magnetic effect used by magnetic accelerators. His principals are applied to coil guns.