"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.

Specs Edit

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.

Railguns 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. Larger ships, however, can carry turreted railguns. The MCRN's Donnager-class battleships and UNN's Leonidas-class battleships and Truman-class dreadnought carry pairs 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 can take down a stealth ship with one shot. However, if the shot does not hit critical components, it will simply over-penetrate, leaving small holes that can be plugged relatively easily such as when Naomi sealed one with an instruction manual and special glue.

Still, 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, although slower ships like the Leonidas-class are easier targets. Because of their short-range lethality, it was considered 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."
— -Leviathan Wakes-

Ships and Stations carrying Railguns Edit

Martian Congressional Republic Martian Congressional Republic NavyEdit

UN logo United Nations NavyEdit

OPA logo Outer Planets AllianceEdit


  • Amun-Ra-class: 1 ✕ prototype internally-mounted S-24 Khopesh Light railgun.

Laconian Imperial NavyEdit

Slow ZoneEdit

  • Ring Station railguns: Multiple railguns.

Appearances Edit

*Possible Spoiler Alert*
Railguns 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 revealed 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 brought her integrated railgun to bear against Rocinante at point blank range, scoring a hit on the corvette's hull. The shot hit nothing vital but drove the Corvette back into the cover of the station until Amos could fix a thruster hampering the ship's agility.

Rocinante later acquired a spinal railgun of her own to further enhance her combat capabilities.

The UNN has deployed about half a dozen particularly large rail guns in Earth's orbit to serve as planetary defense platforms. These were used to eliminate several stealthed MCRN nuclear missile batteries aimed at Earth from long range, although one missile did fire before its launcher's destruction and struck a major South American city.

Once Fred Johnson recovered and claimed the Nauvoo, he rechristened it the OPAS Behemoth and, as well as installing 170 PDCs and 6 torpedo bays to the hull, had 6 capital-grade railgun turrets mounted to the bow. However, while seemingly an impressive armament, the ship's structure had not been designed to handle such weapons. As such, it was feared that the firing of one of the guns would buckle the entire hull or would cause power failures. The mounting of these guns made the Behemoth the System's largest-ever weapons platform.

Known Models Edit

Dawson-Pattern Medium Rail Gun Edit

A railgun used by some UNN warships. Part of the UNN's failed attempt at upgrading the fleet, Dawson-pattern turrets cannot be articulated under thrust, forcing ships that are armed with them to fire while drifting or to have to come to a relative stop. The Leonidas-class battleship is equipped with 2 Dawson-Pattern Rail Gun turrets mounted opposite of each on the port and starboard sides of the hull.

Farren-Pattern Heavy Rail Gun Edit

One of the most powerful and accurate weapon systems available to the UNN, matched only by the most advanced MCRN rail guns and the UNN's fixed orbital gun platforms. Its rounds impact almost instantly on targets within 100km. The Truman-class dreadnought is armed with 2 turret-mounted high-yield Farren-Pattern Rail Guns mounted opposite of each other on the dorsal and ventral hull.

V-14 'Stiletto' Light Rail Gun Edit

The V-14 'Stiletto' is a light rail gun turret employed by the Martian Congressional Republic navy in its Scirocco-class assault cruisers. It features a higher effective range than the UNN's medium and heavy railguns, a testament to Martian technological prowess and giving MCRN cruiser-type vessels a fair chance against even UNN battleships at long range.

Zakosetara-series Heavy Rail Gun Edit

Six railguns of this type were attached to the bow of the OPAS Behemoth. While powerful weapons, it was feared that the recoil from these guns would buckle the entire hull of the ex-generational ship as it was not designed for combat, as well as causing ship-wide power grid failures.

S-24 "Khopesh" Light Rail Gun Edit

The first ever railguns to be mounted onto a Frigate-type vessel, one of these weapons was integrally mounted onto each of the Protogen Corporation's experimental Amun-Ra-class stealth frigates. While requiring the ship to turn and aim the cannon, these gave a comparatively small warship a massive amount of firepower.

Trivia Edit

  • 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.[1]
  • 21st century US Navy testing of Railguns[2] employ tungsten projectiles. Should the weapons be deployed, they will use tungsten or depleted uranium projectiles.[3]
  • 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.

External links Edit