"Enough of this. Bring up the railguns, let's finish this and go home."
— -Theresa Yao-

A railgun is a powerful ship-to-ship weapon used by the United Nations Navy, the Martian Congressional Republic Navy, the Outer Planets Alliance, 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.

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 Amun-Ra-class stealth frigate. 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 by their ability to take down a stealth ship with one shot. However, if the round does not hit any critical components, it will simply perforate the ship being attacked, leaving small holes that can be plugged relatively easily, such as when Naomi sealed a hole with an instruction manual and specialized adhesive.

Though powerful, 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 more vulnerable. Because of their short-range lethality, it was considered suicidal to attack spacecraft such as 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 railgunsEdit

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.

Laconia-mockup Laconian Imperial NavyEdit

Slow ZoneEdit

  • Ring station railguns: 6✕ railguns. Mounted at intersections between metal rings wrapped around the Ring Station.


*Possible Spoiler Alert*

Railguns first enter the stage on the MCRN Donnager, a Martian battleship, during the Attack on the Donnager against an attacking squadron of Protogen stealth craft, taking out the attackers with single hits. The "bandits" then revealed their own railguns, 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 Assault on Thoth Station, a Protogen stealth ship brought her integrated railgun to bear against Rocinante at point blank range, scoring a hit on the frigate'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 numerous UNN railgun platforms in Earth's orbit to serve as planetary defense platforms. These were used to eliminate several MCRN Stealth C ballistic missile platforms 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 ModelsEdit

UN logo Dawson-Pattern Medium RailgunEdit

A sub-standard 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 Railgun turrets mounted opposite of each on the port and starboard sides of the hull.

UN logo Farren-Pattern Heavy RailgunEdit

One of the most powerful and accurate weapon systems available to the UNN, matched only by the most advanced MCRN railguns 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 Railguns mounted opposite of each other on the dorsal and ventral hull.

Martian Congressional Republic V-14 'Stiletto' Light RailgunEdit

V-14 Stiletto light rail-gun sciroccoclass

V-14 'Stiletto' Light Railgun

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.

Martian Congressional Republic VX-12 'Foehammer' Ultra-Heavy RailgunEdit

An entirely new railgun design purpose-built for the Martian Congressional Republic Navy's Donnager-class Battleships, the VX-12 Foehammer boasts the longest range and greatest firepower of any ship-mounted railgun ever constructed. The barrel alone being longer than an entire Martian frigate, two such weapons are mounted on MCRN Donnager-class Battleships. Another two 'Foehammer' railguns could potentially be mounted on hardpoints on the dorsal and ventral hull in the future.

OPA logo Zakosetara-series Heavy RailgunEdit

Six railguns of this type were attached to the bow of the OPAS Behemoth. Zakosetara-series railguns were extremely powerful, and it was feared that the recoil from these guns would buckle the entire hull of the onetime generation ship, as well as causing ship-wide power grid failures, due to the ship not being designed for combat.

Protogenlogofromspacedockvideo S-24 "Khopesh" Light RailgunEdit


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.


  • A railgun uses the Lorentz Force, in which it will move perpendicularly, or at a right angle, with respect to the direction of the current path and magnetic field to accelerate a projectile. The effect is initiated when a pair of electrically charged rails is bridged with an electroconductive material such as tungsten.[1]
  • 21st century US Navy testing of rail guns[2] employ tungsten projectiles. Should the weapons be deployed, they will use tungsten or depleted uranium projectiles.[3]
  • In the Expanse series, rail guns are sometimes referred to as Gauss guns. This is inaccurate, as "Gauss gun" is a term for coilguns, which use magnetic coils to propel the projectile instead of 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 coilguns.
  • The names of these weapons come from a variety of sources.
    • Foehammer references Tolkien's "Lord of the Rings," being the literal interpretation of Gandalf's sword "Glamdring." It is also referencing Stephen King's "Eye of the Dragon" and the callsign of a UNSC pilot in the "Halo" science-fiction franchise.
    • A khopesh is an ancient Egyptian curved sword.
    • A stiletto is a short knife with a thin, tapering blade resembling the heel of a woman's formal shoe.

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