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Terminal.png This article, Weapon/Anti-Ship Model 21 Directed Ion Cannon, was written by Ajax 013. Please do not edit this fiction without the writer's permission.
Weapon/Anti-Ship Model 21 Directed Ion Cannon
Production information



Directed Ion Cannon

Technical specifications
  • 212 meters
  • 405 meters B version
  • 1010 meters C version
Damage Per Hit


Ammunition Type

Compressed Hydrogen gas/plasma core

Rate of Fire

1 pulse per fifteen seconds


variable upon line of sight, atmospheric conditions, 1200km max


Necros War




"It had us cold. The Assault Carrier swung right around the Zeus and was coming on our flank, our MAC turret wouldn't dent its shields. Then, the UNSC Thunder Lord fired off both its Ion Cannons, took that bastard's shields off straight away. It fired one of them again, blew out its wing section, screwed it with EMP. We blasted our MAC turret right into it's nose plasma turret and it just about blew off the whole entire prow section."
―Lieutenant Leonard Iridan

The Weapon/Anti-Ship Model 21 Directed Ion Cannon is a experimental UNSC energy weapon, being mounted on warships. The weapon fires a particle beam of ionised atoms.


The weapon ionizes hydrogen gas by either stripping an electron off of each hydrogen atom, or by allowing each hydrogen atom to capture an extra electron. When hydrogen gains electrons it forms anions. The weapon accelerates anions uses a travelling wave type particle accelerator. In this kind of ion accelerator, the negative ions are released inside a cylindrical ion acceleration chamber. This chamber has an electrode with an alternating electric charge of up to 1,000,000,000 (109) volts inside it. While the charge on the electrode is positive, the ions are attracted to the negative charge on the electrode, and thus bunched around it. The alternating voltage switches the charge to negative on the accelerating electrode. The negative charge electrostatically repels the negative ions and accelerates them to near the velocity of light. The resulting high energy beam of anions passes through a chamber filled with low pressure gas. There, collisions with the gas strip the extra electrons from the anions, and thus make the particle beam neutral. The particle beam proceeds straight to its target, and damages it by running into it, and by disrupting the structure of the target with its kinetic energy. The weapon has the background effect of Electromagnetic Radiation.

The weapon was in experimental stages during the Remnant War, being mounted on a limited number on Heimdall-class Frigates, Indra-class Destroyers, the larger, 21B version, mounted Thermopylae-class Cruisers and the larger still C version being mounted on Talion-class Battlecruisers. During the Necros War it was brought out of experimental stages and mounted in increasing numbers, though no where near the same as the MAC and its varieties. The weapon was placed in lieu of MACs and had a augmentive effect when used in conjunction with MACs. The weapon was highly effective against ship shielding and its background EMP pulse could leave unshielded ships dead in the water. The weapon is less than effective against ship armour though, capable of moderate penetration, its damage is nothing comparable to that of a MAC.

The most basic version has a output of 90,000 megawatts, while the B has a output of 360,000 megawatts, and the C has a 23,000,000 megawatt output.

UNSC Comments

Individual and Crew Served Weaponry of the UNSCDF


M6L Personal Defence Weapon System | M57 Pistol | M98 Compact | M19 Modular Pistol

Submachine Guns

M20A Submachine Gun | M12 Special Operations Carbine | M8Z Submachine Gun

Assault Rifles, Carbines, and Battle Rifles

MA6A Individual Combat Weapon System | M2A Carbine | M81 Special Purpose Carbine | M55C Enhanced Battle Rifle

Designated Marksman Rifles

M396 Designated Marksman Rifle | M97 Special Purpose Rifle | M113 Special Purpose Rifle

Machine Guns

M397 Individual Automatic Rifle | M739C Squad Automatic Weapon | M122 Light Machine Gun | M247B2 General Purpose Machine Gun | M247H2 Heavy Machine Gun | AIE-486K1 Heavy Machine Gun | M343A3 Heavy Machine Gun | M780 Special Purpose Machine Gun

Sniper Rifles

M22 Scout Rifle System | M818D Enhanced Modular Sniper Rifle System | M1091 Sniper Rifle System | Sniper Rifle System 99G-S6 Anti-Materiel | M99CA1 Special Application Scoped Rifle | M133 Precision Anti-Materiel Energy Weapon System


M45F Close Assault Weapon System | M108A1 Close Assault Weapon System | M77 Extreme Close Quarters Combat System

Energy Weapons

Weapon/Anti-Vehicle Model 6B Grindell/Galilean Nonlinear Rifle | MX4 Light Support Weapon | M921 ARC

Non-Lethal Weapon

M2 Threat-Negation Device | MX9 Pulsed Energy Projectile System | M39 Long Range Tranquillizer Rifle

Missile and Rocket Launchers

M41B2 Medium Anti-Vehicle/Assault Weapon | M899 Light Anti Armour Weapon | M57 Light Multipurpose Assault Weapon | M1 Multiple Launch Rocket System | M25 Underslung Rocket Launcher

Grenade Launchers

M319N Individual Grenade Launcher | M23 Multiple Grenade Launcher | M363B RPD | M460C Automatic Grenade Launcher | M556 Counter Defilade Grenade Launcher | M24 Underslung Grenade Launcher | M26 Grenade Launcher Module


M71 Mortar | M78 Mortar | M81 Mortar


M117 Light-Weight Field Howitzer

Sentry Guns

M55 GUARD DOG Sentry Gun | M601 GARGOYLE Sentry Gun


M9 Dual Purpose/High Explosive Grenade | M2 Anti-Materiel Grenade | M70 Flash Bang Grenade | M43 Smoke Grenade

Anti-Personnel and Anti-Armour Mines

M320 Anti-Tank Mine | M341 Anti-Tank Mine | M362 Anti-Tank Mine | M121 Bounding Anti-Personnel Mine | M127 Anti-Personnel Mine

Explosive Devices

C-7 Foaming Explosive | C-13 Gertex | C-14 Plastic Explosive | C-15 Liquid Explosive | M303 Thermite Cord | M311 Detonation Cord | M382 Special Munition Attack Charge (Kinetic) | M390 Breaching Charge | M394 Clearance Charge | M404 Special Lightweight Attack Munition | M366 Demolition Charge | M376 Satchel Charge | M379 Explosive Pack