The Plasma Cannon, also sometimes called the Heavy Plasma Gun, is an Imperial heavy weapon that relies on plasma technology to deliver lethal blasts of superheated matter to the target. Plasma Weapons work by using hydrogen fuel suspended in a cryogenic state, in either fuel flasks or backpack containers. As the fuel is fed into the miniature fusion core inside the weapon, the hydrogen energises into plasma which is held in the core of the weapon by powerful electromagnetic containment fields. When fired, the fields dilate open and the plasma is ejected via a linear magnetic accelerator as a bolt of superheated matter akin to a solar flare in appearance and temperature. This bolt will explode on impact and can generate the destructive heat of a small sun. For this reason, Plasma Weapons are sometimes called “Sun Guns” by the common Imperial population.
Plasma Weapons tax their cooling systems considerably, and Space Marines push the limits of their own resilience by using hydrogen in a higher quantum state in their plasma weaponry than is common in more standard Imperial patterns of the weapon. Plasma Cannons are the largest kind of portable Plasma Weapons, and rather than using the standard fuel flasks that are attached to the weapon, the wielder must wear a large hydrogen fuel canister that can attach to their backpack unit. Plasma Cannons have a greater range and ammunition supply than the standard Plasma Gun, and its violent discharge hurtles like a minature sun from its barrel, impacting a large area and producing a significant area of effect. Plasma Cannons also can fire in a maximal mode setting, where the weapon will exhaust even more fuel to provide an even larger blast of plasma on impact, creating a fireball that is capable of destroying heavily-armoured targets. However, like all Imperial Plasma Weapons, Plasma Cannons are prone to overheating and can prove as deadly to the user as to the target.
The Space Marines represent one of the few Imperial infantry units that are capable of carrying Plasma Cannons because of the weapon's heavy weight. A Space Marine's Power Armour also offers better protection against the weapon when it overheats or malfunctions. Plasma Cannons are commonly only wielded by Devastators within Space Marine Chapters, although a member of a Tactical Squad can also carry one. However, Gun Servitors are also capable of carrying Plasma Cannons into battle, and their expendable nature makes them suited to the task of wielding such a dangerous weapon. Plasma Cannons are more commonly mounted on vehicles, however, due to as the effects of overheating are then less severe to the vehicle's crew, who can take refuge within the vehicle's armoured shell. Imperial vehicles such as the many variants of the Leman Russ Battle Tank can mount Plasma Cannons as sponson weapons, while Imperial combat walkers such as Sentinels and Dreadnoughts can also carry Plasma Cannons into battle.
Known Imperial Plasma Cannon Patterns
- Erasmus Pattern Mark I - Heavily utilised by the Dark Angels Space Marine Chapter, the Erasmus Pattern Plasma Cannon uses replaceable charges rather than a carried power-supply. This makes the weapon lighter, allowing for other gear to be carried, but reduces the overall number of shots possible.
- Mark XII "Comet" Pattern - A notable pattern of Plasma Cannon utilised by the Novamarines Space Marine Chapter.
- Mark XII Ryza Pattern - A notable pattern of Plasma Cannon utilised by the Red Scorpions Space Marine Chapter.
- Mark XIII "Ragefire" Pattern - The Mark XIII is the most common pattern of Plasma Cannon used by the Chapters of the Adeptus Astartes in the late 41st Millennium.
- Monocore Ryza Pattern - A notable pattern of Plasma Cannon utilised by the Executioners Space Marine Chapter.
- M31 Pattern - An ancient pattern of Plasma Cannon still used by the Traitor Legions of Chaos Space Marines
- Plasma Storm Battery - A Plasma Storm Battery is an ancient form of Plasma Cannon utilised by the Dark Angels Space Marine Chapter. It can fire in two modes: a rapid burst mode, or a slower; supercharged mode that emits a toroid of plasma to explode over a larger area for higher damage.
- Sol Militaris "Helion Fire" Pattern Plasma Cannon - The "Helion Fire" Pattern Plasma Cannon was of the duplex magnacore type; it was manufactured on Terra and issued to the Space Marine Legions during the Great Crusade and Horus Heresy eras. It was considered particularly effective when used against constructs and armoured infantry.
Xenos Plasma Cannons
Analogues of this weapon can also be found in other intelligent races of the galaxy including:
- Starcannon - An Eldar Starcannon, while based on the same Plasma technology as the Imperial variant, does not suffer from overheating problems. The Adepts of the Imperium have never really harnessed the full power of plasma technology; only the Eldar have truly mastered its potential. To the Eldar, it is further testament to the idiocy of Man that he has created a weapon that frequently maims or even kills the wielder. The sophisticated Starcannons and Suncannons of the Eldar have no such flaws. Each weapon's plasma core produces the incandescent heat of a star, but sophisticated containment fields ensure that the gun's exterior remains cool to the touch. However, a Starcannon is too large to be carried by infantry and is only mounted on Eldar vehicles, such as Wave Serpents, Falcons, and War Walkers, or fire support platforms which commonly accompany Guardian squads. Despite this limitation, the Starcannon is favoured by many Eldar commanders due to its sheer destructive power.
- Disintegrator Cannon - A Disintegrator Cannon fires a particle of unstable matter harnessed from a stolen sun, and is a far more sophisticated weapon than other forms of conventional plasma-based weaponry. A Disintegrator Cannon is able to maintain a high rate of fire and always remains cool to the touch despite the ravening energies housed within.
- Kustom Mega-Blasta - Sometimes built by Ork Mekboyz, Kustom Mega-Blastas are weapons that are far greater than the sum of their parts, a marvel of Ork technology that fires a focused blast of pure energy at its targets.
- Tau Plasma Cannon - So far, Tau Plasma Cannons have only been mounted as a variant turret on Hammerhead gunships, and were first identified by the Imperium during the Taros Campaign where it is believed they were being field-tested. They use the same plasma technology as that incorporated into Tau Plasma Rifles, but are far larger in size. Because of this, they are more powerful than the Plasma Rifle and also fire more rapidly. However, a Plasma Cannon sacrifices some of its armour penetration power for this advantage, making it similar in damage output to an Ion Cannon.
Change of Terminology
The term "Plasma Cannon" was first used to refer to the weapon during the 3rd Edition release of the Warhammer 40,000 rules set. Prior to the 3rd Edition, the weapons now referred to as Plasma Cannons were called Heavy Plasma Guns.
- Black Crusade: Core Rulebook (RPG), pg. 158
- Codex: Blood Angels (5th Edition), pp. 58-59
- Codex: Chaos Space Marines (6th Edition), pg. 65
- Codex: Chaos Space Marines (4th Edition), pg. 82
- Codex: Chaos (2nd Edition), pp. 74-75
- Codex: Dark Angels (6th Edition), pg. 60
- Codex: Dark Eldar (5th Edition), pp. 56, 59
- Codex: Eldar (6th Edition), pg. 63
- Codex: Imperial Guard (5th Edition), pg. 69
- Codex: Orks (4th Edition), pp. 89-90
- Codex: Space Marines (5th Edition), pp. 99, 101
- Codex: Space Marines (4th Edition)
- Codex: Space Wolves (5th Edition), pp. 59-60
- Codex: Tau Empire (6th Edition), pp. 50, 66
- Deathwatch: Core Rulebook (RPG), pg. 147
- Imperial Armour Volume Nine - The Badab War - Part One, pp. 86, 120
- Imperial Armour Volume Ten - The Badab War - Part Two, pp. 90, 138
- Only War: Core Rulebook (RPG), pg. 180
- The Horus Heresy - Book One: Betrayal (Forge World Series), pg. 232
- The Horus Heresy - Book Two: Massacre (Forge World Series), pg. 17
- Warhammer 40,000: Battle Manual (2nd Edition), pg. 64
- Warhammer 40,000: Rogue Trader (1st Edition), pg. 84
- Warhammer 40,000 Rulebook (6th Edition), pg. 57
- Warhammer 40,000 Wargear (2nd Edition), pg. 80
- Warhammer 40,000: Eternal Crusade - Rogue Trader Store: Erasmus Plasma Cannon Mk I