Plasma Drive

An Ark Mechanicus underway under the power of its Plasma Drive.

A Plasma Drive is a form of Imperial subluminal propulsion technology utilised by the vessels of the Imperial Navy as well as civilian voidcraft. A Plasma Drive is a Newtonian reaction drive powered by a vessel's nuclear fusion reactors. It uses internally-generated magnetic fields to eject a form of superheated matter known as plasma at high speeds from the drive's engine housings. Since every action produces an equal and opposite reaction, the vessel is then driven forward at a significant fraction of the speed of light.

Imperial starships utilise this technology as their principle method of in-system propulsion to reach destinations that do not require Warp-based interstellar FTL travel. A Plasma Drive is an ancient and reliable technology of Mankind that is not nearly as dangerous to use as a Warp-Drive.

Notable Plasma Drive Variants

• Jovian Pattern Class 8.1 Drive - The Class 8 drives produced by the Jovian shipyards are constructed from an incomplete STC discovered less than a millennia ago. Although they burn cooler than other Jovian drives, they are far more robust, able to absorb crippling damage without performance loss. These engines are typically reserved for military vessels, and the 8.1 is designed specifically for frigates.
• Jovian Pattern Class 8.2 Drive - Second in the Class 8 series of drives produced by the Jovian shipyards, the 8.2 is designed for light cruisers.
• Jovian Pattern Class 8.3 Drive - Third in the Class 8 series of drives produced by the Jovian shipyards, the 8.3 is designed for cruisers.
• Jovian Pattern class 8.4 Drive - Fourth in the Class 8 series of drives produced by the Jovian shipyards, the 8.4 is designed for grand cruisers. It is rarely produced due to the lack of new grand cruisers constructed by Imperial shipyards.
• Mezoa Pattern Theta-7 Drive - A logical progression of the trend towards ultra-fast clipper style engines, the Theta-7 is a massively powerful and hugely space-intensive civilian plasma drive designed purely for speed. The Theta-7 is constructed using potentially unsafe techniques that involve shoehorning deliberately semi-unstable plasma chambers into the cramped confines of existing transport vessels.
• Saturnine Pattern Class 4a "Ultra" Drive - The popularity of the battlecruiser concept led to a general acceptance that it was theoretically possible to overload the hulls of existing cruisers with weaponry capable of challenging the grand cruisers of previous millennia. The existing power-generating systems of most cruisers were simply not capable of supporting the immense demands of such upgraded systems, so cunningly redesigned plasma drives capable of being mounted within the confines of existing cruiser hulls were created by the Tech-adepts of Mars. These engines are now revered by many Magi as the pinnacle of human technological achievement in the realm of void propulsion.
• Saturnine Pattern Class 5 Drive - For over 10,000 standard years, the grand cruisers of the Imperial Navy have traversed the stars in stately majesty, huge and powerful vessels lined with banks of heavy weapons capable of destroying small moons. The power demands of these regal voidcraft are immense, necessitating gigantic engine rooms larger than whole transport ships. These drives are not space-efficient, but generate more pure power than anything save the engines of the mighty battleships.

Sources

• Rogue Trader: Battlefleet Koronus (RPG), pg. 31