Components of a warp engine, generating the energy needed to form a warp field and propel a spacecraft into transluminal speeds.
Nacelles are usually located near the rear of a ship, connected to the engineering hull by long support pylons. This keeps the potentially dangerous warp fields away from inhabited areas. The shape of the hull has typically been designed to help it achieve warp speed, and to work with the nacelles in influencing the geometry of the field.
Inside the nacelles, warp plasma generated by the warp core is turned into energy that propels a ship. In emergencies, when plasma is unable to reach the nacelles, the Bussard ramscoop assembly at the front of each is able to draw in low-grade galactic matter, and use this as an energy source instead. There are two major components to warp nacelles: the plasma injection system, and the warp field coils. The former is located at the terminus of each of the power transfer conduits. These carry plasma from engineering, where it is generated, to the warp field coils, where it is turned into energy. There is one injector for each of the coils, and each pair is fired in variable sequences, allowing for the permutations to be specified for different types of flight function. The open-close cycle can vary between 25 and 50 nanoseconds; low warp factors require the injectors to be fired at low frequencies, remaining open for short periods, higher warp speeds require higher frequencies and longer openings. The longest cycle for which an injector can be open safely is 53 nanoseconds. The warp field coils generate the actual warp field that propels a ship, by forming an intense, multi-layered effect around the vessel. The ship is propelled beyond the speed of light by manipulation of the field’s shape.
The number of coils varies from ship to ship. On a Galaxy-class vessel, each nacelle contains 18 of them. The Sovereign-class, meanwhile, has 26 sets. Combined, they account for almost a quarter of the ship’s weight.