Impulse Drive section on a Galaxy Class starship


Impulse Drive diagrams


The impulse engines of Starfleet vessels are fusion powered. They have two primary function, both of which are shared with the warp engines; they propel the ship through space and supply power for the ship's systems.

Impulse engines propel ships at sublight speeds. During normal operations, full impulse is only one quarter the speed of light - above this, problems tend to occur. If a ship travels at half the speed of light engine efficiency will fall to 85 percent, and if it travels at impulse speeds above three-quarters the speed of light relativistic problems may occur.

Control and location

The impulse drive is normally used within a solar system or within regions of space such as the Badlands, which are incompatible with the warp field. Control of the impulse engines is maintained by computer automation and crew command input.

On Constitution-class starships the impulse engines were on the aft edge of the saucer section; on later Galaxy-class starships the main impulse engine is actually four grouped engines located on the aft of deck 23 of the engineering hull. The saucer section is propelled by two engines, each forming a group of two at the aft of deck 10. Each engine has four parts; the impulse reaction chamber, the accelerator/generator, the driver coil, and the vectored exhaust director.

Because of the nature of the energy released during the fusion process, the impulse propulsion system needs slightly more maintenance than the warp propulsion system, even though warp engines are a million times more energetic than impulse engines.

Impulse engines may be used to propel the ship and as a power source at the same time; they can also be used to maneuver a ship and keep it aloft in planetary atmospheres, even if it does not have an aerodynamic shape. Impulse engines should not be confused with maneuvering thrusters, which are used when pinpoint accuracy is needed, such as inside Spacedock.