Sublight speeds

Sublight or space-normal speed is a term that refers to anything below the speed of light, approximately 3 × 108 meters/second.

Sublight is usually used to describe non-warp speeds, typically when either an impulse drive or maneuvering thrusters would be used as propulsion for a vessel. This speed is typically expressed as a fraction of the speed of light, c.

Full impulse is .25c, or a quarter of the speed of light. Though many starship engines can achieve a speed greated than full impulse, as soon as .25c is exceeded issues with relativity are experienced. These problems get exponentially worse the closer one gets to c.

Star Fleet vessels are not permitted to travel at speeds greater than full impulse without going to warp.