Impulse Drive
From FEInfobase
Impulse Drive is the standard sublight engine design for many people across the galaxy, including the Federation.
Speed
Impulse drives are capable of speeds up to about 0.98c, but due to time dilation effects as velocity approaches c, which are negated by warp travel, impulse drives are not used in excess of 0.25c, except for in the case of some fighter craft.