Sleeper ship

A sleeper ship was a type of Earth spaceship in service in the late 20th and early 21st centuries. The crew of the ship would be placed in suspended animation for all or part of a journey.

Sleeper ships proved necessary because of the time involved in space travel, as it could take years to travel from one planet to another. However, at some point after 2018, propulsion technology advanced and sleeper ships were gradually phased out. 

Despite this, many sleeper ships left Earth bound for other planets with the hopes of colonizing them. Amongst the many planets colonized by Earth sleepers ships was Macedon III. (SS TOS (Under Twin Moons))