• Sleeper:
Sleeper ships place their occupants into
cryostasis or temporal
stasis during a long trip. This includes
cryonics-based systems that freeze passengers for the duration of the journey. This is a common trope in science fiction, with some notable examples including
To Sleep in a Sea of Stars by Christopher Paolini and
Edward Bellamy's
Looking Backward. • Generation:
Generation ships are ships in which the destination would be reached by descendants of the original passengers. These ships would necessarily be self-sustaining and self-maintaining for possibly thousands of years. Notable examples of this in fiction are the
Godspeed in Beth Revis'
Across the Universe (and subsequent sequels), as well as the
Vanguard from
Robert A. Heinlein's
Orphans of the Sky. -based generation ship, proposed by
Project Hyperion •
Relativistic: Ships that function by taking advantage of
time dilation at close-to-light-speeds, so long trips will seem much shorter (but still take the same amount of time for outside observers). • Frame shift: Ships that take advantage of the fact that certain dimensions are less "folded" than others, to allow shorter travel by shifting one's
frame of reference into a higher, more flat dimension to cut down on travel time, such as in science fiction with inter-dimensional
hyperspace. Generally this results in speeds close to (but importantly, not greater than) light speed. •
Faster-than-light (FTL): A ship that functions by reaching a destination faster than the speed of light. While according to the
special theory of relativity, faster-than-light travel is impossible, drives like a
warp drive or using a
wormhole, that is in principle similar have been hypothesized.
Theoretical possibilities paper of
Miguel Alcubierre The
Alcubierre drive is a speculative
warp drive conjectured by Mexican physicist
Miguel Alcubierre in a 1994 paper. The paper suggests that space itself could be topographically warped to create a local region of spacetime wherein the region ahead of the "warp bubble" is compressed, allowed to resume normalcy within the bubble, and then rapidly expanded behind the bubble creating an effect that results in apparent FTL travel, all in a manner consistent with the Einstein field equations of
general relativity and without the introduction of wormholes. However, the actual construction of such a drive would face other
serious theoretical difficulties. ==Fictional examples==