While NASA's Voyager and Pioneer probes have traveled into local interstellar space, the purpose of these uncrewed craft was specifically interplanetary, and they are not predicted to reach another star system; Voyager 1 probe and Gliese 445 will pass one another within 1.6 light years in about 40,000 years.[3] Several preliminary designs for starships have been undertaken through exploratory engineering, using feasibility studies with modern technology or technology thought likely to be available in the near future.
Examined in an October 1973 issue of Analog, the Enzmann Starship proposed using a 12,000-ton ball of frozen deuterium to power pulse propulsion units. Twice as long as the Empire State Building is tall and assembled in-orbit, the proposed spacecraft would be part of a larger project preceded by interstellar probes and telescopic observation of target star systems.
A common science-fiction device is to posit a faster-than-lightpropulsion system (such as warp drive) or travel through hyperspace, although some posit starships as outfitted for centuries-long journeys of slower-than-light travel. Other designs posit a way to boost the ship to near-lightspeed, allowing relatively "quick" travel (i.e. decades, not centuries) to nearer stars. This results in a general categorization[according to whom?] of the kinds of starships:[citation needed]
Generation: 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"
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. 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 (using inter-dimensional shortcuts or wormholes). According to the theory of relativity, faster-than-light travel is impossible.
Theoretical possibilities
The Alcubierre drive is a speculative warp drive conjectured by Mexican physicist Miguel Alcubierre in a 1994 paper which has not been peer-reviewed.[8] 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.[9] However, the actual construction of such a drive would face other serious theoretical difficulties.
There are widely known vessels in various science fiction franchises. The most prominent cultural use and one of the earliest common uses of the term starship was in Star Trek: The Original Series.