A starship, starcraft, or interstellar spacecraft is a theoretical spacecraft designed for traveling between planetary systems. The term is mostly found in science fiction; as of 2020 no such craft has ever been constructed. Reference to a "star-ship" appears as early as 1882 in . 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. 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. In April 2016, scientists announced Breakthrough Starshot, a Breakthrough Initiatives program, to develop a proof-of-concept fleet of small centimeter-sized light sail spacecraft named StarChip, capable of making the journey to Alpha Centauri, the nearest extrasolar star system, at speeds of 20% and 15% of the speed of light, taking between 20 and 30 years to reach the star system, respectively, and about 4 years to notify Earth of a successful arrival. In November 2018, SpaceX CEO Elon Musk announced that SpaceX was renaming the second stage and spaceship of the Big Falcon Rocket, a fully reusable launch vehicle and spacecraft system, to Starship. Though the spacecraft does not possess any reasonable interstellar capability, Musk defended the name by claiming that "later versions will."
Research
To travel between stars in a reasonable time using rocket-like technology requires very high effective exhaust velocity jet and enormous energy to power this, such as might be provided by fusion power or antimatter. There are very few scientific studies that investigate the issues in building a starship. Some examples of this include:
A common literary device is to posit a faster-than-light propulsion system or travel through hyperspace, although some starships may be 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 to nearer stars. This results in a general categorization of the kinds of starships:
Sleeper, which put their passengers into stasis during a long trip. This includes cryonics-based systems that freeze passengers for the duration of the journey.
Generation, in which the destination would be reached by descendants of the original passengers.
Relativistic, taking advantage of time dilation at close-to-light-speeds, so long trips will seem much shorter.
Certain common elements are found in most fiction that discusses starships.
Slower-than-light
Fiction that discusses slower-than-light starships is relatively rare, since the time scales are so long. Instead of describing the interaction with the outside world, those fictions tend to focus on setting the whole story within the world of the starship during its long travels. Sometimes the starship is a world, in perception or reality.
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 .