Generation ship

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A generation ship is a hypothetical starship that travels across great distances between stars at a speed much slower than that of light (see interstellar travel). Since such a ship might take from as little as below a hundred years to tens or even hundreds of thousands of years to reach even nearby stars, the original occupants might either grow old or die during the journey and leave their descendants to continue traveling, depending on the life span of its inhabitants and relativistic effects of time dilation.

It is estimated that, in order to assure genetic diversity during a centuries-long trip, a generation starship would require at least 160 inhabitants (according to http://www.newscientist.com/article.ns?id=dn1936). Sperm banks or egg banks can drastically reduce the requisite number. Additionally, the ship would have to be almost entirely self-sustaining (see biosphere and life support), providing food, air, and water for everyone on board. It must also have extraordinarily reliable systems that could be maintained by the ship's inhabitants over long periods of time.

It has been suggested that humans create large, self-sustaining space habitats before sending generation ships to the stars.^{[citation needed]} Each space habitat could be effectively isolated from the rest of humanity for a century or more, but remain close enough to Earth for help. This would test whether thousands of humans can survive on their own before sending them beyond the reach of help.

Some have compared planets with life to generation ships; this idea is usually called "Spaceship Earth".

[edit] In fiction

Generation ships are often found in science fiction stories. The invention is credited to J. D. Bernal in his 1929 novel The World, The Flesh, & The Devil. A common theme is that inhabitants of a generation ship have forgotten they are on a ship at all, and believe their ship to be the entire universe.

Other examples of fictional generation ships include:

The Trigun anime and manga
Captive Universe, novel by Harry Harrison
Non-Stop aka Starship, novel by Brian Aldiss
The Dark Beyond the Stars, novel by Frank M. Robinson
Orphans of the Sky, novella by Robert A. Heinlein
Book of the Long Sun, four-novel series by Gene Wolfe
The Starlost, short-lived 1970s TV series by Harlan Ellison
The Ballad of Beta-2, novella by Samuel R. Delany
Colony, novel by Rob Grant
Original Video Animation Megazone 23
The Rama series of books by Arthur C. Clarke and Gentry Lee
Kelvan Multi-Generation Ship - from the Andromeda Galaxy in the Star Trek episode "By Any Other Name".
The Star Trek episode "For the World is Hollow and I Have Touched the Sky"
The Star Trek: Voyager episode "The Disease"
All Judgment Fled and The Watch Below, stories by James White
Mayflower II, a novella by Stephen Baxter
The Naked God, a novel by Peter F. Hamilton
Learning the World: A Novel of First Contact by Ken Macleod
The Exiles Trilogy, a series by Ben Bova
"Ship of Fools" by Richard Paul Russo
Nemesis by Isaac Asimov
Seed of Light by Edmond Cooper
Chasm City by Alastair Reynolds
Le Papillon des Etoiles by Bernard Werber.
The 1981 BBC Radio 4 show Earthsearch
The novella "Paradises Lost" in The Birthday of the World collection of stories by Ursula K. LeGuin
The Koros-strohna worldships of the Yuuzhan Vong in the Star Wars Expanded Universe are an organic form of generation ship.
In the Star Trek: Enterprise episode "E²", the Enterprise becomes a generational ship in an alternate timeline.
In the computer game Elite by David Braben and Ian Bell, although generation ships are never actually seen in the game, they are discussed in the manual and novella included with the game.

Bruce Sterling's short story Taklamakan is about a group of Chinese habitats that simulate generation ships in a cave under the Taklamakan desert.

The oft-lampooned, low-budget film Space Mutiny takes place aboard a generation ship known as the Southern Sun.

The television series Firefly is set in a far-away planetary system that was colonized by generational ships.

The Marathon series of video games were based around a Generational Interstellar vessel called the "Marathon". The vessel itself is known as a "Colony Ship" and was converted from the Martian moon Deimos.

The Sega Genesis video game Phantasy Star III takes place on a generation ship (although this is not revealed specifically until very late in the game).

Sid Meier's Civilization II allows for the construction of a generation ship (though the in-game transit time can be brought as low as twelve years, much less than what would be required of a generation ship).

The 1977 science fiction pop music concept album "The Intergalactic Touring Band" features a storyline based on generation ships.

In the upcoming MMOG Infinity: The Quest for Earth, The Geodesan people construct a massive generation ship named IOS - 1 (Interstellar Operational Spaceship) to carry 1.1 million Geodesans away from their dying star, Delta.

The first science fiction role-playing game, Metamorphosis Alpha (published 1976), is set on a generation ship whose crew was mostly wiped out, leaving the ship adrift and the mutated occupants unaware that their ship is not the entire world.