A generation ship is an immense, relatively slow-moving spacecraft, also known as an interstellar
ark, aboard which many generations would live and die on a voyage
between stars. The generation ship has been offered as an alternative to
spacecraft that travel at much higher speeds carrying conventional-sized
crews. The idea of a vessel carrying a civilization from a dying solar system
toward another star for a new beginning was envisioned in 1918 by Robert Goddard. But, perhaps concerned about professional
criticism, he placed his manuscript in a sealed envelope and it didn't appear
in print for over half a century. Konstantin Tsiolkovsky and J. D. Bernal wrote about artificial
planets and self-contained worlds in the 1920s, as did Olaf Stapledon in his visionary novels, and by the 1940s the generation ship concept had
been fully expanded by science fiction writers in the publications of Hugo
Gernsback and others. Perhaps the earliest example of a true generation
ship appears in Don Wilcox's "The Voyage That Lasted 600 Years" (1940).
Robert Heinlein, in Orphans of the Sky (1958), first published in 1941 as a serial in two parts, "Universe"
and "Common Sense," raised the possibility that the crew of such
a vessel might eventually forget they were aboard a ship and believe instead
that they were the inhabitants of a small world – a theme taken up
in one of the original Star Trek episodes:
"For the World is Hollow and I Have Touched the Sky." Another generation
ship appears in the Star Trek: Voyager episode "The Disease".
In 1952 L. R. Shepherd examined the idea of the generation ship in more
technical detail and described a nuclear-propelled million-ton interstellar
vessel shaped as an oblate spheroid, which he called a "Noah's Ark". Such
a ship would be a microcosm of human civilization with a substantial and
highly varied population, extensive educational,
recreational and medical facilities, food production areas, research laboratories
and so forth – effectively, a miniature, nomadic planet. There is
perhaps a strange attraction in the idea, though whether anyone would willingly
volunteer to exile themselves to such an environment knowing that they would
die some fraction of the way to the ultimate goal is hard to say. Perhaps
there would be less of a psychological problem for subsequent generations
who were born aboard the ship and therefore never knew what life was like
on the surface of a planet under open skies. Then, again, how difficult
would it be for those who finally reached journey's end to step outside
the confines of their artificial world? Like many other old ideas in space
travel, including Lucian's waterspout and
Well's cavorite, the generation ship now
seems quaint and romantic. Almost certainly, interstellar
travel will never be accomplished by this means though it is still possible
that the related concept of the space colony will come to fruition.
|The Varro generation ship in Star
Trek VOY: "The Disease"
The AAAS held a session on interstellar travel in 2002 where the anthropologist
John Moore estimated that a population of 150–180 was just big enough
to allow normal reproduction for 60-80 generations. [Thanks to Michael H.
from Australia for this notification and for his valid comment: "The generation
ship will be extremely difficult to build, but there don't seem to be any
show-stoppers," and also to Larry MacCaskill for details of Heinlein's works.]