  World ships are hypothetical, large, self-contained spacecraft for crewed
interstellar travel, taking centuries to reach other stars. Due to their crewed
nature, size, and long trip times, the feasibility of world ships faces an
additional set of challenges compared to interstellar probes. Despite their
emergence in the 1980s, most of these topics remain unexplored. This article
revisits some of the key feasibility issues of world ships. First, definitions
of world ships from the literature are revisited and the notion of world ship
positioned with respect to similar concepts such as generation ships. Second,
the key question of population size is revisited in light of recent results
from the literature. Third, socio-technical and economic feasibility issues are
evaluated. Finally, world ships are compared to potential alternative modes of
crewed interstellar travel. Key roadblocks for world ships are the considerable
resources required, shifting its economic feasibility beyond the year 2300, and
the development of a maintenance system capable of detecting, replacing, and
repairing several components per second. The emergence of alternative, less
costly modes of crewed interstellar travel at an earlier point in time might
render world ships obsolete.
