Space habitats

A space habitat (also called space settlement) is a permanent human settlement in space. Currently (2024), no space habitat has ever been built, and none is expected to be built in the next years, but many space habitat design concepts have been conceived.

Bernal sphere

A Bernal sphere is a space habitat first proposed in 1929 by John Desmond Bernal, with a spherical shape and a diameter of 16 km, to house a population of 20,000 to 30,000 people. In 1975 and 1976, Gerard K. O'Neill envisioned a modified version of Bernal sphere: Island One (500 m in diameter, with a population of 10,000 people).

Detailed design of a Bernal sphere
External view of a Bernal sphere
Internal view of a Bernal sphere
Cutaway view of a Bernal sphere
Cutaway view of agricultural modules in a Bernal sphere
A Bernal sphere under construction

Stanford torus

A Stanford torus is a space habitat, proposed by NASA in 1975, with the shape of a doughnut-shaped ring, that has a 1.8 km diameter, in the version for a 10,000 people population. It can be scaled up to reach a population of up to 140,000 inhabitants.

Collage of figures and tables of Stanford Torus space habitat, from «Space Settlements: A Design Study» book. Charles Holbrow and Richard D. Johnson, NASA, 1977
Cutaway view of a Stanford torus
Internal view of a Stanford torus
External view of a Stanford torus
A Stanford torus under construction
Stanford torus structural cross section

O'Neill cylinder

An O'Neill cylinder is a space habitat consisting of two counter-rotating cylinders, five miles (8.0 km) in diameter and capable of being scaled up to twenty miles (32 km) long. An outer agricultural ring, twenty miles (32 km) in diameter, rotates at a different speed to support farming. It was proposed by American physicist Gerard K. O'Neill (who initially named it as Island Three) in 1976. A space habitat (of extraterrestrial construction) similar to O'Neill cylinder in some respects, but different in many others, was included in Arthur C. Clarke's novel Rendezvous with Rama.

Detailed design of a pair of O'Neill cylinders
Multiple pairs of O'Neill cylinders in space
External view of a pair of O'Neill cylinders
Internal view of an O'Neill cylinder
Another internal view of an O'Neill cylinder
Landscape inside an O'Neill cylinder
Artistic representation of interior of Rama O'Neill cylinder-like spacecraft, from Arthur C. Clarke's novel Rendezvous with Rama
Another artistic representation of interior of Rama O'Neill cylinder-like spacecraft
Space habitat based on O'Neill cylinder, taking advantage of the entire surface area of 5 concentric cylinders
Space habitat based on O'Neill cylinder, taking advantage of the full cylinder volume
Space habitat based on O'Neill cylinder, including an island like Manhattan