Space stations can be used for observing the Earth and sky, and for carrying out scientific experiments and engineering processes in the conditions of weightlessness and the high-vacuum environment that exist in space.

The Soviet Union launched the first space station, Salyut 1, in April 1971. It was cylindrical, with a length of 12 m (39 ft) and a maximum diameter of 4.1 m (131 ft). The first crew to occupy Salyut died during the return to Earth when their Soyuz ferry craft depressurized. The first American space station was Skylab, weighing 75 tonnes and measuring 25 m (82 ft) long, made from the converted top stage of a Saturn 5 rocket. Three crews, each of three astronauts, spent periods of 28, 59, and 84 days respectively aboard Skylab in 1973 and 1974.

In all, seven Salyut space stations were launched by the Soviet Union. An improved space station, Mir, was launched in February 1986. Mir was originally similar in size to Salyut1, but has been expanded by the addition of extra compartments launched separately and docked to it. Crews have spent a year or more aboard Mir to assess the effects of long-term weightlessness on human beings. Crews visit Mir on shorter flights and have included astronauts from many nations, among them the first Briton in space, Helen Sharman. However, the space station has been plagued with increasingly frequent technical problems, and its continued operation into the 21st century seems unlikely.

A small European-built space station called Spacelab can be carried in the cargo bay of the American space shuttle, remaining there throughout its mission for scientific and engineering studies.

The United States, Russia, the European Space Agency, Canada, and Japan are collaborating on the International Space Station. The plans called for the first section to be launched on a Russian Proton rocket from Baikonur cosmodrome and the second to be launched on the space shuttle from Kennedy Space Center at Cape Canaveral, Florida. The station is due for completion in 2002, after five years' construction work in orbit. Future space stations may spin to provide artificial gravity, like the wheel-shaped station in the classic science-fiction film 2001: A Space Odyssey (1968) by Stanley Kubrick. Artificial gravity may be a medical necessity for long-term use of space stations: already cosmonauts are forced to undertake hours of exercise every day to avoid the weakening of bones and muscles that can result from long-term exposure to weightlessness.

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