Why build a station
Early crewed capsules were designed for short trips: a few hours in orbit, or a couple of weeks at most. They were cramped, and every flight needed a new rocket and spacecraft. A space station is a different idea. It stays in orbit, is visited by crews and supplies, and offers room for experiments and for people to live and work for months.
The concept appeared in early writing about spaceflight, and by the 1950s designers were considering large wheel-shaped habitats. Reality began more modestly. Stations are limited by launch size, life support, power, and the need to resupply food, air and equipment, and each generation of station was shaped by what rockets could lift.
Salyut and the first stations
The Soviet Union launched the first space station, Salyut 1, in April 1971. A crew arrived aboard a Soyuz and stayed for about three weeks. The mission ended in tragedy when the next crew, returning on Soyuz 11 in June 1971, died after the capsule lost air pressure during the return. The accident led to design changes, including requiring crews to wear pressure suits during launch and landing in later flights.
The Soviet Union continued with more Salyut stations through the early 1980s, some of them civilian and some military. These stations developed techniques that later became routine: docking of crew ships and unmanned cargo ships, longer stays, and exercise routines to reduce the effects of weightlessness on muscles and bones.
Skylab
The United States launched Skylab in May 1973, using a Saturn V rocket left over from the Apollo program. It was a large, roomy station built partly from rocket stage hardware. During launch, a meteoroid shield and a solar panel were damaged or lost, which threatened overheating, and the first crew had to improvise repairs in orbit. Three crews visited Skylab between 1973 and early 1974, with the longest stay lasting 84 days. They studied the Sun, Earth and the human body.
Skylab had no resupply capability and was not meant to be permanent. After the last crew left, it remained in orbit and came down in 1979, with debris falling over the Indian Ocean and parts of Australia. Its main legacy was the data on the human response to long stays.
Mir and the Shuttle years
The Soviet Union launched the core of the Mir station in 1986. Unlike earlier stations it was built to be expanded: new modules were added over the next decade. It was occupied for most of its life, and cosmonauts set long-duration records. Valeri Polyakov spent about 437 days aboard in 1994 and 1995, a record for a single spaceflight that has stood since.
In the 1990s Mir hosted the Shuttle-Mir program, in which American astronauts lived on the station and the Space Shuttle visited it. Mir also had serious problems, including a fire and a collision with a cargo vehicle in 1997. These incidents gave useful lessons about spare equipment and procedures. Mir was brought down in a controlled reentry in March 2001. The Shuttle itself also carried Spacelab, a laboratory module that flew in the cargo bay, as a way of doing station-like science on shorter trips.
The International Space Station
The International Space Station grew out of the earlier plans of several countries. The United States had proposed its own station design in the 1980s, and after the Cold War ended these plans were combined with Russian experience. The first piece, the Russian-built Zarya module, launched in November 1998, and the first resident crew arrived in November 2000. People have lived aboard continuously since then. It is built of modules from the United States, Russia, Europe and Japan, with contributions from Canada.
Assembly depended on the Space Shuttle, which carried many large parts into orbit, and station crews have done many spacewalks to connect and repair them. The station works as a laboratory for microgravity research, which includes biology, materials and human health. It is also a testing ground for the life support, recycling and medical practices needed for longer trips, and the effects on astronaut health remain an important study area. After the Shuttle retired in 2011, crews and cargo reached it on Russian spacecraft, and later on U.S. commercial vehicles as well.
China and the newer generation
China launched its first experimental station module, Tiangong-1, in 2011 and a successor, Tiangong-2, in 2016. It then began assembling a larger modular station, with the core module launched in 2021. The station is crewed by Chinese astronauts on rotating stays. Other countries and private companies have discussed or planned future stations, but schedules change frequently and details should be checked against current announcements.
What the progression shows
Each stage solved some problems and exposed new ones. Salyut proved that stations were possible, Skylab showed a large volume of workspace, Mir showed modular expansion and long stays, and the ISS showed that international cooperation could sustain a long-term presence. Reliability, maintenance, supply costs and aging hardware remain key limits for any station, which is why planners continue to debate what should replace the current generation.