Understanding Space Station
From Salyut to Tiangong: a brief history
The Soviet Union launched the first space station, Salyut 1, in April 1971; its Soyuz 11 crew set an early endurance record but tragically died during re-entry. NASA followed with Skylab in 1973, built from surplus Apollo hardware. The modular era began with Mir (1986–2001), which pioneered the docking-and-assembly techniques the ISS later scaled up. Today two stations are permanently crewed — the ISS and China's Tiangong — with a wave of privately built outposts on the way.
| Station | Operator | Years | Notable for |
|---|---|---|---|
| Salyut 1 | USSR | 1971 | First space station in history |
| Skylab | USA (NASA) | 1973–79 | First US station; built from Apollo hardware |
| Mir | USSR / Russia | 1986–2001 | First modular, long-duration station |
| ISS | USA, Russia, ESA, Japan, Canada | 1998–present | Largest structure ever built in orbit |
| Tiangong | China | 2021–present | T-shaped; about one-fifth the ISS's mass |
How a space station stays in orbit
Space stations orbit in low Earth orbit, typically 350–450 km up — high enough to clear the densest air, yet below the Van Allen radiation belts that would expose crews to harmful doses. Even there, the wisp of remaining atmosphere causes steady orbital decay, so docked cargo ships periodically reboost the station. The ISS circles Earth about every 90 minutes — roughly 16 orbits a day — at a 51.6° inclination, an angle chosen so launch sites in both Russia and the United States can reach it.
What space stations are for
A station's defining asset is sustained microgravity, which lets researchers study fluid behaviour, combustion, crystal growth and new materials without gravity masking the effects. Just as valuable is human research: tracking how bones, muscles, the heart and eyesight adapt over months in space — data essential for planning voyages to the Moon and Mars. Stations also work as Earth-observation platforms and technology testbeds, and as bases from which crews stage spacewalks (EVAs) to assemble and repair hardware.
The end of the ISS and the commercial era
NASA and its partners plan to retire the ISS around 2030, then guide the 420-tonne complex to a controlled deorbit over a remote stretch of the South Pacific in roughly 2031, using a purpose-built deorbit vehicle. Its intended successors are privately operated: Vast's Haven, Axiom Station, Blue Origin and Sierra Space's Orbital Reef, and Starlab, several aiming to fly in the late 2020s. These outposts are designed to host both scientific research and paying space tourists. China's Tiangong, meanwhile, is expected to keep operating through the 2030s and may add further modules.