Two Programs Hidden Under One Name
The word Salyut, meaning 'salute' or 'firework', was a cover. Under it ran two completely different space station programs that the Soviet public was never told apart.
The civilian line was DOS (Dolgovremennaya Orbitalnaya Stantsiya, Long-Duration Orbital Station), built by the bureau that Sergei Korolev had founded. DOS stations did science, Earth observation, and long-duration human-factors research.
The military line was Almaz (Diamond), built by Vladimir Chelomei's competing OKB-52 bureau. Almaz stations were crewed photo-reconnaissance platforms, essentially crewed spy satellites with high-resolution cameras pointed at the ground.
To keep the military program secret, both lines launched under the same public 'Salyut' designation. Salyut 2, 3, and 5 were Almaz stations; Salyut 1, 4, 6, and 7 were civilian DOS stations. Western analysts worked out the distinction only gradually.
The Salyut Series, 1971-1986
The first station, Salyut 1, is covered in full on its own page: the first space station and the Soyuz 11 tragedy that killed its only resident crew. What followed was a fifteen-year run of stations that steadily solved the problems of living in orbit.
All Salyut stations were launched on the heavy-lift Proton rocket, Chelomei's hypergolic workhorse, which had the throw weight to put a 19-tonne station into orbit in a single launch.
| Station | Type | In orbit | Notes |
|---|---|---|---|
| Salyut 1 | DOS | 1971 | First space station. Sole crew (Soyuz 11) died on return. |
| Salyut 2 | Almaz | 1973 | Depressurized days after launch; never crewed. |
| Salyut 3 | Almaz | 1974-75 | Military recon. Test-fired a 23 mm cannon in orbit. |
| Salyut 4 | DOS | 1974-77 | Civilian science station; two long crews. |
| Salyut 5 | Almaz | 1976-77 | Last military Almaz station. |
| Salyut 6 | DOS | 1977-82 | Two docking ports. Progress resupply + Intercosmos guest crews. |
| Salyut 7 | DOS | 1982-91 | Last Salyut. Famous 1985 in-orbit rescue of a dead station. |
Salyut 6 and 7: The Stations That Made It Work
Every station before Salyut 6 had a single docking port. That meant a station could host exactly one spacecraft at a time, so it could not be refueled or resupplied. When the consumables ran out, the station's useful life was over.
Salyut 6, launched in 1977, changed everything by adding a second docking port. With two ports, an uncrewed Progress freighter could dock and deliver propellant, food, water, and equipment while a Soyuz with the crew stayed attached at the other end.
The second port also enabled crew handovers and short 'visiting' missions. Salyut 6 hosted the Intercosmos program, which flew guest cosmonauts from allied countries. Vladimír Remek of Czechoslovakia, who visited Salyut 6 in 1978, became the first person in space who was neither Soviet nor American.
Salyut 7, the last of the line, flew from 1982 and pushed mission durations past 200 days. It is best remembered for a near-impossible repair in 1985.
Mir: The First Modular Space Station
Mir (meaning both 'peace' and 'world') was a different kind of station. Where every Salyut was a single launched unit, Mir was assembled in orbit over a decade from separately launched modules, each docking to a central core.
The core module launched on February 19, 1986. Over the next ten years, five more large modules and a docking module were added, each carried up on a Proton and maneuvered into place. The relative scale of the finished station is shown on the scale of Soviet spacecraft page.
Fully assembled, Mir massed about 129,700 kg, roughly the weight of seventeen city buses, and enclosed about 350 cubic meters of habitable volume, comparable to a three-bedroom house.
| Module | Year | Purpose |
|---|---|---|
| Core (DOS-7) | 1986 | Living quarters, command, main docking node |
| Kvant-1 | 1987 | Astrophysics; X-ray and UV telescopes |
| Kvant-2 | 1989 | EVA airlock and upgraded life support |
| Kristall | 1990 | Materials processing; Shuttle docking adapter |
| Spektr | 1995 | Geophysics; damaged in the 1997 collision |
| Docking Module | 1995 | Dedicated port for U.S. Space Shuttle dockings |
| Priroda | 1996 | Earth remote sensing; the final module |
Living Aboard Mir
Mir's defining achievement was endurance. From September 5, 1989 to August 28, 1999, the station was continuously occupied for 3,644 days, just under ten years, a record no other station held until the International Space Station surpassed it.
It was also where the single longest human spaceflight took place. Physician-cosmonaut Valeri Polyakov spent 437 days and 18 hours aboard Mir, from January 1994 to March 1995, to study how the body holds up over a span equal to a round trip to Mars. The record still stands in 2026.
The medical and life-support knowledge built up across this period, much of it descended from the regenerative systems described on the technology page, is the foundation that all later long-duration human spaceflight has been measured against.
Shuttle-Mir: The Bridge to the ISS
The agreement to let U.S. Space Shuttles dock with Mir, reached under Mikhail Gorbachev's policy of openness and carried forward after the Soviet collapse, turned a Cold War rival's station into a joint laboratory.
Between 1995 and 1998, Space Shuttles docked with Mir nine times, and seven American astronauts lived aboard for long-duration stays alongside their Russian crewmates. Norman Thagard, who launched to Mir on a Soyuz in March 1995, was the first American to live on a Russian station.
The program, formally Phase One of the International Space Station, taught both sides how to build, dock, and operate joint hardware and joint crews. The diplomatic arc that led here is covered on the cultural impact page.
1997: Fire and Collision
By the late 1990s Mir was aging, and 1997 brought its two most dangerous days.
On February 23, a lithium-perchlorate oxygen-generating canister ignited, sending a blowtorch-like flame and thick smoke through the station for about 90 seconds. The fire blocked the path to one of the two Soyuz escape craft. The crew donned respirators and fought it out; no one was seriously hurt.
On June 25, during a manual test of a new docking method, an uncrewed Progress freighter struck the Spektr module, puncturing its hull and the station began losing pressure. The crew cut the cables running through the hatch to Spektr and sealed it off, isolating the leak and saving the station, but losing Spektr's power and science permanently.
Mir survived both, but the incidents hardened the case that its successor should be an international station built fresh rather than another aging solo outpost.
Legacy: From Mir to the ISS
Mir was deorbited on March 23, 2001, breaking up over an empty stretch of the South Pacific after fifteen years in orbit.
But its architecture did not end. The central module of the International Space Station's Russian segment, Zvezda, is a direct derivative of the Mir-2 core that was already being built when the Soviet Union dissolved. The docking systems, life-support hardware, and modular assembly methods all carried straight over.
In a real sense the ISS is the grandchild of Salyut 1: a continuous line of orbital-station engineering that runs from 1971 through Mir and into the station crewed in 2026. The modern operational story is on the legacy page.
Soviet Space Stations by the Numbers
Frequently Asked Questions
What was the first space station?
Salyut 1, launched by the Soviet Union on April 19, 1971. It was the first space station of any kind, beating the U.S. Skylab into orbit by two years. Its full story, including the Soyuz 11 disaster that killed its only crew, is on the dedicated first space station page.
Why were some Salyut stations secretly military?
The 'Salyut' name covered two separate programs. The civilian DOS stations (Salyut 1, 4, 6, 7) did science and long-duration research. The military Almaz stations (Salyut 2, 3, 5), built by Vladimir Chelomei's bureau, were crewed photo-reconnaissance platforms, effectively crewed spy satellites. They were launched under the civilian 'Salyut' designation to keep the reconnaissance mission secret. Salyut 3 even test-fired a 23 mm cannon in orbit in 1975.
How was Mir different from the Salyut stations?
Every Salyut was a single spacecraft launched complete in one piece. Mir was the first modular station: a central core launched in 1986, then expanded in orbit over a decade by docking six more separately launched modules to it. This let Mir grow far larger (about 129,700 kg assembled) and host specialized labs for astrophysics, materials science, geophysics, and Earth observation. The modular approach Mir pioneered is exactly how the International Space Station was later built.
How long was Mir occupied, and who holds the spaceflight record?
Mir was continuously occupied for 3,644 days, from September 5, 1989 to August 28, 1999, a record until the ISS surpassed it. The single longest spaceflight in history also happened on Mir: physician-cosmonaut Valeri Polyakov spent 437 days and 18 hours aboard from January 1994 to March 1995, a record that still stands in 2026.
What happened to Mir in 1997?
1997 brought Mir's two worst days. On February 23, an oxygen-generating canister caught fire and burned for about 90 seconds, blocking the route to one escape craft. On June 25, an uncrewed Progress freighter collided with the Spektr module during a manual docking test, puncturing the hull and causing a depressurization; the crew sealed off Spektr to save the station. Both incidents were survived, but they made the case for replacing Mir with a fresh international station.
Does anything from Mir still fly today?
Yes. Mir was deorbited in 2001, but the central module of the International Space Station's Russian segment, Zvezda, is a direct derivative of the Mir-2 core that was under construction when the Soviet Union dissolved. The docking-port architecture, regenerative life-support systems, and modular-assembly methods all carried over from Mir to the ISS, where they remain in use in 2026.
Sources
- RussianSpaceWeb: Mir - Anatoly Zak's detailed Mir program history
- RussianSpaceWeb: Salyut stations - the full Salyut/DOS/Almaz series
- NASA: Shuttle-Mir history - the joint U.S./Russian program archive
- ESA: Mir - European Space Agency Mir reference
- Wikipedia: Mir - cross-referenced station article
- Wikipedia: Salyut programme - the overall station program
