The Salyut programme (Russian: Салют, IPA: [sɐˈlʲut], meaning "salute" or "fireworks") was the first space station programme, undertaken by the Soviet Union. It involved a series of four crewed scientific research space stations and two crewed military reconnaissance space stations over a period of 15 years, from 1971 to 1986. Two other Salyut launches failed. In one respect, Salyut had the space-race task of carrying out long-term research into the problems of living in space and a variety of astronomical, biological and Earth-resources experiments, and on the other hand, the USSR used this civilian programme as a cover for the highly secretive military Almaz stations, which flew under the Salyut designation. Salyut 1, the first station in the program, became the world's first crewed space station.
Salyut flights broke several spaceflight records, including several mission-duration records, and achieved the first orbital handover of a space station from one crew to another, and various spacewalk records. The ensuing Soyuz programme was vital for evolving space station technology from a basic, engineering development stage, from single docking port stations to complex, multi-ported, long-term orbital outposts with impressive scientific capabilities, whose technological legacy continues as of 2023. Experience gained from the Salyut stations paved the way for multimodular space stations such as Mir and the International Space Station (ISS), with each of those stations possessing a Salyut-derived core module at its heart.
Mir-2 (DOS-8), the final spacecraft from the Salyut series, became one of the first modules of the ISS. The first module of the ISS, the Russian-made Zarya, relied heavily on technologies developed in the Salyut programme.
History of Salyut space stations
The programme was composed of DOS (Durable Orbital Station) civilian stations and OPS (Orbital Piloted Station) military stations:
- The Almaz-OPS space station cores were designed in October 1964 by Vladimir Chelomey's NPO Mashinostroyeniya (OKB-52) organization as military space stations, long before the Salyut programme started. For Salyut, small modifications had to be made to the docking port of the OPS to accommodate Soyuz spacecraft in addition to TKS spacecraft.
- The civilian DOS space station cores were designed by Sergei Korolev's OKB-1 organisation. Korolev and Chelomey had been in fierce competition in the Soviet space industry during the time of the Soviet crewed lunar programme, but OKB-52's Almaz-OPS hull design was combined with subsystems derived from OKB-1's Soyuz. This was done beginning with conceptual work in August 1969. The DOS differed from the OPS modules in several aspects, including extra solar panels, front and (in Salyut 6 and 7) rear docking ports for Soyuz spacecraft and TKS spacecraft, and finally more docking ports in DOS-7 and DOS-8 to attach further space station modules.
It was realized that the later civilian DOS stations could not only offer a cover story for the military Almaz programme, but could also be finished within one year and at least a year earlier than Almaz. The Salyut programme begun on 15 February 1970 on the condition that the crewed lunar programme would not suffer. However, the engineers at OKB-1 perceived the L3 lunar lander effort as a dead-end and immediately switched to working on DOS. In the end it turned out that the Soviet N1 "Moon Shot" rocket never flew successfully, so OKB-1's decision to abandon the lunar programme and derive a DOS space station from existing Soyuz subsystems and an Almaz/OPS hull proved to be right: The actual time from the DOS station's inception to the launch of the first DOS-based Salyut 1 space station took only 16 months; the world's first space station was launched by the Soviet Union, two years before the American Skylab or the first Almaz/OPS station flew.
Initially, the space stations were to be named Zarya, the Russian word for "Dawn". However, as the launch of the first station in the programme was prepared, it was realised that this would conflict with the call sign Zarya of the RKA Mission Control Center (TsUP) in Korolyov – therefore the name of the space stations was changed to Salyut shortly before launch of Salyut 1. Another explanation given is that the name might have offended the Chinese, who purportedly were preparing a new rocket for launch, which they had already named Shuguang or "Dawn". The Salyut programme was managed by Kerim Kerimov, chairman of the state commission for Soyuz missions.
A total of nine space stations were launched in the Salyut programme, with six successfully hosting crews and setting some records along the way. However, it was the stations Salyut 6 and Salyut 7 that became the workhorses of the programme. Out of the total of 1,697 days of occupancy that all Salyut crews achieved, Salyut 6 and 7 accounted for 1,499. While Skylab already featured a second docking port, these two Salyut stations became the first that actually utilised two docking ports: this made it possible for two Soyuz spacecraft to dock at the same time for crew exchange of the station and for Progress spacecraft to resupply the station, allowing for the first time a continuous ("permanent") occupation of space stations.
The heritage of the Salyut programme continued to live on in the first multi-module space station Mir with the Mir Core Module ("DOS-7"), that accumulated 4,592 days of occupancy, and in the International Space Station (ISS) with the Zvezda module ("DOS-8"), that as of 21 August 2012 accumulated 4,310 days of occupancy. Furthermore, the Functional Cargo Block space station modules were derived from the Almaz programme, with the Zarya ISS module being still in operation together with Zvezda.
First generation – The first space stations
The first generation served as a space station engineering test bed. The aim from the beginning of the Almaz program was to construct long-living multi-modular stations.
Salyut 1 (DOS-1)
Salyut 1 (Russian: Салют-1, lit. 'Salute 1'), also known as DOS-1 (Durable Orbital Station 1), was the world's first space station. It was launched into low Earth orbit by the Soviet Union on April 19, 1971. Salyut 1 was adapted from an Almaz airframe and comprised five components: a transfer compartment, a main compartment, two auxiliary compartments, and the Orion 1 Space Observatory. It was visited by the Soyuz 10 and Soyuz 11 missions. While the crew of Soyuz 10 was able to soft dock, the hard-docking failed, forcing the crew to abort their mission. The Soyuz 11 crew successfully docked, spending 23 days aboard Salyut 1 conducting experiments. The Soyuz 11 crew died of asphyxia caused by a valve failure just before reentry, making them the only humans to have died above the Kármán line.
Following the deaths, the mission of Salyut 1 was terminated, and the station reentered Earth's atmosphere, burning up on October 11, 1971.
DOS-2
DOS-2 was lost in a launch failure on 29 July 1972, when the failure of the second stage of its Proton-K launch vehicle prevented the station from achieving orbit. It instead fell into the Pacific Ocean. The station, which would have been given the designation Salyut 2 had it reached orbit, was structurally identical to Salyut 1, as it had been assembled as a backup unit for that station.
Salyut 2 (OPS-1, military)
Salyut 2 (OPS-1) was launched in 1973. It was the first Almaz military space station to fly. Within two weeks of its launch, the station had lost altitude control and depressurized, leaving it unusable. Its orbit decayed and it re-entered the atmosphere on 28 May 1973, without any crews having visited it.
Kosmos 557 (DOS-3)
Kosmos 557 (Russian: Космос 557 meaning Cosmos 557), originally designated DOS-3, was originally intended to be launched as Salyut-3, but due to its failure to achieve orbit on May 11, 1973, three days before the launch of Skylab, it was renamed Kosmos-557.
Due to errors in the flight control system while out of the range of ground control, the station fired its attitude thruster until it consumed all of its attitude control fuel and became uncontrollable before raising its orbit to the desired altitude. Since the spacecraft was already in orbit and had been registered by Western radar, the Soviets disguised the launch as "Kosmos 557" and quietly allowed it to reenter Earth's atmosphere and burn up a week later. It was revealed to have been a Salyut station only much later.
Salyut 3 (OPS-2, military)
Salyut 3 (Russian: Салют-3, lit. 'Salute 3', also known as OPS-2 or Almaz 2) was launched on 25 June 1974. It was the second Almaz military space station, and the first such station to be launched successfully. It was included in the Salyut program to disguise its true military nature. Due to the military nature of the station, the Soviet Union was reluctant to release information about its design, and about the missions relating to the station.
It attained an altitude of 219 to 270 km on launch and NASA reported its final orbital altitude was 268 to 272 km. Only one of the three intended crews successfully boarded and operated the station, brought by Soyuz 14. Soyuz 15 attempted to bring a second crew but failed to dock, after which the third planned mission to the station was cancelled.
Although little official information has been released about the station, several sources report that it contained multiple Earth-observation cameras, as well as an on-board gun. The station was deorbited and re-entered the atmosphere on 24 January 1975. The next space station launched by the Soviet Union was the civilian station Salyut 4; the next military station was Salyut 5, which was the final Almaz space station.
Salyut 3 would make history by conducting the first test-fire of a conventional weapon in space. During Salyut 3's mission span, cosmonauts would fire the onboard 23mm cannon, which was reported to be a modified Nudelman aircraft cannon. To operate the cannon, the crew had to maneuver the whole space station in the direction of the target. Sources state that the firing was to deplete the ammunition on the craft. However, others sources say that the station conducted 3 tests of the gun through the whole mission span of Salyut 3.
Salyut 4 (DOS-4)
Salyut 4 (DOS 4) was launched on December 26, 1974, into an orbit with an apogee of 355 km (221 mi), a perigee of 343 km (213 mi) and an orbital inclination of 51.6 degrees. It was essentially a copy of the DOS 3 (or Kosmos 557), and, unlike its ill-fated sibling, it was a complete success. Three crews attempted to make stays aboard Salyut 4 (Soyuz 17 and Soyuz 18 docked; Soyuz 18a suffered a launch abort). The second stay was for 63 days duration, and an uncrewed capsule, called Soyuz 20, remained docked to the station for three months, proving the system's long-term durability despite some deterioration of the environmental system during Soyuz 18's mission. Salyut 4 was deorbited February 2, 1977, and re-entered the Earth's atmosphere on February 3.
Salyut 5 (OPS-3, military)
Salyut 5, also known as OPS-3, was launched in 1976. It was the third and last Almaz space station to be launched for the Soviet military. Two Soyuz missions visited the station, each crewed by two cosmonauts. A third Soyuz mission attempted to visit the station but failed to dock. A fourth mission was planned but never launched.
Second generation – long-duration inhabitation of space
In 1977, another marked step forward was made with the second generation of Salyut stations. The aim was to continuously occupy a space station with long-duration expeditions, for the first time in spaceflight.
Although Salyut 6 and Salyut 7 resembled the previous Salyut stations in overall design, several revolutionary changes were made to the stations and programme for the aim of continuous occupation. The new stations featured a longer design life and a second docking port at the aft of the stations – crew exchanges and station "handovers" were now made possible by docking two crewed Soyuz spacecraft at the same time. Furthermore, the uncrewed Progress resupply craft was created based on the crewed Soyuz, to resupply the crew and station with air, air regenerators, water, food, clothing, bedding, mail, propellants, pressurant, and other supplies. While the Progress docked to the station's second docking port, the crew's Soyuz spacecraft could remain docked to the station's first port. The Progress spacecraft even delivered hardware for updating onboard experiments and permitting repairs to the station, extending its life.
Salyut 6 (DOS-5)
Salyut 6, alternatively known DOS-5 as it was the fifth of the Durable Orbital Station series of civilian space stations, was launched on 29 September 1977 by a Proton-K rocket. Salyut 6 was the first space station to receive large numbers of crewed and uncrewed spacecraft for human habitation, crew transfer, international participation and resupply, establishing precedents for station life and operations which were enhanced on Mir and the International Space Station.