Salyut 6 (Салют-6; lit. Salute 6) was a Soviet orbital station. Launched on September 29, 1977, the station was the first of the 'second-generation' type of space station, possessing several revolutionary advances over the earlier Soviet space stations, which it resembled in overall design. The most notable upgrade was a second docking port which allowed for crew handovers and for station resupply by unmanned Progress freighters. The launch of Salyut 6 allowed the Soviet space station programme to evolve from short-duration to long-duration expeditions, and marked the beginning of the transition to multi-modular, long-term research stations in space.

From 1977 until 1982 Salyut 6 was visited by five long-duration crews and 11 short-term crews, including cosmonauts from Warsaw Pact countries. The very first long-duration crew on Salyut 6 broke a long-standing endurance record set on board the American Skylab station, staying 96 days in orbit. The longest flight on board Salyut 6 lasted 185 days. After Salyut 6 manned operations were discontinued in 1981, a heavy unmanned TKS spacecraft, derived from hardware left over from the cancelled Almaz military space station programme and flown under the designation Cosmos 1267, was docked to the station as part of a hardware test. Salyut 6 was deorbited on July 29, 1982, almost five years after her launch.

Description

Salyut 6, launched on a Proton 8K82K rocket on 1977-09-29, marked the switch from engineering development stations to routine operations, and united the most effective elements from each of the previous stations. The power system, consisting of a trio of steerable solar panels (together producing a peak of 4 kilowatts of power over 51 metres²), was based on the arrangement used on Salyut 4, as were the navigation (the Delta semi-automatic computer to depict the station's orbit and the Kaskad system to control its orientation) and thermal regulation systems (making use of a sophisticated arrangement of insulation and radiators). Salyut 6 also made use of environmental systems first used on Salyut 3, and controlled its orientation using gyrodenes first tested on that station.

The most important feature on Salyut 6, however, was the addition of a second docking port on the aft end of the station, which allowed two spacecraft to be docked at once. This, in turn, allowed resident crews to receive shorter, 'visiting' expeditions whilst they remained on board, and for crew handovers to take place. Such handovers, with one expedition vacating the station only after the next had arrived, permitted the long sought-after aim of continuous occupation to move a step closer. Some of the visiting expeditions were flown as part of the Intercosmos programme, with non-Soviet cosmonauts visiting the station. Vladimír Remek of Czechoslovakia, the first space traveller not from the US or USSR, visited Salyut 6 in 1978, and the station also hosted cosmonauts from Hungary, Poland, Romania, Cuba, Mongolia, Vietnam, and East Germany.

In addition, the rear port also featured plumbing to allow the station to be refuelled by unmanned Progress spacecraft, which also brought supplies and extra equipment to keep the station replenished and ensure the crew were always able to carry out useful scientific work aboard her (in all, twelve of the unmanned freighters delivered over 20 tonnes of equipment, supplies and fuel).

The addition of the extra docking port also caused the adoption of the Almaz-derived twin-chamber propulsion system first used on Salyut 3 and 5, with the two engine nozzles (each producing 2.9 kilonewtons of thrust) mounted peripherally on either side of the aft port. Salyut 6 also introduced a Unified Propulsion System, with both the engines and the station's control thrusters running on unsymmetrical dimethylhydrazine and nitrogen tetroxide, drawn from a common set of pressurised tanks, allowing the refuelling capabilities of the visiting Progress tankers to be exploited to the maximum effect. The entire engine and fuel storage assembly was contained within an unpressurised bay at the rear of the station, which was the same diameter as the main pressurised compartment. However, the replacement of the Soyuz engine used on previous stations with the bay meant that the station kept a similar overall length to its predecessors.

Salyut 6 was also equipped with an inward-opening hatch for spacewalks on the side of the forward transfer compartment, which could be used as an airlock in a similar way to the system used on Salyut 4. The compartment also contained two new semi-rigid spacesuits which allowed much greater flexibility than earlier suits, and could be donned within five minutes in case of an emergency. Finally, the station offered considerable improvements in living conditions over previous outposts, with machinery being soundproofed, the crews being provided with designated 'cots' for sleeping and the equipping of the station with a shower and extensive gymnasium.

Instrumentation

The primary instrument carried aboard the station was the BST-1M multispectral telescope, which could carry out astronomical observations in the infrared, ultraviolet and submillimetre spectra using a 1.5 metre-diameter mirror which was operated in cryogenic conditions at around −269°C. The telescope could be operated only when Salyut 6 was on the night side of the Earth, and had its cover closed for the rest of the time.

The second major instrument was the MKF-6M multispectral camera, which carried out Earth-resources observations. An improved form of a camera first tested on Soyuz 22, the camera captured an area of 165x220 kilometres with each image, down to a resolution of 20 metres. Each image was captured simultaneously in six bands in 1200-frame cassettes, which required regular replacement due to the fogging effects of radiation. Salyut 6 also featured a KATE-140 stereoscopic topographic mapping camera with a focal length of 140 milimetres, which captured images of 450x450 kilometres with a resolution of 50 metres in the visible and infrared spectra, which could be operated either remotely or by the resident crews. The photographic capabilities of the station were, therefore, extensive, and the Soviet Ministry of Agriculture had planted a number of specifically-selected crops at test sites at Salsky in the Ukraine and Voronezh near Lake Baikal to examine the capabilities of the cameras.

To further expand its scientific capabilities, Salyut 6 was equipped with 20 portholes for observations, two scientific airlocks to expose equipment to space or eject rubbish, and various pieces of apparatus to carry out biological experiments. Later on in its flight, a Progress spacecraft delivered an external telescope, the KRT-10 radio observatory, which incorporated a directional antenna and five radiometers. The antenna was deployed on the rear docking assembly, with the controller remaining inside the station, and was used for both astronomical and meteorological observations.

Support craft

Salyut 6 was primarily supported by the manned Soyuz spacecraft, which carried out crew rotations and would also have been used in the event of an emergency evacuation. The ferries docked automatically to the station, making use of the new Igla automatic docking system, and were used by departing crews to return to Earth at the end of their flight.

The station was also the first to be able to be resupplied by the newly-developed unmanned Progress freighters, although they could only dock at the rear port, as the plumbing which allowed the spacecraft to replenish the station's fluids was not available at the front port. The Progress also docked automatically to the station via the Igla, and were then opened and emptied by the cosmonauts on board, whilst transfer of fuel to the station took place automatically under supervision from the ground.

In addition to the Soyuz and Progress spacecraft, after her final crew had left, Salyut 6 was visited by an experimental transport logistics spacecraft called Cosmos 1267 in 1982. The transport logistics spacecraft, known as the TKS, was originally designed for the Almaz programme, and proved that large modules could dock automatically with space stations, a major step toward the construction of multimodular stations such as Mir and the International Space Station.

Station operations

Docking operations

Dates and times are 24-hour Moscow Time, ISO 8601 format. Source:

Station crewing

Dates and times are 24-hour Coordinated Universal Time, ISO 8601 format.

Spacewalks

References

• Soviet Space Stations as Analogs - NASA report (PDF format)
• Mir Hardware Heritage