Salyut 6 - Description

Description

Salyut 6, launched on a Proton 8K82K rocket on 29 September 1977, marked the switch from engineering development stations to routine operations, and united the most effective elements from each of the previous stations. Its navigation system, made up of the Delta semi-automatic computer to depict the station's orbit and the Kaskad system to control its orientation, was based on that used on Salyut 4, as was its power system, which consisted of a trio of steerable solar panels together producing a peak of 4 kilowatts of power over 51 m². The station's thermal regulation systems, which made use of a sophisticated arrangement of insulation and radiators, was also derived from that used on Salyut 4. In addition, Salyut 6 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. The very first long-duration crew to visit the station broke a long-standing endurance record set on board the American Skylab station, staying 96 days in orbit, whilst the longest expedition lasted 185 days. 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 hosted cosmonauts from Hungary, Poland, Romania, Cuba, Mongolia, Vietnam, and East Germany.

The rearward of the two ports was fitted with plumbing to allow the station to be refuelled by unmanned Progress spacecraft. These freighters, which brought supplies and extra equipment to keep the station replenished, helped ensure that the crew were always able to carry out useful scientific work aboard the station. In all, twelve Progress flights delivered over 20 tonnes of equipment, supplies and fuel.

The addition of the extra docking port 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 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.

To enable spacewalks, Salyut 6 was equipped with an inward-opening EVA hatch for 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. This compartment 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.