The DOS Space Stations
2016 May 31
Tuesday, Day 152
The next Salyut gets a new name
First Expedition to Salyut 6 - Sep 1977 to Mar 1978
The first occupation of Salyut 6 spans two sets of missions. The launch of Soyuz 25 within a couple of weeks of Salyut 6 going into space was probably intended to be an occupation of the station lasting about two months. Cosmonauts Kovalyonok and Ryumin may have received a visit from a second crew and would have hosted the first Progress re-supply craft. As it was, their docking failed and led to a significant rescheduling of events.
The real Expedition 1 did not start until the Soyuz 26 crew got aboard but the chronology below includes events from the Soyuz 25 mission.
Mission planners took a risk by orbiting Soyuz 26 during December - the next launch opportunity when orbital safety constraints permitted a mission to take place. The crew then stayed in space over the winter, something normally avoided because of the extreme weather around Baikonur and in the landing zone. Until this mission, the Soviet Union's piloted space programme had generally been limited to an 'open' season between about April and October each year.
By having the Soyuz 27 crew return to Earth in Soyuz 26 (which had been docked at Salyut's aft port because of the Soyuz 25 failure), Salyut 6 was finally configured as required for the first visit by a Progress spacecraft. Mission planners had also demonstrated the ability to exchange Soyuz spacecraft part-way through a mission. This was going to be a necessity over the next few years as mission durations were to increase and eventually become longer than the safe lifetime for a Soyuz vehicle in space.
Business then took off in earnest and Salyut 6 was ready to receive a steady stream of visitors over the next few years.
One "first", in 1978, was the orbiting aboard Soyuz 28 of Vladimir Remek of Czechoslovakia - the first non-Soviet and non-American citizen to go into space.
Another 'first' was the refuelling of Salyut 6 by Progress 1, the first in a long line of space freighters. They started by supporting the Soviet Union's later Salyut stations and Mir. They are now a major element of supporting the ISS. They saw the project over a particularly difficult period while the US Shuttle was out of action following the destruction of 'Columbia'.
The In-Flight Refuelling of Salyut 6 by Progress 1
The following was written by Novosti Correspondent G Lomanov.
Successful in-flight refuelling of Salyut-6 by the automatic freight carrier Progress-1 is regarded by Soviet space engineers as a significant step towards the long-term maintenance of orbiting space laboratories.
Salyut-6 carries its fuel and oxidiser separately in six tanks fitted with metal bellows which force the fuel to the engines under pressure of nitrogen stored in pressure bottles at about 200 atmospheres.
At the time refuelling was due to take place, the pressure in the tanks themselves was about 20 atmospheres. The simple solution of providing the refuelling tanks of Progress-1 with even higher pressures to overcome the back pressure of Salyut's tanks would have involved an unacceptable weight penalty in the freight carrier.
Equally it was not possible to generate assisting gravity forces by accelerating the Salyut-Soyuz-Progress complex in an appropriate direction without upsetting the flight plan. The most rational solution available was to reduce the pressure in Salyut's tanks by pumping back nitrogen into supply bottles before refuelling started.
In the event, a powerful compressor on Salyut-6, run from the batteries which are recharged from the solar cell array, reduced the nitrogen pressure in the tanks to three atmospheres.
This pressure was low enough for the Progress-1 pressure vessels to overcome, so refuelling then took place.
It was a slow process owing to the heavy drain on the batteries but it ensured that no gas bubbles could be created in the fuel supply.
All the fuel involved had been cleared of dissolved gases by flushing with helium before loading.
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