Meanwhile, the TsKBEM engineers were hard at work developing modifications to the Soyuz to eliminate the weaknesses revealed by the investigation conducted by the State Commission of Academician Mstislav Keldysh. At the recommendation of Konstantin Bushuyev, the issue of pressure suits was reconsidered, and it was duly decided that henceforth cosmonauts should wear them for launch and the return to Earth, even though this would mean reducing the number of couches to two in order to accommodate the system that would automatically pump air into the cabin in the event of a decompression. In fact, this oxygen supply system was designed in such a way that the crew would be able to survive decompression even if they were not protected. Gay Severin quickly adapted the Sokol ('Falcon') stratospheric pressure suit, designating the cosmonaut version the Sokol-K.1 As regards the problematic valve, this was modified in such a manner that a premature opening would cause it to reclose automatically. Once the list of revisions was agreed, it was found that the Soyuz would be overweight for its launch vehicle - at 6.8 tonnes it would be some 100 kg heavier than its predecessor. Something had to go. Because the spacecraft was to be used to ferry crews to and from space stations, and hence would require an endurance in independent flight of only two or three days, it was decided to discard the heavy solar panels in favour of chemical storage batteries. The revisions were completed within a year. One curious fact is that although the new model was significantly different from its predecessor, the 7K-T designation was not extended by an 'M' to indicate that it was a modified version.
The spacecraft which would have flown as Soyuz 12 to deliver Leonov's crew to Salyut was launched unmanned as Cosmos 496 on 26 June 1972, and placed into an orbit with the parameters 195 x 342 km to test the modifications, returning six days later having suffered no problems.2 This success prompted the TsKBEM managers
1 In Sokol-K, the 'K' was for 'kocmoc', the Russian word for 'space'.
2 This test could last six days because the unmanned spacecraft placed a lower load on its batteries.
to push ahead with the manned programme by preparing the DOS-2 space station, which was identical to Salyut in terms of construction and apparatus for the reason that it had been the backup vehicle to its predecessor.3
In October 1971 four teams of two cosmonauts had been formed, two of which were to fly to DOS-2:
• Aleksey Leonov and Valeriy Kubasov
• Vasiliy Lazaryev and Oleg Makarov
• Aleksey Gubaryev and Georgiy Grechko
• Pyotr Klimuk and Vitaliy Sevastyanov.
Initially, Rukavishnikov was considered for the first crew, but when it was certain that Kubasov did not have tuberculosis Leonov succeeded in having him appointed
The 'first crew' for the DOS-2 station: Leonov (left) and Kubasov wearing the new Sokol-K pressure suit.
as his engineer. Gubaryev and Sevastyanov were carried over from DOS-1. But the fact that the new crews had an Air Force cosmonaut as commander and a TsKBEM cosmonaut as flight engineer meant that the military cosmonauts who had trained to serve as engineers for DOS-1 were dropped, which was bad news for Pyotr Kolodin and Anatoliy Voronov.4 Lazaryev, Makarov, Grechko and Klimuk were transferred from the Contact programme, which had been terminated some time earlier, to train for DOS crews.
4 Although recruited as military cosmonauts, the fact that Kolodin and Voronov were not military pilots meant that they were unlikely to be assigned as spacecraft commanders.
During the first half of 1972 two of the new spacecraft were built and sent to Baykonur along with DOS-2. All the necessary preparations were concluded by the end of July. With the four crews in attendance, a Proton lifted off at 6.21 a.m. on 29 July 1972 with DOS-2, but 182 seconds later an engine on the second stage failed and the vehicle fell to Earth. If the station had made it into orbit it would have been named Salyut 2, which was the name written on its side. However, since the flight failed at such an early point, the launch was never declared, with the result that for many years the existence of this station was kept secret.
After the loss of DOS-2 the first three crews were reassigned to an autonomous mission to be flown in August-September 1972 using one of the Soyuz spacecraft, but when this was cancelled all four crews from DOS-2 began to train to operate the DOS-3 space station, the construction of which was underway. However, there was a parallel development in progress.
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