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Soyuz-10: First trip to a space station

Anatoly Zak, Spaceflight Correspondent
Feb 23, 2016, 0:22 UTC

Sen—The loss of the Moon Race to the US in 1969 required Soviet space leaders to do some serious soul-searching. Although political inertia continued dragging forward the ill-fated Soviet lunar program, many top engineers as well as their patrons in the Kremlin had already started looking elsewhere for future goals. Within Korolev’s OKB-1, then renamed TsKBEM, a group of engineers proposed to develop a space station, which could be built quickly and economically. As usual, the move was designed to preempt a similar US project—the Skylab orbital laboratory scheduled for launch after the end of the Apollo program in 1972.

TsKBEM’s bare-bone space station would “borrow” hardware, which had already been developed under a code-name Almaz ("diamond") by a rival organization led by Vladimir Chelomei. The overly complex Almaz was under construction for the Soviet military, but fell years behind schedule due to its technical complexity and the lack of support in the Kremlin.

Now, TsKBEM’s team proposed to outfit Chelomei's all-but-ready space station with off-the-shelf systems from the flight-proven Soyuz spacecraft, including engines, electronics and solar arrays.

On Feb. 9, 1970, the Soviet government officially endorsed the space station program, under a code name DOS-7K. In parallel, Vladimir Chelomei was allowed to continue the development of Almaz, which would be used exclusively for military goals under cover of civilian DOS stations.

Despite the tight schedule, the world's first space station, DOS-1, was launched on April 19, 1971. Upon reaching orbit, it was announced as Salyut ("fireworks"). In-orbit checks were performed successfully and the orbital home was cleared to host its first crew. The first expedition on Salyut was expected to last from three weeks up to a month, which would be another record-breaking flight duration.

After a one-day delay due to technical problems, the world's first expedition to the space station lifted off from Tyuratam on April 23, 1971, at 02:54 Moscow Time. The crew included commander Vladimir Shatalov, flight engineer Aleksei Yeliseyev (both veterans of the Soyuz-8 and Soyuz-4 and -5 docking missions) and a rookie flight engineer Nikolai Rukavishnikov.

The Soyuz-10 spacecraft successfully entered orbit, but during automated orbit correction to intercept the station, the flight control system misbehaved. Fortunately, the crew onboard quickly switched to manual mode and was able to keep the rendezvous process on track.

After a day-long solo flight, the automated system successfully brought Soyuz-10 in the vicinity of the station and from a distance of a few hundred meters, Shatalov switched to manual controls for the final approach.

The physical contact between the two spacecraft was registered on April 24, at 04:47 Moscow Time, however neither crew, nor mission control could confirm that the docking process had been completed. For some reason, electric motors failed to drive the two ships together, failing to form a pressurized tunnel in the docking port or to connect electrical interfaces between the two vehicles. All attempts to fire thrusters on the Soyuz in order to press the transport ship into its port were also futile.

Engineers on the ground suspected mechanical failure of the docking mechanism on Soyuz-10 and had no choice but cancel an effort to get the crew into the station, just inches away from the destination. However, soon mission control had a much more serious problem to deal with. After a four-orbit joint flight, Soyuz-10 initiated the undocking process, but that failed too. As a last resort, the crew could jettison the docking port from Soyuz-10, leaving it hanging on the receptacle of the station and thus blocking any future access to the lab. Instead, a docking engineer on the ground instructed Rukavishnikov to open an avionics unit responsible for the docking mechanism and re-connect internal wiring of the electric driving mechanism in the port. The bypass worked and Soyuz-10 was finally able to free itself from its trap.

After the nearly two-day arduous flight, the descent module of the Soyuz-10 spacecraft made a successful night landing in Kazakhstan.

The post-flight investigation traced the problem during the docking to the ship's motion control system, which kept firing thrusters on Soyuz-10 after it had made an initial contact with the station. As a result, a delicate mechanism responsible for proper alignment of the two docking ports failed under pressure and stuck. For future missions, the docking port was reinforced and upgraded with a special mechanism for manual completion of docking.