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Mir in 1986: Tale of two space stations
The Core Module of the Mir space station lifts off on Feb. 20, 1986. The premature return of the last crew from the Salyut-7 space station in November 1985 caused by illness of the expedition commander Vladimir Vasyutin left unfinished a number of critical experiments onboard the station. Program managers considered sending a fresh crew to Salyut-7 to finish the job, but it would require to sacrifice the Soyuz T-15 spacecraft for the mission, while the upgraded Soyuz TM vehicle was not expected to be ready to carry cosmonauts until at least the end of 1986. With many systems for Soyuz T already out of production, planners resorted to borrowing a descent module which survived a narrow escape from an on-pad rocket explosion in September 1983 in order to assemble Soyuz T-15. Under the circumstances, it was decided to launch Soyuz T-15 to Mir and after opening the new station for business shuttle the crew to Salyut-7 and back, in order to fulfill its unfinished program. Launch! The original piece of the Mir space station, known as the core module, blasted off from Baikonur on February 20, after a four-day delay caused by problems with a telemetry transmission device aboard the spacecraft. The station was inserted into the same orbital plane as that of the Salyut-7 space station to enable flights between the two outposts. All antennas and a pair of solar panels were successfully deployed. The module entered an initial orbit which would decay in around four days, however it maneuvered to a safe altitude during its fourth orbit. Still, during the maneuver, the station experienced unexpected vibrations, which exceeded allowable limits at the rotation points of solar panels -- more than 500 kilograms per meter. The investigative commission established that during the dynamics evaluation, the strength of solar panels had not been estimated correctly. To resolve the problem, future maneuvers were split into shorter firings. A series of such maneuvers eventually inserted the station into its operational orbit. Still ground controllers initially struggled with much more complex flight control system onboard Mir. To make matters worse, on the eve of the first crew launch on March 13, ground control detected that the automated engine control unit, Elbrus, fired one of the attitude control thrusters while beyond the range of ground stations. (Elbrus was already known to issue faulty commands during ground tests and was associated with a prolonged operation of the system causing overheating). Fortunately, the motion control system, SUD, quickly detected unplanned rotation of the module and cut off the offending engine. It was decided to deliver a modified Elbrus machine with the Progress-25 cargo ship. First expedition to Mir The first crew, including Leonid Kizim and Vladimir Soloviev followed the new station into space onboard the Soyuz T-15 spacecraft on March 13. To conserve propellant, Soyuz T-15 flew a rendezvous profile lasting more than 50 hours instead of then standard two-day profile. The automated system made several short burns bringing the spacecraft within 20 kilometers from the station, where the two rendezvous systems began interaction. The automated rendezvous continued until a distance of 200 meters. The docking took place on March 15, 1986, at 16:38 Moscow Time, a bit earlier than planned thanks to extensive experience of Leonid Kizim. One of the first tasks along with the activation of all systems was testing communications with ground control via Luch data relay satellite. It was scheduled right after re-fueling of the station from the Progress-25 tanker that arrived few days after the crew. As the station's antennas tracked the satellite under a computerized commands, Mir and mission control successfully conducted two-way transmissions of both telemetry and TV images. Kizim and Soloviev then prepared for a two-way trip between Mir and the soon-to-be-retiring Salyut-7 space station. However, first mission control had to deal with a number of problems on the old outpost. On March 8, after a test activation of the Igla rendezvous system, a command to deactivate the dynamic mode of the station failed to go through as scheduled after 200 milliseconds and instead continued to "hang" in the electric system of the onboard avionics. As a result, a number of avionics and valves of the propulsion system remained under power of 20 amperes. Moreover, the control of the station's motion was no longer possible, because any attempt to activate engines would be blocked by the presence of an deactivation command. Moreover, nobody new the resulting condition of the electromagnetic valves, which could burn under constant current. Ground tests showed that there is little hope to preserve valves. All efforts to get rid of the cutoff command from the ground had failed. The switch which generated that command hopelessly stuck. The only hope was to send the crew, find the faulty hardware and replace it. The Soyuz T-15 undocked from Mir on May 5, 1986, and a day later, docked at the Salyut-7-Kosmos-1686 dual complex, after a series of orbital maneuvers. Obviously, after the successful docking, the first order of business was to try to get rid off of the offending command and possibly returning the station to full control. However all efforts to probe electric circuits did not produce results. The particular avionics unit with a stuck switch had never been found. Plan B was to insert a cable bypass, which would exclude the turnoff command. The crew successfully completed that job. Immediately, the power consumption onboard went down. However, the station was still lacking the maneuvering capabilities. Fortunately, the large TKS space tug, then part of the station, allowed to conduct maneuvers. During the crew's absence on Mir, the unmanned Soyuz TM spacecraft docked at the station for a two-day orbital flight test. After 50 days onboard Salyut-7, the crew undocked Soyuz T-15 from the station on June 25, 1986, and one day later re-docked at Mir. (160) During this unique operation, around 360 kilograms of equipment was shipped from the retiring Salyut-7 station to the brand-new Mir. (52) The crew of Soyuz T-15 then continued working aboard Mir. The return to Earth was originally planned for Aug. 20, 1986, based on the certified life span of the transport spacecraft. But because the flight program on both Mir and Salyut-7 was successfully completed and the launch of the Kvant module to Mir had to be delayed, the decision was made to return Soyuz T-15 to Earth more than a month earlier, on July 16, 1986, after a four-month expedition. The Descent Module of the Soyuz T-15 with cosmonauts Leonid Kizim and Vladimir Soloviev successfully touched down 55 kilometers northeast of the town of Arkalyk in Kazakhstan on July 16, 1986, at 16:34 Moscow Time.
Missions to Mir in 1986:
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