Salyut 7 ceased to communicate with the Soviet mission control in February 1985, its batteries drained. On February 11, more precisely, a failure of the electrical system emptied its accumulators and cut the heating. This station weighing 19,824 kg then orbited the Earth for nearly four months, silent, and no automatic pilot could bring it closer.
It had to be berthed manually.
- Salyut 7 lost all electrical power on 11 February 1985 and drifted silently for four months around the Earth.
- Vladimir Djanibekov manually docked the Soyuz T-13 spacecraft to the inert station on 8 June 1985 without an automatic guidance system.
- The cosmonauts found an interior temperature of −10 °C, frost on the walls, and water tanks frozen.
A partner that no longer responds
Soviet spacecraft usually docked themselves automatically using the Igla system. This relies on the computers of both vessels exchanging data continuously. But a dead station sends no signal, and Igla becomes unusable. Engineers therefore modified Soyuz to add manual-control levers intended for close-quarters maneuvers, and entrusted the mission to Vladimir Djanibekov, who had already docked with Salyut 7 when it was operational.
Soyuz T-13 lifted off from Baikonur on 6 June 1985, with Djanibekov and flight engineer Viktor Savinykh. After two days of pursuit, the station was in sight.
Sight-guided piloting of a spacecraft spinning on its own axis
In automatic mode, the crew closes the distance to within a few kilometers, then switches to full manual control. Djanibekov then gauges the distance with a handheld laser rangefinder, with no station radar to guide him. He must also align his craft with Salyut 7’s slow rotation, as if trying to place a finger on a piece that is turning on a table.
On June 8, it was accomplished, at 08:50 UTC.
No Soyuz had ever yet docked with a dead station. Once the docking was secured, the electrical connectors of the collar-links confirmed to the crew that Salyut 7’s electrical system was dead. The two men vent some air from the station before opening the airlock, as a precaution. The air is very cold, but breathable.
Frost on the walls, ice in the tanks
Inside, the temperature hovered around −10 °C, according to mission records kept by RKK Energia. Frost covered the walls and equipment, and the water in the tanks froze. The cosmonauts donned winter gear, fur hats included.
The priority was power. Two of the eight batteries were destroyed, the other six completely discharged. Djanibekov determined that a sensor in the solar panel attitude-control system had failed, preventing recharging. The crew then rewired the panels directly to the batteries, and within about ten days the station came back to life. The attitude-control system was brought back online after three days.
The wall radiators were only reactivated once all the frost had evaporated.
The reason is simple: frost melting suddenly turns into water, and water in spacecraft electronics is another failure. The tanks thawed by the end of June, but the water heater, damaged by the freezing, was replaced by a powerful television projector to warm the liquids. The humidity in the air did not return to normal until the end of July 1985.
The rescue did not end there. Progress 24 remained docked from 23 June to 15 July, with spare parts, and the two men later reinforced the starboard solar panel with two extension panels that had been brought along. Savinykh stayed in orbit for 169 days, Djanibekov for 110 days. Salyut 7 eventually re-entered Earth’s atmosphere on 7 February 1991, after a total of 816 days in space.
Sources : spacedaily.com | hackaday.com
