Soviet space program may gain dividends from Salyut's troubles
Hundreds of miles above Earth, possibly the greatest spaceflight drama since the struggles to save Apollo 13 and the crippled Skylab space station has been unfolding in recent weeks.Skip to next paragraph
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Soviet Cosmonauts Vladimir Lyakhov and Alexander Alexandrov remain in orbit long past their scheduled return date: Their replacements narrowly escaped death when their launch rocket blew up underneath them. Widespread reports have it that the cosmonauts in orbit are marooned. Their Salyut 7 space station has also been the subject of dramatic rumors. The most critical one concerns a possible rocket fuel leak that may have crippled most of the station's maneuvering capability.
To make sense out of these events it is necessary to understand what the Soviets have been trying to do in space recently.
What the Soviets attempted to do Sept. 26 was nothing short of making space history with a new ''giant leap for mankind'' - a continuous human presence in space. Cosmonauts Vladimir Titov and Gennady Strekalov were to have undertaken the world's first space station relief mission, allowing the two current inhabitants of Salyut 7 to return home while the space station continued to function.
In the past, long-term crews have flown to an empty station, activated it, received visiting crews, then after many months deactivated the station and left it empty. That was not supposed to have happened this time - and this goal may still be reached.
Formerly, visiting crews spent about a week aboard the Salyut. This time, the overlap may have been scheduled to last two or three weeks: The aborted launch attempt (to have been called Soyuz T-10) occurred at least 10 days earlier than would have been the case for a routine week-long visit. This would have given the new crew sufficient time to get used to space conditions and to be fully briefed by the departing crew on the station's routines and idiosyncrasies.
The purpose of routine week-long visits is tied in with another problem that the launch failure led to. The seven-ton Soyuz craft, unlike the multiyear-mission, 20-ton Salyut module, has a limited lifetime in orbit. As a general rule, such spaceships only spend 60 to 80 days in orbit before returning. Three times before, Soyuz ships had remained in space for slightly more than 100 days, but all three were contingency cases.
During missions of six or seven months' duration, the Soyuz craft attached to the Salyut must be periodically swapped for a fresh one. About every 58 days a new visiting crew is launched.
Soviet space officials have never directly explained the reason for the duration limitation rule, but reasonable analogies with American space vehicle characteristics can provide some insight. First among them is the presence of highly corrosive ''hypergolic'' propellants - fuels that, when mixed, ignite spontaneously - in the Soyuz service module tanks. As weeks pass, the exposed valves and seals in the engine could be expected to deteriorate. They may suddenly leak all the fuel, or they may not function at all when called upon during the critical return to Earth. Also, batteries aboard the Soyuz may slowly lose their charges. Finally, exposure to 16 cycles of daily sunrise-sunset thermal stress may have a cumulative impact on the mechanical hardware of the ship.
It was this gradual aging of the Soyuz T-9, which brought cosmonauts Lyakhov and Alexandrov to Salyut 7 late in June, that set off alarms around the world on Oct. 19, the day that the Soyuz exceeded in age the previously longest Soyuz mission.
The alarm was sounded in a BBC report from London, which said that the cosmonauts could not return home safely, nor could they remain aboard the failing Salyut space station.
The report was based on authentic anxieties. With the danger of a return to Earth aboard the aging Soyuz T-9 growing daily, the cosmonauts may also have been faced with serious doubts about the security of the Salyut. A report by Aviation Week & Space Technology magazine described a serious rocket fuel leak that was said to have occurred Sept. 7. Two of three sets of fuel tanks on the Salyut were reportedly involved. The magazine, evidently relying on United States intelligence sources that routinely monitor conversations between the cosmonauts and mission control in Moscow, claimed that the tanks drained overboard due to a ruptured pipe. Aviation Week also reported that the cosmonauts were about to evacuate the station in emergency mode before mission control advised them to stay. At that time, the station had been pumping a new supply of rocket fuel from the unmanned tanker spacecraft Progress 17, so a failure in the fuel transfer apparatus may also be plausible.