Ground controllers are carefully monitoring an air leak in the Mir space station that could affect plans to send another crew to the Russian orbital facility in March.
The pressure in the interior of the station as of last week was just over 700 mm Hg (i.e., millimeters of mercury, a measure of pressure), according to Sergei Gromov, a spokesman for RKK Energia -- the company that operates Mir.
At the time of the last crew's departure at the end of August, the station's interior pressure was 800 mm Hg (15.5 pounds per square inch). Standard atmospheric pressure at sea level is 760 mm Hg or 14.7 psi.
When Mir's next crew arrives at the station in March, the pressure in its interior may very well be below 560 mm (10.8 psi), the lowest level acceptable for safe crew presence. In this case, the Soyuz spacecraft delivering cosmonauts to Mir would have to bring tanks with several dozen kilograms of compressed air.
Since Mir's docking mechanisms are equipped with pneumatic lines, the cosmonauts should be able to replenish Mir's atmosphere from the safety of Soyuz, before opening the hatches between the transport ship and the station.
Initially, Mir was losing air at the rate of 2 mm Hg a day. However, as pressure inside decreased, the escape rate reduced to the current rate of 1 mm Hg a day, Gromov said.
Currently, except for the sealed-off Spektr module which was punctured during a collision with a Progress cargo ship, all hatches between Mir's modules are open to allow cables to connect equipment in different parts of the station, including wiring for the driving mechanisms of Mir's numerous solar panels. As a result, all of the station's pressurized modules are losing air at the same rate.
The air leak on Mir was discovered before the last crew left the station in August. Prior to their departure, the cosmonauts conducted a test in which the hatches between all but two of Mir's modules were closed and the pressure loss was closely monitored in the isolated parts of the station.
Ground control narrowed down possible leak areas to either the core module or the Kvant-1 module docked at the rear port of the core. The hatches between these oldest parts of the station could not be closed for the test due to the large number of cables running through them.
All further efforts to locate the exact trouble spot in the interior of the station, which is crowded with equipment, proved fruitless.
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