If the station is to be deorbited in the August to September period, RKK Energia, which operates Mir, wants to make sure that a further loss of pressure in the coming months won't disable the station's control system.
The failure of crucial hardware could prevent a controlled reentry of the station into the atmosphere, which could potentially lead to a rain of debris from the 100-ton spacecraft over populated areas.
And, if efforts to raise money from the private sector to continue operating Mir are successful, the isolation of the leak will be the first step in renovating of the station for commercial operations.
During Mir's dormant flight this winter, the pressure inside fell significantly. It was partially restored by the Progress M-1-1 spacecraft, which arrived at the station at the beginning of February. By the time the crew enters the station, RKK Energia plans to raise pressure to a comfortable 650 millimeters.
Searching for the leak
Yuri Grigoriev, deputy designer general at RKK Energia and Alexander Markov, manager of the RKK Energia division responsible for the program of activities on board Mir, said that the first two weeks of the crew schedule on Mir will be dedicated specifically to the search for the leak.
The cosmonauts will start by identifying the module or compartment where the leak is. They plan to hermetically isolate different compartments of the station one by one to narrow down the source of the leak. The cosmonauts then will use on-board sensors to measure pressure change. This work will be complicated by the numerous cables that have, over the years, been drawn through the hatches between each module. The newest addition to Mir, the Priroda module and a small docking compartment, will be inspected first.
About two days will be dedicated to search each sealed compartment for the leak. Once the leaky module is identified, the cosmonauts will spend the next two to three days customizing hardware used to find the exact location of the leak.
Armed to their teeth
A total of four super-sensitive instruments will ride with the crew aboard the Soyuz spacecraft that will carry them to Mir. Those instruments should allow the cosmonauts to take advantage of almost every physical property of air to pinpoint the location of the leak:
- An infrared thermometer code-named "Kelvin" will be used to measure slight variations in the temperature change in the interior of the station. A gun-like device is sensitive enough to detect 1-degree temperature changes at the distance up to 5 feet (1.5 meters). Engineers believe that an area of cold air will form around the source of the leak.
- To measure temperature changes in places that are hard to reach with "Kelvin," the crew will use a heavier instrument called Perren. Its sensors are mounted on a 5-foot (1.5-meter) flexible probe equipped with lights. Markov said that the wide range of temperatures aboard Mir could compromise the effectiveness of the device. "They (the instruments) will certainly bring us a lot of interesting data," Markov said. "However, to catch a leak with them, I think, will be difficult. As a method we will try that anyway."
- The third instrument code-named "Iva" is a called a thermo-hygrometer. Along with the temperature, it also measures humidity, which according to physical models developed by RKK Energia also changes near the leak. As with the previous two instruments, due to moisture on board, many experts question the effectiveness of the device.
- The engineers put their heaviest bets on an acoustic monitor called OT 2-K, which showed amazing sensitivity during testing. In the test, the device would "hear" air escaping from a surgical needle from a distance of 16 feet (5 meters), Markov said. The main concern is the range of sensitivity of the device in an environment with extensive background noise, like fans. But once sources of noise are determined, most of them can be shut down, Markov said. Two sets of earphones and monitors will be sent with the crew, so both crewmembers will be able to work at the same time.
The search will start at the hatches, which divide Mir's modules. Windows will be checked next. If this effort proves fruitless, ground control will instruct the crew to look at a number of valves, which connect the interior of the station with open space. The last and the least appealing option is to remove the station's decorative interior panels and literally search every square centimeter of the station's interior walls, Markov said.
Plenty of other tasks
After the leak is isolated and patched, the Mir crew will be able to switch full-time to science experiments. Although the detailed flight plan is still evolving, it currently includes more than 50 experiments, Markov said. Ten of these can run with or without a crew on board.
According to Markov, the crew will power up around 70 out of the 119 currently operational instruments aboard Mir. Of all the complex's research modules, only Priroda will remain unpowered, except for a short period of time when the search for the leak will take place in the module.
In addition to Mir's existing science hardware, in April the Progress M-1-2 cargo ship is expected to deliver 330 pounds (150 kilograms) of additional equipment for the crew's science program. The highlight in that load will be a 302-pound (137-kilogram) experimental radiator, code-named Pelena. RKK Energia and the Russian Academy of Sciences hope to use the device to test an advanced way of removing heat from equipment in the extreme environment of space.
The problems of overheating have been one of the long-standing issues in space technology and both, the U.S. and Russia have expended considerable effort to improve the efficiency of the existing space radiators. The Pelena experiment will use droplets of oil moving along very hot surface and vaporizing into the vacuum of space, removing the heat with it.
The crew will attach the experimental device to a valve inside the station, which releases into the vacuum of space. A special hydraulic pump is expected to drive oil through the system, while monitoring equipment will evaluate the effectiveness of the whole process. Grigoriev said that in the future, an oil vapor collector could be added into the cooling loop, recycling the oil and maximizing system efficiency.
All these plans are contingent on the time required to find a leak, Markov said. Since a plan to send an actor along with the crew never materialized, the amount of food and other resources delivered to Mir by the Progress M-1-1 spacecraft would easily allow the extension of the mission by 15 days. In fact, a decision to extend the mission up to 60 days could be made during a meeting of the State Commission at the Baikonur Cosmodrome launch complex shortly before liftoff, Markov said.
Beyond first the two months
If private money to operate Mir is found and the Russian government approves the move to extend the outpost's life, the next Progress with a load of propellant to push up Mir's orbit will have to arrive at the station in August or September.
Due to increased solar activity in 2000, which makes Earth's atmosphere more dense, Mir's orbit is degrading faster this year and has become less predictable. As a result, it takes more propellant to adjust the station's orbit and more frequent Progress flights to maintain a safe altitude.
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