Space station stars in a tale of endurance

The 30-month gap
Over the 30-month hiatus between shuttle visits, station crew members conducted a lot of routine maintenance as well as assembly operations. Sometimes they encountered puzzling anomalies, such as a "thump" in the Russian module that might have been an external impact but which eventually was written off an air fan hiccup. Occasionally, out their windows they would see pieces of their station harmlessly floating away.

About halfway through the hiatus, the station crew was faced with a puzzling, slow air leak, which they eventually traced to the main viewing window in the U.S.-built Destiny laboratory module. Although NASA never explicitly confirmed it, program sources revealed that the leak had been caused by a crew error made possible by a design flaw, and their first attempts at repair actually made the problem even worse.

Reducing the crew size from three to two was initially of concern to psychologists, but as it turned out, the teams got along fine, just as two-man Russian crews had done. They developed various techniques to keep morale high, and one man even got married, by proxy, to his earthbound girlfriend.

The six-month limit
But six months — the standard time between Soyuz launchings — seemed to be an upper limit for routine missions. At one point, the Russians proposed extending a crew's flight to a year's duration. NASA rejected the suggestion, saying longer tours of duty would put too much strain on the crews, particularly when the space station was in a "reduced operational state."

NASA TV / Reuters Russian cosmonaut Gennady Padalka and NASA astronaut Mike Fincke install equipment on the international space station during a spacewalk in August 2004. The station experienced "phantom torque" during the outing.

Despite the limitations, the space station expeditions have offered key lessons for planning missions to Mars.

The lack of a third crew member was a significant drawback during spacewalks, when the two astronauts had to go outside and leave the station empty. Sometimes hardware problems on these spacewalks taught unexpected lessons, or required all the flexibility that was available because of redundant U.S. and Russian systems, even if these changed plans involved the Russians sending NASA a bill for extra services.

One baffling anomaly on spacewalks even threatened to become hazardous. When using Russian suits, some unknown effect caused the entire space station to slowly drift out of proper orientation, and during one recent spacewalk, Russian steering thrusters fired while the American crewman was close to the exhaust plume. Although corrective procedures were developed, the source of the ‘phantom torque’ disturbance remains unresolved.

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