NASA is considering the potential for two- or three-crew missions lasting a year aboard the International Space Station (ISS), starting in October with the launch of the tenth expedition crew.

This follows Russia's call for an extension to the six-month shifts presently flown by expedition crews. While it needs more data on long-duration spaceflight now that journeys to Mars are being considered, NASA is concerned that longer flights mean fewer test subjects, halving data on individual bone and muscle loss, the major concern on long-duration missions.

While doubling the length of ISS shifts would provide needed data on long-duration missions, it would also free space on Russia's three-seat Soyuz TMA crew ferry for more commercial flights. NASA has been rankled that Russia can fly $20 million commercial missions with a space tourist in the third seat alongside two ISS crewmembers, and is likely to recommend that year-long missions be flown by three crew. Russia will have to finance and arrange tourist flights separately.

A two-person crew can operate the ISS, but "we miss the amount of research we can do", says Mike Suffrediuni, NASA manager of ISS integration and operations. Two-person extravehicular activity outside the ISS without a person inside is not ideal.

ISS crews comprised a commander, flight engineer and science officer until the Columbia accident stopped Space Shuttle flights in 2003.


Source: Flight International