Mounting delays stress space station systems

Growing delays in the delivery of space hardware have begun to significantly affect the day-to-day operations of the international space station and the flight schedules for the second half of this year.

Aboard the station, the hard failure of the Elektron oxygen generation system and the imminent exhaustion of a secondary source of oxygen will force the crew by Monday to begin burning chemical canisters known as "oxygen candles" in order to continue breathing. Normally a robust and reliable system, these units have burst into fire on occasion, nearly killing the crew of Mir in a 1997 incident.

Replacement parts for the Russian Elektron system, originally expected to reach the station on a robot supply ship next month, will now not be available until later in the year. Although a small electronics box may still fly in June, it’s a long-shot repair, sources say. The more promising repair of the system needs a 300-pound liquid unit whose manufacture in Russia has been seriously delayed.

Even more significantly, the launch of the next space station crew may be put back a full month. NASA internal documents obtained by MSNBC.com yesterday show that the date for launching the Soyuz TMA-7 is now listed a Oct. 22, instead of the original Sept. 27 date.

This delay means the mission of the current crew, Russian Sergei Krikalev and American John Phillips, would be extended from 175 days to 200. That would push their own Soyuz vehicle, in which they arrived at the station last month, close to its maximum certified orbital lifetime, but past Soyuz capsules have spent up to 210 days in space before returning safely.

The extension would also give Phillips the record for the most time spent in space by an American on a single flight. Krikalev will acquire the world record for career total time over all flights, even without the extension.

Burning the candles
Of the four sources of oxygen aboard the space station, two are now unavailable: The Elektron system doesn't work and the store of oxygen bottles sent up on a supply ship in March will be exhausted by Monday. While extra bottles have been loaded into the next unmanned supply ship, it is not scheduled to launch for the station until June 17.

So the crew must now rely on the third source, the so-called "oxygen candles." These "solid-fuel oxygen generators" (known as SFOGs to NASA and TGK in Russian) are scuba tank-sized cylinders containing a briquette of solid lithium perchlorate. Each canister provides a little less than two pounds of oxygen, enough for one crewman for one day.

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