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Shuttle commander fixes faulty air purifier with tape

Space shuttle Columbia's astronauts successfully restarted a critical air purifier Saturday after it failed and threatened to cut short their two-week science mission.

With a few twists and snips, commander Richard Searfoss removed one end of a small hose in the stalled carbon dioxide removal unit and blocked it with tape. He then reinstalled the hose, bypassing a leaky valve.

When he turned on the carbon dioxide removal unit, the light came on. To everyone's relief, it stayed on.

"We've got some good news for you, Rick," Mission Control said. "It seems to be working as expected, so it looks like we've headed off the possibility of a shortened mission."

The unit had to operate reliably for the seven astronauts to remain in orbit for all 16 to 17 days of their mission to study the brain. Its failure would have forced the crew to return to Earth as early as Wednesday _ four days sooner than planned.

Mission operations representative Lee Briscoe said the seven astronauts were never in any danger during the 18-hour ordeal because the level of carbon dioxide gas in the shuttle rose only slightly. "It should be coming down," he said Saturday evening.

The carbon dioxide removal unit shut down without warning late Friday _ twice within 10 minutes. Columbia's astronauts immediately switched to a more complicated but reliable method of purifying their air.

That method involves the repeated installation of canisters of lithium hydroxide, carried on each mission as a backup. Each time a can becomes saturated with carbon dioxide _ the result of breathing and perspiration _ it has to be replaced and stored. Until 1992, this was the only way to remove carbon dioxide from the shuttle atmosphere.

The newer removal system, by contrast, automatically absorbs carbon dioxide with a different chemical and dumps it overboard. Flight controllers suspected a leaky valve might be causing the unit to shut itself off, and they instructed Searfoss to bypass the valve and an attached compressor.

"Be careful what you touch," Mission Control warned.

After reassuring flight controllers the unit was "cool and copacetic," Searfoss likened the job to auto repair.

"It must be Saturday," Searfoss said. "Time to work on our car like down on Earth."

All told, it took him only several minutes to complete the job with just a screwdriver and tape.

Briscoe said engineers won't know why the valve leaked until they examine it after the flight. It may have become contaminated with debris, he said.