Installation of a urine processor on the International Space Station has paused after a caution alarm unexpectedly tripped today. NASA officials say they believe it was a false alarm and they think they understand the cause, but they've stopped sending commands to the hardware while crews are sleeping, to avoid waking them with another accidental alarm.
The urine processor is one of the key components of a system shuttle Endeavour shipped to the station after launching last Friday from Kennedy Space Center. It's designed to replenish water supplies so permanent station crews can double to six people by next year.
ISS Flight Director Ginger Kerrick said even if the urine processor takes a bit longer to activate, tests can proceed of a water processor that will recycle sweat and other condensation.
She said it's still possible enough samples can be collected for testing that it won't be necessary to extend the 15-day shuttle mission by a day.
"We think this is just a small setback," she said.
Managers praised the Endeavour and station crews' work today.
A few issues of possible concern arose during the day's spacewalk, the second of the mission, but were not considered major.
Spacewalker Shane Kimbrough's carbon dioxide levels reached the allowable limit, which would have forced him back inside. However, he was already in the process of returning to an airlock at that time, so his workload wasn't cut short.
Officials said Kimbrough was fine and felt no ill effects from the higher carbon dioxide levels.
Kimbrough also had trouble communicating by radio as he returned to the airlock. Officials believe he may have accidentally bumped a volume control knob.
John Ray, the mission's lead spacewalk officer, said he believed Saturday's spacewalk could proceed as planned by continuing today's use of grease-covered wipes instead of a straight-nozzle grease gun, one of which was lost Tuesday.
"It sounds like that technique worked as least as well as the nominal going in plan for wet scraping," he said, referring to a cleaning step during repairs of a starboard rotary joint. "We think that's going to be a technique that can use on rest of (spacewalk) three."
Finally, there was a problem with one trundle bearing assembly installed on the rotary joint's gear ring, when a bolt was inserted with too much torque. Concerned that the bolt could fail, a different bearing assembly was installed.
A change was made late in today's spacewalk plan: Instead of cleaning around one set of bearing assemblies, Kimbrough was diverted to another. The latter area was one where protective thermal covers could be left off until the next spacewalk, saving time.
For those keeping score at home, Endeavour's spacewalkers have completely removed and replaced five of 11 bearing assemblies designated for replacement. Another five must be removed and replaced, and a sixth set removed today will be replaced.
A 12th bearing set was already replaced during the STS-124 mission. Endeavour spacewalkers will take it out and clean around it, then reinstall the same set of bearings.
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