From: Irene Klotz -Reuters
Published October 29, 2007 07:49 AM

NASA ponders space station power problem

CAPE CANAVERAL, Florida (Reuters) - Two spacewalking astronauts on Sunday found metal shavings inside a huge gear that spins a pair of the International Space Station's solar wing panels, raising concerns about power supplies and the long-term health of the orbital outpost.

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The inspection of one of the $100 billion space station's two solar panel rotary joints was added to the second of five spacewalks planned during the space shuttle Discovery's ongoing construction and servicing mission to the station.

NASA immediately laid out plans to minimize the number of times the affected device rotates, cutting the amount of power the station can produce. The joint spins a pair of panels studded with solar cells to track the sun for power.

Space station program manager Mike Suffredini said he was hopeful engineers would come up with a plan to manage the station's power that would allow NASA to launch Europe's Columbus laboratory on schedule aboard the space shuttle Atlantis on December 6.

"We have lots of time to work through this problem," Suffredini said. "It's not an immediate issue."

He said, however, that some experiments planned to be carried out in the new lab may have to be postponed if the station's power supplies are inadequate.

During Sunday's spacewalk, astronauts Scott Parazynski and Dan Tani prepared another solar wing segment for relocation to the outer edge of the station's frame.

The gear problem makes it even more critical that the twin panels unfurl as planned later this week.

A fourth set of solar wings to complete the outpost is not due to arrive until late 2008 or 2009. NASA has a 2010 deadline to complete construction of the station before the space shuttle fleet is retired.

Tani used tape to collect samples of the metal shavings, which engineers believe may be bits of aluminum from the inner lining of thermal covers attached to the rotator.

NASA is considering having spacewalkers on a future outing pull off the joint's 21 other thermal covers to see if there are contaminants inside those compartments as well. While the debris eventually will need to be cleaned up, NASA's immediate concern is to prevent further damage.

The long-term concern is that vibrations from the extra power needed to drive the gear will reduce the orbital lifespan of the station itself. The outpost is being designed to last until at least 2015, though NASA and its international partners expect the station to remain operational for years beyond.

Though it would be extremely time-consuming, NASA has spare parts to rebuild the entire rotator, if necessary, Suffredini said.

During the first spacewalk of shuttle Discovery's planned 14-day mission, astronauts installed the Italian-built Harmony module, which has berthing ports for Europe's Columbus and Japan's Kibo laboratories.

Discovery, which arrived at the station on Thursday, two days after launching from the Kennedy Space Center in Florida, is due back at the spaceport on November 6.

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