Spacewalk to repair solar panel
Updated on 30 January 2008
The space station's two American astronauts have gone out on a riskier-than-usual spacewalk to fix one of two equipment failures that have crippled their power system and threatened to stall construction.
Commander Peggy Whitson and Daniel Tani floated outside the space station, hauling a new motor that Nasa hoped would enable a solar wing to tilt toward the sun again and draw more power for the orbiting complex.
The spacewalk had barely begun when a radio-relay problem cropped up, preventing Whitson and Tani from hearing Mission Control. Flight controllers managed to restore communication through a back-up channel within 20 minutes, allowing the spacewalk to proceed.
The tilting mechanism stopped working in early December, complicating a power problem that arose three months earlier when a solar wing rotating joint jammed up and had to be shut down.
Engineers traced the most recent trouble to a suspect motor. Luckily, the international space station had a spare on board.
To avoid being shocked, Whitson and Tani had to perform the replacement job on the dark side of Earth, pausing during daytime passes when 160 volts of electricity would course through the cables, which had to be disconnected. As an added precaution, the spacewalkers were advised not to point any non-essential lights at the solar wing in question to prevent power generation.
The motor weighs close to 250lbs (113kg) and is enclosed in a two-foot can with two handles on the end, looking somewhat like a rubbish bin. It serves as the structural backbone for the solar wing, and the spacewalkers had to be careful that the wing didn't come off and fly away.
Nasa is still uncertain what to do about the clogged joint, which is supposed to continuously rotate 360 degrees to keep the solar wings pointing toward the sun. As many as four spacewalks will be required later this year to remove metal shavings from the joint and get it working again.
Even with both failures, Nasa could still launch space shuttle Atlantis to the space station next week with the European science lab, Columbus. But unless the tilting mechanism is fixed, any further shuttle missions would be in jeopardy. The joint problem alone, if left unresolved, could delay shuttle flights starting later this year.
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