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Astronaut frees two solar array grommets

NASA approves 4th spacewalk

Astronauts Robert Curbeam (left) and Sunita Williams left the international space station's airlock to begin their spacewalk. (NASA TV VIA REUTERS)

CAPE CANAVERAL, Fla. -- A spacewalker manually shaking a stubborn solar array managed to free two stuck grommets yesterday, but a third problem grommet is still stuck.

The progress inspired Mission Control in Houston to plan an attempt to retract the array once the International Space Station orbits into sunlight again after spending 45 minutes in darkness.

"Beamer, you've been amazingly effective," Mission Control radioed up to astronaut Robert Curbeam, using his nickname.

Curbeam seems to have had success where other attempts via remote control failed the past few days. It was Curbeam's third spacewalk in a week and the first ever for rookie astronaut Sunita Williams.

Williams, a former resident of Needham, Mass., yesterday joined an elite group of eight other female spacewalkers. Only seven other US women and a Russian woman have participated in the 281 spacewalks made since 1965.

"Welcome to the club, Suni," Curbeam told her.

Earlier, NASA approved conducting a fourth, unplanned spacewalk if astronauts were unable to get the accordion-like array to fold up into a box properly. Curbeam pushed on the box several times, shaking the 115-foot array in an attempt to loosen wire tension.

The extra spacewalk, if carried out tomorrow, would delay space shuttle Discovery's landing at the Kennedy Space Center by a day to Friday, and push back other activities such as undocking and a late inspection of the shuttle's heat shield.

The half-retracted solar wing was part of the space station's temporary power system.

A primary goal of Discovery's visit to the station was to rewire the lab and hook a new set of solar wings delivered in September onto the permanent electricity grid. To do that, NASA needed to retract the old solar panel so that the new ones had room to rotate with the movement of the sun to maximize the electricity generated.

The old solar panel had retracted enough to give the new ones clearance, but it did not fold all the way as NASA wanted.

Curbeam and Williams headed over to the array after completing the main task of their spacewalk.

The astronauts shifted the space station's electrical system to a permanent power source from a temporary one.

About half the lights, a fire alarm, some ventilation ducts, and some communication on the US section of the space station were powered down as a precaution to the spacewalkers, who unhooked and plugged back in connecting hoses to half of the lab's electrical system.

Less than two hours into the spacewalk, the rewired electrical system was powered back up, and Mission Control reported that it was operating without problems.

"It's great to have some good, on-orbit electricians working for us," said astronaut Stephen Robinson at Mission Control.

NASA had to race to get the space station's ammonia cooling system operating before the equipment overheated. The ammonia flowed without trouble, drawing a sigh of relief from Curbeam.

"Excellent. That is awesome news," said Curbeam, whose spacesuit was inadvertently contaminated by a leaking coolant line during a similar spacewalk in 2001.

NASA can keep the halfway retracted array in its current position until April, leaving open the possibility that the next shuttle crew in March or even the current station crew could fix the problem during a spacewalk. In a worst-case outcome, the array could be jettisoned.

The astronauts were heading into the last stretch of their 12-day mission, which includes seven days at the space station. Discovery delivered a 2-ton, $11 million space station addition, which was installed during the first spacewalk, and will carry back a station crew member upon undocking tomorrow.

Discovery is scheduled to return to the Kennedy Space Center in Florida on Thursday. It has enough supplies to remain in space until Saturday, to allow for any weather-related delays in landing.

Other spacewalk tasks included rewiring power feeds to the Russian side of the space station and relocating protective panels which stacked together are known as "the Christmas tree."

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