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Spacewalkers overcome snag to station upgrade
By Associated Press
Sep 13, 2006, 22:11

HOUSTON (Reuters) - Two spacewalking astronauts on Wednesday freed a stubborn bolt that could have kept the International Space Station's newly installed solar arrays from turning properly.

The successful spacewalk was the second of three planned during space shuttle Atlantis' week-long stay at the station which is slowly being assembled. It is NASA's first assembly mission since the 2003 Columbia disaster.

"Whoo-hoo!" sang out one of the astronauts as the stuck bolt finally gave way.

Freeing the bolt broke a socket tool and required the combined muscle power of astronauts Dan Burbank and Steve MacLean, oversight from crewmate Heidemarie Stefanyshyn-Piper and advice from flight controllers at NASA's Mission Control at the Johnson Space Center in Houston.

"We had a bolt that required some superhuman strength," flight director John McCoullough told reporters after the spacewalk. "But it was a great day."

Removing the bolt was essential for the station's new power-producing solar arrays to track the sun.

"We appreciate your answering that age-old question 'How many astronauts does it take to unscrew a bolt?"' joked astronaut Pam Melroy from Mission Control.

"Apparently it takes three, two outside and one inside. We're very pleased. You guys did an awesome job and that was great teamwork."

Burbank and MacLean, both spacewalking rookies, spent most of their seven-hour, 11-minute outing removing equipment installed to protect the rotary joint from the vibrations and stresses of launch. The joint had 16 launch locks on its primary gear, as well as other launch restraints.

When a thermal cover was removed to reach one of the locks, a spring-loaded bolt drifted off into space despite the extra precautions the astronauts took after a similar incident occurred during the mission's first spacewalk on Tuesday.

After checking to make sure the bolt didn't float inside the station's girder-like structure, MacLean reattached the thermal cover with the three remaining bolts.

NO DANGER

The flyaway hardware is not expected to have any impact on the station or shuttle, managers said.

Once the spacewalkers were safely back aboard the station, flight controllers sent commands to rotate the new joint for the first time.

"We did a 180-degree motion that was all in the light of day and beautiful as could be," McCoullough said.

The crucial moment for the new array comes early Thursday when ground controllers remotely command it to unfurl.

If the automated systems fail, astronauts Stefanyshyn-Piper and Joe Tanner will be ready to manually deploy the arrays during a third and final spacewalk on Friday.

The shuttle needs to leave the outpost by early Monday to allow a Russian Soyuz rocket carrying the next space station crew and an American tourist dock at the outpost on Wednesday.

If the solar arrays are extended without problems, Atlantis will leave the station on Sunday. Touchdown at the Kennedy Space Center in Florida is scheduled for next Wednesday.

NASA plans at least 14 more construction missions to the space station over the next four years and must complete assembly before the fleet is retired in 2010.