Spacewalkers overcome glitches

JOHNSON SPACE CENTER, Texas -- Despite a computer hard drive crash before they ventured outside, two spacewalking astronauts Wednesday worked so speedily and efficiently that mission managers let them get a head start on tasks planned for a third and final spacewalk Friday.

In four hours, astronauts Mike Gernhardt and Jim Reilly breezed through installation of an oxygen tank and a nitrogen tank on the outside of space station Alpha's new air lock.  Mission control in Houston then gave the pair the go-ahead to install a second oxygen tank.

The tanks are three feet in diameter and weigh about 1,200 pounds each. They are needed to use the air lock, which Gernhardt and Reilly attached to the orbiting outpost during the first spacewalk on Sunday.  The fourth tank (nitrogen) will be attached to the air lock during the Friday spacewalk.

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The third walk is scheduled to be staged from the new air lock, a $164 million portal that will make it easier for Alpha crew members to conduct spacewalks without assistance from visiting shuttles.

There were some glitches in the second spacewalk. Before it started, as the crews were getting ready to power up the space station's robot arm, one of three critical command and control computers in the space station's Destiny science lab gave an error message.

"It was troubling," said NASA spokesman Greg Lange. He said the computer is critical for controlling the space station robot arm which was needed to lift the tanks out of the space shuttle's cargo bay for attachment to Alpha.

The Atlantis crew: Seated with the insignia, Commander Steve Lindsey, right, and pilot Charles Hobaugh. In the rear, Mike Gernhardt, left, Janet Kavandi and Jim Reilly

The computer was reset and worked fine throughout the spacewalk, Lange said. But the spacewalk started about an hour late.

Later, a mislabeled valve caused more tense moments.

After installing the first tank, Gernhardt opened a valve to test whether oxygen was flowing from the tank into the air lock. It wasn't. It turned out one of the valves had been mislabeled. Once the correct valve was located, the oxygen flowed properly inside the air lock.

Just as during the first spacewalk Saturday night, much of the heavy lifting was done by the space station's new robot arm.  Station resident Jim Voss used the arm to hoist the oxygen and nitrogen tanks from the shuttle's cargo bay and position them for the astronauts to attach them to the air lock.

The two spacewalkers provided Voss with visual guidance and helped attach the tanks. Gernhardt rode the shuttle's robot arm, piloted by mission specialist Janet Kavandi. A tethered Reilly clung to the side of Alpha.

The pair took time out from their work to speculate about future missions.

"We can see Mars up there, Mike. Our next stop," Reilly said to Gernhardt.

"One of these days," Gernhardt replied.

The Alpha crew: Jim Voss, left, Yury Usachev and Susan Helms

On Tuesday, NASA decided to extend the shuttle's mission by a day. The crews of the two spacecraft got behind schedule when they were troubleshooting what NASA described as minor problems.

-A valve in the new air lock sprang a small leak. The crews will replace it and bring the faulty valve back on Atlantis.

-Earlier, a small amount of water leaked near the air lock during installation. The crews quickly mopped it up.

-The cooling system, which prevents lab equipment from becoming too hot, shut down setting off a loud alarm. The system resumed operations without a problem.

-On Friday, Atlantis astronauts discovered suspected battery acid leaking from a spare spacesuit. The possible toxic leak triggered a swift emergency cleanup by the Atlantis crew, which donned gloves and wiped down the area. NASA said it would return the spacesuit to Earth instead of storing it in the space station as originally planned.

Now that the mission has been extended, Atlantis is scheduled to land at Kennedy Space Center early next Tuesday. The current Alpha crew is scheduled to return to Earth in August after spending almost half a year in orbit.