Spacewalkers finish job; female astronaut sets record

Feb. 4, 2007, 11:21PM
Spacewalkers finish job; astronaut sets record
2 astronauts encounter leak of ammonia as they repair station's cooling system

By MARK CARREAU

U.S. astronauts Mike Lopez-Alegria and Sunita Williams overcame a small toxic spill on Sunday as they finished a two-spacewalk upgrade of the cooling system aboard the international space station.

Their activities established the groundwork for future construction work at the orbital base, including a March shuttle mission to increase solar power production.

At the end of Sunday's outing, Williams had set a record for time accumulated on spacewalks by a woman, 22 hours, 37 minutes. The milestone was accumulated over three spacewalks. The previous record was set by NASA astronaut Kathy Thornton in 1993.

Early in Sunday's seven-hour-plus spacewalk, the two astronauts dodged pinpoint-sized flakes of ammonia coolant that froze as it escaped from an external plumbing fixture they were reconnecting.


Taking extra care
The astronauts took measures to ensure the respiratory irritant would not stick to their protective suits and make its way back into the space station to mix with the breathing air.

"All indications are that it was a very, very small leak," said NASA flight director Derek Hassmann, who supervised the outing from Mission Control. "I would call this spacewalk very successful."

Neither astronaut found traces of ammonia on his or her space garb. Nonetheless, they followed procedures to evaporate any unseen contaminant by exposing the suits to sunlight while they worked.


Walk No. 3 set for Thursday
Later, neither spacewalker nor Russian Mikhail Tyurin, who remained in the station, reported ill effects.

The astronauts encountered a similar leak on Wednesday, when they conducted their first cooling-system spacewalk.

On Sunday, Lopez-Alegria and Williams disconnected and reconnected four external cooling tubes. The re-plumbing finished a deactivation of a temporary 6-year-old cooling system. The change will channel a flow of ammonia through external radiators to discharge heat accumulated from life support and flight control systems as well as scientific gear housed inside the outpost.

The spacewalkers also began the installation of an extension cord that will permit future shuttle crews to draw electricity from the station, allowing them to remain docked longer.

Lopez-Alegria also snapped photos of a 110-foot-long solar panel that the shuttle Atlantis crew has trained to retract in March. In December, the Discovery astronauts encountered problems with the retraction of a companion panel when it became snagged on misaligned guide wires and guide pins. The photos will be transmitted to Mission Control, where experts will look for snags that could pose a similar problem on the upcoming mission.

Lopez-Alegria and Williams are slated for a third outing on Thursday. Their three spacewalks in nine days will be the most attempted in so brief a time by previous space station astronauts.
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