Image: Spacewalkers
In this image from NASA Television, astronauts Sunita Williams, left, and Michael Lopez-Algeria work on the international space station's exterior during a spacewalk on Wednesday.
updated 1/31/2007 10:27:08 PM ET 2007-02-01T03:27:08

Four or five flakes of toxic ammonia dripped from a cooling line cap Wednesday but apparently didn’t touch two U.S. astronauts conducting the first of three spacewalks planned outside the international space station over the next nine days.

The leak occurred late in the almost eight-hour spacewalk, as astronauts Michael Lopez-Alegria and Sunita Williams disconnected and prepared to stow away two fluid lines that had been connected to an ammonia reservoir outside the space station.

Tests in the airlock later showed no contamination, and the spacewalk officially ended at 6:09 p.m. ET, seven hours and 55 minutes after it started.

Ammonia, which can cause contamination upon contact, was a big concern since the toxic substance leaked out of a cooling line onto astronaut Robert Curbeam’s spacesuit when he performed a similar task in 2001.

Lopez-Alegria and Williams did not face the same problems as Curbeam did with ammonia. Nevertheless, Mission Control told the spacewalkers to remain in their spacesuits for an extra 25 minutes once they entered the station’s airlock to make sure there was no ammonia on their suit that could contaminate the orbiting lab.

“We don’t think we have contamination, but that’s probably for the lawyers,” Lopez-Alegria said.

Replied Mission Control: “We’re going to follow the path of safety.”

During Wednesday’s spacewalk 220 miles (350 kilometers) above Earth, the astronauts successfully switched coolant lines from a temporary cooling system to a permanent one and secured a thermal cover around an obsolete radiator that Mission Control retracted by remote control. Lopez-Alegria made electrical connections for a new system that will allow power from the station to be shared with a docked shuttle.

The astronauts ran out of time and only got one of two fluid lines stowed, and they didn’t get to “get-ahead” such tasks as taking photos of a solar array that will be retracted during the next shuttle mission, in March.

The astronauts will perform identical tasks during their second spacewalk, set for Sunday. The astronauts will take a third U.S. spacewalk together on Feb. 8 to jettison thermal blankets.

U.S. astronauts have never attempted three spacewalks in such a short time without a space shuttle docked at the station. If the spacewalks go as planned, Lopez-Alegria will have two weeks to rest before going on a fourth spacewalk, set for Feb. 22.

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