August 3, 2006

Space station crew members complete spacewalk

WASHINGTON (Reuters) - Two astronauts from the International Space Station floated outside their orbital home for a six-hour spacewalk on Thursday to prepare the $100 billion, half-built complex for future construction.

NASA's Jeffrey Williams and the European Space Agency's Thomas Reiter, both experienced spacewalkers, slipped outside the U.S. airlock at 10:04 a.m. EDT (1404 GMT) as the orbiting outpost flew over Australia and southeast Asia.

Among a long list of tasks, they replaced broken equipment in what will become the station's primary cooling system, tested an infra-red camera designed to detect damage to the station's thermal surface and installed two experiments.

One will monitor the buildup of static electricity around the station, which could pose a threat to spacewalkers. The other will test how different materials react to the heat, cold and radioactivity of space.

NASA had planned to hook up the station's new coolant lines more than three years ago, but all space shuttle flights were suspended after the fatal February 1, 2003 Columbia accident. The U.S. shuttles are the only spacecraft capable of taking large components to the station.

The agency's first two shuttle flights after Columbia fell apart over Texas were aimed at testing safety upgrades.

It was only with the return of the shuttle Discovery last month after a successful equipment shakedown and maintenance call at the station that NASA cleared the shuttle fleet to resume assembly of the multi-nation project.

Shuttle Atlantis is targeted for launch between August 27 and September 7 to deliver a new set of solar power arrays to the station. Discovery is scheduled to bring more equipment in December. NASA plans 16 station assembly missions before the shuttle fleet is retired in 2010.

(Additional reporting by Irene Klotz in Cape Canaveral, Michael Christie in Miami)