SPACE CENTER, Houston - A pair of spacewalking astronauts installed power converters on the international space station Tuesday during a third straight day of exterior work.
''Woo-hoo!'' Bill McArthur shouted just before going out space shuttle Discovery's hatch. He yelled the same thing, repeatedly, during his work outside on Sunday.
McArthur was barely out when he saw the cap for a shuttle depressurization valve floating away. The small aluminum cap bounced against the space station's newly installed truss segment, then against Discovery's robot arm.
''It was a nice billiard shot,'' McArthur said. ''It's become the latest addition to tiny bodies orbiting the Earth.''
Mission Control said the lost cap was not a problem for the valve or the spacewalk. Its tether either came loose or broke.
During the planned 6-hour spacewalk, McArthur and Leroy Chiao put in a pair of power converters. Other tasks included connecting a few final cables and mounting a toolbox to the truss, which they helped install during a spacewalk on Sunday.
Astronaut Michael Lopez-Alegria, the shuttle robot arm operator, had the difficult challenge of ferrying Chiao from the shuttle cargo bay to the newly installed space station truss. Chiao called out directions: ''Keep going, keep going, stop there.''
Chiao removed the converters, one at a time, from the wall of the cargo bay. Lopez-Alegria then lifted Chiao to the truss, where he installed the units.
On Monday, the other pair of spacewalkers, Lopez-Alegria and Jeff Wisoff, helped guide a docking port into place during the mission's second spacewalk.
Their seven-hour spacewalk started rocky when Wisoff and Lopez-Alegria's power drills wouldn't loosen the four latches holding down the docking port in Discovery's cargo bay.
''Who's scripting this, anyway?'' one of them asked.
To free the latches, the duo cranked up the torque on their drills. Wakata then lifted the 2,700-pound port up to the station on the end of the shuttle's 50-foot arm, and Lopez-Alegria and Wisoff called out verbal instructions to help Wakata push it into place.
The docking port will be used by space shuttle Endeavour when it delivers huge solar panels in December and by Atlantis when it carries up the American lab Destiny in January.
Lopez-Alegria and Wisoff have a fourth and final spacewalk ahead of them Wednesday, two days before Discovery is to leave the space station. If all goes well, the next crew to dock will be the station's first residents.
Their planned Oct. 30 launch aboard a Russian rocket from Kazakstan could be delayed a couple of days, but mission managers won't know the exact launch date until Discovery completes all of its station-raising maneuvers, said flight director Chuck Shaw.
''I guess it's stay tuned for the actual launch date for that mission,'' Shaw said.
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