Two Discovery shuttle crew members, Robert Curbeam and Christer Fuglesang, spent more than six hours in outer space, clearing the way for a critical power rewiring later this week.
The first of three spacewalks began hours after engineers said Discovery's heat shield did not need any further inspection.A 2-ton girder-like structure installed by the astronauts will act as a backbone for the ISS.Discovery is now docked to the International Space Station.