CAPE CANAVERAL, Fla. (AP) -- Space station astronauts are taking a spacewalk to replace a dead computer and get their orbiting home back up to full strength.
The two Americans on board, Rick Mastracchio (muh-STRAK'-ee-oh) and Steven Swanson, stepped out Wednesday for the urgent repair job.
The computer is a critical backup outside the International Space Station that failed nearly two weeks ago. The prime computer has been working fine, but NASA wanted to install a fresh spare as soon as possible.
Mission Control waited until after the arrival of a capsule full of fresh supplies on Sunday
The spare computer is a compact 50-pound box. Engineers don't know why the original failed. The astronauts will check for any damage.
It's expected to be a short spacewalk, involving just three bolts.