CAPE CANAVERAL, Fla. - Two astronauts - including Britain's first spacewalker - are working to restore full power to the International Space Station.

British spaceman Timothy Peake and NASA's Timothy Kopra (KOE-pruh) floated outside Friday morning. They need to replace an electronic box that failed two months ago, slashing station power by one-eighth.

The breakdown didn't disrupt work 250 miles up. But NASA wanted the power grid fixed as soon as possible, in case something else failed. The box - a voltage regulator - is about the size of a 30-gallon aquarium.

The spacewalkers will make the switch in darkness, to prevent electricity from flowing through the solar power system and shocking them. They have just 31 minutes on each swing around Earth to complete the repair on the far reaches of the space station.