US Discovery astronauts step out on last spacewalk

"Once again rock stars, very impressive work today," said astronaut Nicole Stott, who choreographed the spacewalk from inside the space station, as the pair wrapped up their work after six hours and 14 minutes.

Steve Bowen and Alvin Drew embarked on their second spacewalk together at 1542 GMT to complete work on a failed ammonia pump, remove installation on the Tranquility module and install spare parts on the Canadian robot Dextre.

The walk was briefly delayed by a minor leak in American Steve Bowen's spacesuit, caused by a faulty O-ring seal in a lithium hydroxide canister that scrubs out carbon dioxide. A new O-ring was installed to replace it.

Bowen was a late addition to the six-member US crew that blasted off aboard the Discovery on February 24, after astronaut Tim Kopra was injured in a bicycle accident.

Kopra, who was standing with the help of crutches, was among colleagues at mission control in Houston on Wednesday, and NASA said he would be "helping out" with the spacewalk from there.

Tuesday was Drew's second spacewalk and marked the seventh for Bowen.

The Discovery shuttle is the first of three US shuttles set to become museum pieces later this year.

Endeavour is to lift off on April 19 followed by Atlantis on June 28, marking the official end of the US space shuttle program after 30 years.

(c) 2011 AFP