Astronauts work on space station water recycler

HOUSTON (Reuters) -- Astronauts aboard the International Space Station on Sunday tried to revive a urine recycling machine needed to provide fresh water for an expanded crew scheduled to arrive next year.

The device is part of a $250 million life-support system delivered by the visiting space shuttle Endeavour.

NASA hopes to double the space station's crew from three members to six in May but needs to make sure the station has reliable way to produce fresh water for drinking and cooking and to operate their oxygen generator.

The station now gets most of its water from visiting shuttles, which produce water as a byproduct of their electrical systems. Astronauts bag the water and transfer it to the orbital outpost. The shuttles, however, are to be retired in two years.

"We want to get this system running as soon as possible so we can process urine and verify that we have good portable water coming out the other side," said station flight engineer Sandra Magnus during an in-flight interview.

A problem with a centrifuge has stymied attempts to distill urine samples so far and shuts down the machine. "The centrifuge would spin around for a few hours and then all of a sudden would get a little bit unbalanced," station commander Mike Fincke told reporters.

Despite the problem, NASA says it has processed enough urine for samples to be brought back to Earth for testing.

The Endeavour crew also prepared for their fourth and final spacewalk on Monday to work on the truss joints that pivot the station's solar wing panels to collect energy from the sun. One of the joints was contaminated with metal filings and has been cleaned and lubricated.

Astronauts plan some preventative maintenance on a second joint during Monday's outing.

The shuttle astronauts also had a few hours off-duty Sunday, their first break since arriving at the station on November 16. The shuttle is scheduled to depart on Thursday and return home to the Kennedy Space Center in Florida on Saturday.

NASA plans eight more flights to the station, a $100 billion project of 16 nations, before the shuttles are retired in 2010.