Astronauts make space station repairs inside and out

By Irene Klotz

HOUSTON (Reuters) - Two shuttle Endeavour astronauts floated outside the International Space Station on Monday for a fourth and final spacewalk to restore the research outpost to full power.

Stephen Bowen and Shane Kimbrough slipped through the station's Quest airlock about shortly after 1:30 p.m. EST (1830 GMT) for what was expected to be a 6 1/2-hour outing.

It was the third spacewalk for Bowen and the Kimbrough's second since the shuttle arrived at the space station on Nov. 16 for what was scheduled to be an 11-day visit.

NASA managers decided on Monday to extend Endeavour's stay by one day in hopes of achieving one of the mission's prime goals; producing water samples from a urine purification system in time to return them to Earth with the shuttle.

The device, which was carted into orbit aboard Endeavour and installed in the station's Destiny laboratory, has been shutting down due to a suspected mechanical problem.

While Bowen and Kimbrough were working 225 miles (360 km) above the planet outside the station, crewmate Don Pettit and station commander Mike Fincke made a second round of modifications to the urine recycler's centrifuge.

The device is needed to separate solid particles from liquid as part of the distillation process. The purified urine is treated and combined with water recovered from the air and other sources to become drinking water.

NASA needs the new system operating before it expands the space station's crew size from three members to six, a milestone slated for May.