NASA clears shuttle for space station visit

CAPE CANAVERAL, Florida (Reuters) - NASA managers on Wednesday cleared the space shuttle Endeavour and seven astronauts for launch on Friday on a mission to make the International Space Station a bit more like home.

Endeavour's cargo includes two sleeping chambers, a second toilet and a water purification system that will let NASA double the station crew size to six and allow them to recycle urine and waste water for drinking. Launch is set for 7:55 p.m. EST from Kennedy Space Center in Florida.

"This mission is all about home improvements, both inside and outside of the International Space Station," said Endeavour commander Chris Ferguson. "We've had some large modules delivered in the last year. It's time to fill them up."

Meteorologists were watching an approaching cold front that may trigger rain and thick clouds over central Florida around launch time. Overall, they predicted a 60 percent chance the weather would be suitable for an on-time liftoff.

NASA is eager to get back into orbit after an expectedly long hiatus between its last shuttle mission in May.

The agency had planned to fly a Hubble Space Telescope servicing call in October but delayed the mission until May 2009 to add more repairs after a new problem surfaced with one of the telescope's computers.

"We're looking forward to the launch," said Mike Leinbach, who oversees the shuttle launch team in Florida. "It just feels way too long."

NASA will need to step up its flight rate if it is going to complete construction of the space station and retire the three space shuttles by September 30, 2010, as ordered by outgoing U.S. President George W. Bush. Nine more missions to the outpost are scheduled.

NASA has slowed retirement plans in the wake of President-elect Barack Obama's possible interest in keeping the shuttles flying for an extra mission or two.

In a report to Obama's transition team, the Government Accountability Office, the investigative arm of Congress, identified the shuttles' retirement as one of the top 13 issues facing the new administration.

In addition to an extra $2 billion a year to keep the shuttles flying, NASA would have to assess how to keep the aging ships safe for additional flights.

"The safety aspect is a little bit elusive, so we need to be very open minded and very creative in how we think of it," said Leroy Cain, the deputy shuttle program manager.

Among the options under consideration: using one shuttle for parts for its sister ships and to serve as a test subject to uncover unknown hazards.

"It's one of the things we're looking at to help us improve our confidence," Cain said.

(Editing by Jim Loney and Eric Beech)