NASA clears Discovery for liftoff on Wednesday

CAPE CANAVERAL, Florida (Reuters) - NASA managers on Friday cleared the space shuttle Discovery for launch Wednesday on a construction mission to the International Space Station.

The space shuttle Discovery lifts off from launch pad 39A at the Kennedy Space Center in Cape Canaveral, Florida May 31, 2008. REUTERS/Scott Audett

Liftoff of the 125th shuttle mission, the first of five planned for this year, is scheduled for 9:20 p.m. ET from the Kennedy Space Center in Florida. The mission had been on hold to resolve safety concerns with the ship’s fuel pressure valves.

“We’re feeling really, really good,” shuttle launch director Mike Leinbach told reporters at a press conference. “It’s great to have a launch date.”

The shuttle will deliver the final set of U.S.-manufactured solar wing panels to the station, a $100 billion project of 16 nations that has been under construction for more than a decade.

NASA is scheduled to complete station assembly next year and retire its three-ship shuttle fleet. The shuttle program has been the cornerstone of U.S. human space exploration for nearly 30 years. The replacement vehicles, designed to travel to the moon as well as the space station, are scheduled to debut in 2015.

Discovery’s launch, originally targeted for February 12, was repeatedly postponed while NASA mulled a potential safety issue with fuel pressure valves in the shuttle’s engine compartment. The valves ensure the ship’s hydrogen fuel tank is properly pressurized throughout the 8.5-minute ride into orbit.

During the last shuttle launch in November, one of the three valves cracked, raising questions about what could happen if the damage was more severe or if it occurred at a more critical time during ascent.

Managers replaced Discovery’s valves with spares that have made fewer flights and ordered extensive tests and analysis to understand worst-case scenarios.

After four launch delays, the managers felt confident the ship was safe to fly and unanimously decided to proceed with a launch attempt next week.

“The vehicle is in great shape,” said shuttle program manager John Shannon.

Editing by Jane Sutton