Nasa's shuttle launch off till late next week

CAPE CANAVERAL, Florida - Nasa said today it would be at least late next week before the first shuttle mission since the 2003 Columbia accident can be launched, after Discovery's liftoff was postponed two days ago because of a fuel sensor problem.

"The simple things did not provide us any resolution to the problem," said deputy shuttle program manager Wayne Hale.

The sensors are designed to shut off the shuttle's three main engines before fuel runs out to avoid damaging them.

A premature shutdown could force a shuttle to make an emergency landing or prevent it from reaching its desired orbit.

While the Kennedy Space Center launch team takes the weekend off, 12 teams of engineers around the United States will be analyzing 200 possible scenarios that could explain the problem with one of Discovery's hydrogen fuel sensors.

During a routine test 2-1/2 hours before the planned liftoff on Wednesday, one of four sensors located in the hydrogen fuel tank failed.

Nasa has had problems with these sensors previously, most recently during a test in April, and Nasa officials said there might come a time when they would have to discuss flying Discovery without really knowing what had caused the problem.

"We are putting a full court press on this to resolve this anomaly," Hale said during a news conference.

Shuttle engineering manager John Muratore added: "The bottom line is we don't know if we're having a problem in the tank, if we're having a problem in the wiring, if we're having a problem in the electronics box.

"We don't know if the equipment is fine (and) it's just the environment we're operating in is somehow suddenly different, or we don't know if there's a problem in the equipment. And until we know that, everything is suspect."

Nasa has had two unplanned main engine shutdowns in the fleet's 112 successful launches. Both times, the missions were able to be completed successfully.

Although launch delays are common, the glitches preventing Discovery from getting off the launch pad are receiving heightened scrutiny because the shuttle is the first to fly since Nasa grounded the fleet for safety upgrades following the loss of Columbia.

Columbia's wing was damaged during launch by a piece of foam insulation that fell off its fuel tank. As it flew through the atmosphere for landing, superheated gases blasted into the wing and destroyed the ship.

Nasa has until July 31 to launch Discovery, a deadline dictated by its planned rendezvous with the International Space Station and a new requirement that shuttle launches take place in daylight so cameras will have clear views of liftoff.

The construction of the station - a 16-nation project - is dependent on the shuttle and has been on hold since the fleet was grounded.

The next launch window begins on September 9. Nasa had planned to use the September launch window to fly the space shuttle Atlantis on the agency's second post-Columbia mission.

"We're not pessimistic about making the July launch window, We are here for the duration," Hale said.

He added, however, that flight planners were trying to figure out ways to expand both the July and a three-day launch window in November in case of additional postponements. Hale said the engineers might end up having to consider whether faulty sensors are a fleet-wide problem.

Discovery would be able to fly four days after the problem with the sensor is identified and fixed, NASA said.

- REUTERS