No shuttle launch before Sunday says Nasa

CAPE CANAVERAL, Fla. - Space shuttle Discovery will not launch before Sunday (Monday NZ time) and probably will fly later than that, Nasa managers said a day after delaying the first shuttle launch since the 2003 Columbia disaster.

Wednesday's much-anticipated launch was called off after NASA engineers detected a faulty fuel sensor. Thursday was devoted to troubleshooting that problem, said Wayne Hale, deputy shuttle program manager.

Even a Sunday launch is unlikely, Hale said.

"If we were to get extremely lucky, it is theoretically possible that we could still launch on Sunday," Hale said at a briefing. "This represents a really optimistic, good luck scenario which I think is not very credible."

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 all shuttle launches take place in daylight to let cameras capture images of liftoff.

The next window of opportunity for launch begins Sept. 9.

NASA aims to launch the shuttle this month to carry supplies and equipment to the station, and to test new safety upgrades put in place since the fatal Columbia accident.

All seven astronauts were killed when Columbia disintegrated over Texas on Feb. 1, 2003. The direct cause was a hole in the craft's wing caused by falling debris during launch. However, investigators found a "broken safety culture" at NASA that discouraged questioning of upper-level decisions was also to blame.

FUEL SENSOR PROBLEM

NASA experts acknowledged the sensor problem - which they described as an intermittent event with no obvious cause - represented a difficult challenge.

The faulty sensor is one of four that would cut off the shuttle's three main engines if at least two showed that hydrogen fuel was running low during flight. A premature cutoff might damage the engines, force the shuttle to make an emergency landing or leave it short of its desired altitude.

Wednesday's launch was canceled after engineers conducted a routine test of the sensors and one failed. NASA engineers do not know what caused the problem and are working through about 200 possible scenarios.

Problems with the sensors continued after technicians drained Discovery's tank when Wednesday's launch was canceled. Later, it accurately showed the tank was empty.

Intermittent, unexplained failures are the hardest to troubleshoot, Hale said.

Letting Discovery fly without working to determine the cause and fix the problem is not an option, Hale said: "Could we talk ourselves into going without doing anything? No."

Peppered with questions from reporters, Hale defended NASA's effort.

"Going into space is right at the limits of human technology here at this point in the 21st century. We're doing something that's extremely difficult. This is not like going to the airport and getting on a commercial airline," he said.

"You are watching America do something that frankly most of the world can't do, that only the most innovative and most dedicated countries have the capability to do."

Discovery's crew stayed out of public view Thursday, after being seen on Wednesday strapped into their seats and ready for launch. They are expected to stay at Cape Canaveral if there is a launch scheduled anytime through Tuesday.

The shuttle remained on the launchpad, partly obscured from view by the remote servicing structure, a kind of movable scaffolding that gives workers access to the vehicle.

- REUTERS