Shuttle Discovery launch 'a go' after tiles repaired

CAPE CANAVERAL, Florida - Nasa will go ahead tomorrow morning with the first space shuttle mission since the 2003 Columbia disaster after replacing two damaged heat-resistant tiles on the shuttle Discovery.

"The issue has been resolved. Launch is a go," said Nasa spokesman Mike Rein.

The two tiles were damaged when a plastic window cover weighing less than 1kg fell off Discovery as the spacecraft sat on the launch pad at Cape Canaveral in Florida, during the countdown to the scheduled launch at 7.51am Thursday NZ time (3.51pm on Wednesday local time).

The damage caused by falling debris rang alarm bells because that was precisely the problem that doomed Columbia.

In that case, Columbia's left wing was damaged by a chunk of foam insulation that weighed 0.76kg. The damage opened a hole in Columbia's skin that let in superheated gas during re-entry, tearing the ship apart and killing all seven astronauts.

"This is a minor repair for us," Stephanie Stilson, Discovery's manager, told reporters after a panel that contained the two damaged tiles was replaced. "They have given us a go for launch."

The shuttle's window covers are removed before launch.

The damage repair came just hours after Nasa's administrator, Michael Griffin, had said all issues except possible bad weather had been settled and Discovery was ready for launch.

"Everything is at rest today. Yesterday we were working a couple of ... issues and those were amply put to bed, so we're in good shape," Griffin said, adding that he hoped "the weather gods are kind for tomorrow."

"Can there be something that we don't know about that can bite us? Yeah, this is a tough business, it's a very tough business but everything that we know about has been covered."

Nasa has not flown a shuttle mission since Columbia disintegrated over Texas on February 1, 2003.

TESTING SHUTTLE'S IMPROVEMENTS

Discovery's mission will test improvements made to the shuttle to reduce falling debris at liftoff and experimental procedures for repairing damaged heat resistant tiles.

The shuttle, under the command of veteran astronaut Eileen Collins, will also deliver much-needed supplies and equipment to the International Space Station. The station's construction -- a 16-country project -- has been on hold since the remaining three-shuttle fleet was grounded.

Nasa weather forecasters said the outlook for launch was good, but they increased the risk of thunderstorms.

"For our launch forecast, we did get a little more pessimistic on this today," weather officer Kathy Winters said as the countdown clock ticked toward the scheduled liftoff.

"There's a 40 per cent chance of weather prohibiting launch," she told a briefing.

Any thunderstorm must be at least 20 nautical miles from the shuttle to allow a launch. A network of 112 cameras set up to monitor Discovery's surface as it soars will need clear skies to get good images.

The families of the seven astronauts killed in Columbia's fatal break-up offered their support. "We have had 2 1/2 years to reflect daily on the loss of our loved ones as the shuttle Columbia broke apart over Texas on February 1, 2003," the families said in a statement.

"... We have every confidence that the sacrifice of our loved ones and those that preceded them will be realised for the benefit of mankind. Godspeed Discovery."

If Discovery's launch is delayed, Nasa can attempt it twice more before having to break for a few days to refuel the craft's onboard power generators.

The current launch window runs from July 13 through July 31. The next one opens September 9.

- REUTERS