Nasa chief says risk to shuttle far beyond foam

CAPE CANAVERAL, Florida - While foam falling from the space shuttle's fuel tank has garnered the lion's share of Nasa's attention, the space agency's chief said today it was far from being the only risk facing Discovery, which is set for liftoff from Florida tomorrow.

"I worry that we spend so much time worrying about foam that we won't worry about other things that could get us. We try to address them all," Nasa administrator Michael Griffin said at a prelaunch news conference in Florida.

The US shuttle fleet has been grounded twice for fuel tank redesigns, prompted by the 2003 Columbia accident and Nasa's first post-Columbia test flight last year.

Discovery's launch, which is scheduled for 3.49pm Saturday (7.49am Sunday NZT) from the Kennedy Space Centre, could be Nasa's last chance to get it right.

"If we have a major unexpected piece of foam come off, then clearly we're quite vulnerable. It says that there is a lot about this that we still don't understand," Griffin said.

Griffin has said he would move to shut down the programme if there were another accident or serious problem with the shuttle. The agency's top engineer and safety official had advised Nasa to delay Discovery's launch and fix another suspect area of foam.

The Columbia accident was caused by a piece of insulation that fell off the tank, then struck and damaged the ship's wing. The shuttle broke apart 16 days later as it flew through the atmosphere in preparation for landing. Seven astronauts aboard died.

Even after US$1.3 billion ($2.13 million) in safety upgrades, the odds of another catastrophe were about one in 100, shuttle programme manager Wayne Hale said.

Nasa plans to retire the shuttle fleet in 2010. Except for a possible final servicing call to the Hubble Space Telescope, the 16 fights on the shuttles' manifest are devoted to International Space Station construction.

The outpost, a US$100 billion project sponsored by 16 nations, remains half-built in orbit with dozens of trusses, solar arrays, laboratory modules and other equipment in storage at the Kennedy Space Centre.

"We pared the station down to bare bones to finish the project," Griffin said. "Every single one of (the flights) is important."

In addition to testing the fuel tank's new design, Discovery will be carrying critical gear for the station as well as a new crewmember, Europe's Thomas Reiter. The station has operated for three years with just two crewmembers aboard to save on supplies while the shuttles were grounded.

If Nasa cannot complete the station, it will be difficult to attract support for its next project, which aims to return astronauts to the moon and eventually to move on to Mars.

"If we are unable to complete the project that lies before us, we will have a certain lack of credibility in convincing others to join us," Griffin said.

Weather remained Nasa's only concern for launch on Saturday, with forecasters predicting a 60 per cent chance of a delay due to the possibility of lightning near the launch site.

- REUTERS