Weather threatens shuttle Discovery launch

Thunderstorms threatened NASAีs plan to launch space shuttle Discovery on Sunday on a mission critical to the future of the shuttle programme and the half-built International Space Station.

NASA forecasters predicted a 70-per-cent chance that weather would delay the launch, as it did a planned launch on Saturday. Flashes of lightning were visible before dawn at Cape Canaveral, where the Kennedy Space Centre is located.

No other problems were noted at the centre, as US space agency workers began the process of filling the shuttleีs massive fuel tank with super-cold liquid hydrogen and liquid oxygen. Launch is set for 3.26 pm (19.26 GMT).

The flight is only the second since the 2003 Columbia accident, and another disaster or serious problem likely would end the programme. NASA is hoping to fly 16 more missions to finish building the $100 billion space station before the shuttle fleet is retired in 2010.

Shuttle safety has been at the forefront of the programme since the Columbia disaster, which claimed the lives of seven astronauts. NASA redesigned the shuttleีs fuel tank twice, which triggered the accident.

The agencyีs top engineer and chief of safety wanted more repairs on the tank before Discovery was launched, but were overruled by NASA administrator Michael Griffin.

Griffin decided to fly without the additional repairs, arguing that in the unlikely event foam falls again from the fuel tank and damages the shuttle, the crew could stay aboard the space station and await rescue.

Delaying the launch, Griffin added, would have put more pressure on the shuttle programme, which must finish building the space station before the shuttle fleet is retired. No other vehicles can deliver and install the stationีs remaining trusses, solar arrays and laboratories.