Shuttle Launch Off Due to Bad Valve

CAPE CANAVERAL, Fla. - NASA has called off the launch of space shuttle Discovery because of a bad fuel valve.

Launch officials halted the countdown late Tuesday afternoon, midway through the fueling process. The seven astronauts had not yet boarded the shuttle for the scheduled early Wednesday morning flight to the international space station. A new launch date was not immediately set.

NASA spokesman Allard Beutel says engineers were trying to open and shut the fill-and-drain valve in Discovery's engine compartment when it looked to be broken. The exact condition of the valve is not yet known.

The valve is used for the flow of liquid hydrogen from the external fuel tank to the main engines.

It's the second launch delay in as many days for Discovery. Tuesday's launch was called off because of thunderstorms.