Shuttle launch stopped

The launch of the space shuttle Discovery
planned for today was abruptly cancelled just hours ahead
of blast off, dpa reported.
The launch had already been delayed for weeks to allow NASA time
to examine valves that control the flow of gaseous hydrogen from the
spacecraft's engine to its external fuel tank. A valve was found to
be damaged after the space shuttle Endeavour's November flight,
prompting NASA to delay Discovery's mission as a precautionary
measure.