Washington, Aug 29 (DPA) The space shuttle Discovery was set for a midnight launch on Friday after problems associated with a fuelling valve that forced previous delays were resolved, NASA officials said.
Discovery is set to blast off at 11.59 p.m. (0359 GMT Saturday) from Cape Canaveral, Florida, en route to the International Space Station (ISS).
NASA was fuelling the shuttle for the launch and the readings on what had been a suspect valve were normal. But weather was beginning to emerge as a potential challenge.
Forecasts showed there was a 60 percent chance of acceptable conditions and meteorologists were monitoring clouds and thunderstorms within 30 km of the facility.
“The weather remains the primary concern,” NASA said.
Weather forced a delay of a planned takeoff on Tuesday and then problems with the valve scrubbed a scheduled liftoff Wednesday. NASA then sought to fire up Discovery early Friday, but elected to postpone it again to review data in connection to the valve.
NASA said more time was needed to determine whether the problem lies with the external fuel tank valve or a gauge that was showing the valve to be open when it was supposed to be closed, but said Friday afternoon the gauge showed the valve was closed and fuelling began.
Fuel valve problems have dogged recent shuttle launches as the ageing craft and launch apparatus enters the final phase of the decades-old shuttle programme.
By late next year, NASA hopes to have completed the build-out of the orbiting International Space Station so it can retire the shuttles. In their place, a new spacecraft is being built that will be available in 2015 at the earliest.
Delayed takeoffs are common with space shuttle missions. The last shuttle to blast off, Endeavour, only did so in July after five scrubbed missions due to technical problems and bad weather.