Nasa called off today's launch attempt for space shuttle Endeavourbecause of a second hydrogen gas leak in less than a week.
The space station construction mission is now postponed until July 11th.
A similar leak in the hydrogen gas vent line that connects to the external tank caused a launch attempt last Saturday to be cancelled.
Nasa was already running three hours behind because of thunderstorms that delayed fuelling last night. The leak did not appear until early today.
Nasa had postponed an unmanned moon launch to give Endeavourone last chance of launching before a thermal blackout period begins.
Endeavouris scheduled for a 16-day mission to the International Space Station to complete the assembly of the $1 billion Japanese Kibo research facility.
In March, the launch of the shuttle
Discoverywas postponed after technicians found a leaky valve in the line that transports flammable hydrogen gas away from the launch pad so it can be safely burned off.
That mission, which went ahead from March 15th to March 28th, had already been delayed several times so engineers could test three valves that help deliver hydrogen to the engines at the correct pressure.