NASA announced that it has rescheduled Saturday's launch of the shuttle's STS-127 mission for 5:40 a.m. EDT Wednesday, from the Kennedy Space Center.
Managers postponed the launch because of a leak in the shuttle's hydrogen venting system. The system is located outside the shuttle's external fuel tank. It carries unused hydrogen away from the launchpad.
The postponement has also affected plans to launch the Lunar Reconnaissance Orbiter and the Lunar Crater Observation and Sensing Satellite, which were scheduled to launch from nearby Cape Canaveral Air Force Station on Wednesday. Now, the lunar spacecraft will launch Thursday to allow the space shuttle Endeavour to lift off on Wednesday.
The Endeavour is bound for the International Space Station for a 16-day mission that includes construction of a science laboratory module.
NASA delayed the launch of its STS-119 shuttle mission for four days in early March for similar reasons.
At that time, a gas leak came from a pipe running from the launch tower to the valve on the shuttle's external fuel tank. The pipe carries hydrogen gas from the shuttle to a flare stack, where hydrogen gas burns off at a safe distance from the shuttle and launchpad. After that postponement, NASA Shuttle Launch Director Mike Leinbach said the leak did not pose a danger to the shuttle during fueling.
NASA expects a five-year gap in its manned space program while it transitions from its Ares rockets to new Orion rockets.