Article Posted on : - Aug 26, 2009

Space shuttle Discovery stands on Launch Pad 39A on Tuesday evening after the second launch attempt was called off because of a problem with a fill-and-drain valve. Photo credit: NASA TV

CAPE CANAVERAL (PTI): A ruptured hydrogen valve found while fueling the shuttle Discovery led NASA to postpone a launch planned for Wednesday - the second to be scrapped in 24 hours.

An agency spokesman said that fixing the broken valve, discovered while filling the shuttle's external fuel tank, would push back the launch at least 48 hours.

"At this point we don't know when the next attempt will be," said NASA spokesman Allard Beutel.

Officials said a press conference to discuss the US space agency's revised launch plans was likely later.

NASA had begun refilling Discovery's fuel tank in preparation for a second liftoff attempt, when the decision to call off the launch was made. The space agency scrapped a first launch attempt late Monday due to thunderstorms.

The delays were a reminder of turbulence that surrounded the previous shuttle mission aboard the space shuttle Endeavour, which was postponed five times by weather woes and technical glitches.

The Discovery crew is scheduled to conduct three spacewalks of six and a half hours each during the mission.

A key task during the spacewalks will be to replace an old liquid ammonia coolant tank, which will be substituted with a new, 800-kilogram replacement brought aboard Discovery.

The seven shuttle astronauts also will be retrieving experiment equipment from outside the ISS and returning it to Earth for processing.