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NASA calls off shuttle launch again
(Agencies)
Updated: 2009-06-17 15:00

CAPE CANAVERAL, Florida  – NASA has called off the launch of its shuttle Endeavour for the second time in four days due to a small but potentially hazardous hydrogen leak, according to the US space agency.

NASA calls off shuttle launch again
The space shuttle Endeavour sits on launch pad 39-A at the Kennedy Space Center, on June 16, in Cape Canaveral, Florida. NASA has called off the launch of the shuttle for the second time due to a small but potentially hazardous hydrogen leak. [Agencies] 
NASA calls off shuttle launch again
"At 1:55 am (0555 GMT), launch managers called a scrub, canceling today's planned launch of space shuttle Endeavour on its STS-127 mission," NASA said in a statement.

"Despite troubleshooting efforts, engineers were unable to achieve a decrease in the liquid hydrogen leak," the agency said, adding that the leak was in the same spot that halted the previous launch attempt on Saturday.

The previous leak was in the venting system supposed to carry excess hydrogen safely away from the launch pad.

Shuttle launch director Pete Nickolenko had admitted during intense repair efforts Sunday that the original leak's root cause was still not determined.

The three-hour operation to pump 500,000 gallons (two million liters) to the shuttle tanks was begun late Tuesday for a launch to the International Space Station at 5:40 am (0940 GMT).

With the second scrub, however, the next possible lift-off may not be until July 11 at the earliest.

The shuttle's new launch date caused a scheduling conflict with NASA's moon-bound crater observation and sensing satellite (LRO/LCROSS), with the lunar mission being pushed back one day to June 18. It was unclear if Endeavour's second cancelation would again affect its launch.

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When Endeavour does head out from NASA's Kennedy Space Center in Florida, it will be the 32nd mission to the ISS, orbiting 350 kilometers (220 miles) above Earth, and the last of three missions to assemble the Japanese Kibo laboratory aboard the orbiting space station.

During the shuttle's stay the ISS is set to be a temporary home to 13 astronauts -- the first time so many people have stayed on the orbiting station at once.

The six US astronauts and a Canadian woman astronaut that Endeavour is expected to bring to the ISS will join another US astronaut and one more from Canada, as well as two Russians, a Belgian and Japan's Koichi Wakata who are currently living on the ISS.

Construction began on the ISS a decade ago, and the push is on to complete the building before NASA ends its shuttle missions in September 2010.

Over the five planned spacewalks lasting some 32.5 hours, the astronauts will install a permanent 1.9 tonnes platform to Kibo, which will serve as one of the station's porches for conducting experiments in the vacuum of space.