NASA has scrubbed today's planned launch of space shuttle Endeavour - the second such knock-back due to a gaseous hydrogen leak and despite assurances yesterday that the vehicle was "in good shape" to go.

The agency canned the lift-off at 05:55 GMT after detecting an escape in at the "Ground Umbilical Carrier Plate" (in pic) - part of the system "used to carry excess hydrogen safely away from the launch pad" and at "the same location where a similar leak resulted in a launch scrub on June 13".

NASA reports: "Vent valve troubleshooting took place for about an hour before it became clear the problem could not be solved."

Deputy Space Shuttle Program Manager LeRoy Cain said: "We're going to step back and figure out what the problem is and go fix it. Once we get it fixed, and we're confident that we have a solution that's going to work and allow us to go fly safely, then we'll proceed forward."

NASA has had a lot of trouble with its hydrogen venting. Back in March, the same problem temporarily grounded Discovery's STS-119 mission to the ISS.

The latest set-back means Endeavour's STS-127 mission to the International Space Station will not get under way until 11 July at the earliest. ®

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• Endeavour heads for ISS on sixth try (15 July 2009)
• Fifth time not a charm for Endeavour liftoff (13 July 2009)
• Endeavour launch scrubbed for fourth time (12 July 2009)
• Endeavour set for Saturday launch (10 July 2009)
• NASA patches Endeavour's leaky plumbing (1 July 2009)
• Endeavour 'in good shape' for Wednesday lift-off (16 June 2009)
• NASA bumps lunar 'bots for Endeavour launch (15 June 2009)
• NASA scrubs Endeavour launch (13 June 2009)
• Endeavour 'in really good shape to fly' (12 June 2009)