"We won't know about the nature of the leak before Friday afternoon," said launch director Mike Leinbach, adding that the next launch attempt would aim to take place between Sunday and Tuesday.

It was yet another frustrating delay for the Discovery and its crew which has already seen the launch put back four times from its original date of February 12.

NASA engineers discovered the leak soon after they began filling the Discovery's external tank at noon (1600 GMT), and the hitch came just hours before the planned 9:20 pm (0120 Thursday GMT) launch at the Kennedy Space Center in Cape Canaveral, Florida.

The leak was found to be coming from a valve regulating the hydrogen pressure which is located inside the external fuel tank towards the top, Bill Johnson, communications director, told AFP.

After meeting to assess the problem, Leinbach said NASA engineers would not be able not reach the leaky valve until Friday.

The external tank, which was three quarters full when the leak was spotted with some two million liters of fuel (528,000 gallons) of mostly liquid hydrogen kept at minus 252 degrees Celsius and liquid oxygen, takes all that time to be emptied.

Leinbach said it was almost certain the leak problem lay with ground equipment, not the shuttle's external tank.

If the trouble is quickly located and repaired, he added, the Discovery could be readied for launch by Sunday at the earliest, but not later than March 17, since the Discovery mission would then clash with a Russian Soyouz mission to the ISS.

Space Shuttle Flight Controller Mike Mosis said a Tuesday launch would shorten the Discovery's 14-day mission to only nine days, with only one spacewalk instead of the scheduled four.

The shuttle's crew had arrived at the Kennedy Space Center late Sunday to prepare for their mission to deliver and install a fourth pair of solar panels to the International Space Station.

The panels are to supply power for onboard laboratories and more power for the station's crew, which will double from three to six in May.

Installing the panels, the final piece of a 100-billion-dollar project, was to take a two-astronaut team four space walks of more than six hours each to complete, according to NASA's original plans.

The pairs of solar panels, containing 32,800 solar cells, are each 35 meters long once in place. And the final array, once in place, should boost power available to the ISS to 120 kilowatts from the current 90.

The Discovery's launch has now been delayed five times, mainly due to problems with control valves, which channel hydrogen from the shuttle's three main engines.

Discovery has to be launched by March 17 in order not to hamper the launch of the Soyuz mission to the ISS due to liftoff on March 26, carrying American businessman Charles Simonyi.

The Soyuz is due to arrive on March 28 at the orbiting space station, meaning Discovery must have already left as both craft cannot dock at the ISS at the same time.

Discovery's astronauts include Koichi Wakata of the Japan Aerospace Exploration Agency, who is to become the first Japanese station crew member.

After Discovery finally docks at the ISS, Wakata is to stay aboard the station, while US astronaut Sandy Magnus -- who arrived at the ISS aboard the shuttle Endeavour in November 2008 -- will return home.

Related Links
Shuttle at NASA
Watch NASA TV via Space.TV
Space Shuttle News at Space-Travel.Com

Memory Foam Mattress Review

SPACE MEDIA NETWORK PROMOTIONS Solar Energy Solutions Tempur-Pedic Mattress Comparison ... Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News

Cape Canaveral, Usa (AFP) March 11, 2009
The next planned launch of the US space shuttle Discovery, which was delayed on Wednesday after engineers found a gas leak, could take place as early as Sunday, NASA officials said.