Sunday At The Earliest

Sunday At The Earliest: "

KENNEDY SPACE CENTER - NASA managers won't try to launch the space shuttle Discovery until Sunday at the earliest, as ground crews try to fix a serious hydrogen leak that developed today as they tried to fill the external tank.

NASA TV

The mission could slip until March 17 and perhaps even later, which begins to impinge on plans to double the International Space Station crew from three to six in May. Discovery is set to deliver a fourth big solar array wing and a replacement urine distiller that are both needed to prepare the ISS for a six-person crew.

The problem appeared when the shuttle's liquid hydrogen tank was within 20 minutes of being full for a 9:20 p.m. EDT launch today. When a' valve was opened to allow excess hydrogen to vent into a' flare stack on Pad 39A, three different sensors in the area detected the leak, according to Launch Director Mike Leinbach.

The leak, which apparently was connected with the dropping temperatures as' the supercold liquid hydrogen level reached the vent line near' the top of' the tank, persisted through several cycles of the valve.

'We're sure we have some hardware issues,' Leinbach said.

Launch managers will work through the night mapping a plan for isolating the leak and fixing it, with a report on their timeline due Friday afternoon. But it will take 20 hours just to finish draining the tank so it can be safely repaired, which makes Sunday the earliest possible launch date.

That could slip to Monday or even Tuesday, the latest Discovery could launch and still leave the station before the Russian Soyuz with the replacement ISS crew arrives. The 'Soyuz cutout' is driving the launch date because of the excessive crew workload that would be required if two vehicles were docked at the station at the same time.

But to get Discovery out of the way, the station program is prepared to trim the four spacewalks planned while' Discovery is docked down to two, or even the one that' will be required to attach the new solar array wing, according to Mike Moses, who chairs the STS-119 mission management team.

At the moment the military Wideband Global Satcom satellite is due' for launch from Cape Canaveral AFS on Saturday, and Moses hinted that the military mission may go ahead of the shuttle on the launch range if the shuttle launch slips into next week.

Weather was perfect for a launch tonight, and is expected to remain very good through the weekend. But by Tuesday conditions are' expected to deteriorate, and may prohibit a launch even if the leak is fixed.

If the shuttle launch is delayed for the Soyuz mission, the next opportunity would come at the end of the first week in April, which might not allow enough time to get the new systems running that are needed' to support the crew of six due to arrive the following month.

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(Via On Space.)