Fueling test at key juncture

Space shuttle Endeavour is approaching a key moment in this morning's fuel-loading test.

Loading of liquid hydrogen and liquid oxygen propellants is nearing the "topping phase," the time at which hydrogen gas began to leak at unacceptable levels during countdowns on June 13 and June 17.

During topping, a valve that cycles open and closed during the tanking process switches to a fully open position, significantly dropping the temperature at the valve and a vent line connected to the tank.

In an interview on NASA TV, Test Director Steve Payne said he was confident that repairs had corrected for a slight misalignment of the plate where the vent line attaches to the tank, which is believed to have caused the leaks.

"We think we've got it licked," he said. "This should solve it, and the test we're doing today is just to verify that before we go into countdown next week."

If the test is successful, NASA would proceed with plans to launch Endeavour at 7:39 p.m. July 11.