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| In this image provided by NASA space shuttle Discovery sits on launch pad 39A at NASA's Kennedy Space Center in Cape Canaveral Florida. Space Shuttle Discovery's seven member crew are scheduled to lift off Sunday evening March 15, 2009 on a mission to the International Space Station. NASA has until Tuesday to launch Discovery before having to wait for a Russian Soyuz rocket that is set to blast off to the space station March 26. |
CAPE CANAVERAL, Fla. (AP) -- Growing more confident by the minute, NASA fueled space shuttle Discovery on Sunday for an evening liftoff with none of the leaking that marred the first launch attempt.
Repairs out at the launch pad late last week apparently took care of the dangerous leak, although engineers continued to keep close watch on the system just in case. They also were monitoring a decline in pressure in a helium-purging system for the space shuttle, and a special team was sent out to the pad to set a valve and try to raise the pressure. NASA said the problem was not expected to hold up the flight.
The only other oddity was a bat that attached itself to the back of Discovery's fuel tank, where it posed no debris threat to the shuttle itself.
Discovery was poised to blast off at 7:43 p.m. on the space station construction mission. Good weather was forecast.
During a launch attempt Wednesday, hydrogen gas spewed into the air from a vent line connected to Discovery's external fuel tank. NASA replaced all the hookups, but could find nothing broken. NASA promised to halt the countdown again if the problem recurred.
Early Sunday afternoon, launch controllers anxiously monitored their computers as the fueling reached the point where the leak occurred Wednesday. No leakage was detected this time, to everyone's relief.
"It appears this system is tight," said NASA spokesman George Diller. "At this point, there's a lot of confidence that this is not going to be a recurring problem for this launch."
Concerns about hydrogen gas valves inside Discovery already had forced a one-month delay.
The commander of the international space station, Mike Fincke, called down for a shuttle update as the fueling was close to wrapping up, and was elated to hear there was no leaking.
"That is most excellent news," Fincke told Mission Control. "That's exactly what's been on top of our minds."
NASA has until Tuesday to send Discovery and a crew of seven to the space station. The shuttle needs to deliver one last set of solar wings and some critical parts for the space station's water-recycling system.
If Discovery isn't flying by then, it will have to get in line behind a Russian Soyuz rocket that's set to blast off March 26 with a fresh space station crew. That would bump the shuttle launch into April.
Because of the four-day leak delay, NASA had to shorten Discovery's flight by a day and cut out a spacewalk. Even more reductions will be needed if the launch slips to Monday or Tuesday, increasing the pressure for a Sunday departure.
Assuming Discovery blasts off Sunday, the mission will last 13 days and feature three spacewalks, the first of which will be to install the new solar wings.
Commander Lee Archambault and his crew also will deliver a spare urine-into-drinking water converter to replace one that's broken up at the space station, and a flusher and iodine solution to get rid of bacteria that's lurking in the water dispenser.
NASA wants to double the size of the space station crew to six people at the end of May. Waiting until next month to fly Discovery could jeopardize that plan.
Discovery originally was supposed to lift off Feb. 12, but NASA ordered extra tests for the valves that control the flow of hydrogen gas into the fuel tank. The three valves in the shuttle's engine compartment kept being replaced to ensure they were the best available and safe to fly.
One of these valves - which maintain tank pressure during liftoff - broke during the last shuttle launch in November. No harm was done, but NASA did not want to take any chances.
Two one-time schoolteachers, chosen as educator astronauts in 2004, are on Discovery's crew: Joseph Acaba and Richard Arnold II. There also is one Japanese astronaut, Koichi Wakata, who will move into the space station for at least three months. Many of the 200 Japanese citizens on hand for the first launch attempt were gone by Sunday.
Coincidentally, the last time a bat perched itself on a space shuttle tank, right before liftoff, was Wakata's first flight in 1996.
