Shuttle launch put off again

CAPE CANAVERAL, Fla. - NASA has abandoned hopes of another try at launching the space shuttle Discovery until late next week at the earliest, as engineers puzzle over a faulty fuel gauge.

Ground controllers at the Kennedy Space Center launch site Friday were told to halt all countdown preparations and make way for experts who may need to crawl inside the shuttle's engine compartment and redesigned external fuel tank to see what's wrong.

"The short answer on the troubleshooting is, the simple things we did quickly [Thursday] night did not provide any resolution to the problem," said Wayne Hale, deputy shuttle program manager and chairman of NASA's mission management team.

To buy more time for troubleshooting, Hale told reporters late Friday, agency officials also are considering adding four days to the shuttle's flight opportunity, which is scheduled to end July 31.

The shuttle's first launch attempt was scrubbed less than three hours ahead of liftoff on Wednesday after a crucial sensor showed Discovery 's external fuel tank was empty. At the time, the tank was brimming with 528,000 gallons of liquid hydrogen and oxygen propellants. The small component helps ensure a safe shutdown of the shuttle's three main engines, so the winged orbiter was grounded for repairs.

A second launch attempt could come late next week only if engineers find and fix the problem over the weekend, shuttle engineering director John Muratore said in a news conference. "We have engineering tagups scheduled Saturday, Sunday and Monday, and we're planning to go every day until we have the problem isolated," he said.

The fuel gauge failure is intermittent, and an in-flight breakdown could have catastrophic consequences. "We don't know it won't fail again, and that's why we would really like to find the cause," said Hale.

Muratore said the troubleshooters' fault tree has roughly 100 branches.

The postponement has dealt a blow to NASA's comeback effort 2 1/2 years after the re-entry disaster that destroyed a space shuttle and killed seven astronauts. Discovery's 12-day visit to the International Space Station will be the first mission since the February 2003 Columbia disaster.

As part of its accident recovery, NASA has adopted numerous new safety rules - including a requirement to launch the space shuttle in daylight and take pictures of the ascent from as many angles as possible.

Cameras mounted in the orbiter's belly are supposed to get views of the spent fuel tank being jettisoned and falling back to Earth once the shuttle reaches orbit. July 31 marks the last time until September that lighting conditions will be good for photography with those cameras.

But if the astronauts do the photography themselves with hand-held digital still and video cameras, management sources say there may be a way to extend the so-called "launch window" to Aug. 4 without violating the launch lighting rule.

NASA is eager to return shuttles to flight because they represent both the first step and a stumbling block to the nation's moon-Mars exploration initiative. Current plans call for the shuttle to be used to finish building the International Space Station and then to be retired by 2010.

The agency is developing a replacement for the shuttle that can take astronauts beyond Earth orbit.