NASA teams probe shuttle’s fuel gauge problem

CAPE CANAVERAL, Fla. - NASA has activated a dozen teams across the country to troubleshoot a faulty fuel gauge that scuttled the space shuttle Discovery's first try at liftoff Wednesday.

The scope of the effort means NASA probably won't be ready for a second launch attempt for as long as two more weeks, another setback for the space agency's effort to return to human space flight after the February 2003 shuttle Columbia disaster.

NASA is reserving the option to send Discovery aloft on Sunday, but that requires "a really optimistic, good-luck scenario which, I think, is not very credible," said Wayne Hale, deputy shuttle program director and chairman of its mission management team. "What we are more likely into is several days of troubleshooting."

Thursday, Hale told reporters at the Florida launch site that 12 different NASA and contractor engineering teams are busy examining the broken hardware and scouring archived paperwork. Their goal: to sort out why a hydrogen propellant sensor failed a routine test during the countdown to launch. The gauge flashed empty when the tank actually was full, prompting ground controllers to scrub the mission.

Discovery is slated to carry supplies to the International Space Station. The crew also will make repairs outside the shuttle and test safety improvements that NASA has made in the 29 months since seven astronauts died in the shuttle Columbia's re-entry breakup over Texas.

That accident was caused by a chunk of insulating foam that popped off Columbia's fuel tank and punched a hole in the shuttle's left wing. After the accident, the remaining shuttles were grounded while NASA beefed up their heat shields and redesigned their fuel tanks.

NASA has been vexed with fuel tank problems since April, when engineers tested Discovery's redesigned tank by filling it with 528,000 gallons of super-cold liquid hydrogen and oxygen. Unable to explain the glitches, NASA delayed the comeback mission from May to July while it replaced the fuel tank.

The faulty gauge was working properly Thursday, a few hours after technicians had drained the tank's propellants. "Could we talk ourselves into [launching] after all of this, without doing anything? No," Hale told reporters. "You really have to have a clear and convincing rationale that we're safe to proceed, and that only comes after you've done all the troubleshooting you can."

The nationwide paperwork scan has turned up information about a batch of transistors of questionable technical quality. Several from a particular manufacturing lot are in the faulty fuel gauge aboard Discovery, but Hale said the failure does not appear to be related to the transistors.

If necessary, engineers and technicians at Kennedy Space Center will crawl into the engine compartment of the winged orbiter to try to find the source of the problem.

If the shuttle isn't launched by July 31, the mission will have to be postponed until September. Liftoff timing is governed by a combination of issues, including the position of the space station in Earth orbit. NASA also now is required to launch the shuttle in daylight in order to take photographs of its ascent from multiple viewpoints. The space station won't be positioned properly during daylight hours again until September.