NASA tries to decide when to launch shuttle after delay

CAPE CANAVERAL, Fla. -- An electrical problem forced NASA to postpone Wednesday's liftoff of the space shuttle Atlantis yet again, and engineers faced with a tight launch schedule struggled to understand the problem.

About 11 hours before the scheduled midday launch, engineers discovered that a coolant pump that chills one of the shuttle's three electricity-generating fuel cells was giving an erratic reading. NASA rules say all three fuel cells must be working to launch, and if one fails in orbit, the shuttle must come home promptly.

NASA officials met for hours during the afternoon to figure out whether they could fix the problem, whether they could safely ignore it, or whether they would have to put the flight on hold for perhaps weeks.

Managers, who were divided on the issue, ruled out a launch attempt on Thursday but said Friday was still a possibility.

NASA officials wanted more time to analyze the coolant pump that chills one of the shuttle's three electricity-generating fuel cells since "there's something funny going on in that fuel cell," said Wayne Hale, space shuttle program manager.

The problem, located in a tiny car-like starter motor built in 1976, could be the wiring or something more. Complicating everything is the fact that NASA does not really know the inner workings of the system.

"The vendor sold us the thing and didn't exactly tell us how it works, amazing as that might be," Hale said.

Officials said they were going "above and beyond" the agency's safety requirements since flying with the problem didn't violate any rules.

The space agency's options are to replace the fuel cell or fly Atlantis as is. Changing out the fuel cell would rule out a Friday launch since it would take several weeks.

There was a 30 percent chance that bad weather would prohibit liftoff at the 11:40 a.m. EDT Friday launch time.

If not, the space agency may have to wait until late October -- or relax daylight launching rules instituted after the 2003 Columbia accident and try again at the end of September.

NASA rules say shuttles have to be launched in daylight so that the big external fuel tank can be photographed for evidence of any broken-off pieces of foam of the sort that doomed Columbia.

Atlantis and its six astronauts plan to haul 17 1/2 tons of girders and solar panels into orbit and resume construction of the international space station, which has been on hold since the Columbia disaster 3 1/2 years ago. Astronauts will make three spacewalks to put the pieces together.

The shuttle was supposed to lift off on Aug. 27, but was delayed, first by a lightning bolt that hit the launch pad, then by Tropical Storm Ernesto, then by the electrical problem.

As the managers' discussion of the problem went on for hours, astronauts on the ground and in orbit waited. The three-man crew of the international space station kept asking if Atlantis is visiting them soon.

"We're trying like heck to preserve the options for launching this week, but there's a lot to consider," astronaut Stephen Robinson told the space station from Mission Control in Houston.

Instead of donning their orange spacesuits for liftoff, Atlantis' six astronauts visited the launch pad to take photographs.

NASA is caught in a schedule squeeze. The space agency made an agreement with the Russians not to attempt a launch after Friday because Russia is sending a three-person Soyuz capsule to the space station on Sept. 18. If Atlantis blasts off after Friday, there would be a traffic jam at the space station.

Once the Soyuz comes back, NASA may attempt a launch in late September even though it would be in the dark, spokesman Allard Beutel said.

If NASA doesn't ease its rules, the next launch attempt after Friday would be Oct. 26 and 27.

NASA has to squeeze 15 shuttle launches into the next four years to finish the construction of the half-built space station.