NASA is aiming for a Friday morning liftoff of the space shuttle Atlantis, but the launch still isn't a sure thing.
A launch attempt was scrubbed early Wednesday morning because of troubles with a fuel cell, WESH 2 News reported.
NASA officials have scheduled an 11:40 a.m. liftoff attempt for Friday.
Mission managers spent Wednesday trying to determine what went wrong with the fuel cell, which is part of a complex system that's difficult to access. The problem was identified overnight just before the launch team was to begin filling the external fuel tank. A pump associated with a fuel cell had a voltage spike.
Engineers worked on Wednesday to determine what caused the spike. The fuel cells are located in the back of the payload bay under the floor.
NASA said it thinks the fuel cell will operate OK during the flight, but engineers still have to resolve the probable cause of the electrical short.
"I still am hopeful and I certainly believe that there's an opportunity to launch Friday morning," said shuttle program manager Wayne Hale. "We're going to set up for a launch on Friday morning, but we need to get some satisfactory answers to some of our engineering questions."
The shuttle was on the launch pad ready to go when technicians found the problem in a fuel cell, forcing mission managers to scrub.
The fuel cells are critically important. They produce electricity used to run the shuttle's life-support systems in space.
When a fuel cell broke down in 1997 aboard Columbia, Mission Control immediately ordered the astronauts home. They landed after just five days without completing their mission.
Fuel cell are notoriously difficult to work on. A problem in the fuel cell itself could take days or weeks to solve.
NASA does not have days or weeks right now. After Sept. 8, the Russian space agency has been planning to send a ship of its own to the space station. Safety rules prevent the arrival of both the shuttle and a Soyuz capsule at the International Space Station at the same time.
The Russian mission ends on Sept. 29. The shuttle could launch then, but the launch would come at night.
NASA requires daylight launches to provide visibility of any damage to the shuttle fuel tank on the way up. Some within NASA say that rule is no longer necessary because the shuttle is inspected once in orbit and a safer tank is already in the design stage.
Atlantis was originally scheduled to blast off on Aug. 27, but it was delayed by a lightning strike and then Tropical Storm Ernesto.
"We certainly had our share of tropical weather or potential for tropical weather the past week or two, which put us a little bit behind in the schedule," Hale said.
The crew has been training together since before the Columbia accident. Before Wednesday's scrub, astronauts said they were ready to finally get this mission moving.
"It's time to walk the walk. Speaking for myself and my fellow crew mates, I can assure you that we are ready for the challenge, and we're anxious to restart the station assembly sequence," Atlantis Cmdr. Brent Jett said.
The astronauts will be walking the walk. There are three spacewalks planned as part of their 11-day mission to restart construction on the International Space Station.
If the shuttle doesn't launch this week, its next opportunity probably won't come until late October.
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