Last week the problem was the weather.
Wednesday, NASA postponed the launch of space shuttle Atlantis because of a fuel cell problem. Fueling of the shuttle never got underway this morning before one of three cells providing electricity malfunctioned.
It will try for liftoff again Thursday. If shuttle managers decide the cell has to be replaced, Atlantis will have to go back to the hanger delaying a launch for several weeks.
Atlantis was supposed to launch Aug. 27 but that was put off by a lightning strike, then the approach of Tropical Storm Ernesto.
The shuttle is to carry two girders that are crucial to the construction of the international space station.