Cape Canaveral, Fla. An electrical problem forced NASA to postpone Wednesday's liftoff of the space shuttle Atlantis yet again, and engineers at Cape Canaveral 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.