Hours before its planned liftoff from Kennedy Space Center in Florida, the space shuttle Endeavour had endured pouring rain and nearby lightning—but was still on target for launch, based on weather conditions. Instead, it was a problem with a line of small heaters that ultimately forced NASA to scrub today's 3:47 p.m. launch attempt. NASA's next try will be no earlier than Monday morning, launch officials said today. A planned launch of an Atlas V rocket from Kennedy on May 6 means that the shuttle lift-off can push to no later than May 4. After that date, the next possible launch attempt for Endeavour wouldn't come until May 9.
Endeavour's crew of six veteran astronauts, led by mission commander Mark Kelly, had already boarded their bus for the launch pad when the scrub was announced at 12:19 p.m. ET. The trouble was caused by failed heaters in one of the shuttle's auxiliary power units (APUs), which provide hydraulic power for the craft's engine nozzles, landing gear, and other moving parts used in flight.