Thunderstorms forced NASA to delay the fueling of space shuttle Endeavour, but launch managers held out hope that the bad weather would ease and let them take a shot at an early Wednesday liftoff.
Right at the time fueling should have begun Tuesday night, thunder rumbled across the launch site and it was drizzling.
This is NASA's second attempt to launch Endeavour and seven astronauts on the space station construction mission and the last one this month. If Endeavour is not flying by Wednesday, it will have to make way for an unmanned moon shot and wait until July.
The severe thunderstorms were actually to the north and west of Kennedy Space Center, but they posed a threat of lightning at the launch pad, a fueling violation.
NASA's launch team could wait as long as 1 1/2 hours or more to start pumping more than 500,000 gallons of liquid hydrogen and oxygen into Endeavour's external fuel tank. The storms were not dissipating as quickly as expected, however, and more were popping up elsewhere, said spokesman Allard Beutel.
The odds of the weather cooperating for fueling were 60 percent. The odds for the predawn launch were better: 80 percent.
Endeavour is set to deliver the third and last segment of Japan's massive space station lab. It will be one of the longer international space station visits — nearly two weeks docked at the orbiting outpost — and include five spacewalks.
Once the shuttle pulls up at the space station, there will be 13 people together in space for the first time ever.
NASA bumped its launch of two lunar probes, which had been scheduled for Wednesday, to give Endeavour this second chance. The moon mission is now scheduled for a Thursday liftoff at the earliest.