Stormy weather approaching the Kennedy Space Center on Sunday forced NASA launch managers to order another 24-hour delay for the hard-luck crew of the shuttle Endeavour, their fourth slip since a hydrogen leak derailed an initial launch try in June.
There were no leaks or technical problems of any significance during Sunday's countdown and Endeavour's external tank was loaded with a half-million gallons of rocket fuel without incident.
Commander Mark Polansky and his crew mates began strapping in a few minutes before 4 p.m. EDT, hopeful about finally kicking off a 16-day space station assembly mission.
But as the afternoon wore on, storm cells began pushing in from the west and forecasters predicted thunderstorms or showers within 20 nautical miles of the shuttle's emergency runway. NASA flight rules forbid a launch if forecasters predict rain near the runway a half hour after launch when the crew would have to attempt an emergency landing in the event of an engine failure early in flight.
With a short five-minute window, Launch Director Pete Nickolenko did not have time to wait for improving conditions and with forecasters solidly no-go for launch, he reluctantly called off the countdown during a final hold at the T-minus nine-minute mark.
"Roman, we got the vehicle ready and the weather unfortunately did not cooperate with us today, we had some colliding sea breezes," Nickolenko radioed just after 7 p.m. "We're going to have to declare a scrub for today and try to bring the team back for another attempt tomorrow."
"We understand and we'll be ready," Polansky replied from Endeavour's flight deck.
Endeavour's next launch opportunity comes at 6:51:24 p.m. Monday. Forecasters are predicting a 60 percent chance of acceptable weather Monday and Tuesday.
As it now stands, Endeavour must be off the ground by Tuesday or the flight will be delayed to July 27, after a high-priority Russian Progress resupply mission scheduled for launch July 24.