Stormy weather approaching the Kennedy Space Center forced NASA launch managers to order another 24-hour delay for the hard-luck crew of the shuttle Endeavour Sunday, their fourth slip since a hydrogen leak derailed an initial launch try in June.

Dark clouds gather over the Vehicle Assembly Building. Credit: Stephen Clark/Spaceflight Now

There were no leaks or technical problems of any significance during today's countdown and Endeavour's external tank was loaded with a half-million gallons of rocket fuel without incident.

Commander Mark Polansky and his crewmates 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 that eventually violated NASA's flight rules for launch as well as an emergency return to the launch site in case 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.

The official crew patch for Endeavour's flight to finish building Japan's section of the space station is available in the Spaceflight Now Store.
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Additional coverage for subscribers:
VIDEO: LIGHTNING STRIKES POSTPONE ENDEAVOUR LAUNCH PLAY
VIDEO: FRIDAY'S PRE-LAUNCH NEWS CONFERENCE PLAY
VIDEO: THURSDAY'S STATUS REPORT ON THE COUNTDOWN PLAY
VIDEO: COUNTDOWN PREVIEW AND WEATHER BRIEFING PLAY
VIDEO: ASTRONAUTS RETURN TO CAPE FOR LAUNCH PLAY | HI-DEF

VIDEO: NO LEAKS FOUND DURING SPECIAL TEST PLAY
VIDEO: EXPLANATION OF THE HYDROGEN LEAK AND THE REPAIR PLAY

VIDEO: POST-SCRUB NEWS BRIEFING PLAY
VIDEO: FIRING ROOM UPDATE WITH LAUNCH DIRECTOR PLAY
VIDEO: SCRUB NO. 2 DECLARED DUE TO HYDROGEN LEAK PLAY

VIDEO: SUNDAY'S UPDATE FROM MISSION MANAGEMENT TEAM PLAY
VIDEO: LEAK POSTPONES SHUTTLE ENDEAVOUR LAUNCH PLAY

VIDEO: TIME-LAPSE OF SUN SETTING OVER PAD 39A PLAY
VIDEO: ANOTHER TIME-LAPSE OF GANTRY RETRACTION PLAY
VIDEO: TIME-LAPSE OF LAUNCH PAD TOWER ROLLBACK PLAY

VIDEO: PRE-LAUNCH INTERVIEW WITH MARK POLANSKY PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH DOUG HURLEY PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH CHRIS CASSIDY PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH JULIE PAYETTE PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH TOM MARSHBURN PLAY
VIDEO: PRE-LAUNCH INTERVIEW WITH DAVE WOLF PLAY

VIDEO: THE STS-127 MISSION PREVIEW MOVIE PLAY
VIDEO: THURSDAY'S PRE-LAUNCH NEWS CONFERENCE PLAY
VIDEO: JAPANESE SCIENCE FACILITIES ABOARD STATION PLAY
VIDEO: COUNTDOWN BEGINS TICKING FOR SATURDAY'S LAUNCH PLAY
VIDEO: LAUNCH COUNTDOWN PREVIEW BRIEFING PLAY
VIDEO: CREW ARRIVES JUST BEFORE MIDNIGHT PLAY | HI-DEF
VIDEO: GET TO KNOW ENDEAVOUR'S ASTRONAUTS PLAY

VIDEO: ASTRONAUTS PRACTICE EVACUATION OF SHUTTLE PLAY | HI-DEF
VIDEO: CREW BOARDS SHUTTLE FOR PRACTICE COUNT PLAY | HI-DEF
VIDEO: ASTRONAUTS SUIT UP FOR DRESS REHEARSAL PLAY | HI-DEF
VIDEO: CREW INSPECTS CARGO IN THE PAYLOAD BAY PLAY | HI-DEF
VIDEO: TRAINING SESSIONS AT LAUNCH PAD AND BUNKER PLAY | HI-DEF
VIDEO: INFORMAL CREW NEWS CONFERENCE AT LAUNCH PAD PLAY
VIDEO: ASTRONAUTS ARRIVE FOR PRACTICE COUNTDOWN PLAY

VIDEO: FLIGHT READINESS REVIEW SETS LAUNCH DATE PLAY

VIDEO: PAD 39A GANTRY ENCLOSES SHUTTLE PLAY | HI-DEF
VIDEO: ROLLAROUND MOVES ENDEAVOUR TO PAD 39A PLAY | HI-DEF
VIDEO: ENDEAVOUR IS HAULED OFF LAUNCH PAD 39B PLAY | HI-DEF
VIDEO: TIME-LAPSE OF SHUTTLE'S LAUNCH PAD SWITCH PLAY

VIDEO: SHUTTLE AND STATION PROGRAM UPDATE PLAY
VIDEO: THE STS-127 MISSION OVERVIEW BRIEFING PLAY
VIDEO: PREVIEW BRIEFING ON MISSION'S SPACEWALKS PLAY
VIDEO: THE ASTRONAUTS' PRE-FLIGHT NEWS BRIEFING PLAY

VIDEO: PAD 39B AND ITS LAST SPACE SHUTTLE PLAY | HI-DEF
VIDEO: ENDEAVOUR'S SUNRISE ARRIVAL AT PAD 39B PLAY | HI-DEF
VIDEO: MIDNIGHT ROLLOUT FROM ASSEMBLY BUILDING PLAY | HI-DEF
VIDEO: ENDEAVOUR HOISTED FOR ATTACHMENT TO TANK PLAY | HI-DEF
VIDEO: CRANE ROTATES ENDEAVOUR VERTICALLY PLAY | HI-DEF
VIDEO: ENDEAVOUR MOVES TO ASSEMBLY BUILDING PLAY | HI-DEF
VIDEO: ORION AND ARES ROCKET PROGRESS REPORT PLAY
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