KENNEDY SPACE CENTER, Fla.--For the second day in a row, approaching thunderstorms near the Kennedy Space Center on Monday forced NASA managers to order another launch delay for the shuttle Endeavour's frustrated crew. It was the fifth delay for the space station assembly mission since a hydrogen leak scuttled the crew's first launch try in June.
"Well Roman, again, the vehicle and our teams were ready," Launch Director Pete Nickolenko radioed the astronauts from the firing room at 6:39 p.m. EDT. "But the weather's just bitten us again with lightning within 20 nautical miles in violation of our launch weather. So for that, we're going to have to declare a scrub again for the day today. We'll talk and convene and decide our forward path, whether it's tomorrow or Wednesday."
"We understand, Pete. That's the nature of our business," commander Mark "Roman" Polansky replied from Endeavour's flight deck. "Like I said before, when the timing's right we'll be here and we'll be ready."
Within a few minutes of the scrub, NASA managers opted to pass up a Tuesday launch opportunity and to recycle the countdown for a sixth launch attempt Wednesday at 6:03:10 p.m.
By delaying 48 hours to Wednesday, engineers will have time to repair a rocket thruster rain cover that has pulled loose slightly. The forecast for Wednesday calls for a 60 percent chance of good weather as opposed to a 40 percent chance on Tuesday.
But slipping to Wednesday means the crew will have to re-arrange the mission timeline, deferring some off-duty time and pre-entry packing until after Endeavour undocks from the station to make sure the shuttle is out of the way before a Russian Progress supply ship arrives at the lab complex.
The Progress is scheduled for launch July 24. It can loiter in space for up to five days, but it must dock by July 29.
Going into the current launch campaign, NASA managers said Endeavour had to take off by Tuesday for the crew to carry out a full-duration 16-day space station assembly mission and undock before the Progress arrives.
But space station planners now believe the crew can carry out all five planned spacewalks if Endeavour gets off Wednesday by simply re-arranging the crew's timeline. They also are looking into the possibility of launching Thursday, if necessary.
But in that case, the astronauts would have to give up one of their five spacewalks and it's not yet clear whether that is a viable option or not.
Mike Moses, director of shuttle integration at the Kennedy Space Center, said NASA will not attempt a launch past Thursday. If the shuttle isn't off by Wednesday or Thursday at the latest, launch will be delayed to July 26. In that case, the Progress would dock July 27 and Endeavour would arrive the next day.
There were no technical problems today and as with Sunday's countdown, Endeavour's fuel tank was loaded with a half-million gallons of oxygen and hydrogen without incident. The hydrogen vent line that leaked last month, derailing two launch attempts June 13 and 17, worked normally Sunday and again today.
But Florida's weather has been turbulent for the past few weeks, with thunderstorms developing regularly over the Space Coast. Going into Monday's launch campaign, forecasters predicted a 40 percent chance of acceptable weather.
But late in the day, as western and eastern sea breezes collided near the space center, storms cells popped up and moved into the 40-nautical-mile wide zone that must be clear of showers and low clouds for a launching to proceed. Of particular concern was a towering cell north of the pad that was in the shuttle's flight path.
NASA's launch rules protect a 10 nautical-mile-radius circle around the pad and forecasters at the space center were no-go due to lightning, field mills and electrically charged anvil clouds.
Launch aside, a shuttle crew also must be able to make an emergency landing back at the space center in the event of an engine failure early in flight. NASA flight rules prohibit a launch if forecasters detect rain or heavy cloud cover within 20 nautical miles of the runway.
The Spaceflight Meteorology Group at the Johnson Space Center in Houston, which oversees landing weather, was "no-go" for return-to-launch-site weather.
With only a five-minute launch window, Launch Director Pete Nickolenko did not have time to wait for improving conditions. After forecasters said they were no-go for launch and landing, he called off the countdown during a final hold at the T-minus nine-minute mark.
UPDATED at 9:30 p.m. EDT: Added details from news briefing; full mission possible with Wednesday launch; NASA mulls possible Thursday launch try if necessary.