(AP) -- Hoping stormy skies clear in time, NASA fueled space shuttle Endeavour for a sixth launch attempt Wednesday, the eve of the 40th anniversary of the liftoff for the first moon landing.
Endeavour, in fact, was poised at the very spot where Apollo 11's Neil Armstrong, Buzz Aldrin and Michael Collins rocketed into history on July 16, 1969, aboard a twice-as-high Saturn V rocket. The shuttle and its seven astronauts are bound for the international space station with a Japanese building block.
Thunderstorms - packing lightning, heavy rain and high wind - whipped across the launching site Monday afternoon. Conditions eased just as the astronauts departed for the launch pad. Forecasters said there was a good chance the weather would improve by the 6:03 p.m. launch time.
The astronauts had big smiles and waved as they made their way to their rocketship for the third time in four days.
Besides the weather, NASA was dealing with a possible technical concern.
Mission managers were gathering in midafternoon to discuss the condition of one of the shuttle's fuel cells. It's possible that the fuel cell - one of three identical electrical powerplants - might not be able to operate at low power during the 16-day flight, which could cut short the mission.
NASA has been trying to launch Endeavour for more than a month. The first two tries, in mid-June, were thwarted by hydrogen gas leaks. Then thunderstorms caused three more delays, the latest one Monday evening.
Time is running out. If Endeavour is not flying by Thursday, it will have to wait until July 26 so the Russians can squeeze in a space station supply run. A Thursday attempt, however, would result in the elimination of one of five planned spacewalks and a shortened mission.
Polansky noted that he launched the first time he strapped into the shuttle cockpit for his first flight in 2001, and the second time he strapped in for his second flight in 2006.
"Today is 3rd time" for this mission, his third, he said in a Twitter update. "Hope the pattern holds."
Endeavour's numerous delays have not helped NASA's tight deadline to complete the space station by the end of next year. Eight shuttle flights remain, all geared toward that goal.
Aboard Endeavour is the third and final section of Japan's massive lab. It's a porch for outdoor experiments.
Once Endeavour arrives at the space station, there will be 13 people together in orbit, a record crowd.
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