CAPE CANAVERAL, Fla. (AP) -- NASA fueled Endeavour for a Monday morning liftoff on the next-to-last flight of the space shuttle era, confident an electrical problem that grounded the mission more than two weeks ago had been fixed.
The mission commander is Mark Kelly, the astronaut husband of wounded Arizona Rep. Gabrielle Giffords, who's back for the second launch attempt.
Kelly and his five crewmates waved, gave a thumbs-up and shook their fists in the air as they headed to the launch pad in the pre-dawn hours. Liftoff was slated for 8:56 a.m.
"Good to be aboard," Kelly told launch controllers.
The mood was upbeat this time around. An electrical problem halted the countdown on April 29; NASA said that trouble is behind. Meteorologists also were optimistic.
The astronauts never made it to the launch pad last time. They posed at the base for a group picture Monday, before taking the elevator up and climbing into Endeavour.
"Took my last shower for a few weeks," reported astronaut Mike Fincke in a tweet. "The flight docs gave a good look-over. My only issue: too much boyish enthusiasm. (no known cure)."
Added pilot Gregory Johnson in his own Twitter update: "I am really excited and charged up for this mission! Slept great."
Endeavour is bound for the International Space Station one last time before heading to retirement at a Los Angeles museum. The shuttle's experienced, all-male crew will deliver and install a $2 billion particle physics experiment during the 16-day flight, as well as spare station parts.
NASA anticipated a launch day crowd in the hundreds of thousands. Besides the Kennedy Space Center work force, as many as 45,000 guests were expected to jam the launch site. On top of that, law enforcement agencies told NASA to expect up to 500,000 spectators to jam area roads and towns.
Even more people were expected for the first launch attempt, on a convenient Friday afternoon. President Barack Obama and his family even showed up, but had to settle for a tour and a meet-and-greet with the astronauts as well as Giffords.
NASA spent the past two weeks replacing a switch box with a blown fuse as well as a suspect thermostat, and installing new wiring.
Giffords flew in Sunday from Houston, where she's undergoing rehab for a gunshot wound to the head. Her recovery has been so remarkable that doctors approved both trips to Cape Canaveral.
She was shot at a political event in Tucson, Ariz., her hometown., and nearly died.
By Sunday night, recreational vehicles and cars already were lined up along the Banana and Indian rivers. And signs outside area businesses cheered Endeavour on with messages of "godspeed" and "go."
Endeavour is the baby of NASA's shuttle fleet. It was built to replace the Challenger, lost in a 1986 launch accident. Endeavour first flew in 1992 -- it ended its first mission 19 years ago Monday.
NASA is retiring its three remaining space shuttles after 30 years to concentrate on interplanetary travel. The space agency wants to hand over the business of getting crews and cargo to the space station, to private companies. At least one company, Space Exploration Technologies Corp., said it can get astronauts to the space station within three years of getting NASA approval.
One final mission remains, by Atlantis in July.
(Copyright 2011 by The Associated Press. All Rights Reserved.)