Space Shuttle Discovery and seven astronauts blasted off a minute before midnight on a mission to deliver supplies and a fresh crewmember to the International Space Station.
NASA had called off three countdowns earlier this week, one for stormy weather and two more to figure out a balky fuel valve engineers feared was not working properly.
On Friday night, the weather cleared and no technical glitches cropped up. The launch director radioed the crew 10 minutes before liftoff with the good news they were finally going to fly.
"Thanks to everyone who helped prepare for this mission. Let's go step up the science on the International Space Station," Commander Rick Sturckow called back to the Launch Control Center.
The space shuttle's late-night launch began one of the last seven missions scheduled before the fleet is scheduled to retire in 2010 or 2011, barring a reprieve from President Obama, who has a commission studying NASA's future.
The panel's report, which includes one option to extend the space shuttle program to 2015, is due to the president's desk at the start of next week.
The mission to the space station will deliver supplies and equipment as well as a new permanent member of the crew. Nicole Stott, who once was an engineer working on the space shuttles at the Kennedy Space Center, will live aboard the space station until November. She replaces Tim Kopra, who will return to the Earth aboard Discovery.
The Friday night launch drew a hearty crowd to the beaches, bridges and roadways of nearby Cocoa Beach and Titusville, as throngs took advantage of the chance to see what may be one of the last launches.
The crew will spend Saturday inspecting their spacecraft for launch damage. Discovery is scheduled to dock at the International Space Station on Sunday night. For two weeks, the 13 people on the shuttle and station crews will work to unpack the giant cargo module tucked inside the shuttle's payload bay.
Among the items inside: a treadmill named after cable television comedian Stephen Colbert.
Discovery is scheduled to land Sept. 10.