Space shuttle Discovery thundered into orbit on Nasa's 100th shuttle flight, carrying seven astronauts on a crucial construction trip to the international space station.
"We're going to take a big step here. Let's go!" commander Brian Duffy called out Wednesday evening. Discovery rose from its seaside pad at 23:17pm GMT, just after sunset, on Nasa's fourth launch attempt. The shuttle had been grounded since last Thursday because of trouble with bolts, a valve, a pin and the weather.
The shuttle pierced thin, wispy clouds as it raced out over the Atlantic, its exhaust trail tinged peach, orange and red by the setting sun and surpassing the nearly full moon in brightness.
Throughout Wednesday afternoon, the sky was overcast and a waterspout was spotted a few miles from the launch pad. But the weather improved dramatically by evening, and shuttle managers gave the nod.
"All good things are worth waiting for, and I think you and your crew have waited long enough for this one," launch director Mike Leinbach told the astronauts. "Good luck on this extremely important mission to the international space station - and have fun."
Workers had to hustle to remove the small metal pin that was left on an oxygen line running between Discovery and its external fuel tank. The pin resulted in an embarrassing and costly delay for Nasa on Tuesday.
Following liftoff, Nasa Administrator Daniel Goldin singled out the sharp-eyed engineer, Jorge Rivera, who spotted the pin. "I took a look at the camera angles... it's unbelievable how you did it," Goldin said.
The space station was soaring 240 miles above the Bay of Bengal when Discovery finally soared. The chase will end with a docking on Friday.
Discovery contains two new segments for the international space station. The crew's job is to attach the girderlike truss and docking port; four spacewalks will be needed to make all the connections, beginning Sunday.
The 11-day mission has been on hold for two years, as have subsequent assembly flights, because of Russia's difficulties in launching the space station's crew quarters. The module was finally placed in orbit in July and was outfitted by a visiting space shuttle crew in September.
The truss and docking port aboard Discovery must be installed on the space station before the first permanent crew can move in. Nasa astronaut Bill Shepherd and his two-cosmonaut crew are scheduled to lift off from Kazakstan on October 30.
This will be Nasa's fifth visit to the space station. But it's the first actual construction mission since the first pieces of the complex were launched in 1998.
Six Americans and one Japanese make up the crew. Air Force Lt. Col. Pamela Melroy is making her first space flight; she is only the third woman to serve as a shuttle pilot.
"Pam, welcome to space and congratulations," Mission Control said 8 minutes into the flight.
"It's beautiful," she replied.
In honour of the 100th space shuttle launch, a videotape was played for guests featuring shuttle scenes and the Philadelphia Orchestra playing the theme from '2001: A Space Odyssey'. The orchestra is marking its 100th anniversary.
Nasa's first shuttle flight was in 1981 and the 50th in 1992. The 25th was Challenger's doomed mission in 1986.
Since the first mission, space shuttles have carried 261 individuals and logged an estimated 350 million miles.