CAPE CANAVERAL, Fla. -- NASA had one last chance to get space shuttle Atlantis off the ground Saturday, or it would have to wait as long as two months to restart building the international space station.

It couldn't afford much more of a delay.

The multibillion-dollar space lab's construction has been on hold since the Columbia disaster 3 1/2 years ago, and NASA and its international partners face a 2010 deadline to finish before NASA stops flying the shuttle fleet. The Atlantis mission, initially planned for 2003, was rescheduled for August, then delayed four times in two weeks.

"It looks like your long wait is over," launch director Mike Leinbach told Atlantis commander Brent Jett and his crew as they sat strapped into the shuttle Saturday morning.

Minutes later, Atlantis lifted off from Kennedy Space Center and streaked into space in what NASA Administrator Michael Griffin called a "majestic launch."

Jett and his team have trained far longer than any crew, more than four years, and the extra time will probably be an advantage. They face one of the most challenging construction tasks in space history.

"We're confident that in the next few weeks, and few years for that matter, NASA is going to prove to our nation and our friends around the world that it was worth the wait," Jett said. "We're ready to get to work."

As Atlantis headed for space, more than 100 cameras zoomed in for any signs of foam breaking off its external fuel tank, the problem that doomed Columbia.

A chunk of the hard foam appeared to hit the shuttle's belly, but "it didn't look like there was any damage," Mission Control told the Atlantis crew. That foam loss, and another, came more than four minutes into the launch, when they pose less of a damage threat, said LeRoy Cain, chairman of the mission management team.

NASA also observed some ice falling off after the shuttle reached orbit, again too late in the ascent to worry the space agency.

Leinbach described the launch as "really, really clean."

"The countdown itself went extremely smoothly, which probably shouldn't be surprising considering how many times we tried it," Leinbach said.

There was a slight problem when a freon coolant system didn't work properly during ascent, but NASA didn't view it as a major concern. The fuel cells that forced launch delays earlier in the week were working as expected, NASA spokesman Kyle Herring said.

"Great work!" astronaut Jeff Williams said minutes after the launch from the space station 220 miles above Earth.

Atlantis carried one of the heaviest payloads ever launched into space -- a 17 1/2 ton truss section that will be added to the half-built space station. It includes two solar arrays that will produce electricity for the orbiting outpost. Atlantis' weight was so much that it only had a crew of six, instead of the usual seven astronauts.

The astronauts will make three spacewalks during the 11-day flight to install the $372 million addition.

"In terms of spacewalk tasks, clearly these are the most complicated spacewalk and assembly tasks that ever have been done before," said Wayne Hale, NASA shuttle program manager.

Construction of the space station has been on hold since Columbia disintegrated over Texas on its return to Earth in February 2003, killing seven astronauts. Since then, NASA has struggled to find ways to prevent foam from breaking off the external fuel tank like the 0chunk that had fatally damaged Columbia's wing during liftoff. NASA engineers are still working on a redesign of the tank.

Atlantis' mission was supposed to take place in 2003 but it was delayed for three years as NASA worked to figure on the foam problem.

After training for the flight for a record 4 1/2 years, the six astronauts had to wait a little longer, when the launch was scrubbed four times over the past two weeks: first a lightning bolt hit the launch pad, then Tropical Storm Ernesto threatened -- NASA actually started rolling the shuttle back into its assembly building, then sent it back to the launch pad when the forecast improved -- then it had an electrical system problem, followed by a faulty fuel gauge.

The astronauts were already strapped in Friday morning when NASA scrubbed an hour before the launch time because a sensor in the hydrogen fuel tank gave an abnormal reading. That delay cost NASA $616,000.

If the shuttle didn't get off the ground this week, NASA would have had to wait until late September or even late October to try again.

Russia plans to send a Soyuz capsule to the space station on Sept. 18, bringing two new crew members to the space station and Anousheh Ansari, a Texas entrepreneur who is to become the first female space tourist. NASA also wanted a daytime launch for Atlantis so it could watch for any damage to the spacecraft.

The astronauts with Jett aboard Atlantis are pilot Chris Ferguson and mission specialists Joe Tanner, Dan Burbank, Heidemarie Stefanyshyn-Piper and Steve MacLean of the Canadian Space Agency.

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