The space shuttle Discovery rocketed into space Tuesday, carrying a crew of seven on a challenging two-week mission to continue construction of the International Space Station.
The flight includes five spacewalks, the most of any shuttle mission.
Discovery blasted off from Cape Canaveral in Florida at 11:38 a.m. EDT on an eight-minute jump to space that carried the shuttle from a standing start to more than 17,000 mph. Discovery's engines guzzled fuel equivalent to emptying a backyard swimming pool every 23 seconds.
"We have a tremendous series of challenges in front of us," Bill Gerstenmaier, associate administrator for space operations, said at a post-launch news conference at Kennedy Space Center.
Those challenges include spacewalks Friday, Sunday, Tuesday and Nov. 1 and 2.
Discovery carries in its cargo bay a bus-sized module called Harmony, which was named by schoolchildren in a nationwide competition. The module is a compartment that will connect European and Japanese science laboratories that will arrive on later flights.
The crew will also relocate a port-side section of the station spine, known as the truss, as well as a set of solar arrays that provide power to the station. They will also replace a circuit breaker and demonstrate new repair techniques to be used if the shuttle were damaged.
"We've done a lot of these tasks on previous flights," Gerstenmaier said. "It's the combination of all these things" that makes the mission difficult.
Rain in central Florida had been a concern. Just hours before launch, NASA said there was only a 40% chance the clouds would part in time. Minutes before the final countdown, launch crews discovered a 4-inch-long chunk of ice on a connector between Discovery and the external fuel tank.
The flight went ahead after safety officials decided the piece of ice was too small to pose a hazard, even if it came off during launch and hit the craft.
As many as six pieces of insulating foam were also seen flaking off the external tank during the launch. Flight managers said they didn't think any of them constituted a danger, partly because they came off late in the launch sequence, when aerodynamic forces were too low to accelerate the foam chunks to speeds that could damage the craft.
It will be several days, however, before engineers are able to pronounce the vehicle safe to return to Earth. In the interim, managers will review photos and film, from the ground and from space, of Discovery's heat-resistant outer tiles.
Falling foam became a crucial issue after the shuttle Columbia was destroyed during reentry in 2003. A team of experts concluded that a chunk of foam from the fuel tank hit the leading edge of the left wing, tearing a hole in it during launch.
Though some safety experts raised concerns about foam at the time, managers overruled them and allowed Columbia's disastrous landing attempt. The accident prompted a soul-searching review of its procedures by NASA, as well as sweeping changes in launch preparations.
Some critics, within and outside the agency, have begun raising concerns lately over whether NASA is allowing schedule pressure to once again drive launches. Before Discovery's launch, a safety panel inside the agency recommended replacing three reinforced carbon-carbon panels that protect the leading edges of the wings, based on thermal studies that appeared to show flaws in the silicon carbide coating.
Mission managers voted to go ahead with the launch, concluding that under the worst-case scenario -- a burn-through of a panel amid the friction of reentry -- Discovery could still land safely.
Last week, shuttle commander Pamela A. Melroy, a retired Air Force colonel, said she was confident Discovery was safe to fly.
Melroy is the second woman to command a shuttle mission. She will be at the controls during docking with the space station Thursday. Just before the link-up, she will put Discovery through a complicated bit of space choreography called a rendezvous pitch maneuver that will enable the space station crew to take pictures of the critical underside of the orbiter, looking for damage.
The most arduous work of the mission falls on the shoulders of the principal spacewalkers: mission specialists Scott Parazynski and Douglas H. Wheelock, who is making his first spaceflight, and flight engineer Daniel Tani, who will remain behind on the station when the shuttle returns to Earth.
Other crew members include pilot George Zamka, a Marine colonel; flight engineer Stephanie Wilson, making her second flight to space in two years; and European astronaut Paolo A. Nespoli, an Italian making his first flight.
Discovery is scheduled to return to Earth on Nov. 6.
The Associated Press contributed to this report.