U.S. space shuttle Endeavour blasted off from its seaside launch pad on Wednesday, ending a month of delays to a mission intended to complete construction of Japan's Kibo research laboratory on the International Space Station, Reuters reported.
On its sixth launch attempt, NASA's 127th space shuttle mission began at 6:03 p.m. (2203 GMT) when Endeavour's twin solid-fuel booster rockets ignited, sending the 4.5 million pound (2.04 million-kg) spaceship into the steamy Florida sky.
"The weather is finally cooperating, so it is now time to fly," launch director Pete Nickolenko radioed to the crew shortly before liftoff. "Persistence pays off. Good luck and godspeed."
Riding atop a pillar of smoke and flame, the shuttle soared over the Atlantic Ocean en route to an orbital rendezvous with the space station on Friday 220 miles (354 km) above Earth.
Two launch attempts last month were scuttled by hydrogen fuel leaks. A third attempt on Saturday ended when NASA ordered checks of the shuttle's electrical systems following a spate of lightning strikes, and Sunday and Monday launch attempts were canceled due to poor weather.
Televised replays of the launch broadcast by NASA showed small clouds of debris, possibly foam from the external fuel tank, that appeared to hit the underside of the shuttle about one minute and 45 seconds after liftoff.
"We had some foam loss events," NASA's spaceflight chief Bill Gerstenmaier told a post-launch news conference.
He said a detailed analysis would come after the station crew takes pictures of the shuttle's heat shield prior to Endeavour's docking on Friday but it was too soon to talk about potential damage.
Since losing shuttle Columbia and its seven-member crew in a 2003 accident caused by debris impacts, NASA conducts a suite of inspections and analysis post-launch to determine the condition of the shuttle's heat shield, needed for the return trip to Earth. Columbia broke apart when its heat shield failed as it flew through the atmosphere for landing.
NASA is trying to complete construction of the $100 billion outpost, a project of 16 nations, by Sept. 30, 2010, so it can retire the shuttle fleet and ramp up development of replacement ships that can journey to the moon and other destinations farther from Earth.
Endeavour is carrying a Japanese-built platform to be mounted on the front of the $2.4 billion Kibo complex to hold science experiments that need to be exposed to the open environment of space.
Experiments on the platform can be installed and retrieved remotely with a robotic arm, eliminating the need for time-consuming and potentially risky spacewalks by station crew members. The first two sections of Kibo were attached to the station in 2008.
The platform is to be installed during the first of five spacewalks scheduled during Endeavour's 11-day stay at the station. Astronauts also plan to replace batteries that are part of the station's solar power system and store spare parts needed to keep the outpost operational after the shuttle fleet is retired next year.
None of the other spaceships that travel to the station -- Russia's Progress and Soyuz vessels, Europe's Automated Transfer Vehicle cargo hauler and Japan's HTV vehicle, which is scheduled to make its debut flight this year -- can carry and install the station's large modules, trusses, gyroscopes and other key components.
The space station has been under construction for more than a decade. It consists of nearly 26,000 cubic feet (735 cubic metres) of pressurized space, about as much room as a typical four-bedroom house.
Once the shuttles are retired, NASA plans to pay Russia to fly astronauts to the station, and rely on commercial U.S. carriers for cargo deliveries, although none has yet demonstrated that capability.
Endeavour's mission is among the most ambitious and complicated flights NASA has attempted, with simultaneous use of three robotic arms and an unprecedented 13 people as part of the joint shuttle-station crew.
NASA and its partners doubled the size of the live-aboard station crew to six people in May. Endeavour, with its seven-member crew, is the first to visit the station since then.