CAPE CANAVERAL, US - The US space shuttle Discovery blasted off from its seaside Florida launch pad overnight on a do-or-die mission for Nasa's beleaguered shuttle programme and the half-built International Space Station.
The shuttle and its seven-member crew lifted off at 2.38pm EDT (6.38am Wednesday NZT), following two postponements over the weekend because of poor weather at the Kennedy Space Centre.
"America is ready to return the space shuttle to flight," launch director Mike Leinbach said shortly before the 115th shuttle mission and the second flight since the 2003 Columbia disaster blasted off.
Officials said there were no initial signs of serious problems with the shuttle's foam insulation, which has plagued Nasa in recent years and caused the deadly breakup of the shuttle Columbia in 2003. Further examination was scheduled for later Tuesday.
Nasa needs a successful mission to resume construction of the planned US$100 billion ($165bn) space station, a project sponsored by 16 nations. Assembly of the outpost has been on hold since the 2003 Columbia disaster.
Nasa had hoped to resume station construction last year following the first post-Columbia mission but the shuttle's fuel tank, like the one on Columbia, shed large pieces of insulating foam during launch. Managers grounded the fleet again for repairs.
Columbia was destroyed when a 756-gram chunk of foam broke off the fuel tank and smashed into the ship's left wing. The damage was undetected until after Columbia broke apart 16 days later as it flew through the atmosphere, killing all seven astronauts aboard.
Another accident or serious problem on the current shuttle mission could ground the fleet permanently.
Nasa will get a preliminary look at how Discovery's tank fared during launch later Tuesday when imaging experts pore over hundreds of photographs and videotapes taken during the shuttle's climb into orbit.
Nasa managers said several pieces of foam fell off the external fuel tank during launch but by then the shuttle was beyond the point in its flight where they could be a hazard to the spacecraft.
"This isn't too abnormal," said Bill Gerstenmaier, associate administrator for spaceflight. "We fully expected to lose some foam."
Any flyaway foam was expected to be small and of no consequence to the shuttle. Work remains on one area of the tank foam and the agency's top engineer and chief of safety had wanted to postpone Discovery's launch until after the work was done.
Nasa Administrator Michael Griffin, however, decided to proceed with launch, knowing that the shuttle crew could be housed aboard the space station if their ship was hit by debris and sustained damage too severe to return home safely.
Delaying Discovery's launch, Griffin said, would put too much pressure on the shuttle programme, which needs to fly 16 missions to the station to complete construction before 2010.
Nasa already has spent about US$1.3 billion fixing the shuttle's fuel tank and developing other safety upgrades since the Columbia accident. The agency has no more time or money to spend on major refurbishments if additional problems are discovered.
Shuttle commander Steve Lindsey, 45, pilot Mark Kelly, 42, and mission specialists Mike Fossum, 48, Lisa Nowak, 43, Stephanie Wilson, 39, and British-born American Piers Sellers, 51, waved small American flags as they headed from their quarters to the launch pad, marking the US Independence Day.
Thomas Reiter, 48, of Germany, waved a German flag. He will be the first European to live on the space station and is scheduled to return home with another shuttle crew in December.