Blastoff: Discovery's July 4 Gift to the Nation

Nasa called it "a gift to the nation". Last night the shuttle Discovery finally blasted off after several days of delays to lend a spectacular fiery flourish to America's Independence Day celebrations.

The agency's first July 4 launch in 45 years of manned spaceflight provided a welcome distraction from the continuing controversy about the safety of the fuel tank's foam insulation and the frustration of two aborted liftoffs owing to poor weather at the Kennedy Space Centre. "For the first time in our country's history we hope to be waving the US flag in orbit and leading the day's celebrations," said a Nasa spokesman, Bruce Buckingham.

Discovery and its crew of seven, including the British-born astronaut Piers Sellers, 51, enjoyed an apparently flawless ascent to orbit after the launch at 2.38pm (7.38pm BST). Thunderstorms that had threatened to cause a third postponement remained out at sea.

About a minute after launch into a clear Florida sky, controllers announced: "Everything is looking good on the bird."

Managers at Nasa immediately began a painstaking study of images from 107 cameras on the ground and aboard the spacecraft to check for any damage sustained during the first minutes of its 13-day, 5m-mile mission to the International Space Station (ISS).

It was a briefcase-sized slab of foam peeling from the external fuel tank at lift-off that struck a hole in the wing of the shuttle Columbia in 2003, leading to the death of seven astronauts as deadly hot gases seeped into the spacecraft and blew it apart on re-entry.

Despite a redesign of the fuel tank, the problem happened again during last year's first return-to-flight mission when a 1lb (0.45kg) chunk of foam narrowly missed Discovery. And last night's blastoff was also in doubt when launchpad technicians found a 5in (12.7-cm) crack and a 3in (7.6cm) piece of foam missing near a fuel-line bracket after the tank was drained after the abandoned launch on Sunday.

Engineers spent all Monday assessing the damage before concluding that it was not severe enough to provide a constraint to flight. But Bill Gerstenmaier, Nasa's associate administrator of spaceflight, nonetheless found himself rebutting suggestions that the agency had rushed its decision to press ahead with the launch.

"We've laid out the data and we've looked at it calmly, and we're ready to go fly," he said. "Our teams have done a very good job of avoiding the tendency to get launch fever."

Dr Sellers, who was born in Crowborough, East Sussex, but became a US citizen to join the astronaut corps in 1996, emerged from the crew room and boarded the "astrobus" to the launchpad waving a small stars and stripes flag.

Walking beside him was German Thomas Reiter, 47, the only non-American among the crew. He said he was hoping for an update from mission control in Houston about the result of the World Cup semi-final between Germany and Italy.

When Discovery returns to Earth on July 17, Mr Reiter will remain aboard the ISS, raising its complement to three astronauts for the first time since May 2003.

The mission, only Nasa's second since the Columbia disaster, will deliver two tonnes of supplies and equipment to the ISS and continue testing of $1.3bn (£703m) of safety and repair techniques introduced since the tragedy. Nasa is racing to finish the construction of the ISS before the shuttle fleet is retired in 2010.

Dr Sellers will conduct the first of his scheduled spacewalks on Saturday, when he and colleague Michael Fossum, 48, will test the load-bearing capabilities of the shuttle's 30-metre (100ft) robotic arm extension. If successful, the arm can be used in future missions to transport astronauts to the underside of the orbiter to inspect the heat shield for damage.

The second "extra-vehicular activity", as the spacewalks are known, will come two days later, when the pair will attempt to replace a broken power cable outside the space station. Managers say they may try to extend the mission to allow a third walk, to apply resin to deliberately broken thermal tiles to see if the "repairs" could withstand the 1,650C heat of re-entry.

Dr Sellers, the third Briton in space after Helen Sharman and Michael Foale, is on his second shuttle trip after 12 days in Atlantis in 2002.

The other astronauts are commander Steve Lindsey, 45; pilot Mark Kelly, 41; and mission specialists Lisa Nowak, 42, and Stephanie Wilson, 39.