On board Discovery is 77-year-old veteran astronaut John Glenn - the world's oldest astronaut.

Soon after take-off, mission control assured the shuttle crew that the loss of the panel was not hazardous.

The BBC's Sue Nelson: John Glenn enjoys being the oldest man in space

At a post-launch press conference Nasa said the panel protecting the shuttle's drag parachute, sometimes used during landing, had fallen off two seconds into the flight.

They added the mishap should not affect the mission although they were unsure whether the parachute had been damaged.

"We obviously can successfully land the space shuttle without the drag chute," shuttle manager Don McMonagle said.

'I can't even describe it'

John Glenn: "This is beautiful!"

Shortly after reaching orbit, John Glenn spoke to mission control about his feelings on returning to space and the view out of the shuttle window. "Today is beautiful and great," he said, "and Hawaii is ... I can't even describe it."

The heat of blast off may have damaged Discovery's drag parachute

Mr Glenn returns to the final frontier 36 years after he became the first American to orbit the earth.

Discovery, is a luxurious ship compared to the cramped rocket he used in 1962, successfully blasted off at 1919GMT (1419EST) from Kennedy Space Centre.

After Nasa launch commentator Lisa Malone completed her countdown she added: "Lift-off of Discovery with a crew of six astronaut heroes and one American legend."

Watch the Discovery lift off

Launch was delayed slightly by an aeroplane entering airspace above the craft.

President Bill Clinton and a host of Hollywood stars watched the launch from the VIP boxes.

And about 250,000 spectators caught a fleeting glimpse of the take-off from the surrounding area.

Mr Clinton said: "It's a great day for America and a great day for our senior citizens. I hope that all Americans share the exuberance that I feel."

Studying the ageing process

Veteran observers said public interest in the launch was similar to those for the first missions to the moon and Mr Glenn, now a US senator, was the sole reason.

James Wilkinson: Glenn - America's latest hero

During his nine days in space, Mr Glenn will be a medical guinea pig. Scientists will study his bones, heart and immune system to see how his body is reacting to the stresses of launch and the comparative comfort of zero gravity.

They hope to use the data to find out more about the ageing process and to see how older people fare in space.

Solar experiments

The publicity surrounding the flight has generated interest from all over the world but there has been some criticism of the science.

Some researchers have argued that you can learn very little from studying only one person.

But for the scientists, John Glenn is not the only interest on the flight. The crew of seven will perform more than 80 experiments and release a satellite for two days of solar studies.

Apart from the US crew, Discovery will also be carrying a Japanese researcher and a European Space Agency astronaut from Spain.