Veteran astronaut John Glenn has told how his record-breaking 1998 mission differed from his first space flight.

John Glenn: "We had the fun part"

The world's oldest astronaut said: "I learned a lot about myself. It was a new and different experience.

"I was up in 1962, but this was in zero-G. It was different working in that environment.

"Last time we were just trying to find out if we could do it.

"Now we have had about 127 manned flights and are carrying out research.

"This flight carried 83 experiments at the cutting edge of science and will benefit people on earth."

And he joked that the post-mission press conference was the "dangerous part" of the mission.

Getting used to being back on Earth

Mr Glenn, and his six crew mates, made a text book landing at Kennedy Space Center, Florida, on Saturday, after travelling more than 3 million miles in the Space Shuttle Discovery.

Mr Glenn, 77, said he would love to make another return trip to space although he admitted having no plans other than to spend some time with his wife, Annie.

But he added: "Too often people set their lives by the calendar. That takes the fun out of living as far as I am concerned."

High spirits

Nasa's chief doctor, Philip Stepaniak, called off a press conference planned for Saturday, saying it would have added an unnecessary strain on the astronauts at the end of a long day.

The world's oldest space correspondent interviews the world's oldest astronaut

Dr Stepaniek said initial physical examinations indicated that Mr Glenn and the other crew members were all doing better than expected.

He described Mr Glenn as being animated and in high spirits shortly after the landing.

Mr Glenn was able to walk unaided down the steps before being reunited with his family.

But he admitted to feeling the effects of gravity after getting out of Discovery.

Mr Glenn and his crew mates will spend up to three weeks undergoing further extensive medical tests.

Safe landing of Space Shuttle Discovery

Shortly after the landing Mr Glenn had found the energy to call out on Discovery's communications link with a message, recalling his previous return to earth.

"This is PS2, I'm better known to a lot of you as John," he said.

"I want to reprise a statement that I made a long, long time ago, except this time it is: One-G and I feel fine."

Mission Control said that Discovery had completed a trip of 3.6 million miles and "a moment in history".

First and oldest

In 1962, Mr Glenn was the first American to orbit the Earth and became a national hero. His presence on Discovery fired the imagination of the world.

More than 250,000 people gathered around Kennedy Space Centre to watch the launch. From VIP seats inside the base, President Bill Clinton and a host of Hollywood stars saw the mission blast off.

Mr Glenn has been taking part in a series of experiments, including assessing the effects of weightlessness on the body.

Scientists hope to use the results of the experiments for research into the ageing process.