Stephen Hawking plans a space journey

"This year I'm planning a zero-gravity flight and to go into space in 2009," Hawking, who celebrates his 65th birthday on Monday, told The Daily Telegraph.

During a zero-gravity flight aeroplanes fly in such a way that people inside are temporarily weightless. However, the physcists next step towards the cosmos depends on the Virgin Galactic space tourism plans of Sir Richard Branson, whose SpaceShipTwo will carry six passengers into a low Earth orbit from 2008.

The craft will be launched at 50,000 feet from a mothership and soar into space at around 360,000 ft, reaching a speed of 2,500 mph -- more than three times the speed of sound.

At present, a flight costs about £100,000 but Sir Richard will sponsor Professor Hawking's mission. Hawking, who was struck down by motor neurone disease when he was 21 and given a year or two to live, is the author of A Brief History of Time, which has sold 10 million copies.

The scientist said he had offered to give his DNA to a project to scan the human genetic code for clues to the cause, in an initiative backed by the MND Association.

"Motor neurone disease is as common as multiple sclerosis but it has received much less public attention and awareness," he said.

"This may be because it often kills its victims in two or three years from the first appearance of symptoms, so they aren't around to be noticed.

I am one of a few long-term survivors, so I have a duty to call attention to this terrible disease and to press for research into its causes."