It's been six long years since world-famous physicist Stephen Hawking got a taste of weightlessness during a zero-G airplane flight from NASA's Kennedy Space Center — but he still wants to feel the real deal aboard Virgin Galactic's SpaceShipTwo rocket plane.
The 71-year-old Hawking has been living with neurogenerative disease for decades, but his illness hasn't kept him from taking on adventures that might tax younger, fitter humans. On Tuesday, during a London talk sponsored by the charity Breathe On UK, Hawking noted that he has required assistance with his breathing since his tracheotomy in 1985.
"Being on a ventilator has not curbed my lifestyle," he told the audience, using his instantly recognizable computer-generated voice. "I have been to Brussels, the Isle of Man, Geneva, Canada, California ... and I hope to go into space with Richard Branson's Virgin Galactic. It is possible to have quality of life on a ventilator."
That's music to the ears of Breathe On UK, which was created to help kids who need long-term breathing assistance. It's also a compliment to Virgin Galactic, which put SpaceShipTwo through its supersonic paces for the first time this week. If all the tests go right, SpaceShipTwo could be taking passengers on suborbital space trips as early as next year.
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Richard Branson, Virgin Galactic's billionaire founder, promised to consider Hawking for one of those trips even before the good doctor took his ride into weightlessness in 2007. The invitation still stands, according to George Whitesides, the company's president and CEO.
"Richard and the team would love to welcome him on board," Whitesides told NBC News on Tuesday.
Hawking's health is the big issue for any future spaceflight, just as it was for the zero-G flight years ago. The physicist would have to be fully checked out, and even if he was cleared for takeoff, medical staff would almost certainly have to ride along. Deceleration could be the toughest part of the trip. SpaceShipTwo's flight profile calls for up to 6 G's of force on the way down. That's more force than most space shuttle astronauts have felt, and it ranks right up there with the world's rockiest roller-coaster rides.
If Hawking were to fly into space sometime in the next few years, he'd take the No. 2 spot on the list of the world's oldest astronauts. The only person older would be senator-astronaut John Glenn, who flew on the space shuttle Discovery at the age of 77 and is now 91 years old.
Six years ago, Hawking declared, "Space, here I come!" Should he keep that dream alive, or should he focus on earthly adventures instead? Feel free to weigh in with your comments below.
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Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.