One giant leap for Stephen Hawking

The risks and the resolutions
The main medical concern has to do with how Hawking's breathing will be affected by the periods of heavier-than-normal gravity that must follow every zero-gravity float, Diamandis told reporters.

There could be an effect on Hawking's heart, and he may experience the motion sickness sometimes associated with weightless flights. Because no person in his condition has flown on a weightless flight before, Hawking's caregivers are not completely sure how serious the effects could get. But those uncertainties will have to be resolved if Hawking ever hopes to take a suborbital spaceflight, which involves greater stresses than weightless airplane flights.

To ensure Hawking's safety, several extraordinary measures are being taken:

• The doses of zero-gravity on Thursday won't last as long as they usually do — about 15 to 20 seconds as opposed to 25 to 30 seconds. That means the pullout from weightlessness will be milder as well — 1.5 times as strong as normal gravity rather than 1.8.
• Hawking will be carried from his seat on the plane to an area marked off especially for him, where he will be laid down on a soft head cushion. Two coaches and a nurse will raise Hawking up at the start of each period of weightlessness, and gently bring him down at the end.
• After each float, medical team will check Hawking's blood pressure, cardiac rate and blood oxygen level. Hawking will raise his eyebrows if he feels up to another parabolic rise to weightlessness. If he grimaces, that means he's had enough.
• Diamandis has said that he would count the flight as a success if Hawking flies just one parabola — even though Hawking himself has indicated he'd like to do more. Once Hawking is finished, the plane would return to the landing strip.
• To rehearse the procedures for Thursday's flight, Zero Gravity conducted a practice run on Wednesday, with 14-year-old student Ted Straight standing in for Hawking. Diamandis said the "full-up dress rehearsal" was a success.

Hawking and his team won't be the only ones on the flight: More than two dozen people are on the passenger list, including video game designer Richard Garriott, the son of Skylab astronaut Owen Garriott.

Some of the passengers are on board as the result of a money-raising campaign for the X Prize Foundation, which Diamandis heads, and for several charities serving people with disabilities. Diamandis said about $150,000 had been raised for the charities by selling seats on Wednesday's practice run as well as Thursday's flight.

Additional support was provided by Space Florida, a state agency that promotes Florida's commercial space industry and space-related educational activities; and by the retailer Sharper Image.

Boost for commercial spaceflight
Hawking said he hoped his flight would provide a boost for commercial spaceflight, in line with his oft-expressed belief that humanity's future depended on moving beyond Earth.

"I think that getting a portion of the human race permanently off the planet is imperative for our future as a species. It will be difficult to do this with the slow, expensive and risk-averse nature of government space programs," Hawking told NBC, working in a veiled reference to NASA. "We need to engage the entrepreneurial engine that has reduced the cost of everything from airline tickets to personal computers."

He said tourism could represent a future mass market for space-oriented services, "and zero-gravity flights are the first, most affordable step in that direction."

"I am hopeful that if we can engage this mass market, the cost of spaceflight will drop," Hawking said, "and we will be able to gain access to the resources of space, and also spread humanity beyond just the earth."

MSNBC.com science editor Alan Boyle is in Florida with a team from NBC News to cover Hawking's flight on Thursday. Look for updates throughout the day on Cosmic Log as well as full reports in MSNBC.com's Space News section, on NBC's "Nightly News" and the TODAY show.

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