CAPE CANAVERAL, Fla. - Free of his wheelchair and tethered only to heart-rate and blood-pressure monitors, astrophysicist Stephen Hawking yesterday fulfilled a dream of floating weightless on a zero-gravity jet, a step he hopes leads to further space adventures.

"It was amazing," Hawking said after the flight.

The modified jet carrying Hawking, a handful of his physicians and nurses, and dozens of others first flew up to 24,000 feet over the Atlantic Ocean off Florida. Nurses lifted Hawking and carried him to the front of the jet, where they placed him on his back atop a foam pillow.

The plane then climbed to about 32,000 feet and made a parabolic dive back to 24,000 feet, allowing Hawking and the other passengers to experience weightlessness for 25 seconds.

The plane made eight parabolic dips, two during which Hawking made two weightless flips like "a gold-medal gymnast," said Peter Diamandis, chairman of Zero Gravity Corp., which owns the jet.

"We had a wonderful time. It was incredible, far beyond our expectations," Diamandis said.

Hawking, a mathematics professor at the University of Cambridge who has done groundbreaking work on black holes and the origins of the universe, has the paralyzing disease ALS, also known as Lou Gehrig's disease.

The 65-year-old was the first person with a disability to experience the flight by Zero Gravity, which has flown about 2,700 people out of Florida since late 2004 and began offering the flights in Las Vegas this week.

"As you can imagine, I'm very excited," Hawking told reporters before the flight. "I have been wheelchair-bound for almost four decades. The chance to float free in zero-g will be wonderful."

Unable to talk or move his hands and legs, Hawking can only make tiny facial expressions using the muscles around his eyes, eyebrows, cheek and mouth. He uses a computer attached to his wheelchair to talk in a synthesized voice by choosing words on a computer screen through an infrared sensor on a headpiece that detects motion in his cheek.

He raises an eyebrow to signal "yes" and tenses his mouth to the side to indicate "no."

"I want to demonstrate to the public that anybody can participate in this type of weightless experience," he said yesterday.

Hawking's personal physicians were on hand to make sure nothing went wrong. Hawking was attached to heart, blood-pressure and oxygen-measuring monitors during the flight. Medical equipment sufficient for a miniature intensive-care unit also was on board.

"I'm anticipating everything to nothing," Edwin Chilvers, Hawking's personal physician, said before the flight.

Others on board included financial backers of Zero Gravity and passengers who bid a total of $150,000 toward charities.

The jet's interior is padded to protect the weightless fliers and equipped with cameras to record their adventure. Normally, the plane conducts 10 to 15 plunges for its passengers, who pay $3,750 for the ride; the fee was waived for Hawking.

He hopes the zero-gravity flight is a step toward going on a suborbital flight, which may be offered by private space companies by the end of the decade.

"Space, here I come," Hawking said after the flight.