Stephen Hawking felt free from his wheelchair for the first time in four decades Thursday, joyously soaring through a zero-gravity flight aimed at opening space travel to everyone.

Four physicians, two nurses, two coaches and two dozen other well-wishers surrounded him during his journey — the type of training flight astronauts take when preparing to work in the weightless space environment.

Hawking, who suffers from ALS — also known as Lou Gehrig’s disease — cannot move or speak without help. Yet he floated in the middle of the cabin of a modified 727 during eight parabolas flown over the Atlantic Ocean off Cape Canaveral.

Grinning widely, Hawking was spun in weightless pirouettes, an apple floating beside him as a reminder of Sir Isaac Newton’s Universal Law of Gravity.

The maneuvers put all those aboard into eight separate free falls, rendering them weightless for a half-minute each time.

The medical staff monitored Hawking’s heart rate, blood pressure, breathing and other vitals throughout the course of the two-hour flight.

Two coaches — Zero Gravity founder Peter Diamandis and former shuttle payload specialist Byron Lichtenberg — made certain that Hawking came to rest gently when the aircraft pulled out of each of the nose dives, generating forces 1.5 times normal gravity.

“It was an incredible day,” Diamandis said. “Far beyond our expectations.”

Noah McMahon, chief marketing officer with Zero Gravity, was not surprised Hawking did so well during aircraft maneuvers that often make flyers nauseous. In fact, NASA astronauts have labeled zero-gravity aircraft “vomit comets.”

“You know, he’s a pretty strong guy. He would have done more had we let him,” McMahon said.

“Six parabolas really was the intended cutoff point,” said Richard Garriott, son of former NASA astronaut Owen Garriott.

“But he was having so much fun, we went for two more, and then we thought we’d better quit while we’re ahead.”

Hawking said he wanted to make the flight for a variety of reasons, not the least of which is the fact that he believes Earth is headed for disaster and that the humans species will need a new home in the cosmos.

“I believe that life on Earth is at an ever-increasing risk of being wiped out by a disaster such as sudden global warming, nuclear war, a genetically-engineered virus or other dangers,” Hawking said.

“I think the human race has no future if it doesn’t go into space. I therefore want to encourage public interest in space.”