Gravity's a drag after the exhilaration of experiencing weightlessness in high-speed mid-air manoeuvres.

It was, Dave Mackay assured me, one of the most stunning experiences of his life. And from the man who recently ignited the rockets on a spaceship as chief test pilot for Sir Richard Branson's Virgin Galactic project, that was an impressive recommendation.

And so taking his advice, here I was on the tarmac at Newark airport in New Jersey, kitted out in my blue flight suit with another 25 passengers, about to embark on a zero gravity journey aboard a Boeing 727 plunging and soaring in 3660m arcs over the North Atlantic.

Nine of my fellow flyers were Virgin Galactic space tourists preparing for their US$200,000 ($232,000) forays into sub-orbit by finding their weightlessness legs in advance.

Among their ranks was Cheryl Howard, the actress whose husband Ron took several zero gravity flights when he was directing the film Apollo 13. Howard had just come along to support his wife before the flight and would be remaining on Earth.


Astronauts, of course, conduct their work in a zero gravity environment thousands of kilometres up in space. But for US$4950, the same sensation can be yours on Zero Gravity Corporation's G-Force One, a modified jet whose pilots induce weightlessness through a series of mid-air manoeuvres called parabolas.

As someone who long ago swore never to ride another rollercoaster, the prospect of motion sickness worried me.

But within an hour I was floating, without any stomach churning discomfort, in the remarkable world of zero gravity as we repeatedly dived before then being pinned to the matted floor by the gravitational force (G force) when we accelerated back up to the top of the arc. Around me, my fellow passengers were pirouetting and somersaulting, not to mention delivering passable impressions of Superman, arm punched out ahead.

I was tumbling and flailing rather than executing elegant acrobatic turns, but the sensation was still one of blissful exhilaration. I managed to catch an apple thrown my way in my mouth, then recovered it by hand as it bobbed around mid-cabin.

The back quarter of the jet was fitted with regular aeroplane seats and we took off buckled up as normal after a regular safety announcement and headed towards clear air space southeast from Newark over the ocean.

The front three-quarters of the cabin has been stripped of fixtures and fittings and the inner walls lined with white padding. When we reached cruising altitude some 480km offshore we were warned to avoid clattering into each other as we came out of the weightless curves and fell back to Earth. We lay back as the pilot pulled the nose of the plane sharply up, our bodies held down on the mat by the pull of 1.8G of acceleration - feeling nearly twice as heavy as our weight on Earth.

Some 3650m later, at 9450m, the plane reached the top of its arc and was pushed into the first dip to create the equivalent of Martian gravity - one third body weight - where one-handed push-ups were a cinch.

The next two parabolas replicated the Moon's gravity as the pilots flew tighter shorter turns at the top of the arc. We took bounding steps in the style of Neil Armstrong after completing one-fingered push-ups, before the plane bottomed out again at 5800m.

And now it was time for the full zero gravity experience as the pilots executed a series of 45 degree-angled arcs up and down, generating 25-30 seconds of weightlessness on each drop.

In scientific terms, the pilots controlled the propulsion and steering of the aircraft in these powered dives so that the drag - or air resistance - was cancelled out, leaving the passengers experiencing weightlessness as if the plane were free-falling in a vacuum.

So here we were, spinning, twirling and bouncing off each other in mid-air, with whoops and shouts of excitement as we floated, turned and tumbled.

With 15 parabolas complete, we returned to our seats for the flight back to Newark. It may sound like a rollercoaster, but what was striking was how smooth the experience had been.

"You just can't describe it," said Howard. "Everything that I anticipated was so much more intense ... when you see what astronauts do, the sensitive work they conduct in weightlessness is unbelievable."

Virgin Galactic is encouraging its customers to take a zero gravity flight or experience weightlessness in a centrifuge so that they are prepared for its space flights, which are expected to start within the next year. Those trips will feature several minutes of weightlessness after the space ship has roared into sub-orbit and before it glides back to Earth at the spaceport in New Mexico.

Esther Dyson, a technology investor who had just completed her "sixth or seventh" Zero-G flight, said: "Weightlessness just feels so natural. It's being back on Earth that doesn't feel right."

Gravity did indeed feel like a drag. As Ron Howard was leaving, he recalled the words mouthed by Kevin Bacon as he sailed past the camera on a zero gravity flight in training for Apollo 13. "Better than sex," was his verdict.