NEW YORK - A select group of rich tourists may be blasting into space within a few years in a craft that looks like a cross between a corporate jet and something out of science fiction.

British billionaire Richard Branson and the aerospace designer Burt Rutan unveiled a model Wednesday of SpaceShipTwo, the vehicle they hope will be able to take passengers about 100 kilometres above Earth for the fun of it, with test flights possibly beginning this year.

"Breathtakingly beautiful,'' was Branson's assessment of the ship, now under construction at a hangar in the Mojave Desert.

Speaking to reporters at the American Museum of Natural History, the pair also showed off a model of the big, four-engine jet that will help launch the craft into space.

The twin-fuselage airplane, called the White Knight Two, will carry SpaceShipTwo high into the sky beneath a single 42-metre wing.

The spacecraft, with short wings, a pair of rotating tails and plenty of portholes, would then separate from the plane and rocket into space -- where as many as six passengers and two crew members could unbuckle themselves for a little while and experience weightlessness and an unparalleled view before gliding back to Earth.

Passengers would get about 4� minutes of zero-gravity time, floating about a cabin roughly the size of a private jet with the floor removed, before buckling themselves back in for the descent. The seats in the craft will lay passengers nearly flat to put less stress on their bodies and give them more room to float while they are in space.

Will Whitehorn, president of Branson's space tourism company, Virgin Galactic, said construction on the White Knight Two is already more than 70 per cent complete.

SpaceShipTwo is about 60 per cent complete, and the company and Rutan's aerospace outfit, Scaled Composites LLC, hopes to begin test flights this summer.

About 200 prospective passengers from 30 countries have made reservations, shelling out $200,000 apiece. Many were in attendance for Wednesday's presentation, including Ken Baxter, 58, of Las Vegas.

"You can't even imagine my excitement,'' said Baxter after seeing the models. A real estate marketing executive, he said he recently completed preflight training that included being subjected to extreme g-forces in a whirling centrifuge and hopes to be in space in a year.

"Yeah, I'm scared,'' he said. "But this is about realizing a childhood dream. Space travel is something I've been thinking about since I read Jules Verne as a kid.''

The primary job for the designers will be confirming that the experimental vehicles are safe. Questions about their safety were highlighted last July, when a tank of nitrous oxide exploded during a routine test of SpaceShipTwo's propellant system.

Three people died in the accident. California occupational safety inspectors fined Scaled Composites $25,870 and said the company hadn't sufficiently trained its workers. Investigators and company engineers are still trying to figure out what went wrong.

"We don't know yet exactly what caused it,'' Rutan said. He added that there was "no question'' the accident is delaying the engine's development but did not comment on the delay would disrupt plans for test flights.

Rutan acknowledged the project has risks but said the spacecraft will be at least as safe as early commercial airlines in the 1920s. By modern standards, that era was not a particularly safe one, but Rutan said SpaceShipTwo would be "hundreds of times safer'' than government-funded space flight.

Branson said he has reserved seats on one of the early flights for his elderly mother and father.

Scaled engineers attending Wednesday's news conference said they would keep many of the technical details of their launching system secret, but they offered a few facts about the craft.

White Knight Two will have about the same wingspan as a Boeing B-29 Superfortress, but, in contrast to the Second World War bomber, both it and SpaceShipTwo are being built entirely from ultra-light materials. Virgin Galactic showed a video of workers lifting big sections of the spacecraft as if they were made of light plastic.

The spacecraft doesn't look like its predecessor, SpaceShipOne, which earned Rutan's team a $10 million prize in 2004 by becoming the first privately built, manned rocket to fly into space twice in two weeks.

SpaceShipOne was big enough to carry only one person and looked like something Flash Gordon would have flown.