Thousands of people watched from the ground as the specially-built White Knight jet took off from an airbase in California's Mojave desert carrying SpaceShipOne under its belly.

Mike Melvill, a 62-year-old South African, is at the controls of SpaceShipOne which is aiming to go more than 100 kilometers (60 miles) from the Earth's surface.

The bullet-shaped rocket-plane was developed by Burt Rutan, the 61-year-old chief of the Scaled Composites LLC company, with financing from billionaire Paul Allen, a co-founder of software giant Microsoft. Allen said more than 20 million dollars were put into the project.

The three-tonne rocket-plane will be taken up to an altitude of 15 kilometers (48,000 feet), where it will ignite its rocket engine and begin a vertical rise.

The rocket will burn for about 80 seconds, propelling the craft straight up at a speed of about 3,500 kilometers (2,200 miles) per hour, about three and a half times the speed of sound, to a height of some 50 kilometersfeet) above the planet.

Once the rocket's fuel has been spent, SpaceShipOne will keep going up for about three minutes to reach 104 kilometers (340,000 feet), a height at which it will lose speed like a spent bullet.

During this time, the pilot will feel weightless as do astronauts in space. The zero-gravity effect, lasting three minutes, will continue until SpaceShipOne returns to about 60 kilometers (200,000 feet).

The pilot will gradually take control again and from 80,000 feetkilometers) altitude, the craft will glide for about 17 minutes back to a landing at Edwards Air Base at between 10:30 am and 11:30 am (1730-1830 GMT).

SPACE.WIRE