MOJAVE, Calif. — A test pilot in a stubby rocket plane will try to climb about 100 kilometres above the Mojave Desert and punch through the atmosphere Wednesday in the first stage of a quest to win a $10-million US prize meant to encourage space tourism.

SpaceShipOne, which in June became the first private, manned craft to reach space, was to make two attempts to rocket through the atmosphere in six days, less than half the 14-day span allowed under Ansari X Prize rules. The second flight is set for Oct. 4.

Created by maverick aerospace designer Burt Rutan and funded by Microsoft billionaire Paul G. Allen, SpaceShipOne is poised to take the prize sought by more than two dozen teams around the world.

Its closest competitor, a Canadian team with a balloon-launched rocket, scheduled its first flight for Oct. 2 but then postponed.

The X Prize, funded by the Ansari family of Dallas, was dreamed up nearly a decade ago as an incentive for development of commercial manned rockets that would make space flight a possibility for civilians.

It appears to have achieved that goal even before the first competitive flight.

Richard Branson, the airline mogul and adventurer, announced in London on Monday that his Virgin Group plans to offer passenger flight into space aboard rockets based on the SpaceShipOne design by 2007.

The plan calls for an investment of $108 million US in spaceships and infrastructure for what will be called Virgin Galactic, with fares starting at $208,000 US. The company believes it will fly 3,000 people into space in its first five years.

SpaceShipOne is carried aloft slung beneath the belly of a specially designed jet.

After the mothership climbs to an altitude of some 15,000 metres, the spaceship is released into a glide for a few moments before its rocket motor ignites.

X Prize rules require that a spacecraft be capable of carrying three people, but for the competition it may be flown by a pilot and carry the weight equivalent of two other people.

The exact cost of developing SpaceShipOne has not been disclosed. Allen will only say that he has invested more than $20 million US.