US: A new kind of spacecraft slung from an improbable high flyer could make history today.
SpaceShipOne, carried into the stratosphere by a turbojet-powered sailplane called White Knight, will drop from its mothership, fire its rocket engines and soar to an altitude of more than 100 km on a mixture of rubber and laughing gas.
If all goes well, SS-1 will become the first privately funded passenger-carrying spaceship to break out of the atmosphere and touch the edge of space.
Its pilot will experience weightlessness for up to three minutes before changing the shape of the plane's wings and gliding back to the runway, just one hour and 30 minutes after takeoff.
The project is the brainchild of Mr Burt Rutan, who entered aviation history when he built Voyager, the first jet to make a non-stop voyage around the world. Mr Rutan, backed by the Microsoft co-founder Mr Paul Allen, wants to open the final frontier for a new generation of entrepreneurs and launch a new business: space tourism.
The American Mr Dennis Tito became the planet's first space tourist when he paid the Russians $20 million for a journey to the International Space Station. But so far space holidays have only been for multi-millionaires.
The ambition of Mr Rutan and other would-be pioneers is to open up space to mere millionaires.
Today's flight, watched by thousands of people, will take off from the Mojave desert north of Los Angeles.
It will be a final rehearsal for a formal attempt on the Ansari X prize from New Mexico. This $10 million trophy will be awarded to the first private venture that can take three people to sub-orbital space - which begins at 100 km - and back again. The catch is that the winner must do this twice within a fortnight, using the same spaceplane.