At an aircraft hangar deep in the Mojave Desert this morning, the space tourism company Virgin Galactic unveiled one of the crafts that will boost paying customers up to the edge of space. Called the "WhiteKnight Two" by British tycoon Richard Branson, the vehicle will act as a mothership by flying to 48,000 feet with a smaller spacecraft slung between its twin fuselages. Then the spacecraft, SpaceShip Two, will detach and fire its rocket engines to take the six passengers the rest of the way up.