Virgin Galactic set to launch rocket ship that will take tourists to the edge of space

Sir Richard Branson's Virgin Galactic is preparing to launch the rocket ship that will take tourists to the edge of space.

Virgin Space Ship Unity is undergoing final checks in preparation for a test flight from Mojave, California, that could take it far higher than before and a big step closer to turning the dream of commercial space tourism into reality.

Chief executive George Whitesides said: "It's a day that we've been waiting for for a long time," speaking at Mojave Air and Space Port.

Mr Whitesides said VSS Unity would try to fly higher than 50 miles, which Virgin Galactic considers the boundary of space because it is used by the US Air Force and other US agencies.

Test pilots Mark "Forger" Stucky and Rick "CJ" Sturckow are scheduled to be at the controls.

Virgin Galactic officials emphasised that it would be a test flight and there could be an array of reasons why it could end short of its goal or be aborted altogether.

"Risk is a valuable part of forward progress and intrinsic in risk is sometimes you have good days and sometimes you have bad days," Mr Whitesides said. "I think we can authentically say that we're obviously hoping for a good day tomorrow but the risk of a not good day is still possible."

Reaching the threshold of space would demonstrate significant progress towards the start of commercial flights that were promised more than a decade ago.

Virgin Galactic's development of its spaceship took longer than expected and endured a setback when the first experimental craft broke apart during a 2014 test flight, killing the co-pilot.

More than 600 people have committed up to 250,000 dollars (£200,000) for rides in the six-passenger rocket, which is about the size of an executive jet.

They have been waiting years to feel the kick of the rocket's ignition, a near-vertical high-speed ascent into the blackness of space and several minutes of weightlessness with a view of the Earth far below.

The spaceship is not launched from the ground but is carried beneath a special plane to an altitude near 50,000feet. It then detaches from the plane, ignites its rocket engine and climbs.