The American military is planning a “spaceplane” designed to fly a crack squad of heavily armed marines to trouble spots anywhere in the world within four hours.

At a recent secret meeting at the Pentagon, engineers working on the craft, codenamed Hot Eagle, were told to draw up blueprints for a prototype which generals want to have in the air within 11 years.

Pentagon planners have been encouraged by technical breakthroughs from Burt Rutan, chief designer on Sir Richard Branson’s White Knight spaceship, which is due to begin test flights next year and to carry tourists on suborbital journeys from 2010.

Last week Rutan, 65, who built the first privately funded craft to reach space and won the $10 million X prize for his achievement in 2004, gave his blessing to Hot Eagle, which could be based on White Knight’s technology.

Rutan said it would be an expensive way to transport troops “but it could be done. It is feasible.”

Will Whitehorn, president of Virgin Galactic, which is funding White Knight, recently predicted that it could be used to airlift emergency supplies into disaster zones.

“It could be like Thunderbirds, like International Rescue,” he said. A passenger version would be capable of flying from London to Sydney in four hours.

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