Will Whitehorn, president of the world’s first spaceliner Virgin Galactic, will retire from that role in January.

He will be replaced by George T. Whitesides, a former NASA chief of staff, who was also appointed as Virgin Galactic’s first full-time chief executive earlier this year.

Whitehorn is leaving the company to "concentrate on other business interests," a press release said.

He is the only president that Virgin Galactic has ever had, having accepted the position when the company was formed in 2004. Whitehorn was responsible for leading the company through its design and investment phase -- a crucial time in getting the business off the ground.

He helped the company secure millions in funding for the production of its spacecraft. Both the company’s SpaceShipTwo and WhiteKnightTwo vehicles are now undergoing flight testing at the Mojave Air and Space Port.

Instead of trying to launch a rocket directly into space, the WhiteKnight carrier craft, which resembles a flying catamaran, would lift SpaceShipTwo to an altitude of 50,000 feet. At that point, SpaceShipTwo -- carrying six paying passengers and two pilots -- would separate and blast off to about 325,000 feet, or 60 miles, above the Earth's surface.

At that suborbital altitude, passengers experience weightlessness and see the curvature of the Earth.

The price for the experience? $200,000.

Virgin Galactic, started by British billionaire Richard Branson, has taken reservations and deposits from about 500 people. Virgin Galactic hopes to have routine suborbital flights from Spaceport America in New Mexico as early as 2012.

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-- W.J. Hennigan

Photo: Virgin Galactic's WhiteKnightTwo and SpaceShipTwo on the tarmac at Mojave Air and Space Port. Credit: Virgin Galactic/Mark Greenberg