Winklevoss twins use bitcoin to pay for space trip with Richard Branson's Virgin

Virgin Galactic, a US offshoot of Sir Richard's London-based Virgin Group, is selling rides on its SpaceShipTwo for $250,000.

The twins are not the first to sign up for Virgin Galactic using bitcoins, but it is the highest-profile flight booking to date using the currency. Last November, Sir Richard announced that a flight attendant from Hawaii had become the first person to pay for a seat with bitcoins.

Sir Richard previously wrote a blog entitled Bitcoins in Space, revealing that he is "fascinated" by the virtual currency.

"I have invested in some bitcoins myself, and find it fascinating how a whole new global currency has been created," he wrote. "Bitcoins aren’t yet formally recognised by governments as a currency but with some regulation I hope that it will become more widely accepted... The days of carrying cash and coins could soon be over."

Bitcoin, a digital currency that is traded on a peer-to-peer network independent of central control, has seen its value soar in the past year as it gains attention from growing numbers of investors, entrepreneurs and regulators.

But the virtual currency's struggle for legitimacy has been shaken by recent debacles, including the collapse last week of Tokyo-based Mt Gox, once the world's dominant bitcoin exchange.

Few major retailers have begun accepting payment in bitcoins, and critics say the currency's high volatility makes it unsuitable for everyday transactions.

The six-passenger, two-pilot SpaceShipTwo is hauled into the air by a twin-hull carrier jet and then released.

The upcoming flights are designed to reach altitudes of more than 65 miles (100 km) above Earth, high enough to see the curvature of the planet set against the blackness of space.

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