Sergey Brin, the co-founder of Google, has put down a $5m deposit for a flight aboard a Russian Soyuz space station.

Mr Brin has signed up with the space tourism company Space Adventures for priority seating on a mission that would orbit the earth.

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Space Adventures, founded 10 years ago in Virginia, has brokered space flights for five rich businessmen to date but Mr Brin - the fifth-richest American, with a net worth of $18.5bn (euro11.5bn, pound 9.1bn) according to Forbes magazine - is likely to be their highest-profile passenger.

A Google search suggests that the chances of disaster on a space flight is about one in 150, compared with one in 2m on a commercial airline.

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According to Google's regulatory filings, Mr Brin is "critical to the overall management of Google" and "the loss of any of our management or key personnel could seriously harm our business". Mr Brin did not address whether the adventure would carry too much risk.

"I am a big believer in the exploration and commercial development of the space frontier and am looking forward to the possibility of going into space," he said in a statement.

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Mr Brin and his co-founder Larry Page have shown a keen interest in space. They have added maps of the moon to their services and have sponsored a $30m prize to the team that is first to land a privately funded probe on the moon. Google is also co-operating on research with Nasa, the US space agency, and is building a complex on Nasa-owned land.

Eric Anderson, Space Adventures chief executive, told a news conference in New York that Mr Brin was a founding member of its Orbital Mission Explorers' Circle, where six members would have priority seating on space flights. It has reached a deal with the Russian space agency to buy a Soyuz flight in 2011 for a private mission.