Google co-founder books £18million seat on first tourist flight to International Space Station

Mr Brin will pay around £18million to go on the tour run by the Space Adventure company according to the CEO Eric Anderson.

At a news conference in New York, Anderson announced the creation of an Orbital Mission Explorers Circle of members who will each contribute £2.5million to help finance the company's first private mission to the space station.

Google co-founder Sergey Brin, (centre), as he trains in zero gravity in airspace above northern California, earlier this year

Previously Space Adventures has bought seats on Russian space agency missions to the orbiting International Space Station.

It now plans to build its own Soyuz rocket for private missions that could start as soon as the second half of 2011.

Richard Garriott, Executive Produver of NCSoft, answers questions at a news conference

Anderson said the company aims to send one mission a year to the space station, with two clients on each flight.

Brin, 34, and Larry Page, 35, made history in their twenties when they set up the Google search engine and are now billionaires.

Brin was born in Moscow but his mathematician parents emigrated to the United States when he was six-years-old.

The £2.5million down payment gives members first option on a seat on the mission.

Anderson said he was looking for five more wealthy people to be founder members of the Explorers Circle.

But he said private space exploration should not be just for the very rich. His company offers zero-gravity flights that cost under £2,000 and would like to give away a seat on an orbital space flight in a lottery or competition.

Anderson said: "We've talked to television companies about reality-type shows, we've talked to lotteries, we've talked to sponsors ... I am confident that that will happen at some point in the future, maybe in time for a 2011 mission, maybe afterwards."

While the United States only flies professional astronauts, specially trained tourists and other space travellers have been able to fly to the station aboard Russian Soyuz spacecraft.

So far four U.S. citizens and a South African have travelled to the International Space Station.

Richard Garriott, a computer game developer and son of a former NASA astronaut, will be the next client to visit the space station in October, paying £18million.

A space tourism company plans to send people to the International Space Station

Garriott, who has spent most of the past six months in Russia training for his trip, said he had hundreds of thousands of dollars of contracts from pharmaceutical companies to take protein crystals into space.

Microgravity is believed to enhance crystal formation, which can be used in development of new drugs. He said he believed such commercial ventures could cover the cost of future space trips entirely.

"I'm already thinking about my second trip to space," he said.

Anderson said Brin, who was not present, could choose to fly on the 2011 mission or on one of the subsequent private missions, depending on his schedule.

"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," Brin said in a statement.

Asked how he felt about Brin's space ambitions, Google Chief Executive Eric Schmidt would only say: "I'm not going."

Google's latest quarterly filing noted that if the company were to lose the services of Brin or other senior members of the management team, it "could seriously harm our business."