What do you do if you're Sergey Brin, the co-founder of Google, and you've conquered the world?
You go conquer other worlds.
Brin, 34, with an estimated net worth of more than $18 billion, let it be known today that he is investing $5 million in Space Adventures, the Virginia-based company that's arranged flights on Russian Soyuz spacecraft for five wealthy private space travelers.
"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. "Space Adventures helped open the space frontier to private citizens and thus pave the way for the personal spaceflight industry."
Space Adventures was the first company to succeed in the business of space tourism -- making it possible for millionaire enthusiasts to buy available seats from the Russian federal space agency on flights to the International Space Station. In 2001, its first client, the stock market entrepreneur Dennis Tito, spent a week and a half in orbit, and since then four others have followed.
"What we're doing is opening a frontier," said Eric Anderson, the founder of Space Adventures. "This is public participation in opening the final frontier of space."
Anderson has been, in effect, buying empty seats for his clients on Soyuz ferry craft that were already being launched to the space station.
But with the American space shuttles being retired in 2010, the Russian Soyuz may be, for several years, the only way to get space fliers to and from the station. Seats will be harder to come by.
That's where Brin comes in. Space Adventures will now try to charter its own Soyuz flights, starting in 2011. A Russian cosmonaut would be at the controls, but the two other seats onboard would be available to Space Adventures' clients -- for an estimated $35 million each.
"We will be the first company to undertake a private mission to the International Space Station," said Anderson in an interview with ABC News.
Brin is publicly the first investor in the effort. A Google spokesman said it does not necessarily mean that Brin will actually go into orbit, but his $5 million could be used as a down payment. Brin was not present for Anderson's announcement today in New York.
"Private citizens flying to space actually helps the space programs of the world," Anderson said. "It gets people interested, it makes it more real, it's something that all of us can aspire to."
Of course, not everyone can aspire as easily as Brin. At last count, Forbes magazine listed him as the 32nd richest person on this planet.
ABC News' Matt German contributed to this report.