Despite a devastated economy, entrepreneur and software mogul Charles Simonyi is on his second trip to the International Space Station—a trip that's costing the co-founder of Intentional Software Corporation and former Microsoft exec a cool $35 million.

He's not the only entrepreneur to embark on space tourism as a hobby: he joins Dennis Tito, founder, chairman, and CEO of Wilshire Associates; Mark Shuttleworth, founder of the Ubuntu Project; and video game pioneer Richard Garriot in the growing wave of successful businessmen to travel into space with Space Adventures, a company leading the private spaceflight industry.

In fact, all six of the space tourists to travel to the International Space Station since Space Adventures' maiden voyage in 2001 have been wealthy entrepreneurs.

"Entrepreneurs are forward-thinking," says Eric Anderson, CEO of Space Adventures. "And they're willing to take a little risk for great reward."

Space Adventures itself is a pioneer; since its start in 1998, the company has paved the way for the privatization of space travel. They offer launch tours, zero-gravity flights, spaceflight training, and a $102,000 suborbital spaceflight.

The most popular offering among the world's wealthiest entrepreneurs, pointed out Anderson, is the orbital spaceflight to the International Space Station.

The trips cost up to $25 million—but those who have made the journey say that the price is worth the life-changing experience.