Charles Simonyi made history today as the first space tourist—that is, not a professional astronaut, cosmonaut, or taikonaut—to visit the final frontier twice. The Hungarian-born software billionaire, 60, made his first foray into space in 2007 when he paid $25 million to visit the International Space Station (ISS). He blasted off again earlier today aboard a Soyuz spacecraft launched from a Russian space base in Kazakhstan. The price tag for his latest space adventure: $35 million.

Simonyi is slated to spend 12 days in space, most of it aboard the ISS, before returning on April 7. While on the ISS, he’ll conduct some science experiments designed to study the influence of zero gravity on lower back pain and osteoporosis, as well as the effects of spaceborne radiation, all hazards of spaceflight.  

(Speaking of hazards, hopefully the ISS won’t have to play dodge ball with more orbiting debris while hosting its citizen space traveler: On March 16, station operators considered evasively moving the ISS to avoid flotsam making a close pass, and on March 12 the crew hid out in a Soyuz escape pod during a separate near miss.)

Besides his amateur astronauting, Simonyi has a full-time gig as president and CEO of a software company called Intentional Software in Bellevue, Wash., near his home in Seattle. He made much of his fortune developing programs such as Word and Excel for Microsoft.

Think the $60 million he plunked down for his space trips was a lot? Space Adventures, the Virginia-based company that has arranged for Simonyi and other space tourists to venture aloft, is selling a ticket for a future orbital spin around the moon for a cool $100 million.

You can follow Simonyi on his voyage from his Web site. He has been up there 10 hours now, and counting.