The billionaire software engineer behind Microsoft applications Word and Excel will become the fifth space tourist when he boards a Russian spaceship in two weeks bound for the International Space Station.

Charles Simonyi, 58, speaks during a news conference in Star City outside Moscow, on Thursday, about his upcoming visit to the space station aboard a Russian Soyuz spacecraft.
(Sergey Ponomarev/Associated Press)

But while Charles Simonyi, 58, had to pay over $23 million to join a select group of private citizens who have visited the station, his crew mates insisted he will not be a spectator.

"He will work responsibly and with full dedication," said Russian cosmonaut Oleg Kotov at a press conference on Thursday. "If you look at the program of his flight, he practically doesn't have spare time." 

He will travel to the space station with cosmonauts Kotov and Fyodor Yurchikhin aboard a Soyuz TMA-10 capsule scheduled to launch on Saturday, April 7.

While on board, Simonyi is expected to perform simpler tasks as part of the crew and participate in a number of experiments, including measuring radiation levels and studying biological organisms inside the space station.

He will return to Earth 11 days later with two current space station crew members — Russian cosmonaut Mikhail Tyurin and Spanish-born U.S. astronaut Miguel Lopez-Alegria. Kotov and Yurchikhin will remain aboard the space station with U.S. astronaut Sunita Williams.

The Hungarian-born Simonyi joined Microsoft in 1981, where he developed the world's most commonly used word processing and spreadsheet programs, Word and Excel. He left Microsoft in 2002 to found Intentional Software Corp.

He is the fifth person to travel to the station aboard Russian rockets in trips arranged by U.S.-based Space Adventures Ltd., joining American businessmen Dennis Tito and Gregory Olsen, South African technology entrepreneur Mark Shuttleworth and Iranian-American entrepreneur Anousheh Ansari.

Like the other four space tourists, Simonyi had to train for the mission, learning to handle dizziness in space, walk and breathe in the spacesuit and prepare for helicopter rescues in case of a water landing upon the spaceship's return to Earth.

But Simonyi said that after his training he is confident the mission will go smoothly.

"I am nervous about public appearances and press conferences, but I think that about the flight I am not nervous at all," the soft-spoken Simonyi said. "I've learned about the system, and the more I learn, the more sure I am about the backups … and I think it's perfectly safe."

All three members of the current space station crew will have to don their spacesuits next Friday in preparation for the station's new arrivals.

To make for an easier docking procedure, the station crew will have to pilot the last Soyuz spacecraft module from its Earth-facing docking port to a parking spot at the aft end of the station's service module.