"I have some nervousness and some anxiety — I am not a professional astronaut," Shuttleworth, 28, said as he sat beside his two crew mates, Russian cosmonaut Yuri Gidzenko and Italian Air Force pilot Roberto Vittori.
The three are scheduled to blast off from Baikonur at 2:26 a.m. EDT Thursday. If all goes well, the cramped capsule will dock at an Earth-facing port on the international space station's Zarya module around 4 a.m. Saturday.
The three-man crew is headed to the International Space Station to deliver the Soyuz capsule that they are riding in. A Soyuz is always kept docked at the space station as a lifeboat. Every six months, it is replaced.
The 161-foot rocket, adorned with the crew's three national flags, is expected to reach the space station by Friday.
The official position of the South African Internet tycoon on the Soyuz TM-34 spacecraft is "flight participant." He is paying $20 million to the Russian Space Agency — a sum paid in installments that will be complete only at the end of the 10-day mission, known as "Marco Polo."
In a phone interview with CBS Space Correspondent Bill Harwood, Shuttleworth talked about what he expected Thursday.
"The launch obviously is going to be dramatic," he told Harwood. "It's 526 seconds of high explosives, a controlled explosion, 40 meters below me. I don't think there's any way that that cannot be a complete adrenalin rush."
"It's going to be hard to stay focused and to make sure we do everything we've been trained to do because the sheer exhilaration getting up there is going to be extraordinary. The Soyuz is apparently quite a ride. So I'm looking forward to that."
"We are ready. We are sure of ourselves and our hardware," said flight commander Gidzenko, who is the only one of the three men with space experience.
They have spent the past eight months training together at Russia's Star City, outside of Moscow, and a week at NASA's Johnson Space Center in Houston.
Shuttleworth, determined to be more than simply a passenger, has also been trained by a South African scientist to help conduct an experiment on how sheep and mice stem cells react in zero-gravity.
He wore a patch Wednesday on his blue spacesuit bearing the red ribbon symbolizing the fight against AIDS, saying that he hoped some of the experiments will in "some small way" help in the battle.
Shuttleworth is the second paying space tourist to ride to the space station with the Russians. He follows American businessman Dennis Tito, who also reportedly paid $20 million for his voyage last year.
Struggling to keep alive the space program that astonished the world by sending Gagarin into orbit in 1961, the Russians began exploring alternative sources of funding after the breakup of the Soviet Union. In addition to offering seats to paying riders, the Russians have courted Western companies eager for a chance to work in the world's oldest space facility.
"The Russians were near starving, five or 10 years ago it looked like they were all going to disappear, but now Western money has come in and things are looking brighter," said James Oberg, a U.S. expert on the Russian space program.
CBS News Space Consultant William Harwood has covered America's space program full time for more than 15 years, focusing on space shuttle operations, planetary exploration and astronomy. Based at the Kennedy Space Center in Florida, Harwood provides up-to-the-minute space reports for CBS News and regularly contributes to Spaceflight Now and The Washington Post.