A Russian rocket, carrying the first space tourist, Dennis Tito, has lifted off flawlessly.
The 60-year-old Californian businessman and two cosmonauts are scheduled to dock with the International Space Station on Monday.
A television monitor inside the spaceship showed Mr Tito, in a white spacesuit decorated with an American flag, grinning broadly.
A ground controller asked in Russian-accented English: "How do you feel, Dennis?"
"Khorosho," he replied in Russian. "Great."
At the cosmodrome, Tito's girlfriend Dawn Abraham videotaped the lift-off, then cried as the rocket disappeared from view.
"It's for real. I just can't believe it," she said. "I just want to know if he's OK. That's all that matters."
Mr Tito's 26-year-old son Mike also watched the launch.
"Wow, what an adrenalin rush," he said. "I can imagine what my father must have felt. It felt incredible from here."
Until the eve of the launch, US and Russian space officials had argued behind the scenes about the overlap of the Soyuz rocket launch and the continued docking of US space shuttle Endeavour at the space station.
The eleventh-hour dispute over the timing of the blastoff followed a long wrangle over whether a tourist should go to the space station at all. NASA tried to block the flight, insisting that Mr Tito's presence could jeopardise the work of the ISS crew.
But Russian officials said that Mr Tito, a former rocket engineer who is paying up to $20m (£13m) for the trip, received the equivalent of a professional cosmonaut's training.