At Heaven's Gate: 50 Years After Humans First Reached Space, What Frontiers Remain?

On April 12, 1961, Soviet cosmonaut Yuri Gagarin did something no human had done before. On board the Vostok 1 spacecraft, Gagarin became the first person in space after rocketing into the sky from a launch site in Kazakhstan for a nearly two-hour flight. What is more, Gagarin became the first human to orbit Earth, a feat that the U.S. would not achieve until its third manned spaceflight, John Glenn's three-orbit flight on Friendship 7, February 20, 1962.

Fifty years later, both the space race—and the Cold War of which it was a part—have come to an end. The Soviet Union is no longer, but the Russian space program has become an invaluable partner to NASA's human spaceflight program. Over the past decade more than a dozen countries, including Russia and the U.S., have sent astronauts to the International Space Station, the longest-serving continuously manned orbital outpost in history. Meanwhile, China has built up a formidable program of its own, sending three manned missions into space since 2003.