One of the most complex instruments ever built, the Hubble Space Telescope is expected to transform our understanding of the Universe. But once it is in orbit NASA discovers a serious problem, a defective main mirror. NASA sends a team of astronauts to fix the problem in its greatest and highest profile mission since the Apollo era. It gives NASA the confidence to begin construction on the International Space Station.

For its first 20 years, NASA launches capsules carrying a maximum of three people. But new requirements for a bigger cargo bay prompt a breakthrough in spacecraft design. The development of the re-usable shuttle leads to a revolutionary approach to space travel. Meanwhile, the pioneers of NASA's manned programs are leading the way into the modern era of the space-age.

Apollo 13 puts the astronauts to the ultimate test, returning a damaged spacecraft back safely to earth. Apollo 17 sends man for the longest mission yet to the surface of the moon, but it's the last lunar mission for generations. Now, it's time for a new phase in the program. Converting an unused Saturn V rocket, NASA launches Skylab, America's first space-station.

The Apollo program is set to achieve the ultimate prize of the Space Race, landing men on the moon. But a fire breaks out in the pressurized capsule of Apollo 1, resulting in the deaths of three beloved astronauts. However, NASA rebounds, launching men into deep space and landing Neil Armstrong and Buzz Aldrin on the moon.

Nine new astronauts arrive at NASA - their mission, to test all the procedures required to land men on the moon and bring them safely back to earth. Each Gemini mission launches two men into space, leading to some of NASA's greatest moments - Ed White's spacewalk, the first orbital rendezvous of Gemini 6 and 7, and Neil Armstrong's first space docking.

NASA selects seven men to become the first astronauts. They're all test pilots, prepared to risk their lives. No one has ever survived a vertical launch on top of a rocket, but it's the only way they know to put an astronaut into earth orbit. NASA and America's first astronauts, the Mercury Seven, are on a journey into the unknown. Six of the men ride into space, each launch taking NASA further forward in their quest to conquer space.