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, and a Gemini astronaut is the first to fly it. Tragedy again strikes NASA when the Challenger explodes. Meanwhile, the pioneers of NASA's manned programs lead the way into the modern era of the space-age.