The history of the U.S. space program can be rather neatly divided into two distinct periods. The first, which begins with the launch of Sputnik in 1957 and runs through the end of Project Apollo in 1972, is sometimes referred to as the “golden age” of space exploration. This period was characterized not only by its impressive scientific and technical successes but also by the fact that it possessed a highly supportive social, economic, and political environment. Buoyed by fears and rumors of Soviet achievements in space, the National Aeronautics and Space Administration (NASA) of the 1950s and 1960s usually had little trouble securing an annual budget sufficient to maintain an ambitious set of projects (both manned and unmanned) that stretched from near-earth orbit to the outer reaches of the solar system.