The X-20 Dyna-Soar was designed to provide a piloted maneuverable vehicle for conducting flight research in the hypersonic and flight regime.
The X-20 was the final outgrowth of concepts that had begun with Eugen Sänger in 1928 and progressed through the Bell BoMi and RoBo concepts of the 1950s. At some points during its development, the Dyna-Soar was intended to be a quasi-operational system.
Although the X-20 never progressed beyond the preliminary construction stage, it effectively served as a testbed for a variety of advanced technologies that contributed enormously to various follow-on projects, including the Space Shuttle. In addition, numerous subsystems designed for Dyna-Soar found their way into later X-15 flight research.
The X-20 program was cancelled before the first vehicle was completed. Most of the subsystems manufactured for the uncompleted vehicle were used for various ground tests. Very few vehicles have contributed more to the science of very high-speed flight — especially vehicles that were never actually built.