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Heppenheimer looks back at the shuttle's technical antecedents such as the X-15 rocket plane and rocket booster technologies, and illuminates the principal personalities involved in the space shuttle decision and their motivations. He traces NASA's evolving programme goals, the technical calculations, political maneuvering, and fiscal constraints, and explains the myriad designs that preceded the shuttle concept. In closing, he looks in detail at the circumstances leading to the politically charged development decision of 1972.