The chosen few. The six selected to fly Boeing's X-20, five US Air Force pilots and NASA's Milton O.Thompson stand beside a full-size mock-up of the machine, seen here in its final form, complete with 16.000lb thrust manoeuvring rocket engine at the rear. Cancelled on 15 December 1963, after six years of development effort and the expenditure of around $500 million, the X-20 was to fall victim to the Apollo manned ballistic system, that was to cost in excess of $24 billion in the coming years.
Boeing's promising X-20 Dyna-Soar, seen here in an artist's impression of it shedding its cockpit re-entry heat shield preparatory to landing. This single seat orbital aerospace plane provided its pilot with a large measure of manoeuvrability, or cross-range capability, allowing him to select his landing site from over a broad radius, unlike the Gemini and Apollo capsules, whose watery splash-down sites were extremely predictable. In operation, the X-20 would have been a physically small element in a much larger system, with the Dyna-Soar sitting atop and spearheading a Martin Titan III intercontinental ballistic missile, modified to serve as a launch/boost vehicle, designed to be capable of placing the X-20 into low orbit at around Mach 25, or approximately 18.000mph. The first X-20, with its own 16.000lb rocket engine for orbital manoeuvring, was in assembly and was scheduled to make its first orbital flight in mid-1965 when cancelled.