n the early 1950s, a convergence of interests between the National Advisory Committee for Aeronautics (NACA) and the US military led to the launch of one of the most audacious projects in the history of aviation - the X-15. At that time Scott Crossfield had barely scraped past Mach in the Douglas D-558-II Skyrocket and it would be three years before the Bell X-2 set an altitude record of 126,000 feet - yet NACA's specification called for a plane capable of exceeding Mach 6 and flying outside the sensible atmosphere. To many, it seemed an impossible dream.
Proposals were put forward by Bell, Douglas, Republic and North American, the latter operating under the considerable disadvantage of having never built a hypersonic aircraft of any description, unlike Bell and Douglas, both of which had extensive experience in this specialist area. However, the strength of North American's suit was that it had built the F-100 Super Sabre, which was the first operational aircraft to be supersonic in level flight, and it was in the last stages of designing the Mach 3 Navajo cruise missile.
As history relates, although North American actually withdrew its tender at one stage, it went on to win the competition and began what would eventually total more than 2,000,000 man-hours of design work on the new plane, first metal being cut in September 1956 on a hull which was to be powered by a 57,000 pound static thrust rocket engine. The rapidity of the design process belies the huge technical challenge the project posed, ranging from choosing an alloy which could withstand the phenomenal heating to which the hull would be subjected, to solving the problems of controlling an aircraft that had to be flown outside the atmosphere.
Simulators were extensively used during the hull development, one of the challenges these early systems helped to solve being how the re-entry should be flown, and the use of these systems made a major contribution to safety throughout the entire X-15 flight research program. It is a sobering thought that a minimum spec system for FS2004 is many, many times more powerful than the computers which were used to control those X-15 flights which were among the earliest ventures man made into space.
More here...