the primary purpose of this relatively small and simple booster system was to save money—by allowing numerous test flights to qualify various solutions to the myriad problems associated with the development of manned space flight, especially the problem of escaping from an explosion at or during launch. capsule aerodynamics under actual reentry conditions was another primary concern. to gain this kind of experience as soon as possible, its designers had to keep the clustered booster simple in concept; it should use solid fuel and existing proven equipment whenever possible, and should be free of any electronic guidance and control systems.