in production, one in development, and one in advanced design and component developments 73 . Although DOD people were studying long-range needs for new and higher thrust rated engines, this did not solve ABMA's problem of the moment. This meant that ABMA had to "make do" with the then present NAA engine and suggest modifications to suit the JUPITER missile. Modifications included such items as thrust governing and throttling. As to the method of propulsion system operation, the main 150,000-pound-thrust engine used LOX and kerosene. The thrust chamber was of tubular wall-type  construction, with a self-impinging fuel injector and a regenerative cooling system. Gimballing the engine, which was coupled to hydraulic actuators, permitted missile control in pitch and yaw. There were several engine subsystems. One of these was the propellant feed system that delivered the propellant from the tanks to the thrust unit by means of valves and a turbopump. Also, the propulsion contained a lub oil system to lubricate the moving parts. A pneumatic pressure system was used to operate the valves, and a hydraulic system operated the gimballing unit 74 . In the first stages of development, the vernier engine of the propulsion system was fueled mainly with hydrogen peroxide—90 per cent— and a 10 per cent  catalyst; but, starting with the firing of JUPITER AM-7 on 27 August 1958, a solid propellant engine was adopted. The vernier unit consisted of an engine case that _____________________________

73. Study, Liquid Rkt Engine Dev Prog, 19 Jul 56, Hist Off files. 74. JUP Dev Plan, FY 58, 29 Sep 56. 74. JUP Dev Plan, FY 58, 29 Sep 56