Aerojet's Third Series of Experiments, 1947-1949
 When the Navy renewed Aerojet's contract in mid-1947, the central task was to develop a liquid hydrogen-oxygen rocket engine suitable for a small-scale version of the earth satellite vehicle. The engine was to be in the thrust range of 9-13 kilonewtons (2000-3000 lb), have a minimum exhaust velocity of 2972 meters per second, and be capable of operating for 60 seconds. Maximum mass was specified as 34 kilograms. Propellants were to be supplied to the thrust chamber by a turbopump. Other tasks, which were concerned with drawings and operating instructions, indicated that the Navy intended to be prepared for development of a small-scale experimental vehicle. The contract also called for several analyses and a design study of a rocket engine of 37.8 kilonewtons (85 000 lb thrust), apparently for the Martin minimum-sized vehicle. Although there was little reason for optimism, the Bureau of Aeronautics was keeping its options open.
The Aerojet work with hydrogen from mid-1947 to mid-1949 was the climax of five years of effort along three major lines: (1) the supplying of liquid hydrogen, (2) turbopump development, and (3) thrust chamber development.32 These will be described separately.