NASA selected North American Aviation's Rocketdyne Division in 1960 to develop the high-energy cryogenic J-2 upper stage engine for the Saturn V moon rocket. The J-2, a high-performance, upper stage propulsion system, used liquid hydrogen and liquid oxygen propellants for a maximum thrust of 225,000 pounds. It was the first manned booster engine to use liquid hydrogen as a propellant and the first large booster engine designed to be restarted multiple times during a mission. It was used for both the second and third stages of the Saturn V moon rocket. A modified J-2 engine later was used to demonstrate principles that lead to the development of Rocketdyne's Space Shuttle Main Engine. The J-2 featured independently driven pumps for both liquid oxygen and liquid hydrogen, a gas generator to supply hot gas to two turbines running in series, pneumatic and electrical control interlocks, altitude restart capability, and a propellant utilization system. The third stage of the Saturn V was steered by a single J-2 engine that could be moved in flight to steer the stage. The second stage had five J-2 engines arranged in a cluster. The four outboard engines were mounted on a universal joint to provide the vehicle with pitch, yaw, and roll control. The center engine was mounted in a fixed position. ~ http://www.boeing.com/boeing/history/bna/j2engine.page
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