Viking was a series of twelve sounding rockets designed and built by the Glenn L. Martin Company under the direction of the U.S. Naval Research Laboratory (NRL). Designed to supersede the German V-2, the Viking was the most advanced large, liquid-fueled rocket developed in the United States in the late 1940s, returning valuable scientific data from the edge of space between 1949 and 1955. Viking 4, launched in 1950, was the first sounding rocket to be launched from the deck of a ship. After twelve flights, the Viking was adapted into the first stage for the Vanguard rocket, which launched America's second satellite into orbit in 1958. Origins After World War II, the United States experimented with captured German V-2 rockets as part of the Hermes program. Based on these experiments the U.S. issued a contract 21 August 1946 to the Glenn L. Martin Company for a series of ten large liquid-fueled rockets. The intent was to provide an independent U.S. capability in rocketry, to continue the Hermes program after the V-2s were expended, and to provide a vehicle better suited to scientific research. Originally dubbed "Neptune," it was renamed "Viking" in 1947 to avoid confusion with the Lockheed P-2 Neptune The Viking was the most advanced large, liquid-fueled rocket being developed in the U.S. at the time. Design The Viking was roughly half the size, in terms of mass and power, of the V-2. Both were actively guided rockets, fueled with the same propellant (Ethyl alcohol and liquid oxygen), which were fed to a single large pump-fed engine by two turbine-driven pumps. The Reaction Motors XLR10-RM-2 engine was the largest liquid-fueled rocket engine developed in the United States up to that time, producing (sea level) and (vacuum) of thrust. Isp was and respectively, with a mission time of 103 seconds. As was also the case for the V-2, hydrogen peroxide was converted to steam to drive the turbopump that fed fuel and oxidizer into the engine. As its V-2 counterpart, it also was regeneratively cooled. Viking pioneered important innovations over the V-2. One of the most significant for rocketry was the use of a gimbaled thrust chamber which could be swiveled from side to side on two axes for pitch and yaw control, dispensing with the inefficient and somewhat fragile graphite vanes in the engine exhaust used by the V-2. The rotation of the engine on the gimbals was