Viking was a series of twelve sounding rockets designed and built by the Glenn L. Martin Company under the direction of the US Naval Research Laboratory (NRL). Designed to supersede the German V-2 as a research vehicle, the Viking was the most advanced large, liquid-fueled rocket developed in the United States in the late 1940s, providing much engineering experience while returning valuable scientific data from the edge of space between 1949 and 1955. After twelve flights, the Viking was adapted into the first stage for the Vanguard satellite launch vehicle, which launched America's second satellite into orbit in 1958.
Origins After World War II, the United States Army experimented with captured German V-2 rockets as part of the Hermes program. The number of V-2s available for all research was limited and Hermes was an Army project. The US Navy had the need to develop advanced missiles for both weapons and research purposes. The US Navy issued a contract 21 August 1946 to the Glenn L. Martin Company for a series of 10 large liquid-fueled rockets. The intent was to provide an independent US capability in rocketry, 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 US 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 20,800 lb (92.5 kN) of thrust at sea level, and 24,800 lb (110.5 kN) in a vacuum. The specific impulse was 179.6 s (1.761 km/s) and 214.5 s (2.104 km/s) 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. XLR-10-RM-2 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 controlled by gyroscopic inertial reference; this type of guidance system was invented by Robert H. Goddard amongst others, who had partial success with it before World War II intervened. Roll control was by use of the turbopump exhaust to power reaction control system (RCS) jets on the fins. Compressed gas jets stabilized the vehicle after the main power cutoff. Similar devices are now extensively used in large, steerable rockets and in space vehicles. Another improvement was that initially the alcohol tank, and later the LOX tank also, were built integral with the outer skin, saving weight. The structure was also largely aluminum, as opposed to steel used in the V-2, thus reducing weight. Vikings 1 through 7 were about 49 ft (15 m) long, slightly longer than the V-2, but with a straight cylindrical body only 32 inches (81 cm) in diameter, making the rocket quite slender. They had fairly large fins similar to those on the V-2. Vikings 8 through 14 were built with an enlarged airframe of improved design. The diameter was increased to 45 inches (114 cm), while the length was reduced to 43 ft (13 m), altering the missile's "pencil shape". The fins were made much smaller and triangular. The added diameter meant more fuel and more weight, but the "mass ratio", of fueled to empty mass, was improved to about 5:1, a record for the time.
Flight history
First model RTV-N-12 (Vikings 1-7)
Viking 1
On 3 May 1949, after two static firings (11 March and 25 April), the first Viking rocket took off from White Sands Missile Range in New Mexico. Its engine fired for 55 seconds, ten seconds short of the hoped-for maximum of 65, but the rocket flew on course and reached an altitude of 51 mi (82 km)—deemed a good start to the program.
Viking 2 Viking 2, launched four months later, also suffered from premature engine cutoff and only made it to 33 mi (53 km). Both had suffered from leaks in their turbines, the intense heat of the steam breaking the seal of the turbine casing. The solution was to weld the casing shut, there being no reason to access the turbine wheel again after a flight.
Viking 3 The fix worked, and Viking 3, launched 9 February 1950 and incorporating an integrated (rather than discrete) oxygen tank, reached 50 mi (80 km) and could have gone higher. However, after 34 seconds of accurately guided flight, the rocket veered westward and threatened to leave the launch range. Range safety triggered charges in the rocket to separate the nose from the engine, and both tumbled to the ground, where they were recovered for analysis.
Viking 4
With successful tests of the engine and guidance systems conducted (though not on the same missions), Viking was deemed ready for its most ambitious test: shipboard launch from the deck of the USS Norton Sound. Viking 4 was identical to Viking 3, the first of the series not incorporate design changes to fix a problem on a previous Viking.} On 10 May 1950, from a site in the Pacific Ocean between Jarvis Island and Kiritimati, the fourth Viking became the only Viking rocket sounding rocket ever launched from a sea-going vessel. The flight was perfect, reaching 106.4 mi (171.2 km), more than double that reached by Vikings 1 and 3.
Viking 5 Viking 5, launched 21 November 1950 carried a vast array of photomultiplier tubes, ionization chambers and Geiger counters, for the detection of radiation across a wide variety of energies and types. The rocket also carried two movie cameras to take high altitude film of the Earth all the way to its peak height of 108 miles (174 km) as well as Pirani gauges to measure air densities in the upper atmosphere.
Viking 6
Viking 6, launched 11 December, carried a much lighter payload, but its experiments included a battery of custom built pressure gauges. The rocket underperformed, however, only reaching a maximum altitude of 40 miles (64 km).
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