The Viking rocket series of sounding rockets were designed and built by the Glenn L. Martin Company (now Lockheed-Martin) under the direction of the U.S. Naval Research Laboratory (NRL). Twelve Viking rockets flew from 1949 to 1955.
After World War II, the United States experimented with captured German V-2 rockets as part of the Hermes project. Based on these experiments the U.S. decided in 1946 to develop its own large liquid-fueled rocket design, to be called Neptune but changed to Viking. The intent was both to provide an independent U.S. capability in rocketry, to continue the Hermes project after the V-2's were expended, and to provide a vehicle better suited to scientific research. The Navy, in particular, needed a vehicle to study the atmosphere and learn how to predict bad weather which would affect the fleet.
The V-2 would tumble in the rare atmosphere at high altitudes. Having been designed as a weapon, the V-2 carried a large payload, approximately one ton of high explosive. This was more than was considered necessary for the scientific instrument payload of a high-altitude research rocket, but in the case of the V-2, used for research, most of the payload was lead ballast required for stable flight, limiting the potential speed and altitude that could be reached with the smaller payloads typically needed for early scientific investigations.
The Naval Research Laboratory (NRL), partly at the instigation of the American Rocket Society (ARS), chose to build the advanced sounding rocket. Milton Rosen, head of the Viking project, credits rocket pioneer Robert Goddard, the ARS, the California Institute of Technology and the V-2 for the "profound influence" they had on the design of the rocket.
The Viking was the most advanced, large, liquid-fueled rocket being developed in the U.S. at the time.
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 92.5 kilonewtons (20,800 lbf) (sea level) and 110.5 kilonewtons (24,800 lbf) (vacuum) of thrust. Isp was 179.6 seconds (1.761 km/s) and 214.5 seconds (2.104 km/s) respectively, with a mission time of 103s. 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 gimbals were controlled by gyroscopic inertial reference; this type of guidance system was invented by Robert Goddard, who had partial success with it before World War II intervened. Roll control was by use of the turbopump exhaust to power 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 shedding more weight.
Vikings 1 through 7 were slightly longer (about 15 m, 49 ft) than the V-2, but with a straight cylindrical body only 32 in (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 in (114 cm), while the length was reduced to 13 m (42 ft), destroying 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.
All except Viking 4 were flown from White Sands, New Mexico.
The first launch, of Viking 1, on 3 May 1949 came after a very prolonged and trying period of ground firing tests, and attained an altitude of 50 miles (80 km). The altitude was limited by a premature engine cut-off, eventually traced to steam leakage from the turbine casing.
Viking 2, flown 6 September 1949, also suffered early engine cut-off for the same reason as Viking 1; it reached only 32 miles (51 km). (Subsequent engines had the turbine casing halves welded rather than bolted together, solving the problem.)
Viking 3, 9 February 1950, suffered from instability in a redesigned guidance system, and had to be cut off by ground command when it threatened to fly outside the range. Altitude was again only 50 miles (80 km).
Viking 4, on 11 May 1950, launched from the deck of the USS Norton Sound near the Equator, reached a peak altitude of 105 miles (169 km), almost the maximum possible for the payload flown, in a nearly perfect flight. Guidance system was reverted to that of Vikings 1 and 2.
Viking 5, 21 November 1950 reached 108 miles (174 km). Engine thrust was about 5% low, or altitude would have been slightly higher.
Viking 6, 11 December 1950, suffered catastrophic failure of the stabilizing fins late in powered flight, with loss of attitude control, and associated very large drag. Altitude was therefore only 40 miles (64 km).
Viking 7, 7 August 1951, reached 136 miles (219 km) altitude to beat the old V-2 record for a single-stage rocket. This was the highest and last flight of the original airframe design.
Viking 8, 6 June 1952, first rocket of improved airframe design, lost when it broke loose during static testing, and flew to 4 miles (6.4 km) before ground commanded cut-off.
Viking 9, 15 December 1952, reached 136 miles (219 km) altitude in the first successful flight of the improved airframe design.
Viking 10. The engine exploded on first launch attempt 30 June 1953. The rocket was rebuilt and was flown successfully 7 May 1954, to 136 miles (219 km).
Viking 11 rose to 158 miles (254 km) on 24 May 1954, an altitude record for a Western single-stage rocket up to that time. Earth photography and re-entry vehicle test.
Viking 12 was flown 4 February 1955, for re-entry vehicle test, photography, and atmospheric research. It reached 143 miles (230 km).
Two additional Viking airframes, similar to Vikings 9 through 12, were flown as test vehicles for Project Vanguard. Both were launched from Cape Canaveral, in 1956 and 1957, and were designated Vanguard TV0 and Vanguard TV1.
While the underlying motivation for the Viking Project clearly had a national defense component, since it was a US Navy program, it nevertheless established a number of early space exploration landmarks, some technological and some scientific.
Peaceful space travel and space exploration were clearly important objectives that energized many of the higher level instigators even of the German V-2 rocket program, which was funded by the German Army entirely for military purposes. Viking was probably the most ambitious program up to its time which had significant objectives that were essentially scientific, accompanied by a desire to explore and advance rocket technology for more ambitious peaceful space exploration goals, such as artificial earth satellites.
Technological advances pioneered by Viking included the following:
- An essentially all-aluminum airframe, with a mass ratio (fueled mass to empty vehicle mass) of about 5:1 for the improved (Viking 8 and later) model. This was a significant improvement over the V-2, which was largely constructed of steel. The altitude records achieved by Viking, for a single-stage rocket, were mostly the result of its light-weight structure.
- Thrust vector control by gimbaling the rocket motor, as opposed to the graphite vanes used by the German V-2 and the U.S. Army Redstone missiles. This method of control has become standard since, both for reliability and efficiency reasons.
- Control of the vehicle's orientation, after fuel exhaustion of the main engine, by small auxiliary jets, permitting programmed pointing of scientific instruments, etc.
- Extensive radio telemetry for both engineering and scientific data, which greatly reduced the number of test flights needed before useful results were obtained.
Among its scientific achievements, firsts up to their time, were:
- The highest measurement of atmospheric density (by Viking 7).
- The highest measurement of atmospheric winds (Viking 7).
- The first measurements of the atmospheric positive ion composition at high altitude (Viking 10).
- The highest exposures of cosmic-ray emulsions (Vikings 9, 10, and 11).
- The highest altitude photographs of the Earth (Viking 11).
Through the Viking flights, NRL was first to measure temperature, pressure, and winds in the upper atmosphere and electron density in the ionosphere, and to record the ultraviolet spectra of the Sun.
Viking into Vanguard
The success NRL achieved in this series of experiments encouraged laboratory scientists to believe that, with a more powerful engine and the addition of upper stages, the Viking rocket could be made a vehicle capable of launching an earth satellite. This led to NRL's three-stage Project Vanguard vehicle which launched the second US satellite. Two later rockets in the Viking series, Vanguard TV0 (renamed from Viking 13) and TV1, substantially similar to Vikings 8 through 12, were used as suborbital test vehicles during Project Vanguard, before the first Vanguard vehicle became available for test as Vanguard TV2, in the fall of 1957.
- "The Viking Rocket Story", by Milton W. Rosen, Harper & Brothers, NY, 1955. Rosen, the NRL project manager for Viking, describes the project's context, history, design, and includes chapters on all flights through Viking 11, with an outline of basic design issues for large liquid rockets, together with much interesting detail about the countless problems that inevitably arose in such an ambitious and innovative program.
- "Rockets, Missiles, and Space Travel", by Willey Ley, 3rd Edition, Viking Press, New York, 1951, p. 250ff.
- Rosen, p. 28
- "History of Rocketry & Space Travel," revised edition, Wernher von Braun and Frederick I. Ordway III, Thomas Y. Crowell Co., New York, 1969, p. 151
- "U.S. space-rocket liquid propellant engines". www.b14643.de. Retrieved 2015-06-24.
- Winter, Frank H. (1990). "3 — Rockets Enter the Space Age". Rockets Into Space. Harvard University Press. p. 66. Retrieved 2015-06-24.
- Rosen, p. 66
- "Viking". Encyclopedia Astronautica.
- Rosen, Chapter 14
- The National Air and Space Museum contains a full-size cutaway reconstruction of Viking 12, built from original blueprints.
- Begg's aerospace
- Directory of U.S. Military Rockets and Missiles
- NASA sounding rockets, 1958-1968
- Free paper models of viking 7, 10, 13 and 14
- The Robert Goddard Connection with Viking (see Professional Relations)
- 1948 Rocket Will Double V-2's Record July 1947 article on original Neptune Program