Encyclopedia Astronautica

Aerojet Nitric acid/UDMH rocket engine. Bomarc. Out of Production. Launch thrust 159.583 kN. Development begun 1953. Pressure-fed, uncooled, ceramic-lined engine. First flight 1959.

Development begun 1953. The original design was a pressure-fed, uncooled, ceramic-lined engine providing 16,000 kgf for 4 seconds to boost the missile to ramjet ignition velocity. Tests with the original JP-4 kerosene fuel showed a severe combustion instability, which resonated at a multiple of the natural frequency of the engine gimbal, which led to ever-more powerful pulses until the entire missile failed. This led to destruction of an expensive new test stand at Edwards, sorely aggravating the Air Force. The solution was finally found in switching to UDMH fuel.

Application: Bomarc.


Thrust (sl): 159.583 kN (35,876 lbf). Thrust (sl): 16,273 kgf. Propellant Formulation: Nitric acid/Aniline.

AKA: LR59-AJ-1.
Status: Out of Production.
Thrust: 159.58 kN (35,876 lbf).
First Launch: 1946-1957.

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Associated Countries
See also
Associated Launch Vehicles
  • Bomarc USAF Mach 3 ramjet surface-to-air missile; later converted to target missiles and launched from Vandenberg AFB. More...

Associated Manufacturers and Agencies
  • Aerojet American manufacturer of rockets, spacecraft, and rocket engines. Aerojet, Sacramento, CA, USA. More...

Associated Propellants
  • Nitric acid/UDMH Drawing on the German World War II Wasserfall rocket, nitric acid (HNO3) became the early storable oxidiser of choice for missiles and upper stages of the 1950's. To overcome various problems with its use, it was necessary to combine the nitric acid with N2O4 and passivation compounds. These formulae were considered extremely secret at the time. By the late 1950's it was apparent that N2O4 by itself was a better oxidiser. Therefore nitric acid was almost entirely replaced by pure N2O4 in storable liquid fuel rocket engines developed after 1960. Unsymmetrical Dimethylhydrazine ((CH3)2NNH2) became the storable liquid fuel of choice by the mid-1950's. Development of UDMH in the Soviet Union began in 1949. It is used in virtually all storable liquid rocket engines except for some orbital manoeuvring engines in the United States, where MMH has been preferred due to a slightly higher density and performance. More...

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