Burning of Solid Propellants

Solid propellants may be classified as monopropellants or composite propellants. Monopropellants are substances in which the fuel and oxidizer are both contained within the same molecule or at least in a single phase. These materials may either burn slowly at subsonic rates or may decompose rapidly in detonation. Depending on the use to which this type of material is put, it may be classified either as propellant or high explosive. In general, useful monopropellants are difficult to detonate. The typical example of a monopropellant is the so-called double-base propellant. This substance consists of nitrocellulose which has been colloidized by nitroglycerine along with various minor constituents which have been added to 

The crystalline inorganic monopropellants decompose directly from the solid to the vapor phase and are approximately described by the above mentioned theoretical work, in spite of the fact that the gas phase processes are simplified. However, the double-base propellants and other organic materials liquefy before vaporizing. In their combustion, so-called foam and fizz zones occur before the vapor phase processes. Much work has been done attempting to apply the conservation equations to the series of processes. This work forms the basis for the summary by Geckler (G3). It is the viewpoint of this author that too many parameters are determined empirically in this application of the theory, so that useful extrapolations are not possible. One must admire the manipulative skill of the early workers in this field and also their determination to formulate a complete theory. When and if the rate parameters become available, a useful theory will be developed with the aid of this early work. 

A theory for calculation of burning rates for composite propellants is even more difficult to devise because of the intermediate mixing process necessary. Recent experimental work has led to a semitheoretical description of the structure of composite propellant flames (A2, C5, S7, S8). It is possible to vaporize each of the ingredients of a composite propellant by the application of a heat flux. Experimentally it is possible to measure 

7 References to the earlier literature may be found in the relevant papers of the Symposium, on Combustion, 9th, Cornell Unix., Ithaca, N.Y., 1962, published by Academic Press, 1963. 

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Razdan, M. K., and Kuo, K. K., Erosive Burning of Solid Propellants, Eundamen-tals of Solid-Propellant Combustion, Chapter 10, Vol. 90, Progress in Astronautics and Aeronautics, AlAA (Eds. ... 

STEINZ AND summerfield Burning of Solid Propellants From Equation 6 and the perfect gas law we obtain ... 

The propulsion assembly of a rocket or -> Missile. The driving force can be produced by burning liquid fuels in liquid oxidizers (liquid oxygen, nitric acid, or other oxidants such as liquid fluorine), by burning of solid propellants (-> Solid Propellant Rockets), by burning solid fuels in liquid oxidizers (-> Hybrids), or by catalytic decomposition of endothermal compounds (-> Hydrazine-, - Aerozim, - Aurol). 

Although the most recent studies of erosive burning [102]-[110] have helped greatly to improve our understanding of the process, the theoretical problems remain difficult. Even in laminar boundary-layer flows, erosive burning of solid propellants presents one of the more challenging problems because simplifications achievable for nonpremixed combustion (Chapter... 

A. G. Smith, A Theory of Oscillatory Burning of Solid Propellants Assuming a Constant Surface Temperature, in Solid Propellant Rocket Research, vol. 1 of Progress in Astronautics and Rocketry, M. Summerfield, ed.. New York Academic Press, 1960, 375-392. 

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