Propellant burning mechanism

J. A. Stein, P. L. Stang, and M. Summerfield, The Burning Mechanism ofMmmonium Perchlorate-Based Composite Propellants, Aerospace and Mechanical Sciences Report 830, Princeton University, N.J., 1969. 

The prediction of burning-rate characteristics, on the other hand, has not been possible. This has caused rocket designers to adopt a trial-and-error approach to the development of specific propellants to meet specific mission requirements. In an effort to reduce the large development effort required for each new propulsion system, considerable basic research effort has been directed toward the definition and quantitative characterization of propellant combustion mechanisms. The ultimate objective of this effort is to provide methods for predicting the burning-rate characteristics of particular propellant formulations. 

The burning mechanism of composite propellants differs from that described above. There is no exothermic reaction which can lead to a self-sustaining fizz zone. Instead, the first process appears to be the softening and breakdown of the organic binder/fuel which surrounds the ammonium perchlorate particles. Particles of propellant become detached and enter the flame. The binder is pyrolysed and the ammonium perchlorate broken down, initially to ammonia and perchloric acid. The main chemical reaction is thus in the gas phase, between the initial dissociation products. 

Summerfield, M., Sutherland, G. S., Webb, W. J., Taback, H. J., and Hall, K. P., The Burning Mechanism of Ammonium Perchlorate Propellants, ARS Progress in Astronautics and Rocketry, Vol. 1, Solid Propellant Rocket Research, Academic Press, New York (1950), pp. 141-182. 

Steinz, J. A., Stang, P. L., and Summer-field, M., The Burning Mechanism of Ammonium Perchlorate-Based Composite Solid Propellants, AMS Report No. 830, Aerospace and Mechanical Sciences,... 

Ishihara, A., and Kubota, N., Erosive Burning Mechanism of Double-Base Propellants, 21 St Symposium (International) on Combustion, The Combustion Institute, Pittsburgh, PA (1986), pp. 1975-1981. 

A. Jaumotte, "Remarks on the Burning Mechanism and Erosive Burning of Ammonium Perchlorate Propellants , Ibid, pp 689-93 G2) G.K. Adams et al, "Combustion of Propellants Based on Ammonium Perchlorate , Ibid, p 693-705 Hj) J.Hershkowitz, F. Schwartz J.V.R. Kaufman, "Combustion of Loose Granular Mixtures of Potassium Perchlorate and Aluminum , Ibid, pp 720-27 H2) L.A. Dickinson et al, "Erosive Burning of Polyurethane Propellants in Rocket Engines , Ibid, pp 754-59 H ) S. Kumagai... 

Very little is known about the burning mechanism of these mixtures. There is a two-temperature theory of propellant combustion [2, 3]. 

The AP-HTPB propellant produces relatively high concentrations of solid carbon and hydrogen chloride (HC1). Though the mass fraction of the fuel components increases as the mass fraction of HTPB increases, the self-sustaining burning of AP-HTPB propellant becomes impossible because of the heat of decomposition becomes too low to maintain its thermal decomposition. On the other hand, the N C-NG propellant burns to generate fuel-rich products even when the mass fraction of NC increases. However, the mechanical properties of NC-NG propellant become poor. Furthermore, the burning rate of AP-HTPB and NC-NG propellants becomes low and the pressure exponent also becomes too low for their use as ducted rocket propellants. 

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