SOLID PROPELLANT COMBUSTION MECHANISM STUDIES.
Progress rept. no. 18, 1 Oct-31 Dec 64,
PRINCETON UNIV NJ DEPT OF AEROSPACE AND MECHANICAL SCIENCES
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In general, at sufficiently low pressure, quenching takes place. However, it has been observed that AP polysulfide propellants do not quench but display instead a transition, as the pressure is lowered, from the normal mode of combustion exhibiting a visible flame to one where no flame is visible and a porous ash remains as a combustion product. Quenching is ordinarily explained by a heat loss effect, but the occurrence of this unquenched, flameless burning seemed to require some deeper explanation. It is suggested that the continuation of burning at low pressures is due to the inhibition of the loss of heat to the surroundings by the retained ash. An analysis based on this hypothesis shows that, even without the insulating effect of the ash, steady burning is possible all the way down to zero pressure, provided the gasification process at the solid surface is exothermic, and provided the acitivation energy for this process is small. Conversely, for endothermic processes or for large activation energies, quenching will occur when there is no insulating ash. Thus, the study of low pressure burning opens up the possibility of measuring the heat of gasification at the surface and the activation energy for the gasification process. On the experimental side, before such deductions are possible, it becomes important to verify these predictions. Author