This final scientific report reviews the progress from May 1979 to December 1982 on a program to study various aspects of solid propellant combustion phenomena. The original program included three specific areas of study: Diffusion flame analysis; Kinetic mechanisms of double base propellants; Interaction effects of distributed particle combustion in acoustic environments. The diffusion flame is the controlling mechanism in the combustion of composite propellants. Therefore, a thorough understanding of diffusion flames is prerequisite to understanding solid propellant combustion, and was the objective of one task of the program. The second task of the program was motivated by the desire to better understand transient combustion such as occurs in DDT and combustion instability. Double base propellant combustion is dominated by the flame kinetics which appear to be more easily studied than those of composite propellants. The final task of the program was aimed at understanding the effect of stability additives on combustion instability. During the final year of the contract, work on the first two tasks was discontinued and all work was concentrated on the third task. Interim reports covering the initial work have been published in December 1980 and February 1982. This report summarizes the work performed during the final phase of the contract covering the time from October 1981 through December 1982. Keywords: Solid rocket propellants.

Experimental and analytical investigations were conducted to understand the ignition and nonsteady burning processes that occur at and near the propellant surface, to determine the connection between the ignitability of a propellant and its other nonsteady combustion characteristics, to quantify the peculiarities of radiative ignition, and to develop a means of ranking propellant ignitability. As a result of these investigations, radiative ignition processes have been explained for a wide variety of propellant and test conditions. The stability properties of heterogeneous combustion waves were considered for linear and nonlinear situations. Nonlinear (large disturbances) solid propellant stability boundaries can be immediately defined from the knowledge of the associated restoring function. The restoring function is a property strictly dependent on the nature of the solid propellant.

This third edition of the classic on the thermochemical aspects of the combustion of propellants and explosives is completely revised and updated and now includes a section on green propellants and offers an up-to-date view of the thermochemical aspects of combustion and corresponding applications. Clearly structured, the first half of the book presents an introduction to pyrodynamics, describing fundamental aspects of the combustion of energetic materials, while the second part highlights applications of energetic materials, such as propellants, explosives and pyrolants, with a focus on the phenomena occurring in rocket motors. Finally, an appendix gives a brief overview of the fundamentals of aerodynamics and heat transfer, which is a prerequisite for the study of pyrodynamics. A detailed reference for readers interested in rocketry or explosives technology.

Solid Propellant Rocket Research

A one-dimensional theoretical model, incorporating the Noble-Abel dense gas law, has been developed to describe the transient model combustion phenomena inside a propellant crack. The theoretical model can be used to predict wave phenomena, heat transfer from the gas to the propellant surface and associated thermal penetration, flame propagation, and resultant pressurization at various locations along the propellant cavity. Calculations made with the current theoretical model revealed that the internal pressurization rate, pressure gradient, and flame velocity in propellant cracks (for which gases can penetrate) decrease as: the gap width increases, the rocket chamber pressurization rate decreases, and the propellant gasification temperature increases. Additionally, the predicted flame spreading was found to decelerate in a region near the crack tip; this phenomena has been experimentally observed by others.