Non-steady burning of solid propellants was investigated both theoretically and experimentally, with attention to combustion instability, transient burning during motor ignition, and extinction by depressurization. The theory is based on a one-dimensional model of the combustion zone consisting of a thin gaseous flame and a solid heat up zone. The non-steady gaseous flame behavior is deduced from experimental steady burning characteristics; the response of the solid phase is described by the time-dependent Fourier equation. Solutions were obtained for dynamic burning rate, flame temperature, and burnt gas entropy under different pressure variations; two methods were employed. First, the equations were linearized and solved by standard techniques. Then, to observe nonlinear effects, solutions were obtained by digital computer for prescribed pressure variations. One significant result is that a propellant with a large heat evolution at the surface is intrinsically unstable under dynamic conditions even though a steady-state solution exists. Another interesting result is that the gas entropy amplitude and phase depend critically on the frequency of pressure oscillation and that either near-isentropic or near-isothermal oscillations may be observable. Experiments with an oscillating combustion chamber and with a special combustor equipped for sudden pressurization tend to support the latter conclusion. (Author).

Despite significant developments and widespread theoretical and practical interest in the area of Solid-Propellant Nonsteady Combustion for the last fifty years, a comprehensive and authoritative text on the subject has not been available. Theory of Solid-Propellant Nonsteady Combustion fills this gap by summarizing theoretical approaches to the problem within the framework of the Zeldovich-Novozhilov (ZN-) theory. This book contains equations governing unsteady combustion and applies them systematically to a wide range of problems of practical interest. Theory conclusions are validated, as much as possible, against available experimental data. Theory of Solid-Propellant Nonsteady Combustion provides an accurate up-to-date account and perspectives on the subject and is also accompanied by a website hosting solutions to problems in the book.

Solid Propellant Rocket Research

The overall objective of the research program has been to study the non-steady burning characteristics of solid rocket propellants, both experimentally and theoretically, to establish a basis for avoiding combustion instability in rocket motors and for predicting thrust transients during motor ignition and extinction. A new non-steady burning model for composite propellants was formulated in which the key element, the non-steady heat feedback law from the gaseous flame, was shown to be a function of the instantaneous pressure and burning rate. Solutions to this model showed that burning stability is largely determined by the exothermicity of reactions in the immediate neighborhood of the propellant surface and by the sensitivity of burning rate to surface temperature. The predictions of the model were generally confirmed by T-motor and rapid pressurization experiments. The non-steady burning model was also used to analyze L-star combustion instability in rocket motors and to demonstrate the feasibility of a novel mechanism for suppression of combustion instability by aluminum addition to a propellant. (Author).

Despite significant developments and widespread theoretical and practical interest in the area of Solid-Propellant Nonsteady Combustion for the last fifty years, a comprehensive and authoritative text on the subject has not been available. Theory of Solid-Propellant Nonsteady Combustion fills this gap by summarizing theoretical approaches to the problem within the framework of the Zeldovich-Novozhilov (ZN-) theory. This book contains equations governing unsteady combustion and applies them systematically to a wide range of problems of practical interest. Theory conclusions are validated, as much as possible, against available experimental data. Theory of Solid-Propellant Nonsteady Combustion provides an accurate up-to-date account and perspectives on the subject and is also accompanied by a website hosting solutions to problems in the book.

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.