A critical review of recent research on the mechanism of ignition of solid rocket propellants
- Paper ID
1963-121
- author
- company
Guggenheim Laboratories for the Aerospace Propulsion Sciences Department of Aeronautical Engineering Princeton University
- year
1963
- abstract
An understanding of the details of the physical and chemical processes by which a solid propellant rocket motor is brought to a state of steady combustion is obviously of considerable interest to the designer of propellant ignition systems. By such understanding he may, for example, avoid excessive ignition pressures, minimize the weight of an igniter for a given rocket, eliminate excessive ignition delays, program the shape of the ignition transient, or accomplish other desirable objectives. In general, the overall solid rocket; rgnition transient consists of three phases after the igniter itself has begun its action. At first, the products of igniter combustion heat the exposed surfaces of the propellant grain and bring some areas to ignition. As this process continues, there is an interval of so-called flame spreading during which the burning area increases as a consequence of propellant corobustion itself. Finally, after the entire surface is ignited, there is a chamber filling period during which the equilibrium pressure is established. Figures 1 and 2 illustrate the events occurring during these intervals in a schematic manner., In this review attention will be confined to the mechanism Of the process by which the first flame in a solid propellant sample is ignited. Iri a practical situation the energy impulse which leads to the first flame is always complex and dependent on the type of igniter employed. The processes which contribute to the heat transfer include convective heating'by igniter gases, radiation and conduction from incandescent particles, heat liberated by the condensation of metallic vapors, the action of hypergolic materials, and combinations of these and others. In oc^erimehtal studies of solid propellant ignition, one or mote of these processes are used. Such studies have occupied a number of investigators in recent yêàrss  number of experimental techniques varying in form and concept hâve been used to study the ignition of composite and nitrate ester propellants. Both slow and fast ignitiohs have béeri studied, and ignition delays have ranged from 20 seconds down to less than a millisecond. In the experiments which have been conducted, the propellants hàvâ been heated by hot wires, test furnaces of various types* flowing gas streams at elevated temperatures, shock tubes and shock tunnels, highly reactive oxidizing gases, ax'c-image fumades, etc. This review will contain a description of the various theories which have been used to account for the phenomenon of propellant ignition, a discussion of the experimental methods' Which have been applied to this study, and an evaluation of the reported results.