Showing papers on "Burn rate (chemistry) published in 1972"

Low pressure ballistic system

Abstract: A system for launching a relatively low velocity projectile, which system generates a low pressure propelling gas supply. The propelling gas supply is generated by burning a propellant comprising a small percentage of a primary explosive intimately mixed with a finely divided fuel-oxidizer mixture. The burning rate of the propellant is slower than the detonation rate of the primary explosive, and the propellant sustains burning and generates gas at a rate which is independent of temperature and pressure.

Solid propellant burning rate during a pressure transient

Abstract: It is well known that the burning rate of a solid propellant during a rapid pressure excursion is not given by the steady state relation, r = apn, but instead is generally a function of the pressure change rate, the pressure magnitude change, and properties of the propellant. An approximate but explicit relation for the non-steady burning rate as a function of these parameters is derived and compared with other treatments. Use of a current model for composite propellant combustion is made (Krier, et al., 1968). Discussion of the applicability of such explicit equations to predict burning extinction as a function of the pressure decay rate is also included.

Base drag reduction

Abstract: Means for reducing or eliminating the base drag of a rocket motor is provided by selected configurations of a drag reducing propellant. The drag reducing propellant is a slow burning propellant which is positioned within a rocket motor and burned to provide gases for relieving the partial vacuum experienced after completion of the boost or sustain propellant burning phase. At the end of the burning phase no gases are being ejected from the rocket nozzle. But the drag reducing propellant compensates for this condition by being a source for continued gas ejection whereby the partial vacuum is relieved and the base drag effect of a rocket motor is reduced or eliminated. The drag reducing propellant is tailored and configured for use in combination with a rocket motor having an end burning, start perforated, or cylindrical propellant grain. In an alternate design, the drag reducing propellant is employed in combination with a rocket motor where it is positioned between the rocket nozzle and the rocket shroud. When employed in this design, the drag reducing propellant is independent of the pressure inside the rocket motor case, a distinct advantage for certain combinations.

Ignition of solid propellants

Abstract: At present, the study of solid-propellant ignition is of particular interest owing to the adoption of hybrid motors [1–3]. The status of experimental and theoretical research in this field can be evaluated on the basis of the rather extensive survey of American papers in [2]. It is noteworthy that a common deficiency in available references is the absence of exact ignition criteria; in most cases the propellant is assumed to have ignited when its surface temperature reaches a prescribed level (gasification temperature), or when the rate at which the temperature increases with time at the propellant surface is sufficiently high. Exact criteria for this rate, however, are not given. In this article, we present ignition criteria for solid propellants and these are based on a diffusion-burning model. It is shown that for a diffusion flame to exist above the propellant surface, two conditions must be satisfied simultaneously: 1) the propellant surface temperature must equal the gasification temperature for that propellant and 2) the temperature gradient at the surface must be smaller than some value which depends on the kinetics of the chemical reaction in the diffusion flame and on the rate of oxidizer input to the propellant surface during burning. Two ignition techniques are examined as examples: ignition by hot gases or radiant heat flow and ignition by means of an active film which reacts with a cold oxidizer; the film is applied to the propellant surface prior to ignition.

Numerical Analysis of Nonlinear Longitudinal Combustion Instability in Metalized Propellant Solid Rocket Motors. Volume I. Analysis and Results

Abstract: : The present report is part of a two volume set which describes a nonlinear solid rocket motor instability analysis and computer program. The primary objective of the current effort was the development and solution of a nonlinear analytical longitudinal instability model, which would allow all of the various governing phenomena to be accounted for in a coupled manner. The two primary elements of the current instability analysis are a method of characteristics solution of the two phase flow in the combustion chamber of the motor, and a coupled calculation of a transient burning rate. It is based on an extension of the most popular, linear, harmonic combustion response model. The current method allows the calculation of propellant burning response to a pressure disturbance of arbitrary waveform, for all time, including the period immediately following the initiation of the disturbance. The analysis also includes a model for velocity coupled response. The nonlinear effects of velocity coupling on the growth of pressure waves in a combustion chamber can be computed.

Catalytic behavior in composite solid propellant combustion

Abstract: : The report describes experiments and theoretical analysis concerned with sandwich combustion. The ingredients used in the experiment are compacted polycrystalline ammonium perchlorate as the oxidizer, hydroxyl terminated polybutadiene as the binder and four catalysts: Harshaw catalyst CU-0202, Fe2O3, ferrocene, and iron blue. The pressure range studied is 600-2000 psia. The experimental techniques used are cinephotomacrography for sample observation during burning and burn rate determination, scanning electron microscopy for observation of quenched samples, and electron microprobing for an exploratory study of surface compositon. A theoretical solution to a simple sandwich deflagration problem is attained. The probable sites of catalytic activity are determined, results are compared with actual propellant experience, and the analysis is used to clarify experimental results. (Author)

An Analytical Investigation of the Caseless Rocket Motor

Abstract: : An analysis of a caseless and nozzleless solid-propellant rocket motor employing the external burning concept was made. Performance was calculated for a wide range of supersonic flight conditions. The results of the analysis show that acceptable values of specific impulse and thrust are possible for propellants having sufficiently high burn rates in a base burning configuration. The effect of boattailing with combustion along the boattail was investigated and found to degrade the performance. An analysis of a thin planar airfoil with external burning occurring on part of its surface was also made. The specific lift, that is the ratio of the lifting force to propellant flow rate. was found to be an order of magnitude lower than the corresponding specific lift for a conventional airfoil propelled by a turbine engine. (Author)