Response Of Propellant Research Articles

Dynamic effects on ignitability limits of solidpropellants subjected to radiative heating

The dynamic response of a solid propellant to a rapidly varying radiation flux comprises a problem representative of the general class of transient responses of heterogeneous flames to rapid disturbances. In the present study, the response of double-base propellants to roughly square-wave radiation pulses is examined. It is found that, when such pulses are used to ignite propellants, they may in some cases produce a flame which persists for whatever duration the pulse persists, but which extinguishes as soon as the pulse stops. This tendency to extinction upon deradiation is found to be lessened by increased pressure or increased time interval for reducing the flux to zero. This extinction response upon deradiation is not limited to the ignition situation; it is shown experimentally that a steadily burning propellant can be extinguished by a radiation pulse of appropriate magnitude, duration, and speed of cut-off. It is proposed that this dynamic extinction behavior results from an imbalance in the heat fluxes to and from the burning surface during deradiation. A mathematical model of this phenomenon, deriving from the nonsteady burning approach of Zeldovich, is solved and shown to predict quite well the same type of behavior as that found experimentally.

Evaluation of thermal-ignition models from hot-wire ignition tests

The ignition response of several composite solid propellants was measured by use of embedded, electrically heated wires having diameters from 25.6 to 1024 μ. Reproducible ignition times ranging from 0.02 to 40 see were observed. A comparison of these measured ignition times for the larger wires with the predictions of the thermal ignition model indicates excellent agreement between measurement and predictions when the parameters for the single-interfacial-reaction model are those which best describe data for the ignition of exposed flat surfaces. Ignition data from the fine-wire tests indicate the presence of a distributed reaction, and these data are used to evaluate the characteristies of this distributed reaction.

Three-dimensional Impact Response Of Solid Propellant Based On A Viscoelastic Model

The three-dimensional dynamic response of a solid propellant rocket motor subjected to projectile or fragment impact is modelled on a viscoelastic basis with complex modulus. The propellant is in a form of thick hollow cylinder housed in an elastic metal casing simply supported at both ends. The three-dimensional consistent higher-order theory is employed in that 3-D boundary conditions and interface continuity of transverse stresses are emphasized on the exterior and interior. Dynamic displacement fields are assumed as a combination of Legendre polynomials and double Fourier series in cylindrical coordinates. Upon impact by a high velocity projectile or fragment, hot spots are found theoretically for the highest pressure and temperature via the three-dimensional stresses along with the traditional equation of state. Predicted ignition, growth zone and detonation compared well reasonably with existing literature.

Ignition response of solid propellants to radiation and conduction

Experimental measurements were carried out on the ignition response of solid propellants to radiative and to conductive heat transfer. The propellants were composed of ammonium perchlorate and different organic binders. The experimental results were interpreted in terms of a model including exothermic chemical reaction in the condensed phase of the propellant as the trigger for ignition. The heat release rates in the surface-coupled reactions were measured independently. A comparison of the ignition data demonstrated different reponse of the propellants to the two modes of ignition associated with the temperature/time history of the material.

Finite-amplitude axial instability in solid-rocket combustion

The driving mechanism of high-amplitude axial-mode solid-rocket combustion instability, that appears as an oscillating shock wave in the combustion chamber, is considered. The pressure pulse associated with the traveling shock wave induces a burning rate-perturbation as the wave passes over the propellant surface. Of primary interest, in this paper is the interaction mechanism through which this burning-rate response supports the shock wave, causing combustion instability. A simplified analysis of this complex interaction provides a first-order estimate of the minimum combustion response that will drive the oscillating shock wave. Empolying a theoretical treatment of the propellant response, the, analysis predicts the limits of the stable operating regime on the basis of two criteria: (1) the traveling wave must oscillate at a frequency near the predicted resonant response frequency of the propellant and (2) the predicted response amplitude at the resonant frequency must exceed the theoretical minimum value required to drive the shock wave. The theoretical treatment is compared with data from motors 15 in., 23 in., 40 in., and 82 in. in length, using a range of propellants, and is shown to provide a consistent explanation of the experimental observations.

Effect of surface reactions on the solid propellant response function.

Surface coupled heat release effect on oscillatory amplitude of pressure coupled response in solid propellant

Effect of surface reactions on acoustic response of solid propellants.

Effect of surface reactions on acoustic response of solid propellants.

Effect of pressure and velocity coupling on low-frequency instability.

6 Penner, S.'S. and Fuhs, A. E., On generalized scaling procedures for liquid-fuel rocket engines/' Combust. Flame 1, 229-240 (1957). 7 Hart, R. W. and McClure, F. T., instability: acoustic interaction with a burning propellant surface/' J. Chem. Phys.30, 1501-1514 (1959). 8 Summerfield, M., Sutherland, G. S., Webb, M. J., Taback, H. J., and Paul, K. P., Burning mechanism of ammonium per chlorate propellants/' ARS Progress in Astronautics and Rocketry: Solid Rocket Research, edited by M. Summerfield (Academic Press Inc., New York, I960), Vol. 1, pp. 141-182. 9 Morrell, G. and Priem, R. J., Recent aspects of rocket combustion research/' Proceedings of the NASA University Conference on the Science and Technology of Space Exploration, NASA Sp-11, Vol. II, pp. 37-42 (December 1962). 10 Frank-Kamenetsky, D. A., Temperature distribution in reaction vessel, and stationary theory of thermal explosion. J. Phys. Chem. Soc. Russia 13, 738-755 (1939). 11 Clemmow, D. M. and Humngton, J. D., An extension of the theories of thermal explosion and its application to the oscillatory burning of explosives/' Rocket Propulsion Dept., Ministry of Supply, London, TN RPD 128 (September 1955). 12 Rice, O. K. and Ginell, R., The theory of the burning of double base powders, J. Phys. Colloid Chem. 54, 910 (1950). 13 Capener, E. L., Dickinson, L. A., and Marxman, G. A., Propellant combustion phenomena during rapid depressurization, Stanford Research Institute, Contract NAS7-389, Annual Rept. 1 (September 1966); also Marxman, G. A., Theoretical model of solid propellant response in combustion instability and extinction, Proceedings of the Third ICRPG Combustion Conference (to be published); also AIAA J. (submitted for publication). 14 Denison, M. R. and Baum, E., A simplified model of unstable burning solid propellants, ARS J. 31, 1112 (1961). 15 Novikov, S. S. and Ryazantsev, Yu. S., Toward a theory of stability of powder combustion, Zh. Prikl. Mekh. Tekh. Fiz. (Russian), No. 1, 57-61 (1965). 16 Zel'dovich, Ya. B., K teorii goreniya porokhov i veryvchatykh veshchestv (On the theory of combustion of powders and explosives), J. Exptl. Theoret. Phys. 12, 498 (1942).

Theoretical study of a solid propellant having a heterogeneous surface reaction I—acoustic response, low and intermediate frequencies

Theoretical calculations of the acoustic response of solid propellants based on thermal models of pyrolysis are in unsatisfactory accord with experiments on JPN propellant. Thus, one is led to consider other theoretical models of propellant burning. This paper presents a study of a simple, highly idealized solid propellant for which collisions of a gas phase constituent with the surface may result in a surface gasification reaction. The model leads to reasonable agreement with currently available experimental data for both steady state and acoustic response properties of JPN propellant.

Thermomechanical response studies of solid propellants subjected to cyclic and random loading.

An analytical and experimental study of the interaction between heating and dynamic response of solid propellants is presented. Emphasis is placed on the evaluation of linear viscoelastic theory in predicting thermomechanical behavior and also on the nature of the interaction between displacement, stress, and temperature response. For analytical and experimental simplicity, the investigation deals with a specimen that is loaded in simple shear and insulated such that heat flow is restricted to occur normal to the direction of shear. Two types of loading are considered: constant displacement amplitude and inertial driving by means of an attached mass. The response to both harmonic and stationary random loading processes is determined analytically, and it is shown for both cases that large temperature increases may occur in the specimen with attached mass because of thermal instabilities. Good agreement between experiment and theory was obtained over most of the range of strain and frequency, but some stress-strain nonlinearity and gradual propellant degradation were observed.

Effects of thermal radiation on the acoustic response of solid propellants

Abstract : Theoretical calculations are given for the propellant response function when thermal radiation of the burnt gases is taken into account. Under the assumption that the gas radiates as a gray body, it is found that radiation effects may significantly alter the response function at low frequencies for the low propellant burning rates which are commonly found at low pressures. Thus, this mechanism may offer a partial explanation of the fact that experimental values for the response function at low frequencies and low burning rates tend to be larger than is expected from existing theories. The method of calculation is based on a second order perturbation scheme where the perturbation parameter is a measure of the ratio of energy transfer by radiation to convective energy transfer. (Author)

Theory of acoustic instability in solid-propellant rocket combustion

This paper reviews the problem of unstable combustion in solid-propellant rockets, with special emphasis on the status of theory and, where possible, the comparison between theory and experiment. The manifestation of the problem in terms of the appearance of periodic pressure waves, and the consequences which ensue when these reach sufficient amplitude are first outlined. A rocket motor is then viewed as an acoustic cavity. The possible sources and sinks of acoustic energy are enumerated, and the gain-loss balance is discussed with respect to self-excited oscillation, and also with respect to influences of outside perturbations on a stable cavity which has a high Q . The quantitative approach to the representation of, the various gain-loss mechanisms in the domain of linear stability theory is then reviewed. Particular emphasis is put on the modifications to ordinary acoustic stability theory which are required because of the existence of a mean flow field. The contributions to linear instability of the response of the burning propellant, both to the pressure and velocity components of the acoustic field, are then discussed. Attention is then turned to the fundamental theory of the interaction of the burning surface with a pressure oscillation. The linear (small perturbation) theory of the acoustic response of this region is reviewed in terms of the analytic models, and postulates that have been made, and their theoretical results. Some qualitative comparison with experiment is made. The remaining part of the paper is then devoted to nonlinear effects. The theory of nonlinear instability in such systems is first reviewed to the extent that it exists. Then, the consequences of oscillation of finite amplitude arising from nonlinear effects are discussed. Under this heading, amplitude limitation in unstable cavities, wave distortion, and changes in the mean properties of the system are considered. In the alst category, changes in the mean burning rate due to nonlinear pressure response and due to the erosion associated with the velocity component of the acoustic field are noted. The induction of vortex flow by acoustic streaming, as described by Swithenbank and Sotter and by Flandro, is discussed with particular reference to its consequences in producing increased erosion, decreased nozzle flow, and angular torques. Brief mention is also made of the effects of the amplitude oscillations on combustion, efficiency and the composition of the product gases.

Interaction between Sound and Flow in Acoustic Cavities: Mass, Momentum, and Energy Considerations

This paper investigates requirements for neutral acoustic stability in cavities with a transpiring wall where there is a mean flow in the absence of acoustic disturbances. The growth rates of the acoustic fields are also considered. The method of calculation utilizes time averages of the mass, momentum, and energy-conservation equations to second order in the acoustic-field quantities. It is found that growth rate and neutral stability may be expressed in terms of only first-order quantities. The results are shown to be in agreement with those calculated from first-order admittance considerations, but differ, in general, from those of Dyer, who uses a method of calculation similar to the present paper. The resolution of this conflict is discussed. The effect of mean flow is often of considerable importance, and the extent to which flow tends to excite or damp the acoustic field is related to mode configuration and flow-field geometry. Application to the problem of determining the acoustic response of burning rocket propellants is discussed.

A Simplified Model of Unstable Burning in Solid Propellants

An analysis of the surface temperature, and hence mass flux, response of a solid propellant to a disturbance in gas pressure has been developed. Time lags in the gas phase are neglected while transient heat conduction in the solid is considered. The results are obtained by perturbing the conservation equations in both the gas phase and the solid phase. Stability conditions are obtained in terms of a few dimensionless parameters which depend upon the steady state conditions.