Showing papers on "Burn rate (chemistry) published in 2012"

Solution Combustion Synthesis of Nanosized Copper Chromite and Its Use as a Burn Rate Modifier in Solid Propellants

Abstract: Nano sized copper chromite, which is used as a burn rate accelerator for solid propellants, was synthesized by the solution combustion process using citric acid and glycine as fuel. Pure spinel phase copper chromite (CuCr2O4) was synthesized, and the effect of different ratios of Cu-Cr ions in the initial reactant and various calcination temperatures on the final properties of the material were examined. The reaction time for the synthesis with glycine was lower compared to that with citric acid. The synthesized samples from both fuel cycles were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), BET surface area analysis, and scanning electron microscope (SEM). Commercial copper chromite that is currently used in solid propellant formulation was also characterized by the same techniques. XRD analysis shows that the pure spinel phase compound is formed by calcination at 700 degrees C for glycine fuel cycle and between 750 and 800 degrees C for citric acid cycle. XPS results indicate the variation of the oxidation state of copper in the final compound with a change in the Cu-Cr mole ratio. SEM images confirm the formation of nano size spherical shape particles. The variation of BET surface area with calcination temperature was studied for the solution combusted catalyst. Burn rate evaluation of synthesized catalyst was carried out and compared with the commercial catalyst. The comparison between BET surface area and the burn rate depicts that surface area difference caused the variation in burn rate between samples. The reason behind the reduction in surface area and the required modifications in the process are also described.

Synthesis and Energetic Properties of 4,4′,5,5′‐Tetranitro‐2,2′‐biimidazolate(N4BIM) Salts

Abstract: This paper describes the synthesis and characterization of several salts of 4,4′,5,5′-tetranitro-2,2′-biimidazolate (N4BIM). Each of the salts were characterized chemically, thermally, morphologically, as well as with respect to destructive stimuli (impact, electrostatic discharge, friction, thermal). These salts show promise as propellant ingredient additives, and in particular, the bis-triaminoguanidinium salt of N4BIM displays excellent burn rate and combustion behavior. Our combustion studies have shown that TAGN4BIM displays a fast burning rate and has the lowest pressure dependence exponent yet measured for a triaminoguanidinium salt.

Studies on High Burning Rate Composite Propellant Formulations using TATB as Pressure Index Suppressant

Abstract: High burning rate propellant compositions are generally used in gas generators to eject missile from canister. Because of high burning rate, pressure index of the composition increases during burning. To reduce the pressure index, a high burning rate composite propellant formulations (~20 mm/s) based on AP/HTPB/Al have been prepared by incorporating TATB and studied in detail for viscosity build-up, thermal and mechanical properties, sensitivity as well as burning rate and pressure index (n). The data indicate that there is a decrease in end of mix viscosity on increasing the percentage of TATB. The same trend was also observed with mechanical properties while significant improvement in overall thermal stability was clearly observed. The sensitivity data indicate that impact and friction values show decreasing trend infer better safe to handle. The burn rate data reveal that on addition of TATB from 0.5 to 2% decrease in burning rate was not observed while on addition of further TATB up to 5% and beyond this significant decrease in burning rate was observed. The data on pressure index (n) also reveal that TATB is very effective in reducing the ‘n’ value up to 2% and beyond this ‘n’ value increases close to standard composition. The data on ‘n’ value reveal that it reduces from 0.47 to that of standard composition to 0.36 for the compositions containing TATB up to 2.0% in the pressure range of 60-90 kg/cm2.

Influence of an Electric Field on the Burning Behavior of Solid Fuels and Propellants

Abstract: An experimental study on the effects of an applied external electric field on the combustion behavior of solid fuels and solid propellants has been conducted. In an opposed flow burning configuration, application of an electric field was shown to extinguish a paraffin fuel and gaseous oxygen flame over a broad range of operating conditions. When subjected to the electric field, burning paraffin fuel strands were found to extinguish at various axial locations relative to the exit of the oxidizer gas jet. Extinguishment location was found to be a function of field strength as well as electrode surface area, while changes in polarity did not significantly alter the results. In addition, the combustion behaviors of two composite solid rocket propellants were studied while subjected to an external electric field. Both propellants were based on HTPB/AP combinations, with one propellant containing aluminum and the other being non-aluminized. Application of an electric field to the composite solid rocket propellant strands demonstrated decreases in propellant burning rate under all operating conditions for both propellants including changes in polarity. The flame structure of the aluminized propellant was examined closely as the luminosity, flame length, and flame width varied significantly with field strength and burning location of the strand relative to the electrodes.

Soot burning method for particulate filters

Abstract: Methods and systems are provided for regenerating a particulate filter in an engine exhaust, where burning of soot is initiated by introducing additional oxygen into the exhaust gas upstream of the particulate filter where an exhaust temperature exceeds a threshold, a soot burn rate controlled by adjusting pulsing of the additional oxygen. Further, the pulsing of the additional oxygen is introduced via a high-pressure EGR passage during boosted engine conditions.

Studies on Influence of Testing Parameters on Dynamic and Transient Properties of Composite Solid Rocket Propellants Using Dynamic Mechanical Analyzer

Abstract: Dynamic mechanical analysis is a unique technique that measures the modulus and damping of materiais as they are deformed under periodic stress. Propellants, which are viscoelastic in nature, are subjected to time, temperature, and frequency effects during the analysis to determine their dynamic and transient properties. The choice of parameters during the experiments like temperature, frequency, strain (%), and stress level is very crucial to the results obtained since the propellant behaves differently under different conditions. A series of experiments like strain and temperature ramp/ frequency sweeps, creep, stress relaxation, etc. have been conducted using high burning rate composite propellant (burn rate ~20 mm/s at 7,000 kPa), in order to determine the precise effects of such parameters on the results obtained. The evaluated data revealed that as the temperature increases the storage modulus, loss modulus, and tan delta curves with respect to the frequency shift towards the lower side. Moreover, there is equivalency between the increase in the temperature and the decrease in the frequency, which can be used for the time-temperature superposition principles. Further, in transient tests, the relaxation modulus has been found to decrease when increasing strain levels in the given time range. Also, relaxation modulus versus time curves were found to shift towards the lower side with increasing temperature while creep compliance decreases with the increase in stress and decrease in temperature. The glass transition value of the composite propellant increases when there is an increase in the heating rate.

STUDIES ON THE INFLUENCE OF TESTING PARAMETERS ON DYNAMIC AND TRANSIENT PROPERTIES OF COMPOSITE SOLID ROCKET PROPELLANTS USING A DYNAMIC MECHANICAL ANALYZER doi: 10.5028/jatm.2012.04044012

Abstract: Dynamic mechanical analysis is a unique technique that measures the modulus and damping of materials as they are deformed under periodic stress. Propellants, which are viscoelastic in nature, are subjected to time, temperature, and frequency effects during the analysis to determine their dynamic and transient properties. The choice of parameters during the experiments like temperature, frequency, strain (%), and stress level is very crucial to the results obtained since the propellant behaves differently under different conditions. A series of experiments like strain and temperature ramp/frequency sweeps, creep, stress relaxation, etc. have been conducted using high burning rate composite propellant (burn rate ~20 mm/s at 7,000 kPa), in order to determine the precise effects of such parameters on the results obtained. The evaluated data revealed that as the temperature increases the storage modulus, loss modulus, and tan delta curves with respect to the frequency shift towards the lower side. Moreover, there is equivalency between the increase in the temperature and the decrease in the frequency, which can be used for the time-temperature superposition principles. Further, in transient tests, the relaxation modulus has been found to decrease when increasing strain levels in the given time range. Also, relaxation modulus versus time curves were found to shift towards the lower side with increasing temperature while creep compliance decreases with the increase in stress and decrease in temperature. The glass transition value of the composite propellant increases when there is an increase in the heating rate.

Measurement and Analysis of the Burning Rate of HAN‐Based Liquid Propellants

Abstract: A new device for measuring the linear burning rate of liquid propellants at high pressures is reported. High-pressure environments were generated by the combustion of solid propellants. The coated propellants, which burn progressively, were introduced to maintain the approximate constant-pressure environments. By use of ion probe transducers, measurements were made of the spread velocity of the flame surface, i.e. the apparent linear burning rate of the HAN-based liquid propellant LP1846 (HAN =hydroxylammonium nitrate) was measured quantitatively at pressures from 6 to 28 MPa. The results show that it follows the exponential burning rate law. The burning rate coefficient and exponent were fitted by least-squares methods. Based on the experiment, a simplified model of the linear burning rate of HAN-based liquid propellants at high pressures was developed. The numerical simulation is found to be in good agreement with the experimental data.

Development of a Composite Propellant Formulation with a High Performance Index Using a Pressure Casting Technique

Abstract: There is a continuous demand for high performance composite propellant formulations to meet future requirements. The performance of composite propellant formulations can be enhanced by the addition of energetic oxidizers, like ADN/HNF as well as an energetic binder & a plasticizer. However, on incorporation of energetic ingredients, the composition becomes sensitive, and thus processing, handling and transportation pose a greater threat. Therefore, a moderately high burn rate composition having a burn rate ~ 13-14 mm·s-1 at 7000 kPa was tailored by increasing the solid loading of the propellant from 85.15% to 87.27% with the help of ammonium perchlorate and process aids without affecting the burn rate and mechanical properties. The tailored composition was studied for different properties such as end of mix viscosity, density, mechanical & ballistic properties. The evaluated data reveal that the end of mix viscosity of the tailored composition is higher than the base composition, i.e., 672 Pa·s and 2340 Pa·s at the same temperature; however, this viscosity was castable using a pressure casting technique. The properties of the cured propellant reveal that there is an enhancement of density from 1.74 g·cm-3 to 1.79 g·cm-3 with no other changes in mechanical properties. The performance index of the tailored composition has been increased from 416 to 437, well supported by results of ballistic evaluation motors of 2 kg.

Reaction Rate Analysis for Selected Solid-to-Solid-Reaction Pyrotechnic Compositions

Abstract: ! ! This paper is a continuation of work reported in AIAA-2011-5581. The scope is broadened from ZPP only to cover a wide variety of well-known solid-to-solid pyrotechnic compositions including PP based compositions such as B/KClO4, Al/KClO4, Fe/KClO4 and W/KClO4; and metal/metal-oxide compositions such as Al/Fe2O3, Zr/Fe2O3 and Ti/CuO. Also included are many hypothetical case-study compositions and several new compositions recently examined in nano-composition research (" Al/CuO, Al/MoO3 and Al/Bi2O3). Main features from previous model are retained including a liquid phase oxidizer, free oxygen atoms, formation of an intermediate metal monoxide via an extraction process and a uniform spherical fuel particle diameter at 2-#m. The fuel atom extraction rate is calculated by using the previously established kinetics formulation, with additional methods for estimating the oxidization activation energy. Linear reaction propagation rates are calculated by heat transfer analysis using the cubic unit cell concept. Calculated rates span 0.032 cm/s to 2.28 cm/ms, in agreement with rates typically observed in these compositions. The model can be scaled to predict D -1 dependence for the linear burn rate where D is the average particle diameter. Methods for estimating the effects of non-stoichiometric conditions and the thickness of the liquid oxidizer layer at the reaction front are provided. Several new conceptualization required for the analysis are explored regarding the correlation between enthalpy of formation and the chemical bond energy, universal features of the heat capacity, thermal conductivity, and diffusivity at elevated temperatures.

Chapter 10 – In Situ Burning: An Update

Abstract: In situ burning is recognized as a viable alternative for cleaning up oil spills on land and water. When performed under the right conditions, in situ burning can rapidly reduce the volume of spilled oil and eliminate the need to collect, store, transport, and dispose of recovered oil. In situ burning can shorten the response time to an oil spill, thus reducing the chances that the oil will spread on the water surface or penetrate further into land, thereby aiding in environmental protection. This chapter contains a compilation of information about in situ burning of oil spills and includes the scientific aspects of the burning process and its effects, and practical information about the procedures to be followed and equipment required for carrying out an in situ burn. Ignition is easy for volatile oils and is more difficult for heavier oils, which require a primer such as diesel fuel for sufficient heat. If not enough vapors are produced, the fire will either not start or will be quickly extinguished. The amount of vapors produced is dependent on the amount of heat radiated back to the oil. If the oil slick is too thin, some of this heat is conducted to the water layer below it. Oil that is completely emulsified with water can be ignited, given that sufficient heat is supplied, typically by burning it alongside unemulsified oil. Containment of the oil on water may be necessary to carry out in situ burning as the oil must be thick enough to quantitatively burn. Once burning, the heat radiated back to the slick and the insulation are usually sufficient to allow combustion down to about ½ to 1 mm of oil. The oil burn rate is a largely a function of oil type. The residue from burning oil is largely unburned oil with some lighter or more volatile products removed. When the fire ceases, unburned oil is left that is simply too thin to sustain combustion. In addition to unburned oil, weathered oil is present that has been subjected to high heat. Heavier soot particles are reprecipitated from the smoke plume into the fire and thus become part of the residue. Highly efficient burns of some types of heavy crude oil may result in oil residue that sinks after cooling in seawater. Burning oil on land or wetlands is a technique that can reduce the environmental impact of oil spills. Burning vegetation is a frequent method of maintaining certain ecosystems and these same ecosystems can be protected from the effects of oil spills using burning. The important factors relating to burning are the water level of wetlands and the moisture content of soils. Burning under the correct circumstances will not affect roots and thus restoration is rapid. Firebreaks are created to avoid spreading of fire to other locations. Safety is of prime concern. A burn plan and a safety plan must be prepared to encompass the concerns noted in this chapter. Training of personnel including a field practice, is essential to ensure safety. The emissions of burning can be of concern: Particulate matter/soot—Burns produce an abundance of particulate matter (soot). Particulate matter at ground level is a health concern close to the fire and under the plume. The particulate concentrations from in situ oil fires should be monitored in some circumstances. Polyaromatic hydrocarbons (PAHs)—Oils contain significant quantities of PAHs which are largely destroyed in combustion. The PAH concentrations in the smoke, both in the plume and the particulate precipitation at ground level, are much less than in the starting oil. VOCs (volatile organic compounds)—Many VOCs are emitted by fires, but in lesser quantity than when the oil is not burning. VOCs are not a significant concern. Organic compounds—No exotic or highly toxic compounds are generated as a result of the combustion process. Organic macromolecules are in lesser concentration in the smoke and downwind than they are in the oil itself. Dioxins and dibenzofurans have not been measured as emissions of oil fires. Carbonyls—Carbonyls such as aldehydes and ketones are created by oil fires but do not exceed health concern levels even close to fires. Gases—Combustion gases such as carbon dioxide, carbon monoxide, and sulfur dioxide are produced by oil fires but are significantly below any health concern level. Overall, emissions are now understood to the extent that emission levels and safe distances can be predicted for fires of various sizes and types.

Method of the Model Equation in the Theory of Unsteady Combustion of a Solid Propellant

Abstract: A model equation for the unsteady burning rate of a solid propellant is proposed and justified. In the frequency range of interest for practice, the proposed model agrees with the phenomenological theory of unsteady combustion, but it is even more convenient for applications because it reduces to an ordinary differential equation of the second order with respect to the burning rate. A parametric study of the transitional process in the solid-propellant rocket motor is performed with variations of the nozzle throat area in a wide range of solid propellant parameters. The model predicts oscillatory combustion regimes and propellant extinction in the case of a decrease in pressure. The boundary of stability of the transitional process in the coordinates “sensitivity of the burning rate to changes in pressure—sensitivity of the burning rate to changes in initial temperature.” It is demonstrated that the calculations performed with the use of this model are in qualitative and quantitative agreement with experimental data for a full-scale solidpropellant rocket motor.

Studies on Ignition Delay and Flame Spread in High-Performance Solid Rocket Motors

Abstract: Accurate prediction of ignition delay and flame spread rate in solid propellant rocket motors is of great topical interest. In this paper using a standard k-ω turbulence model numerical studies have been carried out to examine the influence of solid rockets port geometry on ignition delay and the flame spread pattern. We observed that with the same inflow conditions and propellant properties heat flux histories and ignition time sequence are different for different port geometries. We conjectured from the numerical results that in solid rocket motors with highly loaded propellants, mass flux of the hot gases moving past the burning surface is large. Under these conditions, the convective flux to the surface of the propellant will be enhanced, which in turn enhance the local Reynolds number. This amounts a reduction in heat transfer film thickness and enhanced heat transfer to the propellant with consequent enhancement in the dynamic burn rate resulting the undesirable starting pressure transient. We concluded that, the more accurate description of gas phase to surface heat transfer process will give a better prediction and control of ignition delay and flame spread rate in solid propellant rockets.

Decomposition of Solid Propellants in a Combustion Chamber

Abstract: Solid propellants are fuels that do not require an external supply of oxygen for combustion. Once ignited, they rapidly decompose to evolve hot gaseous products. Solid propellants are hence used as fuel for propulsion applications in oxygen rare environments. In this study, a simple model for solid propellant decomposition in a combustion chamber with an exit port was presented. The combustion chamber is assumed to be a 'well-mixed reactor'. The model equations take into account the effect of shape and size of the solid propellant. The phenomenon of 'choking flow' is included while calculating the exit flow-rate. Appropriate methodology for calibrating the model parameters was developed. The calibrated model was validated by comparing simulation results with experimental pressure profiles. This study would be useful for providing guidelines to select appropriate solid propellant configurations and for the development of a system level model for propulsion systems.

Chemistry resolved kinetic flow modeling of TATB based explosives

Abstract: Detonation waves in insensitive, TATB-based explosives are believed to have multiple time scale regimes. The initial burn rate of such explosives has a sub-microsecond time scale. However, significant late-time slow release in energy is believed to occur due to diffusion limited growth of carbon. In the intermediate time scale concentrations of product species likely change from being in equilibrium to being kinetic rate controlled. We use the thermo-chemical code CHEETAH linked to an ALE hydrodynamics code to model detonations. We term our model chemistry resolved kinetic flow, since CHEETAH tracks the time dependent concentrations of individual species in the detonation wave and calculates EOS values based on the concentrations. We present here two variants of our new rate model and comparison with hot, ambient, and cold experimental data for PBX 9502.

Energy skin effect of propellant particles in Electrothermal-Chemical Launcher

Abstract: A numerical model of the radiation has been employed by a Monte Carlo method and statistical physics to simulate the process of a capillary plasma source for Electrothermal-Chemical (ETC) Launcher. The effect on propellants with different physical parameters is discussed. The plasma-propellant interaction is also discussed when combined with a thermal model. Results show that radiant energy only causes a small field around the plasma injector in the propellant bed. The responses of energy flux and propellant particles on radiation are both in the order of picosecond. The strong instantaneous radiation is responsible for the transmission of energy to the propellant particles leading to ignition. Compared with conventional ignition, the energy absorbed by propellant particles is used to increase quickly the temperature in the surface layer of propellant particles. This energy skin effect in the propellant particle surface appears to be the main cause of plasma ignition.

Studies on Gravity Influence on Solid Propellant Burn Rate

Abstract: Experimental studies have been carried out using the in-house developed propellant samples at the atmospheric conditions to examine the influence of propellant surface orientation / attitude on burn rate. A series of burning tests are conducted with different grain orientations, viz., vertical, inverted and horizontal. We have observed 5 % burn rate augmentation on end-burning grains when the burning surface evolution was against the earth gravity compared to the normal vertical candle burning condition. We conjectured that the coupled effects of the instantaneous variations of the propellant burning surface attitude and the flight acceleration during the mission could alter the flame structure due to the local gravitational influence, which in turn alter the burn rate. This paper throws light for developing a suitable gravitational force dependant burn rate model for improving the performance prediction of solid rocket motors for aerospace applications.

Spectroscopic analysis on the laser induced aluminum- oxygen combustion and explosion

Abstract: The laser induced breakdown spectroscopy (LIBS) is used to explore the ignition and explosion phenomena of aluminum in air, in both rich and stoichiometric conditions. A high power laser (Q-switched Nd:YAG at 7 ns, 1064 nm, 3000 mJ/pulse) is used to generate aluminum surface reaction or ablation. The plasma light is detected by the echelle grating spectrometer, coupled to the gated ICCD to obtain both the atomic signals of the fuel (aluminum) and oxygen in air and to estimate the plasma temperature and electron density. The obtained specific electron density ratio provides spectroscopic view on the initiation of highly excited subnano-sized aluminum particles in the plasma plume by the high power laser irradiation. In our previous study, we suggested a method of initiating detonation from metal sample in its bulk form without the need of mixing particles with the oxidizer for a direct initiation (4). The expansion dynamics of a plasma generated by the laser ablation of an aluminum target was investigated by Harilal (5) with low-pressure air conditions from 1.33X10 -9 to 1.33 X 10 -1 bar. At high pressure conditions, an expansion of the plume was made by the strong laser-plasma interaction. The presence of the ambient gas at varying pressures heavily influenced the expansion dynamic of plasma (6). Due to the aluminum property as burn rate modifier in solid propellants, research on the reaction mechanism of aluminum has been a continuous effort starting 1960s, and in the 1970s with the works of Glassman (7) and Brzustowski (8) with the aim of exploring the effect of melting and boiling of the metal and oxides. They suggested that combustion would reach a steady state condition with the aluminum at its boiling point without forming the oxide shell. The aluminum oxide such as Al2O3 for its high meting temperature of 2300K is responsible for deterring ignition. In 1980s, researchers focused on the burning time of aluminum with different particle diameter, oxidizing species, pressure, and temperature to identify optimum environment for combustion (9-10). More recently, investigation for relationship between ambient temperature and the level of oxidation (11), size effect of aluminum particles (12, 13), combustion in the liquid environment (14), explosion characteristics with varying oxygen content (15, 16) have been addressed.

Development of solid rocket propellant

Abstract: This thesis presents a study on development of solid rocket propellant that was carried out at Universiti Malaysia Pahang. Rocket propellant has been identified as a component that played an important role in the development of rockets. The ejected material in rocket propulsion is due to material called propellant. Without propellant, a rocket cannot be launched. A solid rocket is a class of rocket in which the fuel, oxidizer and binder are mixed together and cast into a solid material. Objective of this thesis is to produce potassium nitrate sucrose based solid rocket propellant. Materials used to produce this propellant are potassium nitrate powder and sucrose powder. Potassium nitrate is an oxidizer in the propellant material and sucrose as a fuel in the propellant. This propellant is produce using the method of formation. This method was easy to operate and cost effective. Burning rate test was carried out at 1 atm and 7 atm pressure using a different oxidizer/fuel mass ratio. At 1 atm pressure, it was found that burning rate for the ratio of 65/35 was 2.184 mm/sec. At 7 atm, it was found that burning rate for the ratio 65/35 was 3.791 mm/sec. Propellant must be kept in a cool dry place like it in the refrigerator to prevent it become melt. From the result of this research, the burning rate test rig has been successfully designed, fabricated and tested. As a conclusion, oxidizer / fuel ratio and combustion pressure influence burning rate test.

Continuous Detonation Wave Engine: Literature Study

Abstract: The Continuous Detonation Wave Engine (CDWE) is a new concept of rocket engine based on rotating detonation waves. The detonation process is characterized by a faster burn rate and a higher energy release rate as compared to deflagration, which produces an extreme pressure and temperature rise. Due to the rapidity of the process, it is more similar to a constant volume process than a constant pressure process typical of conventional combustion. Therefore, engines based on detonations can have a higher thermodynamic efficiency and specific impulse compared to conventional engines.

Burning Performance of Grain-molded Propellant

Abstract: The effects of density of grain-molded gun propellant and surface treatment of based-propellant on combustion performance of the grain-molded gun propellant were studied by closed-bomb test and 30 mm simulation ballistic gun test using high energy grain nitramine propellant RGD7A-6/7 as based-propellant.The characteristics of p-t and L-B curves for grain-molded gun propellant with different modular densities and different surface treatment of based-propellant were analyzed.The influences of density and surface treatment on the combustion property of the grain-molded gun propellant were obtained.The results show that in the density range from 1.0 g·cm-3 to 1.5 g·cm-3,the higher the density of the grain-molded propellant is,the better its progressivity is.The progressivity of grain-molded gun propellant MD7 obtained with surface-deterred and then surface-coated for based-propellant is the best.The muzzle velocity of MD7 at chamber pressure of 29.7 MPa increases by 6.6%.The muzzle kinetic energy increases by 13.8%.

Effects of Burn Rate on the Spatial Extent of Fracture Damage in an Underground Explosion (Postprint)

Abstract: : The quasistatic micromechanical damage mechanics originally formulated by Ashby and Sammis has been made fully dynamical by the incorporation of physically motivated crack growth laws. This rate-dependent damage mechanics has been implemented in the ABAQUS dynamic finite element code and tested by simulating strength data for marble measured over a ten order of magnitude range of loading rates. The model is used here to explore the effect of burn rate (loading rate) on the spatial extent of fracture damage (and hence the elastic radius) and on the S waves generated by an underground explosion. The recent observation by that explosives with low burn rates produce more shear wave radiation than do those with high burn rates can be explained by dynamic fracture effects, and may not be due to gas wedging as originally hypothesized.

Two-Mode Active Thrust Modulation of a Solid Propellant Rocket motor

Abstract: An active thrust modulation system of solid propellant motor was proposed and verified experimentally. Candidate propellants have a self-quenched property at intermediate pressure, while they can deflagrate at lower and higher pressure. Appropriate selection of throat diameter presents two combustion modes in the same motor geometry. Propellant with 73 % oxidizer content had demonstrated successfully two-mode active thrust modulation. The propellant with 75 % oxidizer content was examined. While the specific impulse showed little difference from 73 % AP propellant, the thrust density of 75 % AP propellant motor became high. The higher burning rate and the narrowed self-quenched pressure range made the thrust modulation a little difficult. An effect of a negative catalyst LiF was discussed. Slight addition of the catalyst had an effect to widen the intermediate self-quenched pressure range, but little effect to suppress the pressure amplitude in regulating the low mode pressure. More motor combustion tests are needed to confirm its availability.

Solid Propellant Rockets

Abstract: Solid rocket motors and various solid propellant grain configurations are described. Burning rate and grain design effects on thrust-time tailoring are discussed, as well as the sensitivity of the solid propellant to temperature. Analysis of the transient behavior and equilibration of the combustion chamber pressure, the stability of the combustion chamber pressure, and the effects of erosive burning is presented. Solid rocket performance characteristics, dual-thrust solid rockets, rocket motor casings, and transient operation are discussed. Rocket motor nozzle heat transfer and ablative and film-cooling techniques are described. Hybrid rocket motors are introduced and their characteristics and operation are covered.

Impact of liquid propellant properties on small rocket thruster dimensions

Abstract: : A study has been made of how the physical properties of the liquid propellants hydrazine and hydrogen peroxide influence energy conversion device dimensions across multiple operating configurations. The energy conversion device was a staged rocket thruster comprised of a first stage where propellant is decomposed to create a high temperature, low velocity environment and a second stage downstream where propellant is injected and exothermically decomposed. The operating configurations varied chamber pressure, propellant flow rate ratio of first stage to second stage, and ratio of propellant feed pressure to chamber pressure within the thruster. Chamber pressures of 125, 250, and 500 psi; flow rate ratios of 1:3, 1:4, and 1:5; and feed to chamber pressure ratios of 1.25:1 and 1.75:1 were considered. The study utilizes relationships that were empirically derived to estimate droplet sizes as a function of the propellant physical properties and various related operating conditions. As the chamber pressure and feed to chamber pressure ratio increased, the chamber dimensions decreased. As the flow rate ratio decreased, the chamber length increased. Relative to the primary reference, Ryan, instant study theoretical values achieved were consistently 30-50% low. Contributing to the disagreement, was use of injector orifice diameters below those of the reference which would drive increased injection velocity values and drive the results lower.