Solid propellant rocket motors are the most widely used propulsion systems for military applications that require high thrust to weight ratio for relatively short time intervals. Very wide range of magnitude and duration of the thrust can be obtained from solid propellant rocket motors by making some small changes at the design of the rocket motor. The most effective of these design criteria is the geometry of the solid propellant grain. So the most important step in designing the solid propellant rocket motor is determination of the geometry of the solid propellant grain. The performance prediction of the solid rocket motor can be achieved easily if the burnback steps of the rocket motor are known. In this study, grain burnback analysis for some 3-D grain geometries is investigated. The method used is solid modeling of the propellant grain for some predefined intervals of burnback. In this method, the initial grain geometry is modeled parametrically using commercial software. For every burn step, the parameters are adapted. So the new grain geometry for every burnback step is modeled. By analyzing these geometries, burn area change of the grain geometry is obtained. Using this data and internal ballistics parameters, the performance of the solid propellant rocket motor is achieved. To verify the outputs obtained from this study, rocket motor tests are performed. The results obtained from this study shows that, the procedure that was developed, can be successfully used for the preliminary design of a solid propellant rocket motor where a lot of different geometries are examined.

In this study, experimental investigation of solid propellant combustion instability using an end burning T-Burner setup is performed. For this purpose, a T-Burner setup is designed, analyzed, constructed and tested with all its sub components. T-Burner setup constructed is mainly composed of a base part, a control panel and the T-Burner itself. Combustion chamber, pressure stabilization mechanism, pressurization system, measurement instruments and data acquisition systems form the T-Burner. Pressure stabilization mechanism is utilized in two different alternatives, first of which is by the use of nitrogen gas and a small surge tank with a cavitating venturi. This is a brand new approach for this kind of system. The second alternative is the use of a choked nozzle for pressure stabilization. Resonance frequencies of the system with the two different pressure stabilization mechanisms are experimentally evaluated. Helmholtz frequency of the T-burner constructed is calculated and no Helmholtz instability is observed in the system. Constructed T-Burner setup is operated for a specific solid propellant. System worked successfully and pressure data are obtained. Pressure data revealed oscillatory behaviour. Decay and growth rates of pressure oscillations are used for the calculation of pressure response of the propellant tested. By the use of this T-Burner comparison of the behavior of different propellants can be performed. It can be used as a test device for measuring quantitatively the response of a burning propellant to unsteady motions.

Propõe-se aqui uma metodologia de projeto aero-termo-estrutural de motores foguete a propelente sólido. O projeto de um motor foguete deve ser realizado com o objetivo de cumprir requisitos de uma missão. Para cada veículo espacial, com uma nova missão, um novo motor pode ser projetado, necessitando para isso de uma série de ferramentas robustas, capazes de compreender todas as combinações de esforços existentes no funcionamento de um motor, sob condições de altas pressões e temperaturas. A metodologia aqui proposta é testada e validada em bancada de ensaios desenvolvida para este fim. Os resultados obtidos mostram que a metodologia utilizada se aproxima bastante dos resultados teóricos e pode ser ajustada por coeficientes de eficiência com grande facilidade. / It is proposed here an aero-thermo-structural design methodology for solid propellant rocket motors. The design of a rocket motor must be carried out in order to fulfill requirements of a mission. For each new space vehicle, with a new mission, a new motor can be designed, requiring for it a variety of robust tools, able to comprise all combinations of load existing in the operation of a motor under high pressures and temperatures. The methodology proposed here is tested and validated in bank of tests developed for this purpose. The results show that the methodology is very close to the theoretical results and can be adjusted by coefficients of efficiency with great ease.

Cette thèse porte sur la méthode de Fluorescence Induite par Laser (LIF) à haute cadence développée sur deux atomes métalliques (Al et Fe) utilisés comme traceurs fluorescents dans les flammes de propergols solides où ils sont naturellement présents. Deux expériences d’évaporation de l’aluminium sont mises en œuvre pour mettre au point la technique dans des conditions contrôlées sur une large gamme de pressions et températures. Un modèle théorique du processus de fluorescence appliqué à ces deux atomes est élaboré pour calculer les taux de quenching du signal avec la pression et la température. Les données collisionnelles qui sont inconnues sont prédéterminées théoriquement pour Fe et expérimentalement pour Al. Les coefficients de transferts d’énergie et d’élargissements spectraux par collisions de l’atome Al sont déterminés expérimentalement en environnement d’azote pur. Une étude du comportement du signal de Al avec l’énergie laser est effectuée pour mesurer les seuils de saturation avec les gaz N₂, Ar et He en fonction de la pression. Le modèle permet de reproduire correctement les profils temporels et spectraux avec toutefois des approximations et des limitations qui sont explicitées. Une première application de l’imagerie LIF sur Al dans une flamme de propergol solide aluminisé (10 bar et 3000 K) permet de visualiser des gouttes d’aluminium réactives et observer leur évolution dans la flamme. / During the PhD thesis, high-speed laser induced fluorescence (LIF) of two metallic atoms (Al and Fe) is presented, in order to use them as fluorescent markers in solid propellant flames, where they are naturally present. LIF measurements are first performed inside two different evaporation chambers used to generate aluminum vapors in controlled conditions over a broad pressure and temperature range. A theoretical model of the LIF process is elaborated and applied to both atoms in order to calculate the signal quenching rate as a function of pressure and temperature. Unavailable collisional data are determined theoretically for Fe and experimentally for Al. Energy transfer and collisional broadening coefficients are determined experimentally for the Al atom in pure nitrogen environment. Study of the signal level of Al as a function of laser intensity is undertaken to measure saturation thresholds in N₂, He and Ar as a function of pressure. The model is used to properly reproduce the temporal and spectral profiles, though some approximations and limitations remain. A first application of high-speed LIF imaging to the measurement of aluminum in a solid propellant flame (10 bar , 3000 K) is demonstrated. It allows us to clearly visualize reactive aluminum droplets in the flame and to follow their evolution in the flame.

The application of emission spectroscopy to monitor combustion products of solid rocket propellant combustion can potentially yield valuable data about reactions occurring within the volatile environment of a strand burner. This information can be applied in the solid rocket propellant industry. The current study details the implementation of a compact spectrometer and fiber optic cable to investigate the visible emission generated from three variations of solid propellants. The grating was blazed for a wavelength range from 200 to 800 nm, and the spectrometer system provides time resolutions on the order of 1 millisecond. One propellant formula contained a fine aluminum powder, acting as a fuel, mixed with ammonium perchlorate (AP), an oxidizer. The powders were held together with Hydroxyl-Terminated-Polybutadiene (HTPB), a hydrocarbon polymer that is solidified using a curative after all components are homogeneously mixed. The other two propellants did not contain aluminum, but rather relied on the HTPB as a fuel source. The propellants without aluminum differed in that one contained a bimodal mix of AP. Utilizing smaller particle sizes within solid propellants yields greater surface area contact between oxidizer and fuel, which ultimately promotes faster burning. Each propellant was combusted in a controlled, non-reactive environment at a range of pressures between 250 and 2000 psi. The data allow for accurate burning rate calculations as well as an opportunity to analyze the combustion region through the emission spectroscopy diagnostic. It is shown that the new diagnostic identifies the differences between the aluminized and non-aluminized propellants through the appearance of aluminum oxide emission bands. Anomalies during a burn are also verified through the optical emission spectral data collected.

The purpose of this study is to examine the burning behaviour of composite solid propellants (CSP) in the presence of nanoscale, heterogenous catalysts. The study targets the decomposition of ammonium perchlorate (AP) as a key component in the burning profile of these propellants, and seeks to identify parameters of AP decomposition reaction that can be affected by catalytic additives. The decomposition behavior of AP was studied in the presence of titanium dioxide nanoparticles in varying configurations, surface conditions, dopants, morphology, and synthesis parameters with the AP crystals. The catalytic nanoparticles were found to enhance the decomposition rate of the ammonium perchlorate, and promote an accelerated burning rate of CSP propellants containing the additives. Furthermore, different configurations were shown to have varying degrees of effectiveness in promoting the decomposition behaviour. To study the effect of the catalyst’s configuration in the bulk propellant, controlled dispersion conditions of the nanoparticle catalysts were created and studied using differential scanning calorimetry, as well as model propellant strand burning. The catalysts were shown to promote the greatest enthalpy of reaction, as well as the highest burn rate, when the AP crystals were recrystalized around the nanoparticle additives. This is in contrast to the lowest enthalpy condition, which corresponded to catalysts being dispersed upon the AP crystal surface using bio-molecule templates. Additionally, a method of facile, visible light nanoparticle tracking was developed to study the effect of mixing and settling parameters on the nano-catalysts. To accomplish this, the titania nanoparticles were doped with fluorescent europium molecules to track the dispersion of the catalysts in the propellant binder. This method was shown to succesfully allow for dispersion and agglomeration monitoring without affecting the catalytic effect of the TiO2 nanoparticles.

<p>When characterizing a new solid propellant, one of the most important steps in determining its usefulness is discovering how the burning rate changes in response to changes in pressure. While there are many dynamic methods for directly measuring the regression rate of a burning propellant sample, few of them are capable of being used in typical harsh motor conditions: high pressures, high temperatures, and in an environment comprised of propellant exhaust products. This paper describes and evaluates the use of two custom-built microwave interferometers, one operating at 35 GHz and the other operating at 94 GHz, in several different configurations for the measurement of propellant regression rates. Four different configurations of interferometer and waveguide are presented and contrasted, with example results of experiments included. A polytetrafluoroethylene (PTFE) waveguide, utilized in previous works for explosives detonation velocity characterization, was used to directly couple interferometer signal with a burning propellant strand. This PTFE coupling is shown to be applicable to pressure vessel studies by simply using a cable feedthrough. In this configuration, signal quality is high but signal amplitude is low, especially when the waveguide is encased by support structures. A novel PTFE truncated cone waveguide expander is presented which performs three tasks: expanding the microwave signal such that an oversized (relative to signal wavelength) strand may be examined via microwave interferometry, functioning as a weak antenna that can observe phenomena through interstitial material without picking up significant amounts of environmental reflection, and acting as a sealing surface for pressure vessel experiments. Additionally, the use of a more-standard hollow-core waveguide and high-gain antenna is displayed, highlighting the increased signal strength but the larger number of spurious reflections in the signal. This study shows, through various experiments using the aforementioned configurations, the capability of microwave interferometry to quickly characterize a full propellant burning rate curve using a single dynamic-pressure test with 40g of propellant in a 2.5cm diameter propellant strand. Several novel combinations of mechanical configuration and propellant composition are shown that may guide future studies into the use microwave interferometry for solid propellant regression rate analysis.</p>

<p dir="ltr">Smart energetics are energetic materials (propellants, explosives, and pyrotechnics) with on/off capabilities or in real time modification of combustion behavior. Solid propellants are known for many positive qualities such as their simplicity and low cost but also their glaring lack of active burning rate control. Previous proposed methods of active control of solid propellants include pintle valve actuation and electronically controlled solid propellants, however there is a need for improved methods. Surface area modification is one proposed method and can be employed in real time to affect the burning behavior of solid propellants. To this end, derivations were conducted regarding a slot adjacent to a solid propellant strand and the pressure and slot width threshold conditions that allow for burning to occur inside of the adjacent slot. The derivations considered different modes of combustion (convective and conductive) and combustion threshold conditions. The derivations resulted in five equations that were curve fit to existing literature for validation resulting in high R squared values. A demonstration of the creation of an adjacent slot with a piezoelectric actuator, a mini case study of the adjacent slot proposal, and a discussion of methods to create an adjacent slot as well as the effect of propellant selection on convective burning in slots were all done to follow up on the promising results of the theoretical work. </p><p dir="ltr">Furthermore, flexoelectricity is the coupling between strain gradient and charge generation and has been considered to modify the combustion characteristics of energetic materials. This work measured the flexoelectric properties of polymers and their associated energetic composites including polyvinylidene fluoride (PVDF), micron aluminum (μAl)/PVDF, nano aluminum (nAl)/PVDF, poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)), nAl/P(VDF-TrFE), poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)), μAl/P(VDF-HFP), hydroxylterminated polybutadiene (HTPB), ammonium perchlorate (AP)/HTPB, μAl/AP/HTPB, polytetrafluoroethylene (PTFE), and polydimethylsiloxane (PDMS). The measurements made on PVDF, μAl/PVDF, P(VDF-TrFE), P(VDF-HFP), PTFE, and PDMS were all within or near to the range of measurements from the literature. Novel measurements were made on nAl/PVDF, nAl/P(VDF-TrFE), μAl/P(VDF-HFP), HTPB, AP/HTPB, and μAl/AP/HTPB. Additionally, the effect of porosity, particle additions (μAl, nAl, or AP), and manufacturing method (3D printing, casting, different 3D printers, etc.) on the flexoelectric performance of these samples was investigated. It was found that large pores (millimeter scale) added via the infill pattern of 3D printed PVDF and Al/PVDF samples decreased the effective flexoelectric effect relative to the near full density control samples. This contrasts with previous work showing that adding small (micron scale) pores increases the flexoelectric performance of various polymers and energetic materials. Mixed results were found with respect to the effect of particle additions (μAl, nAl, or AP) on the flexoelectricity of a variety of materials. This may be explained by the competing effect of particle additions adding extra local strain gradients which amplify flexoelectricity but also replace some polymer binder material (PVDF, P(VDF-TrFE), P(VDF-HFP), and HTPB) with the particle additions (μAl, nAl, and AP) which are typically less flexoelectric. Our work demonstrates that manufacturing method does affect the flexoelectric properties of polymers and energetic composites. Lastly, our flexoelectric measurements of P(VDF-HFP) and PTFE may help explain accidents related to Magnesium-Teflon®-Viton® (MTV) flare systems that have, in many cases, been attributed to electrostatic discharge.</p>

A microwave measurement system for obtaining continuous burning-rate information from a solid propellant slab-burning rocket motor is described. A previous derivative-based method for reducing the microwave data is reviewed and an improved data reduction technique is introduced. The improved microwave modeling technique is analyzed using simulated data to determine the accuracy of the burning-rate calculations and the sensitivity of the burning-rate calculations to errors in the model parameters. The microwave model is then used to calculate the burning rate of the propellant for a selected firing of the slab motor. / Master of Science

A dual-frequency microwave bum rate measurement system for solid rocket motors has been developed and is described. The system operates in the X-band (8.2-12.4 Ghz) and uses two independent frequencies operating simultaneously to measure the instantaneous bum rate in a solid rocket motor. Modeling of the two frequency system was performed to determine its effectiveness in limiting errors caused by secondary reflections and errors in the estimates of certain material properties, particularly the microwave wavelength in the propellant. Computer simulations based upon the modeling were performed and are presented. Limited laboratory testing of the system was also conducted to determine its ability perform as modeled. Simulations showed that the frequency ratio and the initial motor geometry (propellant thickness and combustion chamber diameter) determined the effectiveness of the system in reducing secondary reflections. Results presented show that higher frequency ratios provided better error reduction. Overall, the simulations showed that a dual frequency system can provide up to a 75% reduction in burn rate error over that returned by a single frequency system. The hardware and software for dual frequency measurements was developed and tested, however, further instrumentation work is required to increase the rate at which data is acquired using the methods presented here. The system presents some advantages over the single frequency method but further work needs to be done to realize its full potential. / Master of Science