Ammonium Perchlorate Composite Propellants Research Articles

EVALUATION OF SOLID ROCKET PROPELLANTS FOR LOW EARTH ORBIT

In contemporary aerospace technology, solid rocket propellants are commonly employed in the thriller and boost of space cargoes to LEO. These are reliable, uncomplicated, and high in thrust; and thus, can be used in both military as well as civil space ventures. This paper provides a comprehensive evaluation of five prominent solid rocket propellants: Five categories namely Ammonium Perchlorate Composite Propellant (APCP), Double-Base Propellant, Composite Modified Double Base (CMDB) Propellant, Hydroxyl-terminated polybutadiene (HTPB)-Based Propellant, and Ammonium Nitrate Composite Propellant (ANCP) have been identified. This also falls under the evaluation and includes aspects such as historical bases to see how the formulation of the propellant has changed over time regarding the development of propellant technology. In the case of each propellant, the chemical properties of the mix and reactions that its fundamental are analyzed. It also shares details regarding the changes and advancements made in the little while to enhance capability, safety, and environmental compatibility of these fuels, such as synthesizing fuels for liquid bipropellants. Some of the modern applications of technologies within the active spectrum of aerospace operations are explained in more detail to provide clients with the most versatile and essential information. Among the essentials of this work, the complex calculation of thrusts developed by the specific propellant with corresponding graphics has significant importance. These estimations afford chances of comparing the efficiency of the propellant in terms of producing thrusts as well as achieving the indicated optimal performance. Thus, the main objective of this study is to identify which of the solid rocket propellants to use in LEO missions and if any, what modifications could be made to improve them. Thus, the purpose of this paper is to contribute to the development of the constantly evolving branch of rocket propulsion by discussing the benefits and shortcomings of each propellant. These findings and recommendations could be useful in perfecting the recipes for the propellants and improving the efficiency of the subsequent missions to planets. Keywords: Aerospace, Solid rocket propellants, Thrust, Low earth orbit.

On‐demand microwave growth of porosity within a granular composite energetic material: Void formation via a dielectric loss phase change binder additive for propellant burning rate control

AbstractThis study demonstrates, for the first time ever, the ability to grow, in an on‐command fashion, porosity within a granular composite energetic material to effect a change in energy output rate. Specifically, the study investigates the change in burning rates of ammonium perchlorate composite propellants as a result of porosity created in situ via microwave field‐driven volatilization of the low boiling point binder additive, ethylene glycol. Theoretical mass densities were measured before and after microwave irradiation finding that the maximum observed %TMD change for tested propellants is 6 %. Propellants were burned at 1.72 MPa to 6.89 MPa pressures, finding that for all propellants, microwave irradiation produced a change in ballistic characteristics. Most propellant formulations demonstrate acceptable burning rate parameters for use within rocket motors; some exhibited a large change in their pressure exponent as well as slope breaks attributed to the onset of convective burning, while microwave irradiation produced no change in burning rate or density in reference propellants without the additive. Microwave heating simulation results are presented to gain insight into the thermal environment of the propellant during microwave irradiation. These results provide valuable insight into propellant formulations that can have their burning rates (and thus the thrust profile for motor grains) altered after casting via microwave irradiation.

Shear and combustion characterization of printable ammonium perchlorate composite propellant formulations

AbstractSeven formulations of ammonium perchlorate composite propellant (APCP) are developed and their properties relevant for successful additive manufacture are characterized. Extrusion in a custom‐built 3D printing system and spindle viscometry are used to collect viscosity measurements of curing primary and non‐curing secondary versions of the formulations. The formulations that behave similarly to a Bingham plastic, with apparent viscosities between 4 and 8 thousand Pa*s at 30 minutes post‐mix, are determined to be most suitable for printing applications. Measurements of one material show a yield stress of 1 kPa. Ambient pressure burn rates of 2.0–2.9 mm/s were measured for the compositions tested. All measured burn rates were comparable to the lower end of typical burn rates for APCP. The results of the characterization demonstrate a propellant suitable for use in a 3D printing system.

Rheological, Ballistic, and Mechanical Properties of 3D Printed, Photocured Composite Propellants

This study explores the rheological, mechanical, and ballistic properties of printed ammonium perchlorate composite propellant at 82.5% solids loading with binders curable with ultraviolet light of wavelength from 215 to 400 nm (UV). A polybutadiene urethane acrylate and two polyester urethane acrylate propellants are printed by an in-house-fabricated fused deposition molding printer. Propellants are all shear-thinning and have significantly lower viscosity than similar hydroxyl-terminated polybutadiene (HTPB) propellants. Uniaxial stress–strain measurements indicate that ultimate tensile strength and ultimate tensile strain of all photocurable propellants are found to be greater than HTPB propellant. In particular, the ultimate tensile strain of polyester urethane acrylate propellant is six times that of HTPB propellant, demonstrating high compliance. Ballistic properties are measured from combustion of printed propellant articles in a windowed Crawford combustion bomb at inert gas pressures of up to 12.1 MPa. The burning characteristics were found to be relatively planar, though strong burning rate anisotropy, expected as a result of print layer inhomogeneities, was observed in two of the three formulations. Overall, pressure exponents of the propellants were mild and ranged from 0.17 to 0.33. These results are compared and contrasted to those of other printed propellants. These results provide valuable insight into the selection of a safe binder system for printing of photocurable composite propellants.

Embracing Anisotropy – Opportunities and Challenges to the Functional Application of Advanced Manufacturing of Energetic Materials

Embracing Anisotropy – Opportunities and Challenges to the Functional Application of Advanced Manufacturing of Energetic Materials

Photoflash and laser ignition of Al/PVDF films and additively manufactured igniters for solid propellant

Solid propellants are employed in a range of applications from the inflation of airbags to propulsion systems for rockets. The ignition of solid propellants must be carefully controlled and modified on a per-use basis due the specific ignition requirements of each application. Using tailored photoreactive materials as a source of ignition for solid propellants, or other energetic materials, could reduce the added weight and risk of traditional initiators and result in safer, more effective solid rocket motor ignition systems. This study demonstrates the tunability of the ignition delay and propagation properties of optically-sensitive, nearly full density reactive aluminum/polyvinylidene fluoride (Al/PVDF) films and additively manufactured igniters. A single printed layer of pure nano-aluminum (nAl) at ideal stoichiometry in PVDF was found to flash ignite, but frequently yielded delayed transitions in steady propagation from the igniter to the propellant. To improve the continuity and steadiness of the transition, fuel particle size, igniter thickness, and a combination of layers of nAl and micron-sized aluminum (μAl) were investigated. In printed igniters with layers of μAl, only a single layer of nAl was needed to flash ignite the material and propagate to the layers of μAl without delay. For igniters cast onto strands of ammonium perchlorate composite propellant, continuous ignition was achieved with a single layer of nAl printed atop a triple layer of μAl for the flash-activated igniters and a single layer of nAl printed atop a single and triple layer of μAl for laser-driven igniters. The nAl/PVDF layer enabled good flash or laser ignition sensitivity, while the μAl/PVDF produced more sustained heat transfer to produce a reliable ignition process.

Studies on Curing of an Aluminized Ammonium Perchlorate Composite Propellant Based on Nitrile Butadiene Rubber Using a Quinol Ether of 1,4-Benzoquinone Dioxime

Studies on Curing of an Aluminized Ammonium Perchlorate Composite Propellant Based on Nitrile Butadiene Rubber Using a Quinol Ether of 1,4-Benzoquinone Dioxime

Cobalt copper zinc ferrite: An efficient catalyst for the thermal decomposition of ammonium perchlorate

ABSTRACT Cobalt Copper Zinc Ferrite (CoCuZnF) was synthesized using the co-precipitation method and characterized by various physicochemical instrumental techniques like UV-Vis, Raman, and N2-adsorption-desorption analysis to identify its structural parameters. Moreover, the catalytic study of nano CoCuZnF on ammonium perchlorate (AP) and AP-based composite solid propellant (CSP) was studied using DSC analysis. Furthermore, many kinetic models were employed to study its kinetics parameters. The thermal decomposition peak of AP was found to be decreased by 65–66°C in the presence of 1% by mass CoCuZnF additive. The activation energy of AP was found to be decreased by ~27-28% in the presence of CoCuZnF. The burn rate of AP-based CSP was found to be increased by 0.77 mm s−1 when CoCuZnF was used as an additive.

Studies on the High Performance Characteristics of an Aluminized Ammonium Perchlorate Composite Solid Propellant Based on Nitrile Butadiene Rubber

Studies on the High Performance Characteristics of an Aluminized Ammonium Perchlorate Composite Solid Propellant Based on Nitrile Butadiene Rubber

Development and Characterization of a Photopolymeric Binder for Additively Manufactured Composite Solid Propellant Using Vibration Assisted Printing

AbstractAn emerging area of research in the energetic materials community is the development of new manufacturing methods, such as additive manufacturing (AM), that can be used to selectively deposit energetic materials into complex geometries, which provides more control over how the energetics perform during combustion. Although ammonium perchlorate (AP) composite propellant has been 3D printed at solids loadings that are comparable to traditional formulations (85 wt.%) with vibration assisted printing (VAP), traditional propellant binders such as hydroxyl terminated polybutadiene (HTPB) are poorly suited for 3D printing large or complex structures because propellant made with HTPB deforms easily under its own weight and isocyanates do not crosslink HTPB fast enough to facilitate rapid polymerization after deposition. Ultraviolet (UV) curable photopolymers have been used for many types of AM processes, such as stereolithography, and there is a variety of commercially available binders with customizable chemical and mechanical properties. However, little work has been done to characterize the optimal cure characteristics of UV curable binders that are compatible with composite propellants. Furthermore, it has also been speculated that aluminized propellants may not be amenable to UV curing since opaque particles impede UV transmission. In this work, the curing properties of a photopolymer that has similar characteristics to HTPB with AP and aluminum were quantified. The ingredients consisted of a polybutadiene urethane acrylate and hexanediol diacrylate (HDDA) polymer binder, which could be mixed in various ratios to control properties such as adhesion to particle surfaces and viscosity, as well as bisacylphosphine oxide (BAPO) which is a well‐known photoinitiator for deep curing in the coatings industry. The effect of wavelength, exposure time, and intensity on cure depth were quantified on the neat photopolymer. In addition, the effect of aluminum content (up to 20 %) on the cure depth of propellant with a solids loading of 85 wt.% was measured. It was shown that at higher intensities (∼20 mW/cm2), aluminized propellants could be cured to depths on the order of 1–2 mm, which is greater than the typical layer thickness of propellants printed via VAP (∼0.25 mm). In addition, it was shown that there were no visible interfaces in aluminized propellant (15 % aluminum) that was cured layer‐by‐layer. The approach taken could be applied to a wide range of other granular, opaque composite materials, such as metal, ceramic, and fibrous mixtures.

Active Interruption of Motor Combustion for Ammonium-Perchlorate Composite Propellant

Active Interruption of Motor Combustion for Ammonium-Perchlorate Composite Propellant

Microwave plasma enhancement of multiphase flames: On-demand control of solid propellant burning rate

This effort explores the microwave-supported plasma enhancement of an aluminized, ammonium perchlorate composite solid propellant flame. The technique is enabled through novel alkali metal doping, which provides increased levels of ionization and allows efficient microwave energy deposition to the flame structure and subsequent perturbation of the steady-state propellant burning rate. Three potential modes of energy deposition are identified in composite propellants: (1) plasma-enhancement promoted by the presence of sodium, (2) strong absorption by high temperature metallic oxide products, and (3) direct absorption of energy by the propellant burning surface condensed phase. Equilibrium calculations are used to identify propellant compositions with high free-electron populations, and solution of the Boltzmann equation using the BOLSIG + code is used to show the significant effects of sodium doping on microwave absorption of the flame. Experimental emission spectroscopy and imaging of the microwave-enhanced propellant flame structure show evidence of these mechanisms. Propellant burning rates can be increased by up to 60% through the application of 1 kW, continuous 2.46 GHz microwave radiation. Propellant doping with 3.5% by weight of sodium nitrate shows significant improvement in the effectiveness of microwave application in modifying the propellant burning rate. This technique provides high levels of dynamic propellant combustion control from a solid-state system. The on-demand control of energetic material burning rates through low level doping and microwave irradiation is a promising technique which could lead to the development of a new class of ‘smart’ dynamically controllable energetic materials.

Theoretical investigation of the catalytic effect of microingredients on ammonium perchlorate (AP) thermal decomposition

This study employed quantum chemical modeling to explore the low‐temperature (i.e., below 300 °C) decomposition of ammonium perchlorate (AP) in terms of the reaction mechanisms, analyzing the kinetics of decomposition in gaseous noncatalyzed and catalyzed systems. Based upon transition‐state theory, the calculated rate constant together with the initial partial pressure of the reaction species were included in the integrated form into the rate law of the elementary reaction to compute the half‐life of AP decomposition and further evaluate the corresponding lifetime of the stored material. The results of this study revealed that upon increasing the reaction temperature, the stepwise decrease in the activation barrier and the stepwise increase in the rate constant of AP decomposition exhibited expected trends. In addition, via proton transfer and bond‐cleavage mechanisms, ammonium chlorate exerted a positive catalytic effect that showed decomposition is unfavorable. However, ammonium dihydrogen phosphate and ammonium halide exhibited negative catalytic effects that slowed decomposition, and both of them may be incorporated into AP composite propellants to prolong their shelf life. The use of these stabilizing catalysts is estimated to increase the relative lifetime of materials under storage by two orders of magnitude, potentially benefiting ammunition storage.

Additive manufacturing of ammonium perchlorate composite propellant with high solids loadings

The effective solid propellant burning rate in a rocket depends on surface area and propellant composition. Currently, the surface area geometry in a rocket is limited to what can be practically cast using molds, etc. Additive manufacturing (AM) could allow the production of unique propellant grain geometries, however printing propellants with high solids loadings and viscosities is not readily possible using currently available printers. A new AM direct write system developed recently in our laboratory, is capable of printing visibly low-void propellants with high end mix viscosities into highly resolved geometries. The system was used to print ammonium perchlorate (AP) composite propellants at 85% solids loading using hydroxyl-terminated polybutadiene (HTPB) and a UV-curable polyurethane binder. The change in HTPB propellant viscosity with time after mixing was measured and the microstructure of the strands was evaluated with X-ray tomography scans. The burning rate of printed and cast strands was measured to compare the quality of the strands at high pressure, since propellants with significant voids should catastrophically fail due to flame spreading. The printed samples burned in a planar fashion up to pressures of 10.34 MPa with consistent rates that were comparable to the cast propellants. The HTPB propellant used was not optimized and showed some porosity due to gas generation, but strands printed with the UV binder exhibited extremely low porosity. A strand printed with no gaps in one half and gaps in the other failed catastrophically where intended at high pressure, demonstrating the ability to spatially grade propellants. This new system can produce adequate strands of composite propellant with high solids loadings without the addition of solvents, special binders (low viscosity, thermal softening, etc.), or restricting use to formulations with lower viscosities, and enables the fabrication of complex propellant grain geometries.

Detection of iron atoms by emission spectroscopy and laser-induced fluorescence in solid propellant flames.

Planar laser-induced fluorescence on atomic iron is investigated in this paper, and a measurement strategy is proposed to monitor the fluorescence of iron atoms with good sensitivity. A model is proposed to fit the experimental fluorescence spectra, and good agreement is found between simulated and experimental spectra. Emission and laser-induced fluorescence measurements are performed in the flames of ammonium perchlorate composite propellants containing iron-based catalysts. A fluorescence signal from iron atoms after excitation at 248nm is observed for the first time in propellant flames. Images of the spatial distribution of iron atoms are recorded in the flame in which turbulent structures are generated. Iron fluorescence is detected up to 1.0MPa, which opens the way to application in propellant combustion.

Agglomerate Sizing in Aluminized Propellants Using Digital Inline Holography and Traditional Diagnostics

Aluminized ammonium perchlorate composite propellants can form large molten agglomerated particles that may result in poor combustion performance, slag accumulation, and increased two-phase flow losses. Quantifying agglomerate size distributions are needed to gain an understanding of agglomeration dynamics and ultimately design new propellants for improved performance. Due to complexities of the reacting multiphase environment, agglomerate size diagnostics are difficult and measurement accuracies are poorly understood. To address this, the current work compares three agglomerate sizing techniques applied to two propellant formulations. Particle collection on a quench plate and backlit videography are two relatively common techniques, whereas digital inline holography is an emerging alternative for three-dimensional measurements. Atmospheric pressure combustion results show that all three techniques are able to capture the qualitative trends; however, significant differences exist in the quantitative size distributions and mean diameters. For digital inline holography, methods are proposed that combine temporally resolved high-speed recording with lower-speed but higher spatial resolution measurements to correct for size–velocity correlation biases while extending the measurable size dynamic range. The results from this work provide new guidance for improved agglomerate size measurements along with statistically resolved datasets for validation of agglomerate models.

Thermal decomposition and combustion characteristics of HTPB-coarse AP composite solid propellants catalyzed with Fe2O3

ABSTRACTMany factors and their mutual interactions induce complexity in the combustion of hydroxyl-terminated polybutadiene (HTPB)–ammonium perchlorate (AP)–ferric oxide (Fe2O3) composite solid propellant (CSP). Among them, we investigated exothermicity of coarse AP decomposition for thermal decomposition and high-pressure combustion of HTPB-AP. Thermal decomposition of coarse AP was characterized by high twin-peak exothermicity, while HTPB-AP decomposed in single-stage at 329°C. Coarse AP improved thermal decomposition due to significant first-stage exothermicity. High exothermicity and predominance of coarse AP dominate thermal decomposition of CSP. Fe2O3 catalyzed decomposition of AP by shifting second exothermic peak to lower temperature and releasing more heat. Fe2O3 increased the burning rate of HTPB-AP and the highest burning rate was achieved for 1 wt % nano-Fe2O3 of average size 4 nm. Similar results for milli- (average size 200 μm) and micro-Fe2O3 (average size 2 μm) were recorded at higher concentrations. Exothermicity of coarse AP and catalytic activity of Fe2O3 on AP speed up subsurface processes and help in the enhancement of burning rates.

The effect of decorated graphene addition on the burning rate of ammonium perchlorate composite propellants

Catalysts are often added to solid propellant formulations to tailor burning rates. Nanocatalysts can increase propellant burning rates over standard catalyst sizes due to the increase in surface area per unit weight. However, the increased surface area that the binder must wet can be prohibitive if large amounts of nanocatalysts are used. Additionally, agglomeration of the nanocatalyst can result in micron-scale particles, reducing catalyst effectiveness. In this study a nanoscale iron oxide catalyst has been used to decorate graphene. By decorating graphene with the catalyst, nanoscale features are kept but the catalyst is stabilized to reduce agglomeration. Changes in burning rate between the catalyzed and uncatalyzed propellants are investigated. The effect on burning rate of encapsulating the catalyst inside the fine AP crystals compared to propellants where it is added to the binder is also investigated. We also compare propellants with decorated graphene and propellants with undecorated graphene catalysts. The three comparisons are made for two different graphene preparation methods. It is found that the highest burning rates occur in propellants where the graphene is decorated with catalyst and encapsulated in the fine AP. The next highest burning rates occur in propellants with decorated graphene that is physically mixed into the propellant. The lowest burning rates are found in propellants where the graphene is undecorated, where there is little difference between encapsulated or physically mixed graphene blanks, or compared to a baseline propellant. Burning rates are found to be similar between graphene preparation methods considered.

Mechanical Properties of Composite AP/HTPB Propellants Containing Novel Titania Nanoparticles

AbstractModern chemical synthesis techniques have allowed for improved incorporation of nano‐scale additives into solid propellants. Various methods were implemented to incorporate titania nanoparticles into three representative ammonium perchlorate composite propellants (APCP), and the mechanical properties of each formulation were tested and compared to those of an analogous baseline. Advanced imaging techniques were applied to all particle synthesis methods to characterize particle size and particle network type and size. Uniaxial tensile testing was performed to measure propellant ultimate strength, ductility, and elastic modulus. In general, the addition of nano‐titania additives to the propellant decreased propellant strength and modulus, but improved ductility. Propellant formulations containing in‐situ titania exhibited an increase in ductility of 11 %, 286 %, and 186 % with a corresponding reduction in strength of 82 %, 52 %, and 17 % over analogous baselines. These trends corresponded to a simultaneous decrease in propellant density, indicating that when implementing nano‐sized additives, care must be taken to monitor the effect of the altered manufacturing techniques on propellant physical properties in addition to just monitoring burning rates. Tailoring of propellant manufacturing procedures and the addition of Tepanol bonding agent to an in‐situ APCP formulation fully recovered the propellant density and ultimate strength while retaining the enhanced ductility.

Oxidizer coarse-to-fine ratio effect on microscale flame structure in a bimodal composite propellant

The microscopic flame structure of a composite propellant is expected to change significantly as the particle size distribution is varied. In this paper we report observations of the diffusion flame structures in burning ammonium perchlorate (AP) composite propellants with varying ratios of coarse to fine AP. The coarse-to-fine ratio (C/F) was varied between 1:16 (mostly fine AP) to all coarse AP. Five kHz OH planar laser-induced fluorescence (PLIF) was used for in situ imaging of the highly transient and microscale flames above single and groups of AP particles at atmospheric and elevated pressures. Jet-like diffusion flames are observed for all propellants above coarse AP crystals at 1 atm. At elevated pressures, both jet-like and lifted arched inverted overventilated diffusion flames (IOF) were observed. Jet-like flames were seen more frequently for propellants with low C/F ratios, and were rarely seen for propellants with the highest C/F ratios. On the other hand, lifted IOF were seldom seen for the low C/F ratio propellants but were more frequently observed for higher C/F ratio propellants. Differences in the flame structures are postulated to be due, in part, to the dissimilar local burning rates and flame temperatures between the fine AP/binder matrix and coarse particles. For the first time, the diffusion flames from multiple coarse particles were observed to merge (group combustion), especially for higher C/F ratio propellants. As a consequence, flame height is affected by this group combustion of clustered coarse AP particles that behave similarly to a larger single particle. The ignition delay and lifetime for single AP particles in a composite propellant were measured at 1 atmosphere (atm). The particle lifetime and ignition delay for coarse AP particles vary as a function of C/F, indicating that nearby coarse particles can significantly affect coarse particle ignition and combustion. The data obtained is useful for comparison to numerical simulations of AP composite propellant combustion.