Properties Of Propellant Research Articles

Study on Improving Low‐Temperature Mechanical Properties of Nitroguanidine Propellant by Triethanolamine

AbstractNitroguanidine (NQ) is one of the most popular ingredients in propellant formula, and always contributes a high weight content due to its outstanding capability in flame temperature controlling. But the mechanical properties of these NQ propellants are usually not good, especially at low temperatures. In order to improve the low‐temperature mechanical properties of the NQ propellant, triethanolamine (TEA) is used to coat NQ before propellant manufacturing. Infrared spectra show that TEA forms hydrogen bond with NQ, and the mechanical properties of the corresponding propellant at low temperatures are improved. Compared with the original NQ propellant, the anti‐impact strength, the compressive resistance and the extension strength of the modified propellant are raised by 44.6 %, 20.6 % and 7.1 % at −40°C, respectively. The low‐temperature maximum burning rate and maximum pressure of TEA‐coated NQ propellant obtained from closed bomb test are 29.6 % and 4.06 % lower than those of the original propellant, which can be attributed to the changes in the combustion process caused by TEA. No accidental combustion occurred during the entire combustion process, indicating that TEA can be considered to improve the low‐temperature mechanical properties of NQ propellant.

Effect of Microstructure on Micro-Mechanical Properties of Composite Solid Propellant.

This study was aimed at determining the effect of microstructure on the macro-mechanical behavior of a composite solid propellant. The microstructure model of a composite solid propellant was generated using molecular dynamics algorithm. The correlation of how microstructural mechanical properties and the effect of initial interface defects in propellant act on the macro-mechanics were studied. Results of this study showed that the mechanical properties of propellant rely heavily on its mesoscopic structure. The grain filling volume fraction mainly influences the propellant initial modulus, the higher the volume fraction, the higher initial modulus. Additionally, it was found that the ratio of particles influences the tensile strength and breaking elongation rate of the propellant. The big particles could also improve the initial modulus of a propellant, but decrease its tensile strength and breaking elongation rate. Furthermore, the initial defects lowered the uniaxial tensile modulus, tensile strength, and the relaxation modulus of propellant, but did not affect the relaxation behavior of the propellant.

Effect of novel graphene-based ferrocene nanocomposites on thermal decomposition of AP

Graphene-based ferrocene nanocomposites play a positive role in improving the comprehensive properties of solid propellants containing ammonium perchlorate (AP). Novel graphene-based ferrocene nanocomposites with different molecular structures were successfully fabricated and characterized systemically using SEM, EDS, FTIR, RAMAN and XPS instruments. Additionally, the catalytic performance of the as-synthesized graphene-based ferrocene nanocomposites on the thermal decomposition and kinetics behavior of AP were studied using DSC and kinetic methods. The result showed the excellent catalytic performance of graphene-based ferrocene nanocomposites, and the molecular structure plays a significant influence on thermal decomposition of AP. Among the nanocomposites considered, the as-synthesized graphene-based ferrocene nanocomposite NG-550-Fe (γ-aminopropyl triethoxy silane as modifier) owns best catalytic activity, and the decomposition peak temperature and activation energy of AP + NG-550-Fe was reduced by 137.7 °C and 151.6 kJ·mol−1 respectively, compared with pristine AP. Combined with the reported studies, the relatively stronger combination of KH-550 and the better dispersion of Fe may be the reason why NG-550-Fe is more effective than other graphene-based ferrocene nanocomposites and traditional supported graphene nanocomposites studied. Results of this study have implications concerning the rational design of graphene-based catalyst, and help to better understand their catalytic performance and mechanism on AP decomposition.

Laser–Accelerated Plasma–Propulsion System

In this paper, the laser-accelerated plasma–propulsion system (LAPPS) for a spacecraft is revisited. Starting from the general properties of relativistic propellants, the relations between specific impulse, engine thrust and rocket dynamics have been obtained. The specific impulse is defined in terms of the relativistic velocity of the propellant using the Walter’s parameterization, which is a suitable and general formalism for closed–cycle engines. Finally, the laser-driven acceleration of light ions via Target Normal Sheath Acceleration (TNSA) is discussed as a thruster. We find that LAPPS is capable of an impressive specific impulse Isp in the 105 s range for a laser intensity I0≃1021W/cm2. The limit of Isp≲104 s, which characterizes most of the other plasma-based space electric propulsion systems, can be obtained with a relatively low laser intensity of I0≳1019W/cm2. Finally, at fixed laser energy, the engine thrust can be larger by a factor 102 with respect to previous estimates, making the LAPPS potentially capable of thrust-power ratios in the N/MW range.

The Influence of the Level of Load in the Mixer on the Processability and Mechanical Properties of the Solid Composite Propellant

AbstractThe present study evaluated the influence of the level of load in the mixer on the processability and mechanical properties of the solid composite propellant. The mixtures were processed with the same composition and process conditions but using different percentages of levels of the maximum mixing capacity of the mixer. Both vertical and horizontal types of mixers were used to verify the existence of an optimal level of operation and whether it would depend on the type of mixer adopted. Levels of 50 %, 60 %, 70 %, 80 %, and 90 % were adopted in each macerator. In terms of processability, the 70 % level for the horizontal macerator and the 60 % level for the vertical macerator was the most suitable ones. Regarding the mechanical properties, the optimal operating level to obtain propellants with better properties would be 60–70 % in the horizontal macerator and 70 % in the vertical macerator. The results were interesting as they demonstrated the influence of the level adopted on the final grain. In addition, it is necessary to avoid using the mixers close to their maximum capacity. Therefore, the mixer level should be considered in any rocket motor casting project, both in single‐batch and multi‐batch processes.

The role of secondary species emission in vacuum facility effects for electrospray thrusters

Theoretical, analytical, and experimental investigations of electrospray operation in vacuum facilities show that secondary species emission (SSE) plays a significant role in the behavior of electrospray thrusters during ground testing. A review of SSE mechanisms, along with an analysis of onset thresholds for electrospray thruster conditions, indicates that secondary species (e.g., electrons, anions, cations, etc.) must be carefully considered for accurate measurements and determination of performance and life. Presented models and experiments show that SSE-induced thruster-to-facility coupling can lead to considerable measurement uncertainty but can be effectively mitigated with an appropriate beam target design. The Electrospray SSE Control-volume Analysis for Resolving Ground Operation of Thrusters model is applied to experimental data to analyze SSE behavior. A heat and mass flux analysis of the Air Force Electrospray Thruster Series 2 (AFET-2) shows that SSE-induced Ohmic dissipation can cause performance limitations in ionic liquid ion source thrusters. The presented analytical models show that backstreaming current density contributing to less than 0.1% of measured emitter current density can cause substantial variation in propellant properties. Additionally, backstreaming current density contributing to less than 3% of emitted current can cause the 0.86 μg s−1 neutral loss rate estimated during AFET-2 testing. Arguments are presented to support the notion that glow discharges observed in electrospray thrusters during vacuum operation are a consequence of secondary species backstreaming to the emission site, rather than a process intrinsically caused by ion evaporation. Recommendations for general best practices to minimize the effects of SSE on electrospray thruster operation are provided.

Analysis of Application of Plasma Ignition in Closed Vessel Tests

This paper presents the results of a comparative investigation into the effects of the ignition method on the ballistic properties of three types of propellants: a single-base propellant, a double-base propellant and a low vulnerability (LOVA) propellant, as determined via closed vessel tests (CVT). Conventional gunpowder ignition and plasma jet ignition methods were used. The influence of the ignition method on the values of the propellant characteristics obtained in CVT was analysed. It was found that the method of ignition has an influence on the values of propellant characteristics, determined in CVT. An analysis of the experimental form functions showed that plasma ignition is not a solution to the problems inherent to the process of determining the ballistic properties of propellants in which the burning process deviates from the geometric burning law.

Structure and property of propellant based on nitroglycerine/glycerol triacetate mixed plasticizers: molecular dynamics simulation and experimental study.

Molecular dynamics simulation has been used to investigate the influence of nitroglycerine (NG)/glycerol triacetate (GTA) mixed plasticizers on the plasticizing ability of nitrocellulose (NC) binder in solid propellant. The radial distribution function and binding energy indicated that NC/plasticizers blends showed stronger intermolecular interaction of van der Waals and hydrogen bonds. The mean-squared displacements of plasticizers and volume distribution revealed that the mobility of plasticizer GTA in the NC polymer binder was higher than that of NG. Then, the mechanical properties of the propellant based on NG/GTA mixed plasticizers were investigated systematically using experimental and simulation calculation method. The results suggested that the ductility of propellant based on NG/GTA mixed plasticizers was improved, implying that NG/GTA mixed plasticizers have a higher plasticizing efficiency for NC. Furthermore, we conducted experimental studies on the effects of NG/GTA mixed plasticizers on the energy and combustion properties of propellants. It was shown that NG/GTA mixed plasticizers could enhance the combustion efficiency of propellants effectively at low pressures. These computational and experimental studies provided guidance for the application of NG/GTA mixed plasticizers in high-performance propellants.

Function and Action Mechanism of Carbon Nanomaterials Used in Propellants

With special structures and properties, carbon nanomaterials have been widely used in propellant. Reviews of application of carbon nanomaterials and derivatives on solid propellant could provide theoretical support for further research. Represented by fullerene, carbon nanotube and graphene, application research progress of carbon nanomaterials in propellant combustion as combustion catalysts, combustion stabilizers and additives were summarized. The structure characteristics and the effects on physical and chemical properties of propellent were analyzed. It has shown that carbon nanomaterials and derivatives have distinct catalytic, stable combustion effects on solid propellant, either on energy or combustion properties. The significance of carbon nanomaterials in the field of propellent was summarized, and the research directions were suggested.

Molecular dynamics simulation of ionic liquid electrospray: Microscopic presentation of the effects of mixed ionic liquids

Micro-propulsion devices based on electrospray have advantages of high specific impulse, high precision and compact structure, and are able to meet the requirements of gravitational wave detection and other drag-free spacecrafts for micro-propulsion system. For electrospray thrusters, ionic liquid is the preferred propellant because of its low volatility, high electrical conductivity and thermal stability. Most of the studies presented today focus on single ionic liquid, while the properties of single ionic liquid are certain, which leads to a limitation of electrospray characteristics and hence propulsion performance. Mixing different kinds of ionic liquids broadens the properties of ionic liquids, and thus adjusts the characteristics of electrospray to meet the requirements of diversified space missions. In this paper, the effects of mixing two typical ionic liquids, 1-ethyltrimethylimidazole dicyanamide (EMIM-N(CN)2) and 1‑butyl‑trimethylimidazolium hexafluorophosphate (BMIM-PF6), on propellant properties and electrospray characteristics are investigated by molecular dynamics simulation and validated by comparing with experimental data. The result shows that the mixed ionic liquid changes the emission mode of electrospray thruster. Compared with BMIM-PF6, the specific impulse and thrust for the 50:50 (by mass) mixture increases by more than half of the difference between the two before mixing. In addition, the analysis shows that the range of extrusion voltage is widened by adjusting the mixing ratios to meet the mission requirements for certain specific impulse and thrust.

The influence of the type and size of the reactor and the influence of the heating interruption during curing on the solid composite propellant properties

AbstractThe solid composite propellant is a viscoelastic material that retains the treatment received during its all‐useful life. As a result, its manufacturing conditions induce differences in its final mechanical properties. The present study aims to evaluate the influence of the type and size of the reactor and the effects of the heating interruption during curing on the final mechanical properties of the propellant. Thus, four production processes with identical propellant formulations were performed in four different reactors. One of them was vertical, while the others were horizontal reactors. The heating interruption during curing was performed in 10 samples, at different moments of the curing process and with different duration. The study determines that vertical reactors tend to produce propellants less rigid than those produced in the horizontal type. In addition, the bigger the reactor size, the less rigid the propellant becomes. Finally, the heating interruptions at the beginning of the curing process tend to be insignificant. However, when they occur in an advanced stage of the curing process, they tend to hinder the curing progress, being more significant for interruptions of medium duration.

Meso-model Optimization of Composite Propellant Based on Hybrid Genetic Algorithm and Mass Spring System

The meso-structure of composite propellant directly affects its macroscopic properties. The primary premise of studying the macroscopic characteristics of composite propellant is to establish the meso-structure model which can reflect the actual formulation characteristics.In order to obtain the optimal composite propellant meso-structure model suitable for numerical analysis and calculation, the hybrid genetic algorithm was used to optimize the reconstructed meso-structure model. In order to avoid different degree of overlap between particles, the mass spring system was further improved. The resulting meso-structure model not only preserves the statistical characteristics of the propellant, but also meets the requirement of minimizing the optimal size. The reconstruction and optimization algorithm of the optimal meso-structure model are established in this paper, which has high theoretical significance and engineering application value for the prediction of mechanical properties of composite propellant.

Effects of AP powder topology on microscale combustion properties of AP/HTPB propellant

A three-dimensional model has been developed to capture burning properties of ammonium perchlorate(AP)/hydroxyl–terminated polybutadiene(HTPB) composite propellant. Interfacial coupling between condensed domain and gas phase was conducted to obtain the surface temperature and burning rate. The condensed phase was governed by heat transfer equation, and reacting Navier-Stokes equations with pressure dependent 3-step and 12-species global kinetics were adopted. The current model was verified and validated by comparing with analytical and experimental results. Thereafter, the influences of ellipsoidal AP's orientation and aspect ratio on the burning rate were investigated. The flame structure of a typical propellant with ellipsoidal AP particle was examined, and the characteristic heights of multiple flames were determined. Besides, the flame properties of a typical propellant with spherical/ellipsoidal AP particle and different AP topologies were analyzed. Furthermore, the temperature sensitivity coefficients were calculated for composite propellant with different AP contents and sizes, matching reasonably with the experimental results.

A Comparison of Ethanol, Methanol, and Butanol Blending with Gasoline and Its Effect on Engine Performance and Emissions Using Engine Simulation

Air pollution, especially in large cities around the world, is associated with serious problems both with people’s health and the environment. Over the past few years, there has been a particularly intensive demand for alternatives to fossil fuels, because when they are burned, substances that pollute the environment are released. In addition to the smoke from fuels burned for heating and harmful emissions that industrial installations release, the exhaust emissions of vehicles create a large share of the fossil fuel pollution. Alternative fuels, known as non-conventional and advanced fuels, are derived from resources other than fossil fuels. Because alcoholic fuels have several physical and propellant properties similar to those of gasoline, they can be considered as one of the alternative fuels. Alcoholic fuels or alcohol-blended fuels may be used in gasoline engines to reduce exhaust emissions. This study aimed to develop a gasoline engine model to predict the influence of different types of alcohol-blended fuels on performance and emissions. For the purpose of this study, the AVL Boost software was used to analyse characteristics of the gasoline engine when operating with different mixtures of ethanol, methanol, butanol, and gasoline (by volume). Results obtained from different fuel blends showed that when alcohol blends were used, brake power decreased and the brake specific fuel consumption increased compared to when using gasoline, and CO and HC concentrations decreased as the fuel blends percentage increased.

Viscoelastic Properties of Inert Solid Rocket Propellants Exposed to a Shock Wave

AbstractInert solid rocket propellant samples were subjected to dynamic inflation experiments, to characterize the viscoelastic response at high strain rates. An oxyacetylene‐driven shock tube created the shock wave, which was used to dynamically pressurize the surface of the samples during the inflation experiments. Two high‐speed cameras captured the deforming samples, which were speckled to measure the full‐field surface displacements using the digital image correlation (DIC) algorithm. An inverse finite element analysis (iFEA) was used to calibrate parameters of a generalized Maxwell model (i. e. Prony series), which was used to characterize the propellants’ viscoelastic response to shock wave exposure. The viscoelastic parameters calibrated using a Prony series with one Maxwell branch provided a better fit with the out‐of‐plane displacement data from DIC. At least 50 % of the energy dissipated, within the inert solid rocket propellant, occurred within 5 ms following shock wave exposure. The softening phenomenon, due to debonding of the particles embedded in the inert solid rocket propellant, occurred since there was a decrease in instantaneous elastic modulus with increased strain rate. The results of this study will add to the limited knowledge of the linear viscoelastic behavior of inert HTPB propellant at high strain rates and may improve the predictive capabilities of health‐monitoring sensors that assess the solid rocket propellant's structural integrity.

Mechanical properties of thermal aged HTPB composite solid propellant under confining pressure

With the purpose of investigating the effects of confining pressure and aging on the mechanical properties of Hydroxyl-terminated polybutadiene (HTPB) based composite solid propellant, tensile tests of thermal accelerated aged propellant samples under room temperature and different confining pressure conditions were performed through the use of a self-made confining pressure device and conventional testing machine. Afterwards, the maximum tensile stress σm and the corresponding strain εm for the propellant under different test conditions were obtained and analyzed. The results indicate that confining pressure and aging can significantly affect the mechanical properties of HTPB propellant, and the coupled effects are very complex. On the one hand, the stress σm increases as a whole when confining pressure becomes higher or thermal aging time rises. Besides, this stress is more sensitive to aging with increasing confining pressure. There are almost three regions in the stress increments σmP−σm0/σm0 and thermal aging time curves for HTPB propellant. The maximum value of the stress increment σmP−σm0/σm0 for the propellant is about 98% at 7.0 MPa and 170 d. On the other hand, the strain εm decreases with increasing thermal aging time under the whole confining pressure conditions. However, the variation of this strain with confining pressure is more complex at various thermal aging time, which is different from that of unaged solid propellant in previous researches. In addition, this strain is slightly less sensitive to aging as the confining pressure increases. Furthermore, there is also a critical confining pressure in this investigation, whose value is between 0.15 MPa and 4.0 MPa. Beyond this critical pressure, the trends of the stress σm and the corresponding strain εm all change. Moreover, there are some critical thermal aging time for the stress increment (σmP−σm0)/σm0 and strain increment (εmP−εm0)/εm0 of HTPB propellant in this investigation, which are about at 35, 50 and 170 d. Finally, based on the twin-shear strength theory, a new modified nonlinear strength criterion of thermal aged HTPB propellant under confining pressure was proposed. And the whole errors of fitted results are lower than 6%. Therefore, the proposed strength criterion can be selected as a failure criterion for the analysis the failure properties of aged HTPB propellant under different confining pressures, the structural integrity of solid propellant grain and the safety of solid rocket motor during ignition operation after long periods of storage.

Study on Main curvature of Stress Relaxation Modulus of a Double-base solid propellant

The mechanical properties of a double-base solid propellant under quasi-static and dynamic conditions are studied experimentally. According to the time-temperature equivalence of a double-base solid propellant, the main curve of stress relaxation modulus and temperature-dependent material parameters are obtained by using the stress relaxation test results at different temperatures. Based on the analysis of the temperature spectrum of a double-base solid propellant material, the main curve of stress relaxation modulus and temperature-dependent material parameters of the double-base solid propellant material are obtained by using the equivalent principle. The results show that the dynamic test results are better. The database of the dynamic stress relaxation modulus main curve should be used as the basic parameters of the constitutive model analysis and the structural integrity analysis of the double-base solid propellant, which lay the foundation for the type selection and the structural integrity analysis of double-base solid propellant grain.

Evaluation of graphene-ferrocene nanocomposite as multifunctional combustion catalyst in AP-HTPB propellant

A novel graphene-ferrocene nanocomposite (G-792-Fe) was designed, prepared and characterized systemically using SEM, EDS, FTIR, XPS and RAMAN methods. The as-synthesized G-792-Fe was used as a multifunctional combustion catalyst in ammonium perchlorate-hydroxyl terminated polybutadiene (AP-HTPB) propellant, and the combustion, anti-migration, safety and mechanical performances of AP-HTPB propellant were revealed. The results showed that anchoring on the surface of graphene can effectively inhibit the migration and volatilization of ferrocene compounds in AP-HTPB propellant. The excellent combustion catalytic performance of G-792-Fe on AP-HTPB propellant (burning rate of AP-HTPB propellant containing G-792-Fe increases from 13.87 mm·s−1 to 17.28 mm·s−1 at 15 MPa) is attributed to its positive effect on AP decomposition, which generates more gas-phase products beneficial to the combustion surface thermal feedback and the gaseous REDOX reaction. Additionally, the G-792-Fe presents positive effects on reducing the electrostatic sensitivity and improving the mechanical properties of AP-HTPB propellant. The ignition energy (E50) and the maximum tensile strength (σm) of AP-HTPB propellant containing G-792-Fe were increased by 24.4 mJ and 0.75 MPa respectively, compared with AP-HTPB propellant containing catocene (156.8 mJ and 1.26 MPa). The positive effects of G-792-Fe on safety and mechanical performances of AP-HTPB propellant can be due the outstanding electrical and mechanical properties of graphene-based material. Results of this study have implications concerning design and application of multifunctional combustion catalyst, which can improve the combustion performance, anti-migration performance, safety performance and mechanical properties of AP-HTPB propellant.

Study of photocurable energetic resin based propellants fabricated by 3D printing

Propellants are the main energy source in the internal ballistic process. The use of 3D printing has promised to produce propellants with complex geometries. However, due to the degraded energy properties of propellants using an inert binder, there is a critical need to develop a printable energetic resin. In this paper, a novel energetic acrylate-terminated poly–3–nitratomethyl–3–methyloxetane (APNIMMO) oligomer was prepared and characterized. The performance of a new composite propellant composed of APNIMMO and CL-20 (Hexanitrohexaazaisowurtzitane Dodecane) was also demonstrated. The new energetic printable resin and its composites are suitable for stereolithography (SLA) 3D printing, offering not only an improved thermodynamic energy, but also a substantially improved burn rate. Compared with the inert binder, the energetic binder offers the possibility to improve the thermodynamic energy by 15% and the burn rate at 100 MPa by 480% for 3D printed propellants.

Microstructural simulations of debonding, nucleation, and crack propagation in an HMX-MDB propellant

The modeling of the deformation and failure process of a cyclotetramethylene tetranitramine modified double-base (HMX-MDB) propellant based on the microstructure is of great importance for its manufacturing process and storage lifetime. In the present work, the debonding, nucleation, and crack propagation in an HMX-MDB propellant were investigated experimentally and numerically. Stress-strain responses and viscoelastic parameters were obtained through uniaxial tensile tests on the HMX-MDB propellant and stress relaxation tests on a nitrocellulose-nitroglycerine (NC-NG) propellant, respectively. A two-dimensional representative volume element (RVE) model was developed based on the molecular dynamics method by embedding HMX particles in the NC-NG matrix. A zero-thickness cohesive element was used to simulate the damage behavior of the matrix and the interface. A piecewise cohesive zone model (PCZM) was established to capture stress-strain responses resulted from the matrix rupture and the debonding process at the particle-matrix interface. The effects of matrix strength and interface strength on the mechanical properties of the HMX-MDB propellant were investigated by PCZM. The different ratio of matrix strength to interface strength revealed three kinds of HMX-MDB propellant’s damage patterns: matrix cracking, matrix cracking followed by particle-matrix interfacial debonding, and particle-matrix interfacial debonding followed by matrix cracking.