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Both glycidyl azide polymer (GAP) and hexanitrohexaazaisowurtzitane (CL-20) are high-energy compounds with very promising applications. However, there are relatively few relevant studies for GAP/CL-20 aluminum-based propellants. In this paper, the CCPs of aluminum-based GAP/CL-20 propellant under different operating conditions were collected by a gas collecting device, and the physicochemical properties of CCPs were carefully studied by various modern analytical and testing instruments. The results show that the CCPs consist mainly of smoke oxide particles (~1 μm), residual oxide particles (~20 μm) and agglomerates. Residual oxide particles are widely available, but have received less attention from researchers. The agglomerates can be divided into two categories: sphere-like agglomerates and non-spherical agglomerates. Sphere-like agglomerates include cracked spheres, solid spheres, hollow spheres, and spheres with oxide caps. Surprisingly, we found an agglomerate with two caps. Non-spherical agglomerates are larger in size than sphere-like agglomerates, and the non-spherical agglomerates include irregular agglomerates, coral-like aggregates, and filamentous agglomerates. As far as we know, coral-like aggregates and filamentous agglomerates in CCPs have not been reported in the literature. Pocket theory and inter-pocket bridge theory were used to explain the formation mechanism of fine filament agglomerates. In addition, the formation mechanisms of different types of agglomerates were analyzed and sorted out. The particle size distribution of CCPs at different pressures shows that the average particle size of CCPs decreases with increasing pressure. It is hoped that this paper can provide a reference for the design of high-energy propellant formulations. [ABSTRACT FROM AUTHOR]

To derive more performance from the conventional composite propellant based on hydroxyl-terminated polybutadiene (HTPB) and ammonium perchlorate (AP), it is envisaged to hydrogenate HTPB, which increases the H/C (hydrogen to carbon ratio) of the base polymer. This paper attempts to describe the partial hydrogenation of HTPB using a catalytic method that uses palladium supported by activated charcoal as a catalyst and HTPB polymer as a precursor. HTPB has a hydroxyl value of 41.0 mg KOH/g with a number-average molecular weight (Mn) of 6150, polydispersity (PD) of 2.25 was used as a precursor. Iso-propyl alcohol (IPA) and toluene were used as a solvent media to disperse the HTPB polymer during hydrogenation. The estimate revealed an increase in specific impulse (ISP) up to 1.2 s with ∼37 % hydrogenated HTPB (HHTPB) as binder in composite solid propellants. Partial hydrogenation is only attempted to retain other process capabilities essential for realizing a defect-free solid propellant grain with good structural integrity. In contrast, others attempted to reach near saturation. A reactor capacity of 100 ml, operating at 60 bar pressure, was used to synthesize HHTPB, and the extent of hydrogenation was controlled based on the numerous experiments varying the reactor parameters like operating temperature, operating pressure, and solvent-to-polymer ratio for a given catalyst concentration. Detailed characterization of the end product by FTIR, 1H NMR and 13C NMR to reveal the degree of hydrogenation along with generic polymer characteristics. The measured hydroxyl value of HHTPB is comparable with HTPB; however, a marginal increase in molecular weight and polydispersity was noticed at 37 % conversion, wherein other researchers found a loss in -OH value. Thermogravimetry analysis revealed that no significant change in the gasification rate. A slight increase in the H/C ratio and calorific value was observed for HHTPB compared to HTPB. Despite the increase in viscosity of HHTPB, the increase in the vinyl-type functional distribution of HHTPB aids for better process-ability during propellant processing. However, the propellant formulation should be optimized with the help of plasticizers, solid loading, etc., to achieve the required properties.

On February 18, 2021, NASA's Mars 2020 mission successfully landed the Perseverance rover in Jezero Crater, the heaviest interplanetary rover ever built, on the surface of Mars. Following up on the successful entry, descent, and landing of the Curiosity rover of the Mars Science Laboratory mission in August 2012, the Mars 2020 mission Descent Stage Propulsion System was a build-to-print sequel. The Mars 2020 Descent Stage Propulsion System had a few minor low risk changes based on the flight performance of the Mars Science Laboratory System to improve performance. The in-flight performance of the Descent Stage Propulsion System was consistent with expectations with the exception of apparent higher than expected delivered thrust from the Mars Lander Engines, which occurred on both the Mars 2020 and the Mars Science Laboratory missions. The Descent Stage Propulsion System completed its mission with significant capability margin with respect to thruster life, maximum delivered thrust, and available propellant at touchdown. [ABSTRACT FROM AUTHOR]

A robust trajectory optimization approach for guidance algorithm gain and target vector selection for powered descent and landing is developed. A genetic algorithm is used to determine optimized guidance algorithm parameters to minimize the impact of initial condition, environment, navigation, and vehicle property uncertainty on flight performance for a given sensor suite. Vehicle state uncertainties are computed efficiently using linear covariance analysis techniques. When implemented in the guidance algorithm, the optimized gains and target vectors shape a trajectory that has more favorable conditions for a given navigation sensor suite, resulting in improved flight performance. As a demonstration of this method, the optimized guidance parameters are found for a multiphase trajectory from powered descent initiation to touchdown for a robotic lunar landing mission. Single-objective optimization results demonstrate a reduction in uncertainty and an improvement in nominal performance. Multi-objective optimization results showing the tradeoff between terminal position uncertainty and total propellant usage are presented for multiple sensor suite compositions. Further, guidance parameters selected using the developed robust trajectory design approach may enable acceptable flight performance with fewer and/or lower-quality sensors. The resulting Pareto fronts present the optimal trade space early in the mission design process to enable informed decision-making. [ABSTRACT FROM AUTHOR]

This research work emphasizes on the development aspects of a cartridge cable cutter for helicopter application. This cartridge is used to rescue hoist system during emergency for helicopter application under adverse conditions. It is an electrically initiated cartridge in which two electrical squibs are used with specified current and voltage. As the cartridge is initiated, the squib gets incandescent and initiates an explosive train. A cartridge cable cutter is a propellant actuated device (PAD) that generates hot combustion gases having high temperature and pressure on burning of gun powder and propellant inside the cartridge case. The cable cutter cartridge under study is filled with energetic materials (EM) such as propellants and gun powder. It releases the energy very quickly which acts on the projectile i.e. the cutter in actual system. A projectile velocity measurement was carried out using Doppler RADAR (radio detection and ranging). To assess the projectile velocity is the unique design feature in armament field. It is responsible for the measurement of the projectile velocity at the muzzle end of velocity test rig (VTR). The minimum and maximum projectile velocities were experimentally measured in between 70 ms−1 and 150 ms−1. The projectile velocity measurement is an evaluation methodology as performance parameter of this cartridge. The cartridge under study has been developed meeting structural, functional and mechanical requirements. The cartridge has undergone various exhaustive qualification tests during development phase. The cartridge was thus designed, qualified and validated through rigorous development trials. The main objective of this article is to address development aspects of the cartridge cable cutter for helicopter application. In conclusion, after successful design, development and qualification trials, the cartridge was found to meet all the functional and operational requirements considering the end use. [ABSTRACT FROM AUTHOR]

Point cloud data obtained from scanning propellant grains with 3D scanning equipment exhibit positional uncertainty in space, posing significant challenges for calculating the relevant parameters of the propellant grains. Therefore, it is essential to normalize the position of each propellant grain's point cloud. This paper proposes a normalization algorithm for propellant grain point clouds, consisting of two stages, coarse normalization and fine normalization, to achieve high-precision transformations of the point clouds. In the coarse normalization stage, a layer-by-layer feature points detection scheme based on k-dimensional trees (KD-tree) and k-means clustering (k-means) is designed to extract feature points from the propellant grain point cloud. In the fine normalization stage, a rotation angle compensation scheme is proposed to align the fitted symmetry axis of the propellant grain point cloud with the coordinate axes. Finally, comparative experiments with iterative closest point (ICP) and random sample consensus (RANSAC) validate the efficiency of the proposed normalization algorithm. [ABSTRACT FROM AUTHOR]

This study focuses on the low-energy transfers to lunar distant retrograde orbits (DROs) from geostationary transfer orbits (GTOs) in the bicircular-restricted sun-Earth-moon four-body problem. The low-energy transfer is essential for low-cost small satellites reaching out to the Moon, and the departure from GTO allows more rideshare opportunities. We first created several large-scale databases of trajectory segments, such as GTO to apogee in the weak-stability area, apogee to perilune, and DRO to perilune. Then, millions of GTO-DRO transfer trajectories with double powered lunar flybys (PLFs) and weak stability boundary (WSB) ballistic transfer were constructed through trajectory patching. The key flight information, such as the ΔV-time-of-flight Pareto fronts, launch windows, and the flight mode via WSB ballistic transfer, is obtained from feasible solutions. Results show that low-energy GTO-DRO transfers can be achieved by exploiting PLFs and WSB ballistic arcs, which suggests potential applications in the cislunar space. [ABSTRACT FROM AUTHOR]

Combustible cartridge cases are parts of modular charges used in modern artillery systems. Some types of combustible cartridge case materials have exhibited problems during pyrostatic measurements caused by their difficult ignition. This article explores the possibility of testing the combustible cartridge case material mixed with a propellant of known ballistic properties and then separating the influence of that propellant using methods of mathematical analysis. The aim of this work is to create methodology for closed vessel tests of combustible cartridge case material. Outcome involves the characterization of combustible cartridge case material ballistic properties, including its burn rate parameters. Calculations described in this paper could potentially be modified to be applicable to other cases of mixture of two propellants. [ABSTRACT FROM AUTHOR]

The purposes of this study were to evaluate the bulk sample concentration and airborne concentrations of phthalate in different types of propellent and triggers in consumer spray products and estimate health risk assessment via inhalation. First, the phthalate concentrations were analyzed in the solutions of all products 174 from markets. Then, among 64 products containing phthalates, 10 propellant-type products were selected that contained high phthalate concentrations; airborne concentrations were measured at distances of 1, 3, and 5 m from the spray nozzle in a clean room. Four phthalates were detected in spray products: diisobutyl phthalate (DiBP), di-n-butyl phthalate (DnBP), butyl benzyl phthalate (BBzP), and bis(2-ethylhexyl) phthalate (DEHP). Among propellant-type products, repellents contained the highest mean concentrations (3.90 ppm), whereas sterilized products contained the lowest mean concentrations (0.59 ppm). Among trigger-type products, cleaning products contained the highest mean concentrations (4.54 ppm), whereas coating products contained the lowest mean concentrations (0.73 ppm). In both propellant- and trigger-type products, DnBP and DEHP exceeded the standard set by the Ministry of Food and Drug Safety of South Korea. No significant patterns were observed for the airborne DiBP, DnBP, and DEHP concentrations at 1, 3, and 5 m (p > 0.05). Children were one of the population groups most susceptible to health risks. Overall, phthalates were detected in both product solutions and the air in consumer spray products; some even exceeded safe limits. Therefore, consumer spray products should be used in well-ventilated areas to avoid respiratory exposure. [ABSTRACT FROM AUTHOR]

Many kinds of non-lethal ammunitions are developed in the last fourty years. The 40x46 mm Non-lethal ammunition is one of several ammunitions ready to be used in riot control. This type of ammunition can be used to subdue the target by implementing impact force. When developing non-lethal ammunition, it should be considered that the ammunition has adequate projectile velocity to ensure that the impact will produce sufficient pain to immobilize the target without risk of permanent injury. Projectile velocity is affected by the propellant weight and projectile weight. Therefore, a study to understand the effect of propellant charge weight on projectile velocity was done experimentally. This experiment was done by preparing several variations of propellant charge weight which were 0.150 gram, 0.200 gram, 0.250 gram, 0.300 gram and 0.350 gram. The desired output of this study is to obtain the correct amount of propellant charge weight to produce projectile velocity in accordance with the 40x46 mm Non-Lethal ammunition specification. The conclusion of this study is that Variation C ammunition with propellant charge weight of 0.250 gram is the closest variation to achieve nominal projectile velocity of 75 m/s. The exact range of propellant charge weight that can be used as production guidelines in order to comply with the product specification is between 0,228-0,280 grams APS350.

With the development of micro-spacecraft technology, micro-nano satellites have the advantages of small size, low power consumption, short development cycle, formation networking, etc., and can complete many complex space tasks at a lower cost. Micro-nano satellites require a micropropulsion system with the capability of performing precise total impulse and thrust to execute maneuvers, such as attitude control, orbital transfer, and gravitation compensation. In contrast to other micropropulsion systems, solid propellant microthrusters (SPM) arrays based on micro-electromechanical system (MEMS) technology possess a simple structure and quick response, which is a potential micropropulsion system. In recent years, many research groups have done a lot of research on SPM arrays. In this paper, the latest progress of SPM arrays is summarized from the aspects of structure design, propellant selection, bonding technology, ignition unit type and micro-thrust test, and some suggestions for the future development direction are given.

Herein, in order to increase the purity and improve the performance of HMX crude products (Raw HMX) isolated from decommissioned propellants, a new method to obtain submicron levels using the solvent-anti-solvent process was proposed. Two different morphologies of HMX, regular prismatic vs. spherical-like, were obtained by means of two solvents (DMSO, DMF). Polyethylene glycol-200 (PEG-200) was used to improve the morphology and dispersion of crystals at low saturation and low crystallization temperatures. Various rates of addition of anti-solvent (water) were studied to prevent HMX crystalline transition and effectively increase purity. Furthermore, the aging process was applied to further modify the crystals with controlled particle size distribution The purity of the samples was tested by High Performance Liquid Chromatography (HPLC) spectroscopy, and the purity of the crystallized samples was improved from 95.53% in Raw HMX to over 99%. The thermal decomposition properties were investigated by differential scanning calorimetry (DSC) and the kinetic parameters of the thermal decomposition reaction of the materials were calculated using the Kissinger and Ozawa method. The samples were also tested for impact and friction sensitivity, which was reduced compared to both Raw HMX and industrial HMX, demonstrating that this type of modified HMX recovered from decommissioned propellants is fully reusable. [ABSTRACT FROM AUTHOR]

Plasticizers are functional additives that have been widely utilized to enhance the mechanical properties and processing technology of explosive systems. However, due to the increasing demand for energetic formulations of explosives and propellants, traditional plasticizers are gradually being replaced by energetic plasticizers. Azido plasticizer, a type of energetic plasticizer, possesses excellent thermal stability and low glass transition temperature. However, the incorporation of a single azido group can lead to issues such as decreased oxygen balance and reduced density. In recent years, novel azido plasticizers containing various energetic groups have been developed. Among these, the introduction of a nitramine group into the azido plasticizer has shown significant improvements in oxygen balance, density, and sensitivity compatibility. This makes azidonitramine plasticizers a promising research direction in the development of energetic plasticizers. Despite the existence of approximately twenty different types of azidonitramine plasticizers over the past few decades, a comprehensive review of these compounds is lacking in the literature. Therefore, this paper provides an inductive review of the synthesis, application, and performance characterization of azidonitramine plasticizers with the aim of inspiring further research in this field.

This 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. [ABSTRACT FROM AUTHOR]

This article reports two accidents caused by defective Takata airbags ruptured, which led to the deaths of the drivers. This is the first public report on the deaths caused by Takata airbags in China. Determine the relationship between the driver death and airbag rupture through autopsy indings and vehicle inspection. Due to defects in the design of Takata's inflator, moist air was permitted to slowly enter the inflator, resulting the PSAN slowly degraded physically. The damaged propellant burned more rapidly than intended and overpressurized the inflator's steel housing, causing fragmentation and flying debris at high speed, killing or injuring vehicle occupants. To date, there are still tens of millions of defective Takata airbags that have not been recalled for repair, posing safety risks. This article suggests taking preventive measures to avoid the occurrence of similar accidents. [ABSTRACT FROM AUTHOR]

This study focuses on an innovative green propellant based on paraffin, stearic acid, and coal, used in hybrid rocket engines. Additionally, lab-scale firing tests were conducted using a hybrid rocket motor with gaseous oxygen as the oxidizer, utilizing paraffin-based fuels containing stearic acid and coal. The mechanical performance results revealed that the addition of stearic acid and coal improved the mechanical properties of paraffin-based fuel, including tensile, compression, and flexural strength, under both ambient and sub-zero temperatures (−21 °C). Macrostructural and microstructural examinations, conducted through optical and scanning electron microscopy (SEM), highlighted its resilience, despite minimal imperfections such as impurities and micro-voids. These characteristics could be attributed to factors such as raw material composition and the manufacturing process. Following the mechanical tests, the second stage involved conducting a firing test on a hybrid rocket motor using the new propellant and gaseous oxygen. A numerical simulation was carried out using ProPEP software to identify the optimal oxidant-to-fuel ratio for the maximum specific impulse. Following simulations, it was observed that the specific impulse for the paraffin and for the new propellant differs very little at each oxidant-to-fuel (O/F) ratio. It is noticeable that the maximum specific impulse is achieved for both propellants around the O/F value of 2.2. It was observed that no hazardous substances were present, unlike in traditional solid propellants based on ammonium perchlorate or aluminum. Consequently, there are no traces of chlorine, ammonia, or aluminum-based compounds after combustion. The resulting components for the simulated motor include H2, H2O, O2, CO2, CO, and other combinations in insignificant percentages. It is worth noting that the CO concentration decreases with an increase in the O/F ratio for both propellants, and the differences between concentrations are negligible. Additionally, the CO2 concentration peaks at an O/F ratio of around 4.7. The test proceeded under normal conditions, without compromising the integrity of the test stand and the motor. These findings position the developed propellant as a promising candidate for applications in low-temperature hybrid rocket technology and pave the way for future advancements. [ABSTRACT FROM AUTHOR]

Stabilisers are an integral part of a propellant composition. They are essential for ensuring the chemical stability of nitrate‐ester based propellants, preventing oxidation, chain scission and uncontrolled heat generation. Progress is being made, especially in Europe, with REACh legislation (1907/2006) to use more environmentally‐friendly compounds. New stabilisers with a greener environmental profile and producing less toxic daughter products have been investigated by several groups, and several compounds demonstrated even better performances – more chemical stability and therefore longer shelf lives than formulations with the currently‐used stabilisers. Additionally, the good efficiencies and lower toxicities of the daughter products of the "green" stabilisers are also evaluated. This paper is a continuation of our previous work and demonstrates that for industrially‐manufactured propellants, that the tests performed by four different entities validate the stability and compatibility of the propellants, investigated previously on a laboratory scale, providing the community with safer formulations for the environment and health. [ABSTRACT FROM AUTHOR]

The advent of space exploration missions, especially those aimed at establishing a sustainable presence on the Moon and beyond, necessitates the development of efficient propulsion and mission planning techniques. This study presents a comprehensive analysis of chemical and electric propulsion systems for spacecraft, focusing on optimizing propellant distribution for missions involving transfers from Low-Earth Orbit (LEO) to Geostationary Orbit (GEO) and the Lunar surface. Using mathematical modeling and optimization algorithms, we calculate the delta-v requirements for key mission segments and determine the propellant mass required for each propulsion method. The results highlight the trade-offs between the high thrust of chemical propulsion and the high specific impulse of electric propulsion. An optimization model is developed to minimize the total propellant mass, considering a hybrid approach that leverages the advantages of both propulsion types. This research contributes to the field of aerospace engineering by providing insights into propulsion system selection and mission planning for future exploration missions to the Moon, Mars, and Venus. [ABSTRACT FROM AUTHOR]

Point cloud data obtained from scanning propellant grains with 3D scanning equipment exhibit positional uncertainty in space, posing significant challenges for calculating the relevant parameters of the propellant grains. Therefore, it is essential to normalize the position of each propellant grain’s point cloud. This paper proposes a normalization algorithm for propellant grain point clouds, consisting of two stages, coarse normalization and fine normalization, to achieve high-precision transformations of the point clouds. In the coarse normalization stage, a layer-by-layer feature points detection scheme based on k-dimensional trees (KD-tree) and k-means clustering (k-means) is designed to extract feature points from the propellant grain point cloud. In the fine normalization stage, a rotation angle compensation scheme is proposed to align the fitted symmetry axis of the propellant grain point cloud with the coordinate axes. Finally, comparative experiments with iterative closest point (ICP) and random sample consensus (RANSAC) validate the efficiency of the proposed normalization algorithm.

In this paper, the precursors of composite aerogels were synthesized based on the homogeneous reaction of natural polymers with ionic liquids. Nitrochitosan (NCS) with nitrogen content of 15.99% and impact sensitivity of 12 J was synthesized under mild conditions, while nitrocellulose (NC) with nitrogen content of 12.52% was synthesized. The NC/NCS composite aerogel was prepared by using phase separation method and supercritical carbon dioxide drying system. The structure and morphology of the samples were characterized by FTIR, XRD, Raman, SEM, element mapping, and N2 adsorption and desorption. The thermal and burning behavior of precursors and composite aerogels were analyzed by TG-DSC, isothermal TG, TG-DSC-FTIR, and high-speed camera. The results show that NCS can be used as propellants in terms of thermal behavior and physicochemical property. The composite aerogel has uniform distribution of nitrogen elements, mesoporous structure with an average pore size of 20 nm, specific surface area greater than 100 m2/g, large heat of thermal decomposition, low activation energy, well thermal stability, stable burning behavior, and large size burning flame. NC/NCS composite aerogels have a great potential for use in high-speed micro-propulsion system. [ABSTRACT FROM AUTHOR]

A series of aziridino[60]fullerenes was synthesized by the reaction of octabromo[60]fullerene with various anilines. Their ability to absorb free radicals and acid gases was studied, and their potential applications as stabilizers in nitrocellulose-containing propellants were discussed. The results of differential thermal analysis showed that aziridino[60]fullerene can increase the exothermic peak temperatures of nitrocellulose by 0.55–2.37 °C. The methyl violet test found that aziridino[60]fullerenes can extend the complete decomposition period by 31–71 min. The results of vacuum stability test and thermogravimetric test indicated that aziridino[60]fullerene can delay the decomposition of nitrocellulose. Furthermore, their stabilization mechanism was studied by electron spin resonance spectroscopy, and the free-radical scavenging rate of 3c reached 86.09%. The findings demonstrate that aziridino[60]fullerenes could effectively eliminate the nitrogen oxides released by nitrocellulose autocatalysis and might be used as a new stabilizer for nitrocellulose-containing propellants. [ABSTRACT FROM AUTHOR]

Seven 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. [ABSTRACT FROM AUTHOR]

Aluminum is widely used in solid rocket propellants to improve the energy performance of the propellant. However, during propellant combustion, aluminum particles may agglomerate, resulting in slag deposition, incomplete combustion of metal particles, increased two‐phase flow losses, and reduced motor specific impulse. Therefore, it is of great scientific significance and engineering value to understand the agglomeration mechanism of aluminum particles and to explore the method of agglomeration suppression. Based on this, this paper firstly briefly introduced the agglomeration process of aluminum particles during propellant combustion. Subsequently, factors influencing the agglomeration of aluminium particles were analysed. The influencing factors can be roughly divided into two aspects: propellant's own formulation and external environment. Immediately afterwards, the existing agglomeration suppression methods were emphasized and summarized and analyzed. Presently, agglomeration suppression methods can be broadly classified into four categories, namely, conventional formulation optimization, use of aluminum nanoparticles, and modification of aluminum particles using fluorine‐containing compounds or alloy particles. Finally, several directions that need to be focused on in the future are proposed to address the problems in the study of aluminum particle agglomeration suppression methods. [ABSTRACT FROM AUTHOR]

The process of solid propellant production, which is the most widely used high-energy material, has garnered significant attention from researchers. However, there have been relatively few studies on its processing, due to the unique nature of the casting process. This paper aims to further analyze the pouring process of the propellant slurry. Initially, we obtained a sample of the propellant slurry and measured its rheological parameters using a rotary rheometer. From the analysis of the experimental results, we derived the viscosity parameters and the yield values of the propellant slurry. Subsequently, we simulated the pouring process, setting the slurry parameters based on the data obtained from the rheological measurement experiment. The simulation results demonstrated that the flower plate significantly impacts upon the cutting and separating effect on the slurry during pouring. Upon leaving the flower plate, the slurry descends onto the core mold platform under the influence of gravity, gradually flowing along the edge of the core mold. Although there may be some small voids in the pouring process, the voids will disappear completely at the end of pouring. A comparison with the actual pouring situation revealed a higher consistency between the simulation results and reality, thus establishing the reliability of the simulation method as a reference for analyzing the pouring process. [ABSTRACT FROM AUTHOR]

Polydopamine (PDA) has been widely used in the field of energetic materials; however, there are few reports on the ammonium perchlorate (AP) coating of PDA. In this article, to improve the mechanical properties of the GAP‐ETPE‐based propellant, a two‐step method was used to coat the AP with PDA and used in glycidyl azide polymer (GAP) based propellant. SEM, EDS, XRD, and XPS were used to analyze the morphology and composition of PDA@AP, while contact angle testing and calculation were performed to measure the wettability and surface energy of both PDA@AP and GAP‐ETPE. In addition, the tensile strength and elongation of the propellant were measured. The results showed that the PDA@AP composite particles were successfully prepared. The crystal form remained unchanged during the preparation process. The wettability of PDA on AP was improved through the coating of PDA, leading to an increase in the surface energy of AP and enhancing the adhesion between AP and GAP. Mechanical performance testing shows that using PDA@AP in propellants increased the tensile strength of the propellant from 1.2 to 1.8 MPa, while the elongation at break decreased from 208% to 155%. The "dewetting ratio" has also decreased from 2.88 to below 2.5. [ABSTRACT FROM AUTHOR]

Changing the mass flow rate of powder propellant with high precision and large range is essential and challenging for adjusting thrust of the powder engine. In this paper, the regulation characteristics of the powder flow rate are investigated by adjusting two gases, namely driving gas and regulating gas. Firstly, the effect of driving gas on powder flow are analyzed, which provides the large ranged flow regulation with the adjustment rate of 2.39 and high precision with resolution ratio of 0.8 g/s. The powder flow rate is successfully predicted based on the Bernoulli equation, not only with an less deviation of 4.73%, but also more conducive to development of the lightweight system. Second, the introduction of regulating gas provides a new method for powder flow regulation. The powder flow rate can achieve a regulation rate of 1.36 with a small amount of regulating gas. The linear relationship between powder flow rate and regulating gas fraction is established to enable its prediction. Finally, the regulation logic is proposed, based on which the flow rate can be increased or decreased by adjusting the quantities of these two gases flexibly. This study can provide a reference for the thrust regulation of powder engines. • Regulation of powder flow in powder propellant supply system was realized. • Predictive model of the driving gas in powder flow regulation was constructed. • A new method of powder flow regulation by changing regulating gas was proposed. [ABSTRACT FROM AUTHOR]

The current paper presents the architecture of a test bench for small (laboratory) scale hybrid rocket motors destined for teaching purposes. The sustainability of the proposed methodology is emphasized, as it addresses the development of small-scale hybrid rocket motor test benches, to be used either as didactic means for students or for research laboratories, by using low-cost materials, while preserving efficiency. In this regard, the entire development process is approached, from designing to manufacturing (including the casting of the fuel rod) and testing of the product. The developed product uses a mixture of 88 % paraffin, 10% stearic acid, and 2% coal for the solid phase and liquid oxygen for the liquid phase. The testing of the hybrid rocket motor demonstrator was performed outdoors, in controlled conditions. The results showed a good correlation between the theoretical testing parameters with the obtained ones. [ABSTRACT FROM AUTHOR]

A series of fullerene anisole derivative stabilizers was synthesized by nucleophilic substitution reaction using hexachlorofullerene and benzyl alcohol as raw materials to extend the service duration of nitrocellulose (NC)-based propellants. Single-crystal X-ray diffraction, nuclear magnetic resonance, high-resolution mass spectrometry, Fourier transform infrared (FT-IR) spectroscopy, and UV–Vis spectroscopy were used to characterize the structures of the synthesized fullerene anisole derivative stabilizers. Methyl violet, differential scanning calorimetry test, isothermal weight loss, vacuum stability test, and adiabatic accelerated test were used to study their compatibility with NC and their ability to stabilize NC. The results show that the designed and synthesized novel fullerene anisole derivative stabilizer has good compatibility with NC, and their overall stabilizing effects on NC are better than those of the traditional stabilizers, diphenylamine (DPA), and N,N′-dimethyl-N,N′-diphenylurea (C2). The stabilizing effects was ranked as: 3b > 2d > 2a > 2c > C2 > 2b > DPA > NC. In addition, FT-IR analysis and electron spin resonance spectroscopy were applied to explore the stability mechanism of fullerene-based stabilizers to NC. The results reveal that the new fullerene stabilizer can adsorb and effectively eliminate the nitrogen oxide free radicals generated by NC degradation; therefore, it can forbid the autocatalytic degradation of NC and stabilize NC.

A mixed nitrate ester propellant composed of nitrocellulose, nitroglycerin, triethylene glycol dinitrate, and dendrimer DP-2 was studied to explore the effects of DP-2 on the rheological properties of the propellant during the solventless extrusion process. The results showed that the apparent shear viscosity of the propellant decreased gradually with the increased mass fraction of the DP-2 from 0 wt% to 2 wt%. Additionally, it was evident that the inclusion of 0.5 wt% DP-2 leads to a notable decrease in both the apparent shear viscosity of the propellant and the torque of screw by over 50%. However, in contrast to the change in fluidity observed from 0 wt% to 0.5 wt%, the enhancement trend of propellant fluidity becomes less significant as the DP-2 content continues to increase. The effects of DP-2 on thermal properties, chemical stability, mechanical sensitivity, mechanical property, and combustion behavior of the propellant were comprehensively assessed. The results demonstrated that DP-2 exhibited promising potential as a flow modification additive for the manufacture of the propellant by solventless extrusion process.

HFC-134 is the main impurity of HFA-134a. In order to verify the rationality of HFC-134 limits in HFA-134a and ensure the safety of HFA-134a as propellant in pharmaceutical metered-dose inhalers, acute inhalation toxicity, seven-day repeat dose inhalation irritation study, 21-day repeat dose inhalation toxicity study and reverse mutation assay of HFC-134 were tested to evaluate its inhalation safety. In acute inhalation studies, Sprague-Dawley rats were exposed nose-only to HFC-134 at levels of 100 000, 200 000, 400 000, 600 000, and 800 000 ppm for 4 h. Based on the mortality incidence, the calculated four-hour LC50 value for HFC-134 is 532 069 ppm for males and 502 058 ppm for females and acute inhalation toxicity is manifested as the lung lobes turn dark red. Exposures to 836 ± 67 ppm for 4 hours/day 7 days/week continuously did not induce local irritation of the respiratory system in Sprague-Dawley rats. Sprague-Dawley rats were exposed nose-only to HFC-134 at levels of 0 (control), 203 929 ppm and 394 871 ppm 2 h/day for 21 consecutive days, no significant treatment-related adverse effects was noted. Results from Ames studies demonstrated that HFC-134 was not mutagenic. Although HFC-134 has a very low acute inhalation toxicity, considering that its acute inhalation toxicity is higher than that of HFA-134a, and due to the high frequency of use of MDI by asthma patients, acceptance criteria of HFC-134 as the impurity in aerosol propellant HFA-134a should be lower than 8-h TWA WEEL value of 1000 ppm to ensure the safety of the MDI. [ABSTRACT FROM AUTHOR]

High test peroxide gel was prepared by low temperature freezing under the action of calcium ion compound with sodium alginate as a gelling agent. The High test peroxide gel was characterized by ultra depth of field microscope, Fourier infrared spectrometer, rheometer, synchronous thermal analyzer, and electron microscope scanner. The thermal decomposition behavior and reaction kinetics of the gel were investigated. The effective content of H 2 O 2 in the gel before and after aging was also analyzed by KMnO 4 titration. The results show that the content of sodium alginate and the concentration of calcium ion compound directly affect the gelling and rheological properties of high test peroxide gel, and the gel with low sodium alginate content had a more uniform tissue structure. The E α and lg(A /s−1) of the high test peroxide gel decomposition reaction are 69.10 kJ mol−1 and 9.13, respectively. Na 2 O, CaO, CaCl 2 and CaSO 4 are the main components of the high test peroxide gel thermal decomposition condensate products. After ignition, a boron-based high test peroxide gel propellant can produce a steady combustion. After being stored at 263 K for 20 days, the effective content of H 2 O 2 in the gel is 96.50%, and the decomposition rate is only 0.63%. • High test peroxide (HTP) gel was prepared with sodium alginate as a gelling agent. • The HTP gel has good shear thinning property, and the HTP gel containing 10% boron powder could achieve stable combustion after ignition. • The kinetic parameters and most probable mechanism function of thermal decomposition of HTP gel were obtained. • The HTP gel can be stored stably for a long time at low temperatures (≤263 K). [ABSTRACT FROM AUTHOR]

The thermal decomposition of an ammonium dinitramide-based energetic compound was conducted for the first time using a dispersive inductively coupled plasma mass spectrometer, DTA-TG analysis, and pyrolysis at a constant temperature. A liquid droplet was injected over synthesized CuO catalytic particles deposited on lanthanum oxide-doped alumina. The thermal behavior of the ADN liquid monopropellant revealed that decomposition in the presence of catalytic particles occurs in two distinct steps, with the majority of ejected gases being detected in real-time analysis using the DIP-MS technique. At a temperature of 280 °C, pyrolysis confirmed the catalytic decomposition behavior of ADN, which occurred in two distinct steps. [ABSTRACT FROM AUTHOR]

Nitroglycerin (NG) is a high explosive that is difficult to handle in its liquid form, where the entrapment of gaseous NG bubbles results in its high sensitivity to impact (<0.25 J). NG‐based materials are traditionally prepared by complex mixing processes where desensitisation is of major concern. Instead of using a mixing procedure here we demonstrate the successful synthesis of dynamite‐like materials by using a single step bottom‐up approach to form a polymeric host matrix (PM) for NG from a solution which contains the explosive and the matrix precursors. For this purpose, an epoxidized vegetable oil mixed with nitroglycerin (oil to NG mass ratio of 60/40) is polymerized at 100 °C for 30 h by using glutaric acid as crosslinking agent. No degradation of NG under these conditions is observed. The activation energy of NG desorption from the PM (51.9 kJ/mol) is of the same order of magnitude as the one reported in literature for a double‐base powder (81.9 kJ/mol). An accelerated NG desorption is observed as temperature increases. This can be attributed to a slow diffusion mechanism of the explosive from the volume to the surface of the material, where it evaporates. The ignition of NG/PM in air by an open flame leads to a self‐sustained combustion, in which a part of nitroglycerin decomposes in the polymer matrix. Conversely, NG/PM monolithic and granular loads are not ignited by the explosion of the primer in a 9 mm calibre casing. The shockwave released by a detonator on a small NG/PM cylindrical charge (≈1.5 g) does not detonate it, but only makes it deflagrate. Our results show that this novel single‐step synthesis of NG trapped in a polymeric matrix is a very effective approach for desensitizing it to any form of stress. [ABSTRACT FROM AUTHOR]

NEPE propellant has high energy and good mechanical properties. However, due to the lack of detailed research on its microscopic pyrolysis mechanism, the combustion rate and energy release rate are still difficult to control, which limits the further development of NEPE propellant. Based on this, quantum chemistry is used to study the pyrolysis mechanism of key components of NEPE propellant, including oxidants HMX and AP, binders PEG, NG and BTTN. The pyrolysis reaction path, rate-determining steps and main pyrolysis products of each component were calculated, and the pyrolysis kinetic parameters are calculated based on the transition state theory. The results show that HMX, BTTN and NG are all transformed into cyclic nitrogen compounds or chain carbon oxides by NO 2 or NO 3 shedding, and then gradually decomposed, while PEG is the gradual pyrolysis of long chain molecules. The main pyrolysis products are nitrogen oxides and various small fuel molecules containing C/H/N. The order of reaction rate constants of NEPE components is NG> AP> HMX> BTTN> PEG at 1500-2000 K. Among them, PEG and BTTN reaction rate constants are sensitive to temperature, and the reaction rate will rise rapidly with the increase of temperature. This study will provide an important theoretical reference for the regulation of NEPE high-energy catalyst pyrolysis behavior. [ABSTRACT FROM AUTHOR]

Separation Distances are used throughout the world to protect people and assets from the potential hazardous effects from propellants, explosives, and pyrotechnics. The current separation distances for Hazard Division (HD) 1.3 substances and articles used in the United States, in some cases, may not adequately protect against the effects from heat flux and debris when those substances and articles are ignited in a confined structure. Multiple tests in such a confined scenario with HD 1.3 substances have shown that the heat flux and debris hazards could result in injury at distances beyond the current specified explosives safety separation distance (ESSD). Herein are the recommended ESSDs for confined as well as unconfined HD 1.3 articles and substances based on the analysis of hundreds of tests. Recommended ESSDs include a smaller value for unconfined quantities less than 145 kg and ESSDs that are consistent with NATO distances for confined substances and articles. [ABSTRACT FROM AUTHOR]

Nitrate ester binders are a unique class of energetic binders containing nitrate ester (-ONO2) pendant groups attached to the polymeric backbones, which have been extensively employed in solid propellant formulations to improve overall energy output and oxygen balance. Both polymerization of nitrate ester monomers and chemical modification of inert polymers are commonly used methods for constructing such binders. Poly(glycidyl nitrate) [PGN] and poly(3-nitratomethyl-3-methyloxetane) [PNIMMO] are well-investigated nitrate ester pre-polyethers formed by cationic ring-opening polymerization (CROP) from nitrate ester monomers, and their synthesis, properties, chemical modification and applications in solid propellants are discussed in detail. It is worth noting that PGN and PNIMMO as soft blocks can further generate energetic thermoplastic elastomers (TPEs) by polyurethane addition polymerization, which have emerged as potential energetic binder candidates for thermoplastic propellants and melt-cast explosives. Therefore, the recent advances of PGN-based TPEs and PNIMMO-based TPEs are subsequently presented. Finally, the synthesis, properties and applications in propellants of several nitrate ester-modified polymers such as cellulose-based nitrates, nitrated hydroxyl‑terminated polybutadiene (NHTPB) and polyvinyl nitrate (PVN), obtained by direct/indirect nitration of inert polymers, are briefly described.

In order to study the long-time safe storage performance of GaTo modified double base propellant, the accelerated aging tests at 65, 70, 75, and 85°C were conducted. The chemical stabilities, mechanical properties, and microstructure of the propellant samples were characterized by differential scanning calorimeter, bromize-titration, impact resistance testing, and field emission scanning electron microscopy in the aging duration. The results showed that the chemical stability of propellant became worse due to nitrate esters decomposition. The impact resistance degradation is the result of binder network collapse, phase separation between binder and plasticizer, and interfacial dewetting during aging. Hence, the storage life of the propellant at ambient temperature has been evaluated based on stabilizer depletion and impact resistance deterioration via Arrhenius approach

What distinguishes the rocket system from airbreathing engines is that the rocket carries its own propellants, fuel and oxidants. The modern rocket was originally developed for ballistic missiles. The operation of the German V2 ballistic missile was not satisfactory because of excessive nose-cone heating, The Soviet Union launched Sputnik 1 to orbit the earth for 21 days. The solid and liquid propellants are widely used in rocket propulsion. Thrust production is necessary in the propulsion of the rocket. Therefore, the purpose of this study is the development of expression through thrust for the study of the performance characteristics of the rocket. Mathematical model has been developed and illustrative solutions obtained, plotted and analysed for the relationship between parameters that affect rocket performance.

Propellant gauging is crucial for a spacecraft approaching the end of its lifespan. Current gauging systems for satellites typically have an accuracy rate of a few months to a year at the end of their operational life. Therefore, it is essential to determine the appropriate gauging system for mission operations. This research focuses on modeling the propellant gauging system for PRISMA, an Earth Observation (EO) satellite of the Italian Space Agency. The analysis centers on implementing algorithms that calibrate the remaining propellant mass in the satellite tank using traditional methods such as bookkeeping (BKP) and pressure-volume-temperature (PVT). To enhance accuracy in quantification, an unconventional approach called thermal propellant gauging (TPG) has been considered. Preliminary computations were conducted using data obtained from the PRISMA thermal model to understand the calibration accuracy of the three methods. At the end of its operational life, the BKP and PVT methods exhibited error rates of 4.6% and 4.8%, respectively, in calculating the mass. In contrast, the TPG method demonstrated a significantly higher precision with an error rate of 1.86%. However, at the beginning of the satellite's operational life, the PVT and TPG methods showed error rates of 1.0% and 1.3%, respectively, while the BKP technique reported an error rate of 0.1%. Based on these findings, it has been concluded that combining the BKP and TPG approaches yields superior results throughout the satellite's lifespan. Furthermore, the researchers have determined the specific time duration for which each of these distinct approaches can be effectively utilized. [ABSTRACT FROM AUTHOR]

Fine porous ammonium perchlorate (PAP) has small holes in its crust, and the voids in the particles are connected to the outside. The porosity of PAP results in fine bubble contamination in a propellant because the voids in PAP cannot be completely charged with a binder. Fine bubble contamination can improve the burning rate characteristics of an ammonium perchlorate (AP) propellant. The influence of the porosity of PAP on the burning characteristics of an ammonium nitrate (AN)/AP propellant and the effect of Fe2O3 as a catalyst on them were investigated in this study. The void fraction of the propellant increased with increasing mass ratio between AP and all oxidizers (ξ) and ranged from 1.3 % to 3.2 %. The porosity of PAP increased the burning rate of AN/AP propellants. This effect increased with decreasing pressure and was independent of ξ. However, porosity had minimal influence on the burning rate of AN/AP propellants with Fe2O3. The effect of the catalyst on the increase in the burning rate due to the porosity of PAP was influenced by pressure and ξ. The effect on the AN/AP propellant was greatest when ξ was in the 0.5–0.6 range. [ABSTRACT FROM AUTHOR]

Injection coupling is a well-known cause of high-frequency combustion instability in hydrogen/liquid oxygen (H2/LOX) rocket engines. This type of instability is commonly explained by the two-way coupling between the dynamics of the combustion chamber and the injection system. Recent experimental studies of the BKD combustor, however, suggest that the LOX injector could be self-excited and driving the acoustic mode of the combustion chamber. To assess the feasibility of this mechanism, here, we study both experimentally and theoretically the acoustic stability of the LOX injector isolated from the combustion chamber. The experimental study was performed in a water facility mimicking the conditions of a single LOX injector. The water injector was then modeled using an acoustic network analysis, where the transfer matrix of the LOX injector inlet orifice was computed numerically using a linear approach. The analysis successfully predicts the experimental peak in unsteady pressure, revealing that the LOX injector can be self-excited. The instability was found to be driven by the whistling of the orifice at the inlet of the injector coupled with the second longitudinal acoustic mode of the LOX post tube. [ABSTRACT FROM AUTHOR]

Glycidyl azide polymer (GAP)/Hexanitrohexaazaisowurtzitane (CL-20) composite propellants have significant advantages, such as high energy density and low characteristic signal. However, the lack of understanding of its ignition combustion and agglomeration mechanism limits its large-scale engineering application in solid rocket motors. In this paper, the ignition, combustion and agglomeration processes of GAP/CL-20 propellants were studied in detail by using modern analytical and testing instruments, such as high-speed cameras, CO2 laser ignition devices and laser particle size analyzers. First, the ignition and combustion process of the GAP/CL-20 composite propellant were observed with a high-speed camera, and its ignition and combustion mechanism were analyzed. On the basis of the BDP model, a multiple flame structure model suitable for the GAP/CL-20 composite propellant was proposed. Then, the agglomeration of aluminum particles in the combustion process of the GAP/CL-20 composite propellant was observed, and an agglomeration mechanism suitable for the GAP/CL-20 composite propellant was proposed based on the pocket model and skeleton layer theory. Subsequently, the particle size distribution, micromorphology and crystal structure of the condensed phase combustion products were analyzed. The particle size distribution of the condensed combustion products (CCPs) showed three modes, and the CCPs contained active aluminum, which indicated that aluminum particles were not fully oxidized during the combustion process of the propellant. Finally, several further research directions were proposed. The research results may have reference value for the engineering application of GAP/CL-20 propellants. [ABSTRACT FROM AUTHOR]

In this paper, a novel ionic liquid plasticizer, 1‐methyl‐4‐methoxyethyl‐1,2,4‐triazole dicyanamide ([MMET][DCA]), was synthesized and characterized. The effect of [MMET][DCA] on the viscous flow properties of HTPB was studied, and then the effect of [MMET][DCA] on the mechanical and thermal properties of the HTPB/TDI curing system was further explored. The results show that the hydrogen bond between [MMET][DCA] and HTPB has a significant effect on the viscosity of HTPB. In the HTPB/TDI curing system, when the di(2‐ethylhexyl)adipate (DEHA) was replaced by an equal amount of [MMET][DCA], the glass transition temperature did not change significantly; the tensile strength of the curing system increased from 0.436 MPa to 0.474 Mpa; the elongation at break increased from 506.2 % to 700.4 %, and the decomposition temperature at 5 % and 10 % mass loss increased by 32 °C and 70 °C, respectively. [ABSTRACT FROM AUTHOR]

In this work, a novel CuO-based nanocomposite was successfully prepared by hydrothermal method. The results of FT-IR, XRD, XPS and SEM indicated that the nano CuO was successfully loaded on GO/MoS 2 sheets. The catalytic ability of the CuO-based composite was researched by the AP thermal decomposition behavior and the combustion behavior of AP/HTPB. The CuO-based composite could significantly enhance the AP thermal decomposition performance through decreasing the activation energy of AP during the thermal decomposition process. Especially for CuO(90)@MG(10), the AP thermal decomposition temperature was reduced from 437.5 to 334.9 °C and the heat release increased from 396.7 to 1576.8 J/g by adding 4% of the CuO-based nanocomposite. After adding the CuO-based nanocomposite, the ignition delay time of AP/HTPB solid propellant decreased obviously from 0.346 s to 0.109 s with a higher flame height and a stronger flame brightness during the combustion process, indicating that the CuO-based nanocomposite could effectively promote the combustion behavior of AP/HTPB composite solid propellant. In summary, the CuO-based nanocomposite could be applied as an excellent catalyst for improving AP thermal decomposition and a combustion catalyst for AP-based composite solid propellants. [Display omitted] • CuO(90)@MG(10) was prepared by one pot solvothermal method. • CuO(90)@MG(10) could increase the heat release of AP by 4 times. • CuO(90)@MG(10) could significantly reduce the thermal decomposition temperature of AP. • CuO(90)@MG(10) could promote the combustion behavior of composite solid propellant. [ABSTRACT FROM AUTHOR]

Mathematical models for the simulation of the operation of various projectile-throwing systems are continuously modified, simultaneously with the development of propellants. For these models, properly determined values of energetic ballistic characteristics of propellants are very important. This paper presents an original test and the results of closed vessel comparative investigations. The study analyses specific combustion characteristics of single-base propellants using conventional black powder ignition, plasma ignition, and gas ignition. The results of the study indicate the need to take into account—in the calculation of the burning rate—not only the dynamics of gas pressure changes but also the real (experimental) form function, which differs from the theoretical one resulting from the assumed geometric burning model. The obtained results allow for a critical analysis of the existing methods used for the determination of values of ballistic characteristics of propellants. Further, it will allow for creating pyrostatic test conditions that would reflect the condition of instantaneous ignition of propellant grains over their entire surface in the most realistic way. [ABSTRACT FROM AUTHOR]