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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.

Copyright of Ordnance Industry Automation is the property of Editorial Board for Ordnance Industry Automation and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Ordnance Industry Automation is the property of Editorial Board for Ordnance Industry Automation and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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 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 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 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]

Copyright of Laser Technology is the property of Gai Kan Bian Wei Hui and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

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.

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.

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.

The study gives a general overview of the CFD-simulated gas flow via the nozzle of a De Laval rocket engine. In CFD software, the mesh is generated using the nozzle’s geometry. In this work, CFD methods are used to compare a number of factors with those derived from classical theory, such as pressure, velocity, temperature, and arear ratios. The results of computational modelling of CFD simulation are comparable to those found from theoretical calculations.

Aluminum powder is the main metal fuel in composite propellants, and upgrading the proportion of aluminum powder loaded in solid propellants is currently one of the most effective means of increasing propellant energy. Nonetheless, the substantial disparity in boiling points between the core aluminum particles and the alumina layer enveloping their surfaces often results in reduced reactivity, inadequate combustion, and combustion agglomeration during the combustion process of the aluminum powder. Herein, copper pentafluorobenzoate (CuPF) interfacial layer was established on the surface of aluminum powder through the self-assembly coordination reaction between pentafluorobenzoic acid and copper ions, and Al-CuPF energy microspheres were successfully prepared. A comprehensive examination was carried out to scrutinize the surface morphology, elemental composition, and distribution of the Al-CuPF energy microspheres. Furthermore, meticulous studies were conducted on the ignition and combustion properties of these Al-CuPF energy microspheres under various atmospheric conditions. It was found that the Al-CuPF interfacial layer within the Al-CuPF energy microspheres plays a pivotal role in enhancing ignition initiation and acting as a catalyst to facilitate the more efficient combustion of aluminum powder. Moreover, the combustion behavior of Al-CuPF energy microspheres when integrated into composite propellants has been exhaustively researched. Notably, composite propellants incorporating Al-CuPF energy microspheres exhibit heightened burning temperatures and an increased burning rate. Additionally, the combustion and agglomeration dynamics of Al-CuPF energy microspheres on the propellant burning surface were meticulously documented using a high-speed camera. The findings revealed that Al-CuPF energy microspheres spend a significantly shorter duration on the propellant burning surface and notably mitigate the occurrence of aluminum agglomeration issues thereon. This research contributes fresh insights into the application of innovative aluminum-based fuels within the realm of composite propellants. [ABSTRACT FROM AUTHOR]

[Display omitted] • Azole-grafted HTPB shows higher heats of formation, densities, and ballistic properties. • Azole-g-HTPB can realise ideal propellant combination with halogen-free oxidizers. • Environmentally friendly grafting method offers cost-effective large-scale synthesis. • Tetrazole-grafted HTPB exhibits favourable physicochemical properties for propellant development. • Results inspire future advancements in HTPB-based propellants and real-time applications. The present study reports on the synthesis, characterisation, and energetic aspects of poly-nitrogen containing azole-grafted hydroxyl terminated polybutadiene (HTPB) based energetic binders (EBs). A comprehensive computational analysis at the B3LYP/6-311++G(d,p) level of theory reveals that azole-grafted HTPB variants exhibit significantly higher HoF (1061.6 to 1659.8 kJ/kg) and densities (1.26 to 1.61 g/cc) as compared to traditional non-energetic binders such as HTPB (specific heat of formation (HoF): 781.8 kJ/kg, density: 0.92 g/cc),. Their ballistic properties, including specific impulse (I sp : 266.2 to 283.8 s) and density specific impulse (ρI sp : 484.5 to 547.4 g/cc.s) are also superior as compared to HTPB (I sp : 283.8 s, ρI sp : 547.4 g/cc.s). Moreover, the synthetic methodology for grafting azole compounds onto HTPB, utilizing cost-effective, metal-free, and environmentally sustainable procedures with straightforward iodine and base mediation, underscores its potential for large-scale industrial applications. In addition to its advantages in synthesis and energetic properties, tetrazole-grafted HTPB exhibits favourable physicochemical properties: it has a low molecular weight ([M n (VPO)] = 3023), high specific gravity (1.25 g/cc at 30 °C), moderate flowability (η = 623.6 Pa.s at 30 °C and 62.7 at 60 °C), a low glass transition temperature (−57 °C), mechanical insensitivity (low impact sensitivity and no ignition up to 400 °C), high thermal stability (onset temperature, T d,onset = 190 °C, T DSC = 246 °C), and a desirable hydroxyl value (47 mg/KOH). These properties make tetrazole-grafted HTPB an appealing choice for advancing novel propellant composites. Overall, these findings not only pave the way for advancements in HTPB-based propellants but also inspire further exploration in real-world applications, highlighting the transformative potential of azole-grafted HTPB in propellant technology. [ABSTRACT FROM AUTHOR]

AlH 3 has gained considerable attention as a fuel additive due to its ability to offer high specific impulse and superior combustion performance. However, few studies have focused on the fragmentation and agglomeration behavior of AlH 3 . This study investigated the effects of fragmentation of AlH 3 and AlH 3 /PVDF particles on the thermal decomposition, ignition, agglomeration, and combustion of HTPB propellants. Thermal analysis indicated that AlH 3 and AlH 3 /PVDF can accelerate the decomposition of ammonium perchlorate by abundant active sites for the adsorption of the decomposition intermediates. Single-particle combustion uncovered the mechanism behind the directional spray of molten Al from the AlH 3 particle and the fragmentation of the AlH 3 /PVDF particle. The melting of porous Al induces particle shrinkage due to solid-liquid interfacial tension and the structural restoration of the oxide shell, which consequently results in the sealing of cracks in the oxide shell of AlH 3 . Additionally, the accumulation of internal tensile stress leads to the reopening of these cracks and the directional ejection of the molten Al. The flexible oxide shell contributes to a smaller minimum normalized diameter of the AlH 3 /PVDF particle, aiding in the generation of internal tensile stress, while the sublimation of AlF 3 induced the fragmentation. Synchrotron-based X-ray imaging revealed the formation of aggregates promoted by molten Al, the splitting of AlH 3 aggregates due to hydrogen explosion, and the enhanced fragmentation of AlH 3 /PVDF due to the synergistic effect of hydrogen explosion and the sublimation of AlF 3 . Compared to raw particles, the CCPs (condensed combustion products) of SP2 propellant display a 48% reduction in average size ( D = 24.5 μm), whereas there is an over 89% decrease in particle size for the CCPs of SP3 propellant ( 50 = 24.5 μm), whereas there is an over 89% decrease in particle size for the CCPs of SP3 propellant ( D 50 = 5.14 μm). This study contributes to understanding the fragmentation of AlH 3 and AlH 3 /PVDF upon ignition and combustion, providing valuable insights for the development and optimization of propellants containing AlH 3 .

We demonstrate the use of nanosecond pulse transient plasma (NPTP) to improve the control (and acceleration) of the combustion of solid rocket propellants. Here, we fabricate end-burning propellant samples (i.e., grains) with a co-axial center wire electrode using hydroxyl terminated polybutadiene (HTPB), isodecyl pelargonate (IDP), modified diphenyl diisocyanate (MDI), and ammonium perchlorate (AP) as the fuel, plasticizer, curative, and oxidizer, respectively. High voltage (20 kV) nanosecond pulses (20 nsec) produce a streamer discharge that provides electronic throttling of the solid rocket propellant. These studies are carried out over a wide range of oxidizer mass fractions, including those considered insensitive munitions (IM). In addition, real time imaging is performed characterizing the plasma-formation, evolution of the ignition process, and plasma enhanced flame-fuel coupling. We believe the plasma-based mechanisms of enhancement are 3-fold: 1.) The plasma provides highly energetic electrons that drive new chemical reaction pathways via highly reactive atomic species such as H, O, and Cl, 2.) The plasma sputters chunks of the solid fuel material up into the flame where it is combusted, producing an agitated flame profile. 3.) The plasma provides increased turbulence and multi-scale mixing due to hydrodynamic effects (i.e., ionic winds), which further improves the combustion process. Having electronic control of the burn rate introduces the ability to "throttle" solid rocket motors and introduce new flight profile options beyond a pre-selected profile such as the typical boost-sustain profile. While we are unable to quantify the burn rate or thrust from these relatively simple observations, we observe clear evidence of the effect of the plasma on the combustion of these solid rocket fuels even at high oxidizer content. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This work implements astigmatic dual-beam interferometric particle imaging (ADIPI) in propellant combustion diagnostics to enable the measurement of the three-dimensional (3D) spatial position and particle morphology of opaque particles. The ADIPI allows the discrimination of different substances, such as metal droplets, flames, and pyrolysis residues. A general theoretical model based on the generalized Huygens-Fresnel integral and the ray transfer matrix model is developed to describe the identification of ADIPI signals for regular and irregular particles. An experimental system combining a 13 kHz time-resolved ADIPI with digital in-line holography (DIH) is built to enable simultaneous measurements of the propellant combustion field. The typical ADIPI signals presented by different substances in the combustion field are analyzed by comparing the experimental results of DIH. The time-resolved 3D trajectory reconstruction of burning particles and the measurement of irregular particle size and morphology are realized. Due to the effect of the flame, the average deviation of the depth locating of the particles is 1.4 mm with a standard deviation of 1.0 mm. The average deviation value of the depth position relative to the measured distance is 1%. In propellant combustion measurements, the motion of burning particles can be accurately determined, proving its feasibility and practicality. [Display omitted] • ADIPI is applied to propellant combustion diagnostics. • Theoretical model and experimental study are both carried out. • 3D trajectory, particle size and morphology of burning particles are measured. [ABSTRACT FROM AUTHOR]