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GAP and nitrate ester compounds are introduced into the solid propellant formulation as energetic binders and energetic plasticizing agents, respectively, to further enhance the energy level of solid propellants. However, under abnormal thermal conditions, various components within GAP propellants, especially nitrate ester plasticizers, can collectively result in the generation of a large number of voids within the propellant due to factors such as thermal stress and slow component decomposition. This phenomenon can impact the safety of solid rocket engines, necessitating research into their thermal decomposition processes and thermal damage structures. In this study, the thermal decomposition characteristics and gas products of GAP propellants with different nitrate ester plasticizer formulations were investigated using DSC‐TG and FT‐IR. The damage structure of GAP propellants heated under unignited conditions was studied through Micro‐CT, examining the influence of heating conditions and nitrate ester plasticizers on the thermal damage structure of GAP propellants. During heating, the thermal damage structure of GAP propellants was found to include voids generated within the GAP binder and cracks at the interface between the GAP binder and particles, with nitroglycerin as a plasticizer exacerbating the thermal damage of GAP propellants (about 2.2–2.9 times). [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]

Ammonium dinitramide (ADN) has appeared as a promising oxidizer for green propellants and thereby a potential substitute for ammonium perchlorate, largely in use in composite propellants for tactical and strategic long‐range missiles. The novelty lies in replacing ammonium perchlorate with a chlorine‐free oxidizer less harmful to the health and environment. However, ADN is hygroscopic and can potentially react with other chemical components, which could be overcome by microencapsulating the particles. The simple coacervation method was tested herein to microencapsulate ADN with a membrane made of hydroxyl‐terminated polybutadiene as pre‐polymer and methylene diphenyl diisocyanate as the curing agent. The effect of polyamine bonding agents on the capsule formation was tested by adding 0.5 or 2 % of Tepan or Tepanol, whose efficacy to bond to ADN was confirmed by detecting ammonia release through infrared spectroscopy. The capsule membrane was examined by optical and scanning electron microscopy. The dissolution time and rate were the parameters adopted to quantify permeability in a straight dissolution test in water, which demonstrated that 0.5 % Tepanol can provide the most effective protection. The infrared spectroscopy indicated that 60 °C temperature for prolonged periods, normally experienced by propellants, does not chemically affect the capsules' membrane but can turn it lumpy. In conclusion, these polyamine bonding agents can assist the capsule formation over ADN particles using the simple coacervation method, however, their functionality on mechanical properties of propellants needs to be substantiated in forthcoming works as well as the effect of the concentration of bonding agents on propellant formulations. [ABSTRACT FROM AUTHOR]

Composite solid propellant is a kind of viscoelastic composite with high filling ratio and multi‐scale composition characteristics, and its macroscopic mechanical properties strongly depend on the microstructure of the propellant materia. However, with the increasing complexity of composition, structure and properties of composite solid propellants, the traditional research paradigm based on experimental observation, theoretical modeling and numerical simulation has encountered new scientific challenges and technical bottlenecks in the mechanical behavior analysis, charge design and manufacturing of composite solid propellants. Among them, the problems such as insufficient experimental observation, lack of theoretical model, limited numerical analysis and difficult verification of results restrict the development of composite solid propellants in future‐oriented engineering applications to a certain extent. The data‐driven computational mechanics method can directly establish complex relationships between variables from high‐dimensional and high‐throughput data, which can capture trends that are difficult to be found by traditional mechanics research methods, and has inherent advantages in the analysis, prediction and optimization of complex systems. This paper mainly reviews and evaluates the research of neural network based modeling, model‐free data‐driven calculation and data‐driven multi‐scale calculation, which provides the correct direction for the subsequent research of multi‐scale mechanical behavior of composite solid propellants based on data‐driven. [ABSTRACT FROM AUTHOR]

A scalable synthesis of azidomethyl bisoxadiazol linked-1,2,3-triazole-(ABT) based potential liquid propellant and energetic plasticizer is obtained from commercially available diaminomaleonitrile in excellent yield. Newly synthesized compounds were fully characterized by various spectroscopic techniques. These materials exhibit good densities (1.77 g cm−3) and high thermal stabilities (Td = 181 °C). Compound 5 has good detonation properties (5, P = 20.81 GPa, D = 7516 ms−1) and propulsive properties (Isp (neat) = 210 s). These are superior to TNT and GAP and comparable to BAMOD, making them potential green liquid rocket propellants and energetic plasticizers. [ABSTRACT FROM AUTHOR]

Fillers play a decisive role in the mechanical properties of polymer composites. In this paper, different particle sizes of nitroguanidine were obtained to regulate the internal filler structure of triple‐base propellants (TBP) to improve their mechanical response in different environments. A series of morphological and structural characterizations on nitroguanidine (NQ) particles were conducted using techniques. The results indicated that the obtained NQ particles maintained a high level of crystalline quality while preserving their molecular integrity. The mechanical properties of TBP were systematically evaluated under various loading conditions, including cryogenic tensile, compressive, and impact loads, as well as dynamic thermomechanical effects. Additionally, three‐point bending simulations were employed to elucidate the mechanical responses and damage mechanisms. Under axial tensile and compressive loads, reducing the particle size of NQ significantly enhanced the tensile and compressive strength. The maximum tensile strength and compressive strength can reach 344.62 MPa and 104.79 MPa. Moreover, the compressive failure mode transitioned from cracking to axial shrinkage. Conversely, when subjected to radial bending loads, TBP exhibited contrasting behavior, including a decrease in the glass transition temperature from 84.73°C to 76.93°C and a non‐monotonic trend in impact strength (initially increasing from 4.96 to 8.85 kJ/m2 and then decreasing to 2.27 kJ/m2). This study provides valuable insights into the mechanical performance of TBP, supporting the development of high‐energy, high‐strength TBP formulations. Highlights: SEM analysis confirms the pronounced orientation effect of rod‐like NQ.The orientation and particle size of NQ decide TBP's radial impact resistance.Submicron NQ enhances the compression resistance property of TBP.Submicron NQ brings about a shift in the microscopic damage morphology of TBP. [ABSTRACT FROM AUTHOR]

In this research, an ammonium perchlorate/polydopamine (AP/PDA) core–shell composite was prepared in a non-aqueous solution to reduce the mechanical sensitivity of ammonium perchlorate (AP). The result showed that the AP/PDA core–shell composite could be successfully constructed in ethyl acetate solution with an AP recovery rate that reached 86%. The mechanical sensitivity of the obtained AP/PDA core–shell composite was significantly reduced with a PDA content of only 0.76%. The DSC and TG also indicated that the coating of PDA showed catalytic activity in the thermal decomposition of AP with a lower decomposition temperature and a decreased Ea value of AP. Thus, this study proposed a simple strategy for achieving a good balanced between harnessing the energy and ensuring the safety of ammonium perchlorate by significantly reducing its mechanical sensitivity by using a very low polydopamine coating layer content, and this shows great potential for the design and fabrication of insensitive energetic composites for use in propellants. [ABSTRACT FROM AUTHOR]

The liquid burning rate suppressants (BRSs) at room temperature were first prepared by combining urea with adsorption group from AP-bonding agents. The novel urea BRSs were applied in triethylene glycol dinitrate (TEDGN) plasticized hydroxyl-terminated polyether (HTPE) propellants. The results show that only 0.5% of them can reduce the burning rate and pressure index of the propellants at the same time. Owing to the adsorption group from AP bonding agents, the novel urea BRSs can adsorb onto the surface of AP during mixing by themselves, which are more suitable for industrial application than nano-sized or encapsulated BRSs. In addition, the desirable mechanical performance can be obtained and the BRSs have little influence on the hazardous properties of propellants. [ABSTRACT FROM AUTHOR]

A superfine microcrystalline powder of bis-(triaminoguanidinium)-5,5′-azotetrazolate (TAGzT) is prepared by the high-energy ball milling method. The microstructure, elemental composition, thermal decomposition mechanism, and sensitivity characteristics of fine TAGzT are studied by means of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), thermal gravimetric and mass spectrometry, and sensitivity tests. The results show that fine TAGzT consists of irregular granules with a rough surface and contains only C and H elements. TAGzT begins to decompose at about 199°C, with the thermal decomposition products being mainly CH4, NH3, and H2O. The sensitivity test shows that fine TAGzT has good stability. As calculated by the EXPLO-5 software, fine TAGzT has better energy performance than HMX. Composite modified double base propellant (CMDB) samples containing fine TAGzT are designed and prepared. The microstructure, elemental distribution, thermal decomposition mechanism, and sensitivity characteristics of CMDB propellant samples are studied by SEM, EDS, XPS, DSC, and mechanical sensitivity tests. The results show that there are tiny bulges and cracks on the sample surface, and the mass ratio of the components is consistent before and after preparation. With an increase in the fine TAGzT content in the propellant, the thermal decomposition peak temperature moves backward, while increases first and then decreases. The value of the CMDB propellant decreases with an increase in the fine TAGzT content. The CMDB propellants are calculated using the CproPEP software, where fine TAGzT is added to the propellant formulation to have higher values of and than those of HMX and lower values of and . By introducing fine TAGzT into the CMDB propellant, higher energy and better safety can be obtained. [ABSTRACT FROM AUTHOR]

This paper explores the relevance of a new class of upper stages commonly referred to as Orbital Transfer Vehicles (OTVs) or Kick-Stages, and the importance of green propellants in the development of such systems. Orbital Transfer Vehicles are currently developed for diverse applications by many entities and are expected to have a major impact in the future of space missions and overall space sector. Such systems are commonly connected to the topic of On-Orbit Servicing with the promise of unlocking new missions, including active space debris removal, multi-payload to multi-orbit delivery, in-orbit experiments, in-orbit refuelling and other generic services. Green propulsion is an increasingly prevalent trend in the space industry that has experienced significant growth in recent decades with the main objective of identifying suitable alternatives to commonly used, toxic liquid propellants for in-space applications. The study investigates the synergies between the two themes, underlining the advantages that a widespread use of green technologies could bring to the overall sector, but also examining the final benefits to the system design of OTVs. Due to the numerous and challenging propulsive system requirements associated with these systems, green technologies are analysed to determine their advantages and disadvantages in comparison with current concepts, outlining current trends and expected future developments. The focus is on attainable performances of propulsion systems with respect to the required dry and inert mass. Various architectures of the different green alternatives based on hydrogen peroxide and the more peculiar self-pressurized propellants are proposed, exploring green propellants-based designs that can offer synergies and advantages over classical ones. These new architectures offer performance comparable to classical and widely available toxic alternatives and present the important advantage of using easy-to-handle propellants. The development of such new options has the potential to enable innovative future designs by improving mass and size requirements of new propulsion systems, thereby enhancing the current landscape. • Orbital Transfer Vehicles are emerging in the space sector as enabling technology. • The propulsion systems of Orbital Transfer Vehicles are crucial for the success of their missions. • Green Propellants offer various synergies possibly advantageous for new OTV designs. • Green Propellants perform well against toxic alternatives, but have less heritage. • Multiple design choices based on green propellants are proposed and compared. [ABSTRACT FROM AUTHOR]

The combination of Al nanoparticles (ANPs) as fuel and H2O2 as oxidizer is a potential green space propellant. In this research, reactive force field molecular dynamics (ReaxFF-MD) simulations were used to study the influence of water addition on the combustion of Al/H2O2. The MD results showed that as the percentage of H2O increased from 0 to 30%, the number of Al-O bonds on the ANPs decreased, the number of Al-H bonds increased, and the adiabatic flame temperature of the system decreased from 4612 K to 4380 K. Since the Al-O bond is more stable, as the simulation proceeds, the number of Al-O bonds will be significantly higher than that of Al-H and Al-OH bonds, and the Al oxides (Al[O]x) will be transformed from low to high coordination. Subsequently, the combustion mechanism of the Al/H2O2/H2O system was elaborated from an atomic perspective. Both H2O2 and H2O were adsorbed and chemically activated on the surface of ANPs, resulting in molecular decomposition into free radicals, which were then captured by ANPs. H2 molecules could be released from the ANPs, while O2 could not be released through this pathway. Finally, it was found that the coverage of the oxide layer reduced the rate of H2O2 consumption and H2 production significantly, simultaneously preventing the deformation of the Al clusters' morphology. [ABSTRACT FROM AUTHOR]

The ammonium perchlorate (AP) plays a key role in the production of highly energetic materials for application in aerospace propulsion; and the development of catalysts for the production of high burning rate (BR) propellants based on AP is an active field of research. Recently, the graphitic carbon nitrides have been used as a metal-free catalyst for the AP thermal decomposition. Following this line of C=N conjugated polymeric systems used as modifiers, herein, the thermal behavior and decomposition mechanism of AP in the presence of hydrogen cyanide (HCN)-based polymers are described. These novel functional materials can be synthesized from the HCN tetramer, diaminomaleonitrile (DAMN) by a very simple one-pot thermal bulk polymerization. In the present work, the morphological characterization of these DAMN polymeric products and their effect in the thermal decomposition of AP was performed by differential scanning calorimetry (DSC). They were shown to exhibit catalytic activity for the thermal decomposition of this relevant oxidizer. Thus, adding 10% by mass of these nitrogen-containing conjugated polymers to AP decreases both the maximum exothermic peak temperature of decomposition and activation energy (Ea). In addition, thermogravimetry–mass spectrometry (TG–MS) analysis has allowed to evaluate the effect of these innovative activators on the AP thermal decomposition mechanism. Evolved gas analysis seems to indicate that nitrogenous species, such as N2 and N2O, are increased in the presence of these two-dimensional (2-D) macromolecular combustion additives. As a result, the DAMN polymers show a notable potential as a new kind of activators for the development of more efficient AP-based composite propellants. [ABSTRACT FROM AUTHOR]

Due to safety requirements, insensitive behavior under slow cook-off conditions is the desirable behavior for HTPE propellant. As a low sensitivity oxidant, PSAN is used to partially replace for AP in HTPE propellant formulation to improve the slow cook-off behavior further. But the effect of PSAN on the slow cook-off behavior of propellant is inconclusive. So, in this paper, two kinds of HTPE composite propellant contained either AP as oxidant or a mixture of AP and PSAN were manufactured, named HTPE/AP/Al propellant and HTPE/AP/PSAN/Al propellant respectively. Then the slow cook-off behavior of the two propellants were tested. The results indicated that the slow cook-off response of HTPE/AP/PSAN/Al propellant was much more violent than the response of HTPE/AP/Al propellant. Then the possible mechanism was proposed. It expressed that, during the slow cook-off test, the PSAN decomposed much more than AP, the crack and hole produced in propellant grain; meanwhile the decomposition of PSAN also accelerated the decomposition of HTPE binder, the the crack and hole or AP particles could not be covered effectively by the liquefied decomposition product of HTPE binder; if the ignition occurred, the combustion of thermal damaged propellant was sensitive to pressure, leading a violent response to slow cook-off. [ABSTRACT FROM AUTHOR]

Experimental results are presented for a rotating detonation engine supplied with liquid kerosene and preheated air without liquid or gaseous additions to the propellant mixture. Various combustion modes for the generic combustor geometry design were observed—from deflagration, through pulsed combustion and high-frequency instabilities, to stable detonation propagation. Attention was paid to detonation stability (if present), its characteristics, and the propulsive performance of the combustor with a focus on specific thrust and pressure gain through thrust and outlet total pressure measurement. These parameters measured for the observed modes were compared. The stability of the detonation combustion proved not to be critical to achieve high performance of the combustion chamber. For example, high performance was achieved for combustion modes with high-frequency instabilities. [ABSTRACT FROM AUTHOR]

Ammonium dinitramide (ADN, [ NH 4 ] + [ N (NO 2) 2 ] - ) and its related propellants are promising high energy density materials for new-generation space propulsion. In order to ensure their safe utilization, it is of primary importance to assess the risk of accidental combustion events such as detonation. Thus, focusing on ADN and its related propellant composed of ADN, monomethylamine nitrate, and urea with weight percentages of 40:40:20 (AMU442), we have studied the properties and steady structure of detonation propagating in gaseous mixtures formed by their thermal decomposition. The AMU442-based mixture exhibits higher von Neumann and Chapman–Jouguet temperatures and pressures than the ADN-based mixture. The study of their steady detonation structure reveals that the gaseous species resulting from the decomposition of AMU442 have higher detonability than the ones resulting from the decomposition of ADN alone. This is in contrast to a previous study about the safety of these propellants in their original (solid or liquid) phase, i.e., AMU442 has lower sensitivity/reactivity to incident impact than ADN. Thermochemical analyses performed for both mixtures show that the decomposition of HNO 3 plays a dominant role for the energy consumption and initiation of the reaction by releasing both OH and NO 2 . For the ADN-based mixture, the reactions involving HN (NO 2) 2 and HNO 3 are the most sensitive, whereas for the AMU442-based mixture, the most sensitive reactions involve CH 3 NH 2 , CH 2 NH 2 , and HNO 3 . Reaction pathway diagrams emphasize the higher complexity of the chemical pathways for the AMU442-based mixture because of the presence of [ CH 3 NH 3 ] + [ NO 3 ] - and CH 4 N 2 O in the initial mixture. An uncertainty quantification study demonstrated that the calculated induction lengths exhibit an uncertainty on the order of 50%. [ABSTRACT FROM AUTHOR]

In the present mini‐review, droplet impacting on a liquid pool, jet impingement, and binary droplet collision of nonreacting liquids are first summarized in terms of basic phenomena and the corresponding nondimensional parameters. Then, two representative hypergolic bipropellant systems, a hypergolic fuel of N,N,N′,N′‐tetramethylethylenediamine (TMEDA) and an oxidizer of white fuming nitric acid (WFNA) and a monoethanolamine‐based fuel (MEA‐NaBH4) and a high‐density hydrogen peroxide (H2O2), are discussed in detail to unveil the rich underlying physics such as liquid‐phase reaction, heat transfer, phase change, and gas‐phase reaction. This review focuses on quantifying and interpreting the parametric dependence of the gas‐phase ignition induced by droplet collision of liquid hypergolic propellants. The advances in droplet collision of hypergolic propellants are important for modeling the real hypergolic impinging‐jet (spray) combustion and for the design optimization of orbit‐maneuver rocket engines. [ABSTRACT FROM AUTHOR]

Conventional ethanol gelling agents methyl cellulose (MC) and hydroxypropyl methyl cellulose (HPMC) have to be added with a certain proportion of water as a solvent to form the gel. In order to prepare high performance ethanol gel green propellants, hydroxypropyl cellulose (HPC) was proposed as an anhydrous gelling agent. The rheological properties of different ethanol gels were tested by conducting shear tests, yield stress tests, strain scans and frequency scans. The results show that HPMC gels require the addition of more than 6% mass fraction of water as solvent and their critical gelling agent mass fraction is 10%, while HPC gels do not require the addition of water and their critical gelling agent mass fraction is 8%. At a shear rate of 100 s-1, the shear viscosities are 2.6 Pa⋅s, 6.9 Pa⋅s and 11.1 Pas for HPC mass fraction of 6%, 8% and 10%, respectively. At a mass fraction of 8% gelling agent, the yield stress of HPMC and HPC gel is around 2.5 Pa and 24.8 Pa, respectively, and HPC gel has a greater yield stress. HPC has a larger linear viscoelastic region than HPMC with a larger critical strain change. Then it has a stronger internal structure, which is beneficial for storage and transportation. Compared with traditional gelling agents, HPC is a good anhydrous ethanol gelling agent as it can be used to obtain the same viscosity of ethanol gels without water or under smaller quantities. [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]

Large-particle porous propellant has good surface-enhancing combustion performance and may improve the muzzle velocity of combustion propulsion system effectively. The proposed particle element method is further refined to investigate particle motion characteristics and flow field distribution in a large-particle charge combustion system with moving boundary. The particle element parameter aggregation is established to describe particle parameter distribution in the system, and the motion is controlled by particle motion equations during combustion and propulsion, so that the particle element is stretched and coupled with the gas phase. The particle element method accurately describes the distribution of the particle movement process and the evolution of the flow field in the chamber, and the numerical simulation results are in good agreement with the AGARD code. In particular, the overall efficiency of the entire calculating procedure is improved by 21.7%. The research results will effectively solve the flow field problem in the large-particle charge combustion system. [ABSTRACT FROM AUTHOR]

In a high-temperature test of the gas generator with a free-loading composite propellant, an abnormal jitter appeared in the latter part of the internal ballistic curve, whereas no such abnormality was observed in the low-temperature and normal-temperature tests. To investigate the cause, quasi-steady-state simulations of the internal flow field, as well as strength and buckling simulations of the grain, were conducted. The strength simulation revealed that the maximum stress experienced by the composite propellant during operation at 323 K is 0.7 MPa, which is lower than the ultimate stress of the grain (1.01 MPa), indicating no stress failure. The buckling simulation demonstrated that the instability arises from an imbalance of pressure on the inner and outer surfaces of the grain. In the original structure, the ventilation effect on each surface of the grain varied with the regression of the burning surface, leading to a pressure imbalance on the inner and outer surfaces of the composite propellant. Consequently, a non-ablative cladding layer was applied to ensure that the ventilation effect of each channel remains constant. The simulation demonstrated that the pressure on the surfaces of the composite propellant gradually balanced with the operation of the gas generator. Upon retesting at high temperatures, no abnormal jitter was observed in the internal ballistic curve. This indicates that maintaining a constant ventilation area for the combustion chamber and preventing changes in the ventilation effect can ensure the structural integrity of the composite propellant during operation. The working state of the composite propellant with this non-ablative cladding layer is not affected by variations in the design of the solid rocket motor. This approach enhances the adaptability and reliability of the free-loading composite propellant under different motor structures. [ABSTRACT FROM AUTHOR]

Aging during storage and confinement pressure during launch are the two major loading conditions that affect the integrity of solid rocket motors. In comparison to other component materials, solid propellants, as highly filled composites, have a low modulus and fracture toughness and are therefore common sources of failure. The key to improving the integrity of the solid rocket motor is in assessing the health of the solid propellants during storage or launch. To address this issue, we revised the previous model for the progressive damage viscoelasticity of solid propellants to include the effect of chemical aging during storage and the influence of confinement pressure during launch. Specifically, the increase in relaxation time due to aging and the nonequilibrium volume dilatation characteristics under triaxial tension and compression of solid propellants have been considered. To validate the developed model, standard relaxation tests and uniaxial tensile tests on solid propellants without aging were used to calibrate the model parameters. Furthermore, the model was validated by comparison with uniaxial tensile tests under confined pressure after aging and well predicts the aging temperature/time‐dependent mechanical responses of solid propellants. After validation, the developed model was used to study the influence of confinement pressure on microscopic damage evolution and macroscopic volume expansion. Overall, the developed model can be used for the analysis of the integrity of the solid rocket motor after the aging process. [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]

Focusing on a new kind of solid propellants, which takes the ammonium dinitramide (ADN) as the high‐energetic oxidant, and 3,3‐bis(azidomethyl)oxetane and tetrahydrofuran copolymers (PBT) as the high‐energetic fuel binder, the burning rates and the theoretical performance of the propellant were measured under different ADN contents, ADN sizes and pressures. The burning rates increased from 7.9 mm/s to 117.4 mm/s and 49.1 mm/s to 74.2 mm/s when the pressure increased from 0.1 MPa to 10 MPa and from 12 MPa to 20 MPa separately, with a singularity in the pressure dependence of the burning rate at around 10 MPa. In terms of the effect of the ADN content, under the experiment pressures from 0.5 MPa to 5.0 MPa, the burning rates of the propellant were promoted by the increase of the oxidizer loading in a range of 50 wt% to 75 wt%, with a transition from a kinetically‐controlled reaction to a diffusion‐controlled one. Within the condition scope of this study, no obvious effect of the ADN sizes on the propellant combustion properties was observed. This could be attributed to the solid‐liquid mixed multiphase layer and the binder which served as a heat sink for the smaller ADN particles. [ABSTRACT FROM AUTHOR]

Addressing the delicate balance between the energy and sensitivity of energetic materials has been a prominent research focus. Here, 7,8-dinitropyrazolo[1,5-a][1,3,5]triazine-2,4-diamine (ICM-104) is assembled with oxidizer ions through coulombic interactions, achieving an increase in energy while maintaining relatively low sensitivity. X-ray diffraction results indicated that the two energetic salts have a layered structure different from that of ICM-104, and have high densities of 1.89 and 1.95 g cm−3, which are higher than most other energetic salts. Both have excellent thermal detonation velocity (8813 and 8857 m s−1) and detonation pressure (33.2 and 35.7 GPa), higher than 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) (D: 8795 m s−1, P: 34.9 GPa). Moreover, compound 1 exhibits low mechanical sensitivities (FS > 360 N, IS > 40 J), which has great potential as an insensitive energetic material. In addition, two energetic salts have favorable laser-ignited combustion and propulsion performances, which provide new strategies for the formulation design of solid propellants. [ABSTRACT FROM AUTHOR]

Passive oxide layer could expose a significant impact on reactive metal combustion. Boron and aluminum experience combustion enthalpy of 59.3 and 31.1 KJ/g and passive oxide layer of 200 and 7 nm, respectively. In this study, surface oxygen of born and aluminum particles (10 µm) was quantified via EDAX analysis. Boron and aluminum demonstrated surface oxygen content of 14.6 and 7.2 wt %, respectively. Reactive particles were integrated into ammonium perchlorate (AP) oxidizer. While boron demonstrated decrease in AP decomposition enthalpy by −14.8%; aluminum offered an increase in AP decomposition enthalpy by 60.8% using DSC. Whereas, aluminum oxide layer could be pealed out more effectively; boron passive oxide layer could melt with the evolution of an insulating barrier. Aluminum particles offered decrease in AP apparent activation energy by 68%, 105%, and 76% using Kissinger, Kissinger-Akahira-Sunose (KAS), and Flyn and Wall (FWO) models, respectively. Solid propellant formulations were developed; ballistic performance was assessed using small-scale rocket motor. Aluminum particles demonstrated stable combustion process with enhanced specific impulse and total pressure impulse compared with boron. Additionally, aluminum particles demonstrated stable burning with pressure exponent of 0.19 compared with 0.4 for boron particles. [ABSTRACT FROM AUTHOR]

This paper presents open challenges and perspectives of propellant management for crewed deep space exploration. The most promising propellants are liquid hydrogen and liquid methane, together with liquid oxygen as an oxidizer. These fluids remain liquid only at cryogenic conditions, that is, at temperatures lower than 120 K. To extend the duration of space exploration missions, or even to enable them, the storage and refueling from a cryogenic on-orbit depot is necessary. We review reference missions, architectures, and technology demonstrators and explain the main operations that are considered as enablers for cryogenic storage and transfer. We summarize the state of the art for each of them, showing that many gaps in physical knowledge still need to be filled. This paper is based on recommendations originally proposed in a White Paper for ESA's SciSpacE strategy. [ABSTRACT FROM AUTHOR]

To accurately characterize the mesoscopic properties of NEPE (Nitrate Ester Plasticized Polyether) propellant, the mechanical contraction method was used to construct a representative volume element (RVE) model. Based on this model, the macroscopic mechanical response of NEPE propellant at a strain rate of 0.0047575 s−1 was simulated and calculated, and the parameters of the cohesive zone model (CZM) were inversely optimized using the Hooke–Jeeves algorithm by comparing the simulation results with the results of the uniaxial tensile test of NEPE propellants. Additionally, the macroscopic mechanical behavior of NEPE composite solid propellants at strain rates of 0.00023776 s−1 and 0.023776 s−1 was also predicted. The mesoscopic damage evolution process of NEPE propellants was investigated by the established model. The study results indicate that the predicted curves are relatively consistent with the basic features and change trends of the test curves. Therefore, the established model can effectively simulate the mesoscopic damage process of NEPE composite solid propellants and their macroscopic mechanical properties. [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]

The relatively poor mechanical properties of extruded modified double base (EMDB) propellants limit their range of applications. To overcome these drawbacks, a novel method was proposed to introduce glycidyl azide polymer-based energetic thermoplastic elastomers (GAP-ETPE) with bonding groups into the propellant adhesive. The influence of the molecular structure of three kinds of elastomers on the mechanical properties of the resultant propellant was analyzed. It was found that the mechanical properties of the propellant with 3% CBA-ETPE (a type of GAP-ETPE that features chain extensions using N-(2-Cyanoethyl) diethanolamine and 1,4-butanediol) were improved at both 50 °C and −40 °C compared to a control propellant without GAP-ETPE. The elongation and impact strength of the propellant at −40 °C were 7.49% and 6.58 MPa, respectively, while the impact strength and maximum tensile strength of the propellant at 50 °C reached 21.1 MPa and 1.19 MPa, respectively. In addition, all three types of GAP-ETPE improved the safety of EMDB propellants. The friction sensitivity of the propellant with 3% CBA-ETPE was found to be 0%, and its characteristic drop height H50 was found to be 39.0 cm; 126% higher than the traditional EMDB propellant. These results provide guidance for studies aiming to optimize the performance of EMDB propellants. [ABSTRACT FROM AUTHOR]

Thermal damage due to microstructure changes will occur in propellants under thermal stimulation. It can significantly affect the sensitization, combustion, and other properties of the propellant, which, in turn, affects the impact safety of the solid propellant rocket engine. A new component which uniformly heats the sample was designed to conduct the Lagrange test and EFP impact test at different temperatures. The thermal decomposition and damage characteristics of the propellant during the heating process were quantitatively analyzed. Additionally, the effects of ambient temperature on impact initiation and detonation growth of the high-energy propellant were elucidated at a mesoscopic level. The results showed that the porosity of the specimen increased by 0.89% under the thermomechanical mechanism, which was mainly characterized by interfacial de-bonding between the AP and the binder. The increase in thermal damage changed the hot spot reaction rate and significantly affected the growth process of propellant impact initiation. A method was proposed to systematically calibrate the reaction rate model for the propellant at different temperatures. The theoretical model parameters of the high-energy propellant at two typical temperatures were calibrated in this way. The critical shell thicknesses computed using LS-DYNA, which, for 20 and 70 °C, were obtained as 15 and 20 mm, respectively. [ABSTRACT FROM AUTHOR]

To replace hydrazine, a deadly toxic monopropellant for RCS (Reaction control system), research on green propellants has been vitalized, and green propellants based on HAN (Hydroxyl Ammonium Nitrate) or ADN (Ammonium Dinitramide) are promising candidates. Because an improvement in combustion characteristics is required to achieve the practical use of green propellants, we focused on the atomization of green propellants. Viscosity and surface tension measurements and injection tests under the condition assuming 1-10 N class RCS were conducted to inspect the atomization characteristics of green propellant candidates. The results revealed a clear highly viscous trend of the candidate materials and the difficulty of atomization by the swirl injector. These results indicate the importance of viscosity reduction in the atomization of green propellants. [ABSTRACT FROM AUTHOR]

Polymers have proven to be challenging to cold spray, particularly with high efficiency and quality when using inexpensive nitrogen (N2) and air propellants. Helium (He), when used as a process propellant, can improve spray deposit properties but is often undesirable due to its limited availability and high cost. In this study, additives of multiple particle sizes and materials were mixed with polymer powder in an effort to improve the performance of polymer sprays using mainly N2 as a process propellant. The effects of hard-phase additives on deposit microstructure were investigated by precise ion beam polishing of deposit cross sections and subsequent electron microscope imaging. Additional metrics including the density and post-spray composition of deposits were investigated to quantify the peening effect and the amount of embedded additive. Additives, regardless of size, were observed to embed in the spray deposits. Additionally, hard-phase additives demonstrated nozzle cleaning properties that continually remove polymer fouling on the nozzle walls. Inversely, sprays with polymer powder and no additives tended to clog the nozzle throat and diverging section because of continual fouling. [ABSTRACT FROM AUTHOR]

The article addresses the material science solutions on the sources and mechanisms of operational and technological destruction in the main units of high-power liquid rocket engines and structural and technological solutions developed to prevent them. [ABSTRACT FROM AUTHOR]

Hydroxylammonium nitrate (HAN)-based propellants have been attracting attention as future low-toxicity liquid propellants owing to their ionic properties. HAN-based propellants are primarily decomposed via catalytic reactions. However, this method has several drawbacks, such as catalyst preheating and deactivation. Therefore, in this study, the electrical characteristics of the electrolysis process of a HAN solution, as well as the by-product gases and reaction residues were analyzed considering the electrode material and applied voltage as the controlling variables. SUS (a designation of stainless steel) electrodes have higher durability than Cu electrodes; however, their decomposition proceeds more slowly because of the suppression of the initial reaction at low voltages. This study confirmed that this suppression could be significantly addressed at a high voltage of 400 V. The investigated electrolytic decomposition mechanism of the HAN solution was validated by analyzing the gases generated during the electrolysis and residue after the reaction, using Fourier-transform infrared spectroscopy. This study has important implications for the development of volume-limited propulsion systems, such as micro-thrusters. • HAN solution can be quickly and easily decomposed using electrical energy. • Electrode materials play a crucial role in determining the performance of HAN electrolysis. • The inhibited reaction of electrolysis can be eliminated at 400 V when using SUS electrodes. • The electrolytic decomposition mechanism of the HAN was investigated by FTIR. [ABSTRACT FROM AUTHOR]

This study establishes the performance requirements for an air-breathing electric propulsion device to operate in very low Earth orbit (< 450 km). We demonstrate that existing electric propulsion architectures, including electrostatic thrusters, fail to generate enough thrust while operating on flow rates of air that can be harvested in orbit. Instead, we develop and characterize a type of electromagnetic pulsed thruster that operates in a magneto-deflagration mode (i.e., forms an expansion wave during the acceleration process) that becomes more efficient as less propellant is used. We show this mode of operation can generate specific impulses up to 1 0 4 s, thrust per power > 2 mN/kW, thrust densities > 100 mN/m 2 , and thrust efficiencies up to 10% while consuming < 100 μ g of air per discharge. We map these performance metrics on a candidate spacecraft to show the deflagration thruster can enable fully air-breathing drag compensation at altitudes ranging from ∼ 200 km to 350 km depending on its geometry and is extendable to other altitudes if stored propellant is utilized. • Air-breathing electric propulsion (ABEP) systems use harvested air to compensate for drag. • ABEP devices cannot generate enough thrust for VLEO with harvestable amounts of air. • This study develops a deflagration thruster that operates efficiently in VLEO conditions. • The thruster achieves I sp up to 104 s and T/P above 2 mN/kW while operating on air. • The deflagration thruster enables air-breathing drag compensation from ∼ 200–350 km. [ABSTRACT FROM AUTHOR]

The combustion behavior of various propellant samples, including double-base propellants, pressed nitramine powders, and modified double-base propellants containing nitramine, was examined using OH-PLIF technology. The combustion process took place within a combustion chamber, and images capturing the flame at the moment of stable combustion were selected for further analysis. The distribution and production rate of OH radicals in both the double-base propellant and the nitramine-modified double-base propellant were simulated using Chemkin-17.0 software. The outcomes from both the experimental and simulation studies revealed that the concentration of OH radicals increased with a higher content of NG in the double-base propellant. In the modified double-base propellant containing RDX, the OH radical concentration decreased as the RDX content increased, with these tendencies of change aligning closely with the simulation results. [ABSTRACT FROM AUTHOR]

Low-thrust propulsion systems are widely used in space missions due to their high specific impulse and reduced propellant consumption. However, current research focuses on eliminating drifts in low-thrust maneuvers, resulting in high operational costs for daily station-keeping. This study aims to achieve autonomous station-keeping by exploiting long-term periodic behaviors caused by geostationary resonances. First, resonance maps caused by the Earth's gravity and lunisolar perturbation are revisited. Then, station-keeping slots are selected based on a phase space study of the resonances. A closed station-keeping track is formed by designing a low-thrust arc to work with the drifting arc. This track moves along the edge of the station-keeping slot, providing a more extended control period and reducing ground-station operational costs. Finally, an indirect optimizing method and efficient initial costate guess technique are proposed for calculating low-thrust maneuvers. [ABSTRACT FROM AUTHOR]

This study delves into the rheological and mechanical properties of a 3D-printable composite solid propellant with 80% wt solids loading. Polybutadiene is used as a binder with ammonium sulfate, which is added as an inert replacement for the ammonium perchlorate oxidizer. Further additives are introduced to allow for UV curing. An in-house illumination system made of four UV-A LEDs (385 nm) is employed to cure the resulting slurry. Rheological and mechanical tests are conducted to evaluate the viscosity, ultimate tensile strength and strain, and compression behavior. Viscosity tests are performed for both pure resin and complete propellant composition. A viscosity reduction factor is obtained for the tested formulations when pre-heating slurry. Uniaxial tensile and compression tests reveal that the mechanical properties are consistent with previous research. Results emphasize the critical role of temperature and solid loading percentage. Pre-heating resin composites may grant a proper viscosity reduction while keeping mechanical properties in the applicability range. Overall, these findings pave the way for the development of a 3D printer prototype for composite solid propellants. [ABSTRACT FROM AUTHOR]

The determination of the composition and timing sequence of products during the detonation of energetic materials is crucial for the evaluation of detonation performance and improvement of the formulation. However, it is difficult to determine the detonation products of energetic materials due to the fast reaction time during detonation. Herein, a new setup is built to detect the detonation products of energetic materials by time correlated laser induced plasma spectroscopy (LIPS) combined with high-speed schlieren imaging. The characteristics of time resolution and spatial distribution of propellant products from laser induced micro-detonation are obtained using the system. According to the time resolved spectrum of the products and high-speed schlieren images of laser induced micro-detonation, we speculate on the timing sequence of gaseous propellant products from laser induced micro-detonation in air: N2, O2, and nitrogen oxides precede hydrocarbon gases, followed by carbon oxides and gaseous containing the element of H. Moreover, the distribution of the gaseous products from laser induced micro-detonation are clarified. This study provides a new method for the detection of products during the detonation of energetic materials. [ABSTRACT FROM AUTHOR]

In special launch scenarios such as armament and aerospace, the scale of the launch system is severely restricted, which causes unstable combustion of propellant. An embedded structure for the small propulsion system driven by solid propellant is proposed to overcome this problem. This study aims to demonstrate the two-phase flow behaviors and launch safety of the combustion chamber with an embedded structure. A two-dimensional two-phase flow model based on the modified two-fluid theory is developed to describe the detailed two-phase flow behaviors in the combustion chamber during launching. Different from most of the existing studies, the constitutive equations determined from actual physical conditions are used to close the system of continuity equations. The numerical results are compared with that of the experiment to verify the accuracy of the numerical model. On this basis, the launch performance of the embedded structure is investigated. The numerical results indicate that the embedded structure facilitates the ignition process and reduces the risk of excessive pressure, but decreases the muzzle velocity at the same time. In addition, the effect of design parameters on launch safety is further investigated. Design parameters directly affect the launch safety, and the selection of reasonable parameters is a useful method for enhancing the launch performance. [ABSTRACT FROM AUTHOR]

This article discusses an experimental study on the combustion of water vapor and aluminum powder for chemical micropropulsion. The study aims to address the constraints and safety requirements that have delayed the development of this propellant combination. The researchers measured the combustion pressure and reacted aluminum fraction under specific conditions, such as water vapor pressure under 100 kPa, aluminum powder diameter over 10 μm, and a combustion chamber smaller than 1 L. The results showed that the nitrogen gas promoted combustion by diffusing the powder, and controlling powder diffusion and ignition timing were important factors. This research provides valuable insights for the development of chemical micropropulsion systems. [Extracted from the article]

We present an extensive study into the influences that the magnitudes of the applied electric (E) and magnetic (B) fields have on collisionless plasma discharges of xenon, krypton, and argon. The studies are performed in a two-dimensional radial-azimuthal configuration with perpendicular fields' orientation. The dependency of the dynamics of E × B discharges on the strength of electromagnetic field and ion mass has not yet been studied in a manner that distinguishes the role of individual factors. This has been, in part, due to significant computational cost of conventional high-fidelity particle-in-cell (PIC) codes that do not allow for practical extensive simulations over broad parameter spaces. Also, the experimental efforts have been limited by aspects such as the measurements' spatiotemporal resolution and the inability to independently control individual discharge parameters. The computationally efficient reduced-order PIC scheme allows to numerically cast light on the parametric variations of various aspects of the physics of E × B discharges, such as high-resolution spatial-temporal mappings of plasma instabilities. In this part I, we focus on the effects of the E -field intensity. We demonstrate that, across all the studied propellants, the E -field intensity determines two distinct plasma regimes characterized by different dominant instability modes. At relatively low E -field magnitudes, the modified two stream instability (MTSI) is dominant. At relatively high E -field magnitudes, the MTSI is mitigated, and the electron cyclotron drift instability becomes dominant. Consequent to the change in the plasma regime, the radial distribution of the axial electron current density and the electron temperature anisotropy vary. [ABSTRACT FROM AUTHOR]

The effects of magnetic field intensity on the properties of the plasma discharge and on the underlying phenomena are studied for different propellants' ion mass. The plasma setup represents a 2D radial–azimuthal configuration with perpendicular electric and magnetic fields. The electric field is along the axial direction, and the magnetic field is along the radial direction. The magnetic field intensity is changed from 5 to 30 mT, with 5 mT increments. The studied propellant gases are xenon, krypton, and argon. The simulations are carried out using a reduced-order particle-in-cell code. It is shown that, for all the propellants, the change in the magnetic field intensity yields two distinct plasma regimes, where either the modified two-stream instability (MTSI) or the electron cyclotron drift instability (ECDI) are dominant. A third plasma regime is also observed for cases with moderate values of the magnetic field (15 and 20 mT), where the ECDI and the MTSI co-exist with comparable amplitudes. This described variation of plasma regime becomes clearly reflected in the radial distribution of the axial electron current density and the electron temperature anisotropy. At the relatively low-magnetic-field intensities (5 and 10 mT), the MTSI is mitigated. At relatively high magnitudes of the magnetic field (25 and 30 mT), the MTSI becomes strongly present, a long-wavelength wave mode develops, and the ECDI becomes suppressed. An exception to this latter observation was noticed for xenon, for which the ECDI was observed to be detectable with a notable strength up to the magnetic field value of 25 mT. [ABSTRACT FROM AUTHOR]

A Hybrid Rocket Motor (HRM) is a type of chemical rocket propulsion in which the propellants are stored in different physical states. To counter the low regression rate characteristic of HRM different grain configurations with innovative port techniques has been evolved with time. It creates better mixing and combustion of fuel with oxidizer without having any special injector and energetic additives. A similar technique has been used in the present study. The fuel used in the present study is a solid grain made from polyvinyl chloride with di-butyl phthalate in the 50:50 ratios with gaseous oxygen as an oxidizer. In this paper, analyses are made to study the performance of a hybrid rocket motor by varying the axial alignment of the grain port at varying locations along the length. Due to the offset of the fuel port at varying locations, recirculation zone were created that enhanced the pressure in the combustion chamber by around 1-2 bar. The thrust generated was increased in the range of 10 to 25 N. Regression rate as well as efficiency was also observed to be increased with the use of this port alignment techniques. [ABSTRACT FROM AUTHOR]

Stabilizers play a crucial role in preventing undesirable decomposition and degradation reactions of propellants, thus ensuring their long-term performance and safe storage. This review highlights recent advancements in stabilizer selection and formulation techniques, aiming to enhance the stability of single base nitrocellulose (SBNC) propellants. It examines several types of stabilizers for SB-NC propellants, including their reaction mechanisms and effectiveness in preventing degradation reactions of the propellants, as well as the effects of their concentrations, particle sizes, and distributions on the propellants’ stability. Furthermore, it explores innovative approaches such as nano and green stabilizers with improved stability and compatibility. This review also provides insights into methods for evaluating the efficiency and propellant stability of the stabilizers, such as thermal analysis and accelerated aging tests. The findings of this review will assist in developing advanced propellant formulations that meet the growing demand for the applications of NC-based propellants. [ABSTRACT FROM AUTHOR]

The burn rate of composite rocket propellants serves as a critical ballistic parameter in the construction of a rocket engine. Due to their large surface areas, carbon-based materials such as carbon nanotubes, graphene, and fullerene have demonstrated promising results as burn rate modifiers (BRMs) for propellants. Unlike their inorganic counterparts, these materials, being combustible, contribute to energy output besides enhancing the burn rate. This study reported a ferrocene-fullerene dyad as a BRM prepared through the thermal decomposition of ammonium perchlorate (AP) in composite solid propellants. By incorporating 0.6 wt% of the dyad, the burn rate of the prepared propellants increased by 70%, accompanied by a rise in their calorific value. [ABSTRACT FROM AUTHOR]

Research into next-generation propellants with green fuel–oxidizer pairs to replace the currently used highly toxic hydrazine–N2O4 system has attracted widespread attention. Ionic liquids (ILs) and hydrogen peroxide have demonstrated their feasibility as a green fuel and an oxidizer, respectively. However, the realisation of effective auto-ignition is the key problem. In this study, a new strategy to trigger the auto-ignition of ILs fuels with hydrogen peroxide by using a unique copper-containing liquid as the promoter is developed. The copper-containing promoter is designed such that its cationic structure is similar to that of the ILs fuels. Based on the principle of “like dissolves like,” the fuel and promoter can be miscible at any ratio to eventually form a catalytic fuel. In addition, the physicochemical properties (e.g. density, viscosity and decomposition temperature) and performance parameters (e.g. ignition delay time and specific impulse) of the as-prepared catalytic fuel are completely characterised. Owing to their excellent hypergolic performance with a short ignition delay time of 16 ms, in combination with the advantages of simple preparation, perfect solubility and green characteristics, the catalytic fuel–oxidizer pair demonstrates promise as bipropellants for rocket applications. [ABSTRACT FROM AUTHOR]

The vented vessel test, as an alternation of the firing practice, is implemented to reconstruct the deterioration process of the gun barrel suffering the thermochemical erosion by propellant combustion gas. High pressure of over 300 MPa with a duration exceeding 20 ms is applied on the rifled specimen. A phase transition layer about 136 μm is observed by scanning electron microscopy (SEM) from the cross section of the test specimen. Some residual oxidation products of the iron can be detected by energy dispersive x-ray spectroscopy (EDS) on parts of the inner surface. A comprehensive erosion analysis is conducted, which estimates that the mass loss of the specimen is mainly attributed to the periodical formation and peeling of the chemical reaction layer on the bore surface. The most severely eroded part is located on the corner of the land. On the basis of the examined erosion mechanisms, a proper thermochemical erosion model is employed. The mass dissipation and the geometry evolution under continuous firing are simulated using finite element method (FEM). The simulation phenomenon shows good consistency with results of the experimental tests. [ABSTRACT FROM AUTHOR]

The transition metal complexes of triaminoguanidine (TAGwhere M = Cobalt (Co) or Iron (Fe)) have been prepared. The catalytic effect of these complexes on the thermolysis of energetic composite based on nitrocellulose and diethylene glycol dinitrate? has been investigated. Extensive characterization of the resulting energetic composites was carried out sing scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). Isoconversional kinetic analysis was performed to determine the Arrhenius parameters associated with the thermolysis of the elaborated energetic formulations. It is found that TAG-M complexes have strong catalytic effect on the thermokinetic decomposition of NC/DEGDN by decreasing the apparent activation energy and significantly increased the total heat release. The models that govern the decomposition processes are also studied, and it is revealed that different react io n processes are accomplished by introduction metal complexes of triaminoguanidine. Overall, this study serves as a valuable reference for future research focused on the investigation of catalytic combustion features of solid propellants. [ABSTRACT FROM AUTHOR]

Smart materials, which exhibit shape memory behavior in response to external stimuli, have shown great potential for use in biomedical applications. In this study, an energetic composite was fabricated using a UV-assisted DIW 3D printing technique and a shape memory material (SMP) as the binder. This composite has the ability to reduce the impact of external factors and adjust gun propellant combustion behavior. The composition and 3D printing process were delineated, while the internal structure and shape memory performance of the composite material were studied. The energetic SMP composite exhibits an angle of reversal of 18 s at 70°, with a maximum elongation typically reaching up to 280% of the original length and a recovery length of approximately 105% during ten cycles. Additionally, thermal decomposition and combustion behavior were also demonstrated for the energetic SMP composite. [ABSTRACT FROM AUTHOR]