Hasil untuk "Explosives and pyrotechnics"

Kailing GUO, Yong LIAO, Zhikui ZHU et al.

The pressure characteristics and structural deformation mechanism of aluminum honeycomb sandwich plates (AHSPs) under water-entry impact were investigated through experimental methods. A self-designed drop experimental platform in the water tank was established, and the water-entry impact experiments of AHSPs at different drop heights were carried out. Meanwhile, the deformation of the face sheets was measured by a 3D scanner, and the time history of water impact pressure at different measuring points was monitored. Furthermore, the repeatability of the experiment was verified. On this basis, the water impact load characteristics of AHSPs during the process of water entry were studied and compared with those of other structures in published papers. In addition, the deformation modes and permanent deflection characteristics of AHSPs were analyzed, and the fitting formulas of the permanent deflection of the face sheets and the compression of the core were proposed. Results show that the distribution of the water impact pressure on the front sheet of AHSPs is uneven. However, within the range of drop heights studied, the peak value of the water impact pressure is approximately linear with the drop height. Additionally, compared to the water entry of rigid plates, the peak value of the water impact pressure of AHSPs is smaller. Compared with the mass equivalent aluminum plates, the peak value of the water impact pressure of AHSPs is much smaller, while the pressure duration of AHSPs is longer. The deformation modes of the face sheets of AHSPs at different drop heights are almost the same. Besides, with the increase of the drop height, the permanent deflections of the front and back faces of AHSPs increase approximately in the form of a quadratic parabola with decreasing slope. Suffering from water entry impact loadings, the permanent deflections of the back sheet of AHSPs are smaller than those of the equivalent aluminum plates, indicating that the AHSPs have better impact resistance compared with the equivalent aluminum plates.

Lokmene Boumaza, Ahmed Fouzi Tarchoun, Amir Abdelaziz et al.

This study systematically investigated the stability and thermo-kinetic properties of a high-energy-density nitrated cellulose carbamate (NCC) system stabilized with Kraft lignin. The performance of lignin as a stabilizer was rigorously compared to that of two conventional stabilizers, 2-nitrodiphenylamine (2-NDPA) and 1,3-dimethyl-1,3-diphenylurea (C-II), focusing on their effects on the molecular structure and thermo-kinetic behavior of NCC. Structural characterization techniques, including Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), demonstrated that lignin effectively interacts with and stabilizes the nitroxyl radicals generated during the thermolysis of the NO2 bond in the NCC matrix. Enhanced thermal stability of the lignin-stabilized NCC, relative to the baseline NCC, was confirmed through thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), highlighting the stabilizing influence of the incorporated organic stabilizers. Additionally, the investigation of the thermolysis kinetics of stabilized NCC demonstrated a moderate increase in the Arrhenius parameters compared to the NCC baseline, indicating enhanced thermal stability, improved storage safety, and broader safety margins. Compared to conventional stabilizers like 2-NDPA and C-II, Kraft lignin offers a safer, bio-based alternative with lower toxicological risks. Its stabilization mechanism involves electrophilic nitration, avoiding nitrosamine formation and minimizing hazardous by-products. This finding highlights the enhanced thermal stability of the stabilized system. Importantly, this study contributes to the ongoing development of environmentally friendly stabilizers for nitrate ester-based energetic materials.

Heling ZHENG, Zhanxuan WANG, Mingyang WANG et al.

Aiming at the limitations of traditional metal jets in penetrating concrete targets, such as limited damage range and insufficient dynamic response, a novel double-layer energetic composite liner structure with a truncated inner layer made of high-entropy alloys/aluminum/polytetrafluoroethylene (HEA/Al/PTFE) was proposed for the first time. The hemispherical composite liner’s HEA layer was prepared using vacuum arc melting, while the Al/PTFE inner layer was formed through powder compaction and sintering. To thoroughly verify the performance advantages of the composite liner, two types of shaped charge structures were fabricated during the experimental phase for comparison: one with the composite liner and the other with a single-layer HEA liner. C35 plain concrete cylinders were used as targets, with single-point initiation at the center of the charge top. Additionally, numerical simulations of the jet formation process were conducted using the commercial finite element software ANSYS-LS-DYNA. The explosive and liner were modeled with the Smoothed Particle Hydrodynamics (SPH) algorithm to accurately capture the dispersal behavior during jet formation, while the casing was simulated with the Lagrangian algorithm to describe the expansion and fragmentation process of the outer shell. In the simulation, the high-temperature and high-strain-rate mechanical behaviors of HEA, Al/PTFE, and 45 steel were described using the Johnson-Cook constitutive model. The explosive was modeled with the classical JWL equation of state, and air was treated as an ideal gas. All relevant parameters were sourced from published literature. Based on the axisymmetric curvature characteristics of the hemispherical liner and the material discontinuity introduced by truncation, a partitioned formation theoretical model was further established. An energy loss coefficient η (η=0.2) was introduced to modify the detonation energy transfer process. According to the truncation angle, the composite liner was divided into two regions with different physical mechanisms. The jet radius and slug radius for each region were derived using mass and momentum conservation. Experimental results show that both the composite liner and the single-layer HEA liner can form stable penetrating jets, achieving complete penetration of the concrete targets. Compared to the single-layer HEA liner, the composite structure significantly enhances the fragmentation and crack propagation capabilities inside the concrete. Numerical simulation results indicate that the Al/PTFE inner layer exhibits a “coating and cohesive” effect on the HEA jet, effectively suppressing radial dispersion and improving the continuity of the mid-section of the jet. However, multiple collision-following-separation behaviors between the inner layer and the main jet delay the system from reaching dynamic equilibrium. The established partitioned formation theoretical model demonstrates good predictive accuracy, with relative errors of less than 15% between the predicted jet and slug radii and the numerical simulation results. Further parametric analysis reveals that the thickness and height of the inner layer significantly influence jet formation. The optimal parameter combination is a thickness of 3.5 mm and a height of 12 mm, which achieves the best balance between suppressing radial dispersion, maintaining jet length, and enhancing mid-section cohesion. This composite liner effectively integrates the excellent mechanical properties of HEA with the high energy release characteristics of Al/PTFE. The established partitioned formation theoretical model provides a reliable theoretical basis for the design of hemispherical composite liners. The research findings offer important theoretical and experimental support for the optimized design and engineering application of novel energetic composite liners.

Qi DONG, Jinghan LIU, Lingfeng LI et al.

To investigate the damage mechanism and load characteristics of caisson wharf under underwater contact and near-field explosion, a high-fidelity numerical model was conducted based on the scaled model tests of caisson wharf and verified by comparing the simulation results with the experimental data. The propagation and attenuation characteristics of shock waves inside the caisson, partition walls, and internal backfill soil were analyzed. The destruction process and typical damage mechanisms of the caisson wharf were analyzed by comparing Holmquist-Johnson-Cook constitutive model damage contour maps with experimental results. The results shows that the damage areas and characteristics of the caisson wharf are largely consistent under both underwater contact and near-field explosion. The primary damage areas are blast-facing wall and deck slab. The blast-facing wall exhibits cratering and breaching phenomena, while of the deck slab shows transverse full-length cracks at trench-slab connections, longitudinal cracks, and blow-off. The side walls and internal partitions of the caisson wharf sustain relatively minor damage. Shock wave within the caisson subjected to underwater contact and near-field explosions undergo reflection and transmission at the interfaces between the partitions and fillings within the compartments. The blast-facing wall and side walls of the wharf are subjected to shock loads. The transmitted compressive waves across the transverse bulkheads and blast-resistant back walls exhibited amplification compared to the incident waves, whereas attenuation was observed as the waves traversed the sand-filled compartments. Numerical simulation results revealed that the shock wave load within the caisson undergoes a decay rate that transitions from rapid to gradual. Damage characteristics of caisson wharf is primarily shaped during the underwater explosion shockwave phase. Neglecting large-scale macroscopic movements such as uplift and scattering post panel failure, the damage formation time slightly exceeds twice the shockwave propagation duration through the structure.

Memdouh Chebbah, Ahmed Fouzi Tarchoun, Fouad Benaliouche et al.

In this study, cellulose nitrate (NC), a highly energetic polymer, was supplemented with two distinct classes of stabilizing agents: the usual diphenylamine (DPA) and zeolite molecular sieves (ZSM-5) that were ion-exchanged with transition metal ions, namely copper, silver, and cobalt. The primary objective was to assess the efficacy of these Cu, Ag, and Co-ion-exchanged ZSM-5 microporous materials as stabilizers for NC in comparison to the pristine NC and sample stabilized with DPA. To study their molecular compatibility and chemical compositions, the prepared samples underwent structural characterization employing advanced analytical methods. FTIR and XRD results revealed that the morphology and the original physical and chemical properties of NC matrix were preserved. Additionally, the accelerated thermal aging analysis of the prepared samples demonstrated an enhancement in the thermal stability and overall characteristics. The thermal behavior of the different samples was also investigated by TGA, revealing that the incorporation of 3 wt.% of the Cu, Ag, and Co -ion-exchanged ZSM-5 zeolites as stabilizers considerably affected the thermolysis of NC. Specifically, the weight loss of samples was notably reduced, indicating a remarkable decrease in the thermal decomposition of NC when doped with the zeolite molecular adsorbents. In contrast, the DPA stabilizer exhibited inferior performance in mitigating the pyrolysis of NC. Furthermore, the influence of diverse stabilizers on the thermal decomposition kinetics of NC was studied based on advanced model-free kinetic approaches, namely TAS and VYA/CE. Kinetic results unveiled that the incorporation of Cu, Ag, and Co ion-exchanged ZSM-5 adsorbents provides a pronounced enhancement in the thermal stability of NC. Notably, these zeolite-based stabilizers led to an increase in the activation energy barrier, thereby contributing to improved thermal stability.

Nassima Sahnoun, Amir Abdelaziz, Djalal Trache et al.

The primary objective of this study was the development of a novel energetic composite formulation, focusing on the elucidation of the influence of incorporating an energetic oxidizer, ammonium nitrate (AN), on the thermal decomposition behavior of a double-base composition, comprising nitrated potato starch (NPS) or nitrostarch as the polymeric binder and diethylene glycol dinitrate (DEGDN) as an energetic plasticizer. The optimal composition of the energetic composite was determined through theoretical performance calculations using the CEA-NASA program. The optimized AN@NPS-DEGDN energetic composite was comprehensively characterized using Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). The FTIR results demonstrated that the NPS-DEGDN demonstrated good chemical compatibility with AN. The textural analysis by SEM revealed that the AN particles are homogeneously dispersed within the NPS-DEGDN matrix. Thermal analysis results showed that the introduction of AN significantly enhanced the thermolysis-released heat of the double-base formulation. Furthermore, isoconversional kinetic modeling exhibited a substantial decrease in the composite thermolysis activation energy, corroborating the excellent catalytic effect of AN on the NPS-DEGDN composite. These findings highlight the potential of the developed AN@NPS-DEGDN composite as a promising candidate for advanced energetic applications, offering improved performance and environmental sustainability.

Timur I. Mukhametshin, Dmitry B. Vinogradov, Pavel V. Bulatov et al.

The thermoplastic polyurethane elastomers based on oligo-glycidyl azide (oligo-GA) with oligo-(3,3-bis(azidomethyl)oxetane) (oligo-BAMO), oligo-(3-azidomethyl-3-methyloxetane) (oligo-AMMO) and oligo-(3-nitraminomethyl-3-methyloxetane) (oligo-MNAMMO) were synthesized. Thermoplastics were characterized using 1H and 13C NMR, IR spectroscopy, CHN elemental analysis and GPC techniques. Depending on the nature of initial oligomers, such as oligo-MNAMMO, oligo-AMMO, oligo-BAMO and oligo-GA, features of formation of supramolecular structures in segmented polyurethanes were studied. The results of X-ray diffraction analysis of the samples with crystalline segments were shown. Phase separation factors in the structure of thermoplastics were interpreted based on FTIR, DSC analysis and the solubility parameters of the initial polyethers.

Ibrahim Amila, Abdelaziz Fedoul, Mohammed Janati Idrissi et al.

This study presents the development of an analytical method for calculating vibrational energy levels and dissociation energy of diatomic molecules by solving the Schrödinger equation (SE) via the Floquet theorem and the resonating averages method (RAM) in the presence of a cubic together with a quartic anharmonic perturbation. Our technique reposes on the identifying coefficients of the Taylor expansion series of Morse potential in terms of polynomial anharmonic perturbation parameters. The accuracy of our results is illustrated through numerical calculations for different examples of diatomic molecules: H2, HF, HCl, LiH, CO, and NO, taken from the literature. Furthermore, we present comparisons of the calculated values obtained using the Morse potential parameters of the above-mentioned molecules, with those of authors existing in the literature.

Nawel Matmat, Amir Abdelaziz, Ahmed Fouzi Tarchoun et al.

This study explores a dual-biopolymer-based energetic composite, emphasizing the synergistic effects achieved by combining nitrocellulose (NC) and nitrostarch (NPS) biopolymers with ammonium nitrate (AN), as an oxidizer. The optimal formulation for the AN@NC-NPS composite was determined through theoretical specific impulse (Isp) calculations using CEA-NASA software. Comprehensive spectral and thermal characterizations were conducted, where FTIR analysis confirmed the effective integration of AN within the NC-NPS matrix, revealing distinctive absorption bands of nitrate esters and AN, indicating a strong chemical compatibility. TGA and DSC analyses demonstrated a two-stage thermolysis, attributed respectively to NC-NPS matrix and AN oxidizer, with a mutual catalytic effect between them, shifting the decomposition process to lower temperatures for both stages. Advanced thermo-kinetic analysis employing various isoconversional approaches enabled precise estimation of key kinetic parameters, including Arrhenius parameters (Ea, Log10(A)) and the most probable decomposition mechanisms (g(α), f(α)/f(0.5)). The observed reduction in activation energy across both decomposition stages confirmed the role of AN in enhancing AN@NC-NPS reactivity, further supporting the synergistic catalytic effect revealed by the DSC findings.

Ch. Devi Vara Prasad, P. Kanakaraju, R Vinu et al.

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

Luca Boccioli, Lorenzo Roberti

Explosive nucleosynthesis is affected by many uncertainties, particularly regarding assumptions and prescriptions adopted during the evolution of the star. Moreover, simple explosion models are often used in the literature, which can introduce large errors in the assumed explosion energy and mass cut. In this paper, our goal is to analyze the explosion properties and nucleosynthesis of a large range of progenitors from three different stellar evolution codes: FRANEC, KEPLER, and MESA. In particular, we will show the differences between the neutrino-driven explosions simulated in this work with the much simpler bomb and piston models that are typically widely used in the literature. We will then focus on the impact of different explodabilities and different explosion dynamics on the nucleosynthetic yields. We adopt the neutrino-driven core-collapse supernova explosion code GR1D+, i.e. a spherically symmetric model with state-of-the-art microphysics and neutrino transport and a time-dependent mixing-length model for neutrino-driven convection. We carry out explosions up to several seconds after bounce, and then calculate the nucleosynthetic yields with the post-processing code SkyNet. We find that our 1D+ simulations yield explosion energies and remnant masses in agreement with observations of type II-P, IIb, and Ib supernovae, as well as with the most recent 3D simulations of the explosion. We provide a complete set of yields for all the stars simulated, including rotating, low-metallicity, and binary progenitors. Finally, we find that piston and bomb models, compared to more realistic neutrino-driven explosions, can artificially increase the production of Fe-peak elements, whereas the different explodability tends to cause discrepancies in the lighter elements.

Alessandro Ederoclite, Domitilla De Martino, Paul Groot et al.

Novae are thermonuclear explosions on the surface of accreting white dwarfs and are key laboratories for studying explosive nucleosynthesis, particle acceleration, shock physics, and binary evolution. Despite major progress driven by wide-field time-domain surveys and multi-wavelength facilities, our understanding of nova explosions remains limited by incomplete temporal coverage, heterogeneous spectroscopic follow-up, and poorly constrained ejecta properties. In this white paper we outline the open scientific questions that will define nova research in the 2040s, focusing on the mass, composition, geometry, and dynamics of the ejecta, the role of the underlying binary system, and the connection between nuclear burning, shocks, and emission across the electromagnetic spectrum. We argue that decisive progress requires rapid-response, high-cadence, multi-wavelength observations, anchored by systematic high-resolution optical and near-infrared spectroscopy from eruption to quiescence. Finally, we identify key technological requirements needed to enable transformative advances in the physics of nova explosions over the coming decades.

Mengu Dinesh, Sachin Sonage, Kumar Nagendra

This study demonstrates the thrust modulation capabilities of a hybrid rocket motor employing a Multi-Layered Tubular (MLT) fuel grain. The MLT configuration involves arranging the fuel grains with distinct regression rates as layers. As combustion progresses, the regression rate changes based on the burning of each fuel layer, leading to variable thrust while maintaining a constant oxidizer flow rate. Variable-thrust fuel grains are suitable for diverse mission types, including employment in sounding rockets and cruise missiles, particularly those designed for anti-ship operations and missions wherein a boost-sustain thrust profile is required. The MLT fuel grains were designed for a boost-sustain phase thrust profile generally observed in missiles. Wax was used as a booster fuel, and wax with 20%EVA was used as a sustainer fuel. Two MLT configurations with different durations for the boost phase were demonstrated. During the tests, the boost-sustain phase was achieved successfully. However, a transition phase was observed while shifting from the boost to the sustain phase. The delay of the transition phase was observed to increase when the duration of the boost phase increased. The combined effect of axial variation of fuel regression rate and local mass flux is the reason for the transition phase. The Thrust Turn-Down Ratio (TDR) for Multi-Layered Tubular (MLT) fuel grains was calculated. At a web thickness (for booster fuel) of 4 mm, the TDR was approximately 1.23:1, and at a 5.5 mm web thickness, it was 1.28:1. Further, 20%Mg was added to the wax to increase the regression rate of booster fuel. The Wax/20%Mg fuel showed 41% and 14% improvement in regression rate and thrust, respectively. The TDR was improved marginally compared to pure wax-based MLT grain.

Aditya Narkhede, Shafquat Islam, Xingsheng Sun et al.

Lightweight, single-use explosion containment structures provide an effective solution for neutralizing rogue explosives, combining affordability with ease of transport. This paper introduces a three-stage simulation framework that captures the distinct physical processes and time scales involved in detonation, shock propagation, and large, plastic structural deformations. The hypothesis is that as the structure becomes lighter and more flexible, its dynamic interaction with the gaseous explosion products becomes increasingly significant. Unlike previous studies that rely on empirical models to approximate pressure loads, this framework employs a partitioned procedure to couple a finite volume compressible fluid dynamics solver with a finite element structural dynamics solver. The level set and embedded boundary methods are utilized to track the fluid-fluid and fluid-structure interfaces. The interfacial mass, momentum, and energy fluxes are computed by locally constructing and solving one-dimensional bi-material Riemann problems. A case study is presented involving a thin-walled steel chamber subjected to an internal explosion of $250~\text{g}$ TNT. The result shows a $30\%$ increase in the chamber volume due to plastic deformation, with its strains remaining below the fracture limit. Although the incident shock pulse carries the highest pressure, the subsequent pulses from wave reflections also contribute significantly to structural deformation. The high energy and compressibility of the explosion products lead to highly nonlinear fluid dynamics, with shock speeds varying across both space and time. Comparisons with simpler simulation methods reveal that decoupling the fluid and structural dynamics overestimates the plastic strain by $43.75\%$, while modeling the fluid dynamics as a transient pressure load fitted to the first shock pulse underestimates the plastic strain by $31.25\%$.

Dane M. Sterbentz, Dylan J. Kline, Daniel A. White et al.

The ability to control the behavior of fluid instabilities at material interfaces, such as the shock-driven Richtmyer--Meshkov instability, is a grand technological challenge with a broad number of applications ranging from inertial confinement fusion experiments to explosively driven shaped charges. In this work, we use a linear-geometry shaped charge as a means of studying methods for controlling material jetting that results from the Richtmyer--Meshkov instability. A shaped charge produces a high-velocity jet by focusing the energy from the detonation of high explosives. The interaction of the resulting detonation wave with a hollowed cavity lined with a thin metal layer produces the unstable jetting effect. By modifying characteristics of the detonation wave prior to striking the lined cavity, the kinetic energy of the jet can be enhanced or reduced. Modifying the geometry of the liner material can also be used to alter jetting properties. We apply optimization methods to investigate several design parameterizations for both enhancing or suppressing the shaped-charge jet. This is accomplished using 2D and 3D hydrodynamic simulations to investigate the design space that we consider. We also apply new additive manufacturing methods for producing the shaped-charge assemblies, which allow for experimental testing of complicated design geometries obtained through computational optimization. We present a direct comparison of our optimized designs with experimental results carried out at the High Explosives Application Facility at Lawrence Livermore National Laboratory.

Xiaolan Song, Xiaohui Gao, Yong Kou et al.

This investigation was devoted to exploring the thermal decomposition and sensitivity characteristics of solid propellants using nano-AN and nano-AP as oxidizers. The morphology, surface elements, and crystal structure of nano-AP and nano-AN were investigated by SEM, BET, EDS, and XRD. DSC and TG-MS were used to investigate the thermal decomposition mechanism of nano-AP and nano-AN solid propellants. The mechanical sensitivity of the different solid propellants containing nano-AN and nano-AP was tested and their energy performance was also evaluated. The results show that the microscopic morphology of nano-AN and nano-AP is network-like with the one-dimensional scale less than 100 nm, and the crystal phases of the two are consistent with the raw AN and raw AP, respectively. The thermal decomposition activation energy of AN/CMDB-4 propellant containing nano-AN is 717.46 kJ/mol, while that of AP/HTPB-6 propellant containing nano-AP is 422.33 kJ/mol. The main decomposition products of AN/CMDB-4 propellant are CO2, N2O, NO, CH2O, CO, N2, H2O, CH4 and H2. The products of CO2, N2O, NO, CH2O, CO, N2, H2O, CH4 and H2 are also generated during the decomposition of AP/HTPB-6 propellant. With the increase of nano-AN and nano-AP in propellants, the mechanical sensitivity of AN/CMDB solid propellant decreases, while that of AP/HTPB solid propellant increases. The theoretical standard specific impulse Isp of AN/CMDB and AP/HTPB propellants are 2439.5 N·s/kg and 2449.3 N·s/kg, respectively. The above conclusions show that nano-AP and nano-AN can improve the thermal decomposition performance and the safety of solid propellants, which are expected to be widely used in solid propellants.

Miaomiao Li, Zhipeng Zhou, Jingjing Chen et al.

Large-size program temperature controller was used to carry out the slow cook-off test study of PBT, Bu-NENA, PBT/Bu-NENA mixture and PBT/Bu-NENA propellant in the range of gram and kilogram scale. The comprehensive performance of PBT/Bu-NENA propellant was carried out evaluation, including energy performance, mechanical performance, and low vulnerability performance (including fast cook-off test, slow cook-off test, shaped charge jet impact test and bullet impact test). The test results show that the slow cook-off response temperature of gram-weigh PBT, Bu-NENA and PBT/Bu-NENA mixture are 178.5°C, 142.3°C, and 139.0°C, respectively, while that of kilogram-weigh PBT/Bu-NENA propellant is 121.9°C. Analysis believes that high volatility of Bu-NENA plasticizers the main reason for the response temperature to drop from 139.0°C to 121.9°C. The PBT/Bu-NENA propellant has low vulnerability characteristics. Among them, the shaped charge jet impact test has the highest degree, which is an explosive reaction, and the sympathetic detonation test has the lowest response degree, which is below the burning. The theoretical special impulse of the PBT/Bu-NENA propellant is greater than 267 s,the density is greater than 1.80 g/cm3, the glass transition temperature (Tg) is less than -66°C, and the mechanical properties in the range of -60°C ∼ +70°C are excellent.

Yufeng Wang, Gaochun Li, Jinfei Li et al.

The storage environment of solid rocket motor charge is always alternating. In order to study its effect on the performance of solid rocket motor charge, the accelerated aging experiments under different temperature range, temperature change period and aging time were performed. The degradation and failure surfaces of propellant mechanical properties under the condition of alternating temperature aging are given. The results show that with the increase of the temperature range in the alternating temperature aging test, the cumulative damage of the propellant specimen increases and the elongation decreases faster. With the decrease of temperature change period, that is, the faster the temperature change frequency is, the faster the elongation decreases. Compared with traditional high temperature accelerated aging test, alternating temperature accelerated aging test is closer to reality.

Maxim V. Barkov, Praveen Sharma, Konstantinos N. Gourgouliatos et al.

Many explosive astrophysical events, like magnetars' bursts and flares, are magnetically driven. We consider dynamics of such magnetic explosions - relativistic expansion of highly magnetized and highly magnetically over-pressurized clouds. The corresponding dynamics is qualitatively different from fluid explosions due to the topological constraint of the conservation of the magnetic flux. Using analytical, relativistic MHD as well as force-free calculations, we find that the creation of a relativistically expanding, causally disconnected flow obeys a threshold condition: it requires sufficiently high initial over-pressure and sufficiently quick decrease of the pressure in the external medium (the pre-explosion wind). In the subcritical case the magnetic cloud just "puffs-up" and quietly expands with the pre-flare wind. We also find a compact analytical solution to the Prendergast's problem - expansion of force-free plasma into vacuum.

Viktor Bezborodov, Luca Di Persio, Peter Kuchling

We consider the continuous-time frog model on $\mathbb{Z}$. At time $t = 0$, there are $η(x)$ particles at $x\in \mathbb{Z}$, each of which is represented by a random variable. In particular, $(η(x))_{x \in \mathbb{Z} }$ is a collection of independent random variables with a common distribution $μ$, $μ(\mathbb{Z}_+) = 1$. The particles at the origin are active, all other ones being assumed as dormant, or sleeping. Active particles perform a simple symmetric continuous-time random walk in $\mathbb{Z} $ (that is, a random walk with $\exp(1)$-distributed jump times and jumps $-1$ and $1$, each with probability $1/2$), independently of all other particles. Sleeping particles stay still until the first arrival of an active particle to their location; upon arrival they become active and start their own simple random walks. Different sets of conditions are given ensuring explosion, respectively non-explosion, of the continuous-time frog model. Our results show in particular that if $μ$ is the distribution of $e^{Y \ln Y}$ with a non-negative random variable $Y$ satisfying $\mathbb{E} Y < \infty$, then a.s. no explosion occurs. On the other hand, if $a \in (0,1)$ and $μ$ is the distribution of $e^X$, where $\mathbb{P} \{X \geq t \} = t^{-a}$, $t \geq 1$, then explosion occurs a.s. The proof relies on a certain type of comparison to a percolation model which we call totally asymmetric discrete inhomogeneous Boolean percolation.