Explosive Dispersal Research Articles

An Endogenic Origin for Titan's Rampart Craters: Assessment of Explosion Mechanisms

AbstractRampart craters are a class of lakes or depressions in Titan's north polar region that have morphological attributes suggestive of an explosive origin. Two previous studies have proposed that rampart craters form via nitrogen or methane vapor explosions analogous to terrestrial maar explosions. We propose a new terrestrial analog for rampart craters: gas emission craters (GECs) found in permafrost zones. We evaluate the explosive origin of Titan's rampart craters by modeling the dispersal of material from an explosive vent. The dimensions of nine rampart craters with radar‐bright ramparts were used to model the explosion process. The model yields a range of explosion conditions (e.g., gas mass and reservoir depth) producing ejecta dispersal patterns matching the observed features. We find that gas masses of 1011–1014 kg are required to produce a rampart crater. We examine two explosion scenarios: (a) rapid, maar‐like vaporization and explosion of liquid nitrogen or methane, and (b) more gradual gas accumulation and explosion akin to a GEC driven by methane released from destabilizing clathrates. If Titan's crust is composed of pure water ice, the calculated gas pressures are consistent with a rapid, maar‐like explosion mechanism. If the subsurface is predominantly composed of organic materials or clathrate, either scenario may be plausible. Further research on the composition and tensile strength of Titan's subsurface are required to discriminate between hypotheses. Nevertheless, we conclude that explosive dispersal of ejecta from a vent can account for the morphologies of Titan's rampart craters and may contribute to atmospheric methane replenishment.

Confirming the explosive dispersal outflow in DR21 with ALMA

We present Atacama Large Millimeter/submillimeter Array (ALMA) 1.3 mm continuum and CO (2–1) line emission observations toward the high-mass star formation region DR21. Five new continuum sources are found. We identify 18 outflow streamers detected in CO emission that radially arises from a common origin. The velocity spread of the outflow streamers ranges between −100 and +70 km s−1. The radial velocities of each outflow roughly follow linear gradients (Hubble–Lemaître–like expansion motions). Using the CO emission of the whole ensemble of streamers, we estimate a total outflow mass of 120−210 M⊙. Additionally, we derived the dynamical age (8600 yr), momentum (~103 M⊙ km s−1), and kinetic energy (~1048 erg) of the outflow. The morphology and kinematics presented by the CO outflow streamers confirm an explosive dispersal outflow at the heart of DR21. Five dispersal explosive outflows associated with massive star-forming regions have been confirmed in our Galaxy (Orion BN/KL, G5.89-0.39, S106-IR, IRAS 16076-5134, and IRAS 12326-6245). However, their occurrence frequency in the Galaxy and their origin are still uncertain.

Авиационное средство пожаротушения АСП-500. Разработка, проблемы, перспективы

The problem of boosting the efficiency of extinguishing forest and man-made fires with the use of aviation technology can be solved by implementing into practice of new technical solutions based on explosive dispersion method. Fireextinguishing compound explosive dispersion generates an aerosol cloud which suppresses conflagration zones over vast areas. With the aim of expanding capabilities and enhancing fire-fighting efficiency, a 500kg aerial fire-fighting device ASP-500 was developed by JSC “RPA “Bazalt” as part of initiative development project “Aerosol”. The product is intended for extinguishing and localizing forest fires, as well as for suppressing fire zones during man-made accidents and disasters. ASP-500 is capable of being used from fixed-wing aircraft, helicopters, unmanned aerial vehicles (UAVs). It is expedient to use ASP-500 in conjunction with traditional fire-fighting water release systems, thus ensuring improved performance and economic efficiency indicators. ASP500 application could be an efficient addition to the existing system of forests protection and conservation valid in the Russian Federation, especially in remote or hard-to-reach areas.

Experiment and instantaneous driving simulation of explosion dispersion process of central tube for submunition

In order to study the influence of explosion dispersion of submunition on the dispersion velocity and pressure characteristics of subunits, the experimental study of explosive dispersion of the central tube was carried out when the explosives with low detonation velocity were applied in central tube as the main charge. In addition, the explosion dispersion test process was recorded by high-speed photography. RDX-based aluminized explosive samples with low detonation velocity were prepared and tested, and the low detonation velocity performance changes under different charge diameters and densities were obtained. Based on the explosive dispersion test of the central tube of the submunition, the physical model and three-dimensional axisymmetric finite element model of the central tube, subunit and aluminium alloy shell with prefabricated grooves are established. The fluid-structure coupling calculation method is used to simulate the explosive dispersion process. The simulation results are compared with the test results, and the pressure distribution characteristics of the subunit and the variation law of the dispersion velocity are analyzed. The effectiveness of the engineering calculation method of JWL equation model parameters is verified. The results show that using RDX based aluminized low detonation velocity explosive as the main charge of the central tube structure can achieve the design goal of the explosive dispersion for submunition, and the explosion dispersion model of submunition can accurately describe the dispersion characteristics of the subunit. The research results can be used to guide the structural design of submunition warhead.

Numerical analysis of initial cloud of powder dynamic dispersion

Numerical simulations were performed to investigate the explosion dispersion characteristics of powder materials with respect to the implicated velocity, and a fluid–solid coupling simulation model of the explosion dispersion process of the initial cloud was established. Explicit dynamics models of Finite-element method and smooth particle hydrodynamics for the detonation driving stage of central charge and the cloud isentropic expansion stages were developed, the pressure loads of the explosive-driven were generated using the user-defined function program, and computational fluid dynamics models for the isentropic expansion and free expansion stages of the initial cloud were developed. Additionally, the maximum expansion radius of the cloud in explosion dispersion tests and theoretical calculations were compared with the radius in the numerical simulation results to verify the accuracy of the simulation model. Analyses of the morphology, concentration, and turbulence field in the numerical simulation revealed that vortex stratification occurred in the “two wings” of the initial cloud in its development process and that a particle-free “hollow” area is subsequently formed. Analyses also revealed that the vortex stratification occurs earlier as the implicated velocity of powder material increases. Additionally, an increase in the implicated velocity can effectively weaken the concentration of cloud and make the distribution of cloud particles more uniform.

Hypersonic target interception based on short-range damage estimation

Aiming at the interception problem of hypersonic target end phase, the flight interception simulation based on semi-active radar guidance is firstly established, and a warhead based on fragment damage is designed. Secondly, research proposes an effective method of target damage and verifies the interception effect by simulation. AUTODYN was used to establish the 3D finite element model based on the nonlinear flight dynamics model, to simulate the damage process and fragmentation dispersion. In this paper, the probability of success of missile interception is estimated by using conditional probability and the distribution of fragment field combined with the miss distance in the interception process and the fragment explosive dispersion law of the steel ball, so as to ensure the destruction of the terminal hypersonic incoming weapon within the safe range.

A history of mild shocks experienced by the regolith particles on hydrated asteroid Ryugu

Micrometeorites, a possible major source of Earth’s water, are thought to form from explosive dispersal of hydrated chondritic materials during impact events on their parental asteroids. However, this provenance and formation mechanism have yet to be directly confirmed using asteroid returned samples. Here, we report evidence of mild shock metamorphism in the surface particles of asteroid Ryugu based on electron microscopy. All particles are dominated by phyllosilicates but lack dehydration textures, which are indicative of shock-heating temperatures below ~500 °C. Microfault-like textures associated with extensively shock-deformed framboidal magnetites and a high-pressure polymorph of Fe–Cr–sulfide have been identified. These findings indicate that the average peak pressure was ~2 GPa. The vast majority of ejecta formed during impact on Ryugu-like asteroids would be hydrated materials, larger than a millimetre, originating far from the impact point. These characteristics are inconsistent with current micrometeorite production models, and consequently, a new formation mechanism is required.

Near-surface cloud dispersion and detonation propagation law

Fuel/air mixture clouds have important research value in the process industry and military applications. Different from condensed explosions, blast height has a direct impact on the fuel cloud field and the detonation power field. In this paper, we establish numerical models of the detonation process of propylene-oxide clouds generated by the dispersion of 2 kg fuel/air explosives at different blast heights. The process of fuel dispersion, detonation propagation, and the distribution of the near-surface detonation power field are explored. Through theoretical analysis, we establish optimization models of the fuel/air explosive dispersion under different blast heights. The relationship between the proportional blast height, proportional distance, and power field peaks is quantitatively revealed. The results show that the effect of cloud detonation on the ground power field is obvious. The optimal proportional blast height exists. When the cloud mass is 2 kg, the optimum proportional blast height is 0.8 m/kg1/3. At the optimum blast height, the overpressure effect of cloud detonation is the strongest (the peak overpressure is 2.19 MPa, and the action time is 1.77 ms), and the temperature range of cloud detonation is the largest (the peak temperature is 1462.16 K, and the action time is 2.34 ms). Under the condition that the proportional blast height is less than or equal to the optimal proportional blast height, the power field peaks show N-shaped trends with the increase in the proportional distance. When the proportional blast height > proportional ignition radius is > 0.8 m/kg1/3, the peaks decrease with the increase in the proportional distance.

MS-FRCNN: A Multi-Scale Faster RCNN Model for Small Target Forest Fire Detection

Unmanned aerial vehicles (UAVs) are widely used for small target detection of forest fires due to its low-risk rate, low cost and high ground coverage. However, the detection accuracy of small target forest fires is still not ideal due to its irregular shape, different scale and how easy it can be blocked by obstacles. This paper proposes a multi-scale feature extraction model (MS-FRCNN) for small target forest fire detection by improving the classic Faster RCNN target detection model. In the MS-FRCNN model, ResNet50 is used to replace VGG-16 as the backbone network of Faster RCNN to alleviate the gradient explosion or gradient dispersion phenomenon of VGG-16 when extracting the features. Then, the feature map output by ResNet50 is input into the Feature Pyramid Network (FPN). The advantage of multi-scale feature extraction for FPN will help to improve the ability of the MS-FRCNN to obtain detailed feature information. At the same time, the MS-FRCNN uses a new attention module PAM in the Regional Proposal Network (RPN), which can help reduce the influence of complex backgrounds in the images through the parallel operation of channel attention and space attention, so that the RPN can pay more attention to the semantic and location information of small target forest fires. In addition, the MS-FRCNN model uses a soft-NMS algorithm instead of an NMS algorithm to reduce the error deletion of the detected frames. The experimental results show that, compared to the baseline model, the proposed MS-FRCNN in this paper achieved a better detection performance of small target forest fires, and its detection accuracy was 5.7% higher than that of the baseline models. It shows that the strategy of multi-scale image feature extraction and the parallel attention mechanism to suppress the interference information adopted in the MS-FRCNN model can really improve the performance of small target forest fire detection.

Prediction of Peak Overpressure of Charge Enveloped by Polymer Matrix Composite: Theoretical Modeling and Experimental Verification.

This study aimed at elucidating some characteristics of the shock wave overpressure generated by a non-traditional layered charge comprising an inner high-energy explosive and an outer polymer matrix composite. Two models for predicting the peak overpressure (Δpm) of the charge were established, namely, a model based on the initial parameters of the blast wave, and a model considering the weakening of the explosion energy through the introduction of polymer matrix cladding. The overpressure of a typical layered charge was experimentally measured for model validation. It was found that the difference between the Δpm predicted by the two models and the experimental data is less than 15.12% and 14.17%, respectively. The model that was established based on the conservation of energy law, is in best agreement with the experimental data under different cladding/charge mass ratios (αm). The model that was based on the initial parameters of the blast wave obtained a low predicted value when αm was 0.4-0.8, which is attributed to the non-uniformity of the gas-solid mixture during the explosive dispersion stage.

FIB fabrication and electron emission characteristics of overhanging tungsten and platinum nanostructures

The recent advancement in nanofabrication technology has enabled realization of vacuum electron devices with nanogap spacing. These devices have advantages over semiconductor counterparts due to possible operation under hard conditions and some unique functionalities. The challenging task, however, lies with the full understanding of their current–voltage (I–V) characteristics, resulting from various electron emission mechanisms. The reliable extraction of device parameters is, therefore, vital for its potential applications. An attempt has, therefore, been made here to fabricate two three-dimensional overhanging electrodes of tungsten and platinum with a nanoscale gap of 70–100 nm on glass substrates using chemical vapor deposition and focused ion beam milling. Their (I–V) characteristics measured in situ at ∼10−6 mbar are shown to follow the Child–Langmuir law and Fowler–Nordheim field emission at low and high-bias conditions, respectively. The extraction of parameters with a simple procedure suggested earlier yields an effective emission area of ∼3510 Å2, work function of ∼2.5 eV, and field enhancement factor (β) of ∼ 1.8 for tungsten; the values for platinum are 12.5 Å2, 3.0 eV, and 5.0, respectively. The higher β in the case of platinum can be attributed to the formation of a comparatively rough emitter surface with some fine protrusions. The nanostructure gives a current spike at high voltages, which marks its transition to an explosive emission state, breakdown, and dispersion of spherical metal particles over the substrate.

Fabric armour erosion using a buried charge ejecta analog

The threat posed by buried explosive charges and their explosive dispersal of environmental debris is associated with a variety of debilitating injuries. The dispersion profile of such threats includes particulate in a broad range of particle length scales, which are more destructive to ballistic fabrics than larger particles alone. Smaller particles are initially dispersed at higher speeds, degrading armour fabrics prior to the arrival of the larger penetrating particulate. In the present work, we present a low-cost industrial abrasion test method to investigate the abrasive wear in neat and polymer-coated ballistic fabrics to determine the level of degradation of the fabrics under the abrasive load. These fabrics were subjected to the impingement of an abrasive jet with average particle velocity of 187 ± 20 m/s. The results showed evidence of significant degradation and failure within the ballistic fabrics, that would certainly influence their subsequent ballistic performance. The addition of polymer coatings was able to reduce the abrasive degradation of the fabrics. The failure modes of the polymer composites are similarly described. This methodology shows promise as a means of armour material screening for this particular threat.

Explosive dispersal of particles in high speed environments

In this paper, we present the results of the explosive dispersal of particles in high-speed environments. We carry out Euler–Lagrange numerical simulations of a source at quiescent ambient conditions as well as moving at Mach numbers of 3 and 6. Particle volume fractions of 0%, 1%, and 4.5% are presented. The detonation profile is computed with the Jones–Wilkins–Lee equation of state using a reactive burn model. Non-static cases provide a framework to consider the effect of a bow shock and pre-existing high-speed flow conditions on the dispersal process. We also compute averages of both static and dynamic pressures, as well as impulse density histories on virtual probe planes to characterize the momentum of the flow and particles that would deposit on a target. Results suggest that the presence of the particles can have a substantial effect on the pressure average of the virtual target planes.

Possible Explosive Dispersal Outflow in IRAS 16076-5134 Revealed with ALMA

We present 0.9 mm continuum and CO(3–2) line emission observations retrieved from the Atacama Large Millimeter/submillimeter Array archive toward the high-mass star formation region IRAS 16076-5134. We identify 14 dense cores with masses between 0.3 and 22 M ☉. We find an ensemble of filament-like CO(3–2) ejections from −62 to +83 km s−1 that appear to arise radially from a common central position, close to the dense core MM8. The ensemble of filaments has a quasi-isotropic distribution in the plane of the sky. The radial velocities of several filaments follow a linear velocity gradient, increasing from a common origin. Considering the whole ensemble of filaments, we estimate the total mass to be 138 and 216 M ☉, from its CO emission, for 70 K and 140 K, respectively. Also, assuming a constant velocity expansion for the filaments (of 83 km s−1), we estimate the dynamical age of the outflowing material (3500 yr), its momentum (∼104 M ☉ km s−1), and its kinetic energy (∼1048–49 erg). The morphology and kinematics presented by the filaments suggest the presence of a dispersal outflow with explosive characteristics in IRAS 16076-5134. In addition, we make a raw estimate of the lower limit of the frequency rate of the explosive dispersal outflows in the galaxy (one every 110 yr), considering a constant star formation rate and efficiency, with respect to the galactocentric radius of the galaxy. This may imply a comparable rate between dispersal outflows and supernovae (approximately one every 50 yr), which may be important for the energy budget of the and the link between dispersal outflows and high-mass star formation.

The Optical Absorption Force Allows Controlling Colloidal Assembly Morphology at an Interface

AbstractGaining control on particle–particle interactions and in this way on their (self)‐assembled structures is essentialfor colloidal and material sciences. Currently, different strategies are described to achieve such control, however, all of them lack the spatiotemporal resolution required at the microscale. In this work, the potential of combining optical trapping and resonant photoexcitation for modifying particle–particle interactions and subsequent assembling of dye‐doped particles at the solution interface is demonstrated. The particle assemblies prepared by nonresonant 1064 nm optical trapping undergo morphology changes after resonant photoexcitation of the embedded dye molecules. Depending on the physicochemical properties of interface, quick hexagonal close packing (HCP)‐rearrangement or explosive dispersion of assemblies is observed at air/solution (A/S) and glass/solution interfaces, respectively. By contrast, by resonant photoexcitation only, the dispersed dye‐doped particles are pushed toward the A/S interface, followed by association to yield HCP‐structured assemblies. The results are rationalized by considering the optical absorption force coupled with other nonoptical forces (e.g., capillary force, dipole–dipole or electrostatic repulsion) at the solution interface. Due to the inherent spatiotemporal properties of light and electronic transition of materials, absorption force is a unique element to control and modify the structural order of particle assemblies at interfaces.

Impacts of Boundary-Layer Structure and Turbulence on the Variations of PM2.5 During Fog\u2013Haze Episodes

The precise cause of PM2.5 (fine particular matter with a diameter smaller than 2.5 μm) explosive growth and the contribution of intermittent turbulence to the dispersion of PM2.5 are uncertain. Thus, the impact of boundary-layer structure and turbulence on the variations of surface PM2.5 during fog–haze episodes, especially during explosive growth and dispersion episodes, are investigated using turbulence data collected at a 255-m high meteorological tower in Tianjin from 2016 to 2018. Results suggest that the explosive growth of surface PM2.5 during fog–haze episodes is closely related to weak turbulent mixing, nocturnal inversions, or anomalous inversions, and the barrier effect of strong turbulent intermittency. Turbulent intermittency acts as a lid for hindering pollutant dispersion and is favourable for the fast accumulation of surface PM2.5. Apart from the potential causes mentioned above, the persistent moderate south-westerly flow is also a contributing factor for the explosive growth of surface PM2.5 during fog–haze episodes associated with regional transport. In addition, we demonstrate a possible mechanism of how intermittent turbulence affects the dispersion of PM2.5. Results verify that intermittent turbulence induced by the nocturnal low-level jet (LLJ) indeed plays an important role in the dispersion of PM2.5. However, the contribution of intermittent turbulence generated by the nocturnal LLJ to the dispersion of PM2.5 strongly relies on the intensity of the nocturnal LLJ.

Вплив людського фактору на бойову ефективність стрільби зі стрілецької зброї з оптичним прицілом

Розглянуто замкнений контур виконання бойової задачі із застосуванням стрілецької зброї з оптичним прицілом. Показано, що ймовірність виконання бойової задачі залежить не тільки від технічних характеристик зброї, боєприпасів тафоноцільової обстановки, але й від людського фактору. Оцінено ймовірність її виконання, враховуючи достовірність підготовки даних стрільби, виявлення, розпізнавання та ідентифікації цілі, вірного прицілювання і влучання при стрільбі.Для зменшення похибок стрільця при підготовці даних стрільби доцільно використовувати високоточні прилади вимірювання дальності і метеорологічну станцію. Похибки стрільця при прицілюванні суттєво зменшуються при систематичному тренуванні на спеціальному стенді з електронною мішенню. Для скорочення часу при пошуку цілі на великій відстані доцільно використовувати телескопічний приціл. Для підвищення ймовірності розпізнавання та ідентифікації цілі доцільні тренування на спеціальному стенді, на якому імітується різноманітна фоноцільова обстановка.

Systematic Analysis on Gas‐Liquid‐Solid Three‐Phase Flow and Initiation Structure for Fuel‐Air Explosive Weapon Reliability

AbstractThe missile safety and reliability play important roles in its evaluation and design. Failure or inaccuracy of initiation is an occasional but extremely troublesome hazard in weapon system safety. The uneven fuel distribution and uncontrollable motion of initiation structure are both the causations of this hazard in a double‐event fuel‐air explosive missile application. Thus, it is crucial to implement the coupling between the initiation structure and the fuel field to succeed in a reliable application. This paper employs CFD to simulate the explosive dispersal process of fuel and uses MATLAB to investigate the motion trajectory of the initiation structure. As for the solid‐liquid fuel composed of 50 % aluminum powder and 50 % propylene oxide, its optimal concentration for reliable initiation is 186∼275 g/m3. In the case of a 200 kg missile with a speed of 300 m/s, the results imply that, at 250∼300 ms which is a reliable initiation time, the initiation structure gets to the reliable range of 10.8∼14.1 m where the fuel concentration approaches to the optimal range for initiation. Ultimately, for any missile development, the coupled simulation‐based approach is summarized to prevent the initiation failure and enhance its inherent safety, so as to avoid accident casualties and property loss.

Features of Forming Zinc Titanate by Electrical Explosion Dispersion of Titanium and Zinc Wires in an Oxygen-Containing Atmosphere

Features of Forming Zinc Titanate by Electrical Explosion Dispersion of Titanium and Zinc Wires in an Oxygen-Containing Atmosphere

Проявления неустойчивости при схлопывании металлических облицовок кумулятивных зарядов и в родственных струйных течениях динамически деформируемых профилированных тел

The paper briefly analyzes a number of published works devoted to cumulative explosion under conditions of the possible development of surface instability of the collapsing liner of a shaped charge. Most studies stated that surface instability was initially initiated by harmonic surface disturbances or disturbances in the parameters of a given load simulating an explosive one. The instability manifested itself in the form of the development of surface disturbances over time; the absence or limited growth was considered as the preservation of the stability of the deformable shell. In addition to the influence of instability on cumulative processes, related jet flows were also investigated. This is the so-called explosive dispersion (dusting), which occurs both under the influence of the interference of shock waves and unloading waves, and in the presence of initial disturbances of the surface shape. The analysis is built within the framework of the phenomenological approach — both the main results of the experiments and their mathematical descriptions were considered, which in most cases were carried out from the positions established in the mechanics of continuous media, as well as with the help of numerical modeling. Based on the results, conclusions were formulated about the reasons and forms of manifestation of surface instability of collapsing metal liners of shaped charges, the nature of the development and parameters of functioning of such charges, as well as about the features and laws of this process.