Two-stage Light Gas Gun Research Articles

Quasi-1D numerical analysis and Bayesian optimization of two-stage light gas gun operational parameters

Quasi-1D numerical analysis and Bayesian optimization of two-stage light gas gun operational parameters

Shock compression of crystalline TeO2 to the high-pressure fluid regime: Insights from ab initio molecular dynamics simulations

The shock response of fully-dense and porous crystalline tellurium dioxide (TeO2) to the high-pressure and high-temperature fluid regime was investigated within the framework of density functional theory with Mermin’s generalization to finite temperatures. The principal and porous shock Hugoniot curves were predicted from canonical ab initio molecular dynamics (AIMD) simulations, with the phase space sampled along isotherms up to 80 000 K, for densities ranging from ρ=3 to 17 g/cm3. The polymorphs investigated are α-TeO2 paratellurite (P41212), TeO2 cotunnite (Pnma), and TeO2 post-cotunnite (P21/m). Based on the discontinuity found in the calculated Us−up slope of TeO2 post-cotunnite at a shock velocity of Us≃8.35 km/s and a particle velocity of up≃3.64 km/s, the shock melting temperature and pressure are predicted to be ≃6500 K and ≃170 GPa. Results from the AIMD simulations are in line with the static compression data of TeO2 paratellurite and cotunnite, and with the recent shock Hugoniot data for single-crystal α-TeO2 for pressures up to 85 GPa, obtained using the inclined-mirror method and the velocity interferometer system for any reflector combined with powder gun and two-stage light-gas gun.

Hypervelocity impact investigations of composite truss tubes for in orbit assembly risk assessment

As the number of orbital structures increases, so does the threat posed by micrometeoroid and orbital debris (MMOD) impacts. These impacts range from the ballistic range (less than 1.5 km/s) to exceeding 20 km/s and can significantly weaken space structures such as the International Space Station (ISS), leading to further risk as the debris shed could damage the in-orbit assembly field. Space structures, including the James Webb Space Telescope (JWST) and the in-space assembled telescope (ISAT), often employ fiber-matrix composites in various shapes and sizes. While the effects of hypervelocity impacts (HVI) on flat plate composites have been extensively studied, there is a notable lack of research on HVI of composite tubes. Understanding how MMOD impacts affect the integrity of individual truss members, as well as the structure as a whole is essential for assessing the condition of existing space structures and improving future designs. To replicate MMOD impacts, HVI investigations from 1 to over 3 km/s were conducted on a specialized two-stage light-gas gun, showing the transition from single inlet wall damage to cascading internal fragmentation inside the tube, leading to increased damage with increasing velocity. Our investigation focuses on the image analysis of the damage area and ejecta fragmentation in the carbon fiber reinforced polymer (CFRP) tubes, as well as quantifying the resulting hole diameter. This data is crucial for validating corresponding computational models. In this study we present three separate methods of characterizing HVI including: impedance matching through equations of state, a hybrid Lagrangian finite element (FE) model using LS-DYNA with smoothed particle hydrodynamics (SPH), and experimental investigations. All methods agree that HVI can cause nearly three times the amount of damage within a tube compared to similar conditions on a plate. Our findings help enhance our understanding of MMOD impact risks on existing structures and contribute to the development of systems with greater resilience to HVI.

Investigations of high-speed projectile impact on symmetric sandwich structures containing solid propellant with core perforations

The response of solid rocket motors (SRMs) to high-speed fragment impacts is crucial for their safety design and operational use in scenarios such as rocket launches and space applications. The visualized Burn to Violent Reaction (BVR) test is used to observe intense reactions induced by high-speed projectile impacts. Employing a two-stage light gas gun and optical diagnostic techniques including high-speed schlieren imaging and direct photography, the impact-induced deflagration/explosion behavior, and reaction growth behavior were investigated. The damage mechanisms of the casing and propellant samples were assessed, and the reaction growth and afterburn effects of the impact-induced fragment cloud were quantitatively analyzed. The results indicate that the ignition delay time is inversely correlated with the impact velocity, decreasing from ms to μs scale. Across a wide range of velocities (1050–2058 m/s), higher projectile velocities induce more sustained and vigorous combustion reactions within the propellant. Furthermore, increasing the propellant air gap to 7.8 cm does not trigger further reactions under the studied configurations. The reaction mechanisms are closely linked to the characteristics of the fragment cloud induced by the impact. The developed Smoothed Particle Hydrodynamics (SPH) method, incorporating material constitutive models, ignition criteria, and reaction growth models, was used to study the influence of projectile velocity on the reaction mechanisms. The simulation results were compared with experimental data, demonstrating satisfactory accuracy.

Empirical Models for Predicting Two-Stage Light Gas Gun Muzzle Velocity

Empirical Models for Predicting Two-Stage Light Gas Gun Muzzle Velocity

Study on the attenuation pattern of stress wave in granite impacted by 30CrMnSiA alloy steel projectiles at 1.5–5.5 km/s

The damage ability of hypervelocity kinetic energy projectile penetrating ground has become a hotspot in modern military research. In this study, a hypervelocity impact test on a granite target subjected to projectiles using a two-stage light gas gun is conducted to study the stress wave evolution in granite under hypervelocity penetrations. The parameters of the *MAT_JOHNSON_HOLMQUIST_CERAMICS(JH-2) constitutive equation are calibrated using the results of the splinter impact test and the static test, and numerical simulations are performed using the smoothed particle hydrodynamics method coupled with finite element method (SPH-FEM coupled method) to extend the resulting data. A formula for calculating the stress wave peak attenuation is established, indicating that the maximum impact pressure produced by the hypervelocity impact decreases exponentially with scaling distance, and the attenuation coefficient is related to the degree of rock damage. Additionally, the attenuation of the speed of sound is used to characterize rock damage, and the damage deterioration law of granite under hypervelocity impact is analyzed based on the damage factor.

Effects of electron beam and atomic oxygen irradiation on hypervelocity - Impact tested / polyimide coated carbon fiber-reinforced plates

In a low-Earth orbit, space debris orbit at approximately the first cosmic velocity. When space debris strike a spacecraft, ejecta (fragments) from the spacecraft are widely scattered. The reduction in the number of ejecta (fragments caused by impact) must also be considered when selecting spacecraft materials. The authors’ group has previously examined the size of ejecta (fragments) and reduction in the number of ejecta. In general, the mechanical properties of polymer materials and CFRP plates may be damaged by space environments, such as radiation (gamma rays and electron beams (EBs)), atomic oxygen (AO), ultraviolet rays, temperature, and thermal cycling. The authors suggested an anti-AO coating/polyimide CFRP as a material resistant to space environments. The effects of EB and AO irradiation on the fracture behavior and ejecta of anti-AO coating/polyimide CFRP were examined for hypervelocity impacts. The results of static three-point flexural tests were compared with the fracture behavior and ejecta. A two-stage light-gas gun was used for the impact tests. Spherical projectiles formed of aluminum alloy 2017-T4 with a diameter of 1.6 mm were used. Photographs of the ejecta scattered in front of each polyimide CFRP plate were captured from the side using a high-speed video camera. The number and weight of the ejecta on the front side and perforation holes were examined.

Research on ballistic properties of UHMWPE hybrid laminates impregnated with shear thickening fluid

In this paper, a technology of impregnating ultra-high molecular weight polyethylene (UHMWPE) with shear thickening fluid (STF) was proposed to prepare composite laminates, and the ballistic properties of laminates with hybrid configurations were studied. Firstly, two kinds of STFs were prepared using silica particles of 20 nm and 500 nm. Then, STF-impregnated UHMWPE composite laminates were prepared using the hot-press lamination process. Finally, a ballistic experimental study of different combinations of laminates was carried out using a two-stage light gas gun. The results of the study show that the energy absorption rate of the hybridized laminate with the 20 nm + 50 nm configuration scheme is enhanced by more than 9.3 % compared to the laminate impregnated with the single STF. The laminate’s back face deformation depth (BFD depth) after impregnation with shear thickening fluid is only 66.8 % of that of pure UHMWPE laminate. The research work can provide new ideas and references for designing and developing new protective equipment.

Damage effects of aluminum alloy honeycomb sandwich panel double-layer structure induced by reactive projectile hypervelocity impact

In this paper, the experiments of Al2024 and reactive projectiles with hypervelocity impact on aluminum alloy honeycomb sandwich panel double-layer structure respectively were carried out by using two-stage light-gas gun, and the impact processes were recorded through high speed camera. According to the analysis of the experimental results, the debris clouds motion process and the damage effects on double-layer structure were compared. The damage enhancement mechanism of reactive projectile was revealed through numerical simulation and theoretical methods. The impact-induced detonation reaction of the reactive projectile can significantly reduce the "channel effect" of the honeycomb sandwich panel by destroying the honeycomb core cell wall, increase the perforation on the back facesheet of the honeycomb sandwich panel, and generate the debris cloud with higher temperature and faster expansion velocity. The debris cloud induced by the reactive projectile has a larger load distribution area on the rear plate, avoiding the concentration of loads in the center of the rear plate, and cause large area impact and thermal combined damage effects on the rear plate and internal space of the double-layer structure, while ensuring that the target structure cannot be penetrated. The reactive projectile efficiently applies the kinetic energy and chemical energy released by the impact-induced reaction to the interior of the target structure, the waste of kinetic energy caused by whole structure penetration can be avoided, resulting in significantly higher damage effects than the inert Al2024 projectile.

High-velocity oblique impact experiments on ice and snow spheres: Implications for the collisional evolution of icy planetesimals at different thermal evolution stages

In order to determine the effect of impact angle on the impact strength of icy planetesimals, we conducted a range of oblique impact experiments for spherical ice and snow targets simulating icy planetesimals at different thermal evolution stages. The ice targets had no porosity and the snow targets had a porosity of 0.5. A polycarbonate or glass sphere impacted the ice targets at 744–1747 m s−1 and the snow targets at 938–5085 m s−1 over a range of impact angles from grazing to head-on collisions. All experiments were conducted using a two-stage light gas gun and a target chamber set in a cold room of −15 °C at Kobe University, Japan. The impact strength, which is a specific energy, Q, when the largest fragment mass is a half of the original target mass, for the ice and snow targets in a head-on collision was determined to be 12 and 520 J kg−1, respectively, whereas it was found that the impact strength depended on the impact velocity. Thus, the normalized largest fragment mass, ml/Mt, could well scale with the velocity dependent Q, that is, Qviγ (where ml and Mt are the masses of largest fragment and target, respectively, and vi is the impact velocity). At high Q, ml/Mt increased drastically with the decrease of impact angle when the impact angle was smaller than a critical angle, θc, and θc~30° for the ice targets and θc~45° for the snow targets. At small Q, ml/Mt continued to increase as the impact angle became smaller for both types of targets. The ml/Mt for oblique impacts had a good correlation with the effective specific energy, Qeff=Qsin2θ, where θ is the impact angle, and the effective impact strength was determined to be 16 J kg−1 and 499 J kg−1 for the ice and snow targets, irrespective of the impact angle. Furthermore, the scaling parameter, Πs_eff, which was proposed by Housen and Holsapple (1990) but includes Qeff instead of Q, multiplied by 1−ϕλ, where ϕ is the porosity, showed even better correlation with ml/Mt, and all ml/Mt data of ice and snow targets could be merged, irrespective of impact velocity and ϕ. Based on our experimental results and a theory on the oblique impact of solar system bodies proposed by Shoemaker (1962), we could estimate the degree of disruption (ml/Mt) at any impact energy and any impact angle for icy planetesimals. Our findings demonstrate that the degree of disruption for icy planetesimals that have experienced sufficient thermal evolution was larger than that for those that did not experience significant thermal evolution.

Evolution of molecular structure of TATB under shock loading from transient Raman spectroscopic technique

By combination of the transient Raman spectroscopic measurement and the density functional theoretical calculations, the structural evolution and stability of TATB under shock compression was investigated. Due to the improvement in synchronization control between two-stage light gas gun and the transient Raman spectra acquisition, as well as the sample preparation, the Raman peak of the N–O mode of TATB was firstly observed under shock pressure up to 13.6 GPa, noticeably higher than the upper limit of 8.5 GPa reported in available literatures. By taking into account of the continuous shift of the main peak and other observed Raman peaks, we did not distinguish any structural transition or any new species. Moreover, both the present Raman spectra and the time-resolved radiation of TATB during shock loading showed that TATB exhibits higher chemical stability than previous declaration. To reveal the detailed structural response and evolution of TATB under compression, the density functional theoretical calculations were conducted, and it was found that the pressure make N–O bond lengths shorter, nitro bond angles larger, and intermolecular and intra-molecular hydrogen bond interactions enhanced. The observed red shift of Raman peak was ascribed to the abnormal enhancement of H-bound effect on the scissor vibration mode of the nitro group.

Synthesis of Autofluorescent Phenanthrene Microparticles via Emulsification: A Useful Synthetic Mimic for Polycyclic Aromatic Hydrocarbon-Based Cosmic Dust.

Phenanthrene is the simplest example of a polycyclic aromatic hydrocarbon (PAH). Herein, we exploit its relatively low melting point (101 °C) to prepare microparticles from molten phenanthrene droplets by conducting high-shear homogenization in a 3:1 water/ethylene glycol mixture at 105 °C using poly(N-vinylpyrrolidone) as a non-ionic polymeric emulsifier. Scanning electron microscopy studies confirm that this protocol produces polydisperse phenanthrene microparticles with a spherical morphology: laser diffraction studies indicate a volume-average diameter of 25 ± 21 μm. Such projectiles are fired into an aluminum foil target at 1.87 km s-1 using a two-stage light gas gun. Interestingly, the autofluorescence exhibited by phenanthrene aids analysis of the resulting impact craters. More specifically, it enables assessment of the spatial distribution of any surviving phenanthrene in the vicinity of each crater. Furthermore, these phenanthrene microparticles can be coated with an ultrathin overlayer of polypyrrole, which reduces their autofluorescence. In principle, such core-shell microparticles should be useful for assessing the extent of thermal ablation that is likely to occur when they are fired into aerogel targets. Accordingly, polypyrrole-coated microparticles were fired into an aerogel target at 2.07 km s-1. Intact microparticles were identified at the end of carrot tracks and their relatively weak autofluorescence suggests that thermal ablation during aerogel capture did not completely remove the polypyrrole overlayer. Thus, these new core-shell microparticles appear to be useful model projectiles for assessing the extent of thermal processing that can occur in such experiments, which have implications for the capture of intact PAH-based dust grains originating from cometary tails or from plumes emanating from icy satellites (e.g., Enceladus) in future space missions.

Study on the effect of grain size on the microstructure evolution of Q345 steel plate under high-speed impact

This study used a two-stage light gas gun to launch reactive fragments at high speeds into steel plates with different grain sizes (large and small). In addition, utilizing material characterization technologies like SEM, EBSD, and TEM, the microstructure evolution of steel plates with varying grain sizes was measured and analyzed both before and after impact. The results indicate that small-grain steel plates are more prone to intergranular or transgranular crack propagation, and they produce more macroscopic and microscopic cracks on the perforated surface under high-speed impact than large-grain steel plates. At the grain boundaries of both large and small grains of steel plate, as well as high-density dislocations, the impact process produces a significant number of minor angles with local misorientation ranging from 2 to 10°. A small-grain steel plate has an obvious grain boundary-strengthening effect. Small grains are more likely than large grains to cause changes in the crystal structure of BCC-HCP close to the perforation, and some grains form a lot of nanoscale elongated structures with the same crystal structure as the matrix. The interaction between dislocations or the emission of a large number of dislocation cells from grain boundaries may occur within some of the larger grains. The study's findings, which are illustrated in this article, can be used as a reference to understand how grain size influences the steel plates' microstructure changes after impacts.

Simulation of blast propagation and structural effects of accidental hydrogen-air-mixture explosion in a two-stage light-gas gun laboratory for hypervelocity impact experiments

Two-stage light-gas guns allow to accelerate projectiles up to velocities of several kilometers per second to conduct impact experiments. The projectile acceleration is obtained through a mechanism that relies on the expansion of a light gas, such as helium or hydrogen. Hydrogen allows to employ higher projectile velocities and masses than helium, together with lower wear of the launch tube. However, its use requires a thorough assessment of potential risks of explosion. In this work, we present a combined blast and structural numerical analysis to evaluate the effects of hydrogen deflagration as a consequence of accidental leakage scenarios during the operation of a two-stage light-gas gun. As a test case, we study the Large Gun operated at Fraunhofer EMI in Freiburg, Germany. The possible failure of non-structural elements, such as doors and windows, and the subsequent blast propagation into areas adjacent to the room hosting the facility are also accounted for. The simulation procedure presented in this work is scalable to similar and larger facilities for impact research as well as to other contexts involving analogous risks of gas explosions.

Initial study for the response of Ti–6Al–4V plate used in tank material

We have been conducting hypervelocity impact tests and numerical simulations to develop a Japanese spacecraft design guideline for the protection of satellites from a certain degree of M/OD impacts. A working group is formed by members of JAXA, spacecraft manufacturers, experts, and researchers in the field of hypervelocity impacts to investigate the effects of M/OD impacts on satellite critical parts and bumpers by hypervelocity impact (HVI) tests and analysis. The knowledge acquired is now being reflected in the spacecraft design guidelines.We investigated the effect of hypervelocity impacts of micrometeoroids and small-scale space debris on space structures by comparing numerical simulation results obtained using the AUTODYN-2D hydrocode with the results of experiments using a two-stage light gas gun since 2005. We will consider the case of a satellite hydrazine fuel tank and the consequences of a hypervelocity impact from space debris. The final purpose of this study is to better understand the mechanisms of detonation of hydrazine vapor during a hypervelocity impact on a low-pressure reservoir.As part of this effort and an initial study, the response of a Ti–6Al–4V plate which is used tank material to 6 km/s high-velocity impacts is shown and discussed. It was found that the ballistic limit of the titanium tank material for both curved and flat plates was generally predictable using the existing ballistic limit equation. The effect of curvature on the impact scar size of flat (t = 1.2 mm) and curved plates was examined, and no significant difference was found.

Study of the effects of projectile strength and density in the asteroid deflection by hypervelocity impact

In recent years, potentially hazardous asteroids (PHAs), which have orbits approaching the Earth and are a threat to humankind, have been attracting attention. It is necessary to prevent them from impacting the Earth, and asteroid deflection by hypervelocity impact is one of the best impact avoidance. This asteroid deflection needs to be greater, but momentum enhancement factor β, which represents deflection efficiency, is affected by various factors. This study focused on projectile strength and density, and experiments for small-scale impacts and numerical simulations for large-scale impacts were conducted to clarify these effects on β. In experiments, six types of projectiles with different strengths and densities and the same shape and size were impacted into brick targets at 1-3.5 km/s using a Two-Stage Light Gas Gun to investigate the effects in actual impacts. In simulations, three types of projectiles with different densities and the same shape and mass were impacted into granite targets at 3-10 km/s using AUTODTN to investigate the effects in asteroid-deflection-scale impacts, which are difficult for experiments. In conclusion, the effect of projectile strength on β is less, and the one of projectile density on β is high. It is demonstrated that projectiles whose density is close to the target density increase β, namely, are suitable for asteroid deflection regardless of impact scale. Additionally, a crater formed by hypervelocity impact is a preferably flat shape for asteroid deflection, and the effect of crater shape on β is higher at large-scale impact. Further study of this effect and the scaling one could be expected.

Momentum enhancement from 3-cm-diameter aluminum sphere impacts into iron and rock at 5 km/s

Utilizing a large two-stage light gas gun and a large pendulum assembly, experiments were performed to measure the momentum enhancement (or increase in momentum transfer due to the ejecta) of an ARMCO iron target, two large hematite rock targets, a target of stones held by concrete, and a concrete block target. The choice of iron and iron rich materials was motivated by interest in the asteroid Psyche and the planned upcoming mission. The target comprised of a collection of stones, to mimic a rubble pile asteroid, was to provide insight into the Double Asteroid Redirection Test (DART) impact. The role of impactor size is important, and these tests were performed at a large scale, with 3-cm-diameter aluminum spheres as the impactor. Save for the concrete block, these impacts were in the vicinity of 5 km/s. There is a distinct difference in the amount of momentum enhancement (measured by β) that occurs with ductile metals vs. brittle materials and this fact shows in these impacts. The momentum enhancement with a relatively brittle aluminum falls in between the two extremes of rock and iron. Computations were performed to compare with the ARMCO iron impacts. Data at a large scale is desirable to quantify momentum enhancement in the context of hypervelocity impactors deflecting celestial bodies such as asteroids or comet nuclei.

Experimental study on Hugoniot parameters of U71Mn steel under high pressure

The Hugoniot parameters of U71Mn steel under high pressure were studied by hypervelocity impact test of U71Mn steel with two-stage light gas gun. The plate impact test of U71Mn steel sample was carried out by means of symmetrical impact. The minimum impact speed was 1.843km/s and the maximum impact speed was 5.018km/s. The Hugoniot relation and Hugoniot parameter C and λ, then the accuracy of Hugoniot parameters of U71Mn steel under high pressure is verified according to Hugoniot equation of state (the relationship curve between impact pressure and density). The research results can provide reference for the application of U71Mn steel in the field of hypervelocity impact.

Mechanics of hypervelocity simultaneously launched distributed particles

Understanding the complex physics of micrometeoroid/orbital debris (MMOD) cluster impacts to spacecraft structures and particulate impacts such as dust, ice, rain, etc. to hypersonic vehicles is essential to ensure safe space travel and hypersonic flight. Hypervelocity impacts resulting from simultaneously launched distributed particles (SLDPs) can be used to realistically replicate such environments. A method to controllably launch and perform in-situ characterization of SLDPs has been developed and implemented. A powder-driven, 12.7 mm smooth-bore two-stage light gas gun was used to launch collections of 0.79 mm and 1.98 mm diameter 2017-T4 aluminum particles to group velocities ranging from 2.4–5.4 km/s. Ultra-high-speed images recorded at 1 MHz were processed using custom-developed two-dimensional digital particle tracking algorithms to characterize the airborne SLDP clusters. In addition, the three-dimensional (3D) features of the SLDP clusters were quantified using impacts to 1.59 mm thick 6061-T6 aluminum plates. Target damage and interactions between adjacent particle impact sites were studied using a combination of numerical simulations and post-impact forensic analyses. Characteristic Elastic Plastic Impact Computation code simulations were used to estimate critical nearest neighbor distances between impact sites below which damage interactions occur and to subsequently probe plastic damage coalescence. For a given particle diameter, the critical nearest neighbor distance was roughly twice the in-plane radial distance from the impact axis to the location of 1% equivalent plastic strain. The plate-thickness-to-particle-diameter ratio was found to affect the plastic strain field more than the crater/perforation size. The predicted crater geometry agreed well with 3D optical profilometry measurements of target impact sites. The approach developed in this work can be readily applied to other particle/target geometries, materials, and impact scenarios, including MMOD cluster impacts and environmental effects on hypersonic vehicles.

Ballistic Model of Two-Stage Light Gas Gun

A physical model and specificity of a two-stage light gas gun propulsion system are presented in this paper. For the considered system, a mathematical model of phenomena inside a combustion chamber, a light gas filled chamber, and a barrel was worked out. A numerical solution of the proposed model for the considered propulsion system gives pressures of powder gases, pressure of light gas, and motion parameters of a piston and a projectile. On the basis of the results of the accomplished calculations, influence of system structural parameters on the maximum pressure inside a compression chamber and a muzzle velocity of a projectile has been analysed. The final results of this work were used for development of the first in Poland a laboratory station with two-stage light gas gun intended for experimental investigation in the field of terminal ballistics of objects moving at hypersonic velocities.