Hypervelocity Research Articles

3D anatomy of the Cretaceous–Paleogene age Nadir Crater

The Nadir Crater offshore West Africa is a recently proposed near K-Pg impact structure identified on 2D seismic. Here we present 3D seismic data that image this crater in exceptional detail, unique for any such structure, which demonstrates beyond reasonable doubt that the crater-forming mechanism was a hypervelocity impact. Seismic mapping reveals a near-circular crater rim of 9.2 km and an outer brim of ~23 km diameter defined by concentric normal faults. An extended damage zone is evident across the region, well beyond the perceived limit of subsurface deformation for impact craters, except in a ‘sheltered zone’ to the east. The paleo-seabed shows evidence for widespread liquefaction because of seismic shaking, and scars and gullies formed by tsunami wave propagation and resurge. Deformation within the ~425 m high stratigraphic uplift and annular moat allows us to reconstruct the evolution of the crater, with radial thrusts at the periphery of the uplift suggesting a low-angle impact from the east. Structural relationships are used to reconstruct the deformation processes during the crater modification stage, with the central uplift forming first, followed by centripetal flow of surrounding sediments into the evacuated crater floor in the seconds to minutes after impact.

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.

Numerical Analysis of Debris Cloud Formation in UHMWPE Wavy Plates during Hypervelocity Impact

This paper presents and analyses the numerical results of hypervelocity impact against ultra-high molecular weight polyethylene (UHMWPE) plates with four different surface wave profiles. UHMWPE wavy plates (WP) are intended to be used in Whipple Shield bumper plate, which is of paramount importance for space vehicles against micro-meteorite and orbital debris (MMOD) impact protection. Numerical work was carried out as a hybrid combination of smoothed particle hydrodynamics (SPH) and finite element modelling (FEM). Circular plates were subjected to hypervelocity impact of a spherical aluminium projectile travelling at 3000 m/s. The outcomes of the simulations were analysed in terms of debris cloud generation, projectile fragmentation, and impact energy dissipation performance of wavy plates, and compared with a conventional flat counterpart. Results of this study indicate that surface wave profile has a clear positive influence in terms of hypervelocity impact protection performance.

Hypervelocity impact against aluminium Whipple shields in the shatter regime with systematic parameter variation: An experimental and numerical study

Aluminium Whipple shields are commonly used to protect spacecraft against hypervelocity impacts (HVIs) from orbital debris and micrometeoroids. Since numerical models nowadays are vital in the design process of protective shields, experimental studies of HVI are important to ensure that the numerical methods are robust and capable of accurately describing a range of impact conditions and material responses. The shatter regime is the transition velocity range between ballistic impact and hypervelocity impact, typically defined from 3 to 7 km/s. In this region, the debris cloud generated by the impact transitions from a few large, solid fragments at the lower end of the velocity range, to a high number of smaller fragments and partial melting of the projectile at the higher velocities. In this study, an experimental campaign of 22 normal impacts of spherical AA1100 projectiles on AA6061-T6 Whipple shields is performed, where the impact velocity and bumper thickness are systematically varied to study the change in debris cloud characteristics and shield damage. Impact velocities from 2.6 to 5.0 km/s are investigated, combined with bumper thicknesses of 1.0, 1.5 and 2.0 mm. Analysis of the experimental results is conducted using high-speed camera footage of the debris clouds and post-impact analysis of bumpers and rear walls. A numerical model is then established using the Smoothed Particle Hydrodynamics (SPH) method in the IMPETUS Solver, and the numerical results are compared to the experimental data. The simulations are able to capture the main trends found in the experimental study, and show a similar level of damage as the experiments when varying the impact velocity and bumper thickness. The simulations have somewhat smaller fragments generated in the debris cloud than in the experiments, leading to slightly less damage inflicted on the rear wall.

Insight into wave propagation in polyimide films and resistive grid sandwich structures towards a hybrid monitoring of hypervelocity impact

Micro-Meteoroid and Orbital Debris pose a significant threat to the safe operation of orbiting spacecraft, potentially leading to mission failure in space exploration. Quantitative characterization of hypervelocity impact (HVI) is crucial to ensure the safety and successful completion of on-orbit missions. Firstly, this study designed a three-layer sandwich structure of polyimide film with orthogonally laid resistive wires, combined with piezoelectric and resistive wire sensors, for the simultaneous acquisition of acoustic emission (AE) signals generated by HVI and measurement of perforation dimensions. Secondly, a semi-analytical finite element (SAFE) analysis of wave dispersion properties in the periodic sandwich structure is conducted with Bloch’s theorem, together with a hybrid model based on three-dimensional smoothed particle hydrodynamics and finite element methods (SPH-FEM) to comprehensively understand the AE waves and damage characteristics induced by HVI. The resulting anisotropic wave propagation characteristics with SAFE and SPH-FEM are closely matched. Thirdly, a time delay-multiplication (TDM) imaging algorithm considering wave velocity anisotropy is proposed for accurate real-time “visualization” of HVI locations. Lastly, correlations are established between projectile and perforation dimensions. The proposed algorithm for HVI multi-parameter quantification and damage detection helps evaluate the space HVI environment and HVI-induced damage to spacecraft.

Molecular dynamics-informed material point method for hypervelocity impact analysis

This paper introduces a framework specifically designed to simulate hypervelocity impact scenarios precisely. The framework utilizes the multiscale shock technique (MSST) from molecular dynamics (MD) to accurately model material states under extreme impact loading conditions, focusing on calculating the equation of state (EOS). A vital aspect of this work is the acquisition and application of the Mie-Grüneisen EOS, which is highly relevant in impact analysis research. The framework employs the material point method (MPM) to conduct analyses of hypervelocity impacts using the derived EOS. This method offers a detailed insight into the dynamic responses of materials subjected to hypervelocity impacts, underscoring the integration of molecular dynamics with the MPM.

Origin of the Ca-phosphate inclusions in Ivory Coast and Australasian Muong-Nong-type tektites

Tektites are reduced (Fe2+) glasses formed by the quenching of molten material ejected from Earth’s surface as a result of a hypervelocity impact. The vast majority of tektites are usually homogeneous glasses, but rare samples containing mineral inclusions can provide insights about the source material, sample thermal history, and tektite formation process. Tektites from two distinct strewn fields presenting Ca-phosphate inclusions detected from anomalous magnetic susceptibility were studied: one sample from the Ivory Coast tektite (ICT) field ejected at 1.07 Ma from the Bosumtwi crater (10.5 km in size) in Ghana and two Muong Nong type samples from the Australasian tektite field (MN-AAT) ejected at 0.79 Ma from a crater possibly situated in southeast Asia. In ICT, Ca-phosphate inclusions are systematically embedded in lechatelierite (SiO2 glass). In MN-AAT Ca-phosphate are either embedded in lechatelierite or in Fe-rich glass forming schlieren. Multiscale petrographic characterization using correlative microscopy associating scanning electron microscopy, microprobe and, transmission electron microscopy reveals that rounded inclusions in ivoirite are composed of acicular Ca-phosphates (merrillite) embedded in an amorphous P-rich glass. In MN-AAT, inclusions consist mostly of single droplets of Fe-Mg rich Ca-phosphate (structurally related to apatite), but few droplets often forming an emulsion texture show a complex assemblage of apatite, magnetite, pyroxene, and spinel growing from a Pt-rich nucleus. Diffusion profile around lechatelierite domains reveals maximum temperatures greater than 2200–2400 °C in the impact plume of the Australasian tektite and the Ivory coast tektite. Heating time is of the order of seconds-tens of seconds rather than minutes as previously suggested (20 s for MN-AAT and 5 s for ICT). The number, the density, and the fact that inclusions are entirely crystallized in MN-AAT support relatively slow cooling rates (<200 °C/h), in comparison with the faster cooling rates (>2000 °C/h) indicated by the precipitation of amorphous P-rich glass in ICT. In both impact events, ejecta that had been heated to high temperatures did not remain in the vapor plume for an extended period of time and landed rapidly (within tens of seconds) at a relatively high temperature (>1000 °C) on the Earth’s surface.Phosphate inclusions systematically embedded in lechatelierite in ICT provide clues about the source material. It suggests that the parent material for these silica-rich inclusions is not conventional detrital quartz. Rather, parts of lechatelierite domains may be inherited from a biogenic source that could be consistent with tropical soil (source of the phosphor) and its biomass (silica of plant origin). The reduction process that tektites record during their formation may be explained by superficial material since forests can contain a sizable mass of carbon that can reduce iron in tektites and produce platinoid-rich metallic nuclei and the Fe3+/ΣFe gradient recorded by the dendritic spinels.

Proposing novel body-centered cubic lattice core sandwich panels as satellite structure

In the present paper, a comparative study on the load-bearing as well as shielding performance against hypervelocity impact of space debris of sandwich panels with body-centered cubic lattice core is performed numerically in order to evaluate their eligibility to be utilized as the satellite structure. To this end, four types of body-centered cubic lattice structures, with similar areal densities which are assumed to be made of 5A06 aluminum alloy, including BCC, BCCz (BCC reinforced in Z direction), and also BCCz-I and BCCz-II were considered. Whipple shield structure of same material and areal density was also investigated in order to justify the necessity of lattice structures application, especially in protection field. The present study simulates hypervelocity impact of a spherical projectile with 2 mm diameter, represented the space debris, collides with the structures at the velocity range of 2–6 km/s. Current numerical simulation process accuracy and efficiency were verified through comparing its obtained data based on simulating a problem had been investigated at a valid experimental study to the data proposed by the mentioned research. BCCz-II structure which is newly proposed at this study provided outstanding shielding and load-bearing capabilities in comparison to other structures. Furthermore, the detailed effects of projectile impact location and a middle structure placed plate on the protection performance were investigated and the mentioned items were found to have crucial impact on the structure shielding performance.

Fragment Identification Method Based on DBSCAN and Its Application in Hypervelocity Impact of Whipple Shield

Fragment Identification Method Based on DBSCAN and Its Application in Hypervelocity Impact of Whipple Shield

Shock melt in the Cold Bokkeveld CM2 carbonaceous chondrite and the response of C‐complex asteroids to hypervelocity impacts

AbstractMany of the CM carbonaceous chondrites are regolith breccias and so should have abundant evidence for collisional processing. The constituent clasts of these fragmental rocks frequently display compactional petrofabrics; yet, olivine microstructures show that most CMs are unshocked. To better understand the reasons for this contradiction, we have sought other evidence for hypervelocity impact processing of CM chondrites using the Cold Bokkeveld meteorite. We find that this regolith breccia contains rare particles of vesicular shock melt that are close in chemical composition to bulk CM chondrite. Transmission electron microscopy of a melt bead shows that it is composed of silicate glass with inclusions of pentlandite, pyrrhotite, and wüstite. Characterization of shards of another bead by atom probe tomography reveals nanoscale clusters of sulfur that represent sulfide inclusions arrested at an early stage of growth. These glass particles are mineralogically comparable to micrometeoroid impact melt described from the Cb‐type asteroid Ryugu and melt that has been experimentally produced by pulsed laser irradiation of CM targets. The glass could have formed by in situ shock‐melting, but petrographic evidence is more consistent with an origin as ballistic ejecta from a distal impact. The scarcity of melt in this meteorite, and CM chondrites more broadly, is consistent with the explosive fragmentation of hydrous asteroids following energetic collisions. Cold Bokkeveld's parent body is likely to be a second‐generation asteroid that was constructed from the debris of one or more earlier bodies, and only a small proportion of the reaccreted material had been highly shocked and melted.

Polarization Characteristics of Massive HVI Debris Clouds Using an Improved Monte Carlo Ray Tracing Method for Remote Sensing Applications

As a signature phenomenon of massive hypervelocity impacts (HVIs) in space, debris clouds provide critical optical information for satellite remote sensing and the assessment of large-scale impacts. However, studies of the optical scattering properties of debris clouds remain limited, and existing vector radiative transfer (VRT) methods struggle to accurately simulate the optical characteristics of these complex scatterers. To address this gap, this paper presents an improved Monte Carlo VRT program (PGS–MC) for multicomponent polydisperse scatterers to precisely evaluate the radiation and polarization characteristics of complex scatterers. Based on the Monte Carlo ray tracing (MCRT) method, our program introduces a particle grouping strategy (PGS) to further emphasize the importance of accounting for optical property discrepancies between different materials and particle sizes, thus significantly improving the fidelity of VRT simulations. Moreover, our program, developed using the compute unified device architecture (CUDA), can be run parallelly on graphics processing units (GPUs), which effectively reduces the computational time. The validation results indicated that the developed PGS–MC program can accurately and efficiently simulate the polarization of complex 3D scatterers. A further investigation showed that the polarization characteristics of debris clouds are highly sensitive to parameters such as the angle between the incident and detection directions, number density, particle size distribution, debris material, and wavelength. In addition, the polarization imaging of debris clouds offers distinct advantages over intensity imaging. This study offers guidance for analyzing the VRT properties of massive HVI debris clouds. Additionally, it provides a practical tool and concrete ideas for modeling the polarization characteristics of various complex scatterers, such as aircraft contrails and clouds, etc.

Crustal origin for olivine in the lunar Shioli crater ejecta boulders: Insights from the geological setting of Theophilus crater and Nectaris basin

On the Moon, impact craters and basins expose a wide range of crustal and mantle rocks that provide excellent opportunity for sampling them, understanding their origins and reconstructing spatial and temporal evolution of lunar interior. The previous studies detected olivine-bearing mantle rocks in and around large impact craters and basins. The Japanese SLIM mission landed on the ejecta of a ∼ 280-m-diameter Shioli crater that was emplaced on the ejecta blanket of ∼ 103-km-diameter Theophilus crater, for characterizing potential mantle-derived olivine in the Shioli crater ejecta boulders. To test this hypothesis, we studied the geological setting of Shioli crater, host Theophilus crater and Nectaris multi-ring basin using the orbiter data from Chandrayaan-1 and 2, Lunar Reconnaissance Orbiter, and Kaguya missions and the earth-based Arecibo radar observation. The asymmetrically distributed secondary craters and impact melt ponds around Theophilus crater suggests that a northeast-directed oblique impact produced this crater. Composition of Theophilus crater and surrounding region indicates that the crater excavated a heterogeneous target composed of a thin layer of high-Al olivine basalt (Mare Nectaris) underlain by anorthositic highland rocks possibly intruded by Mg-suite plutons; layers of Cyrillus crater ejecta blanket and Nectaris basin materials (both ejecta and impact melt sheets) were also present beneath the mare basalt flows. Hence, the Theophilus ejecta blanket is a mixture of all these materials. Our dating of Theophilus crater suggests that it is a ∼ 2 Ga Eratosthenian crater. Shioli is a fresh simple crater that was formed at ∼ 1 Ma on the uprange ejecta blanket of Theophilus, where the Arecibo radar data indicated the presence of abundant buried Theophilus ejecta boulders. An ESE-directed hypervelocity oblique impact event produced the elongated Shioli crater and its asymmetrically distributed bright ejecta. Shioli is a primary impact crater indicating the role of impact spallation processes associated with this hyper-velocity impact in producing thousands of ejecta (or spall) boulders around Shioli crater, displaying their asymmetric dispersal pattern and spatial variation of boulder sizes and shapes. The larger and elongated boulders are concentrated near the crater rim, while their size and axial ratio gradually decreases outward from the crater rim. The SLIM mission landed on a thin downrange ejecta of Shioli crater, where fewer large-size boulders are present. Our compositional study suggests that the Shioli ejecta boulders are composed of olivine basalt (Mare Nectaris) mixed with highland anorthositic fragments, including the reworked Cyrillus ejecta and Nectaris basin materials. The Shioli ejecta boulders were produced by complex impact fragmentation of already existing, buried Theophilus ejecta boulders. The regional crustal structure of Nectaris basin and its petrological composition suggest that both Nectaris basin and Theophilus crater did not excavate the lunar mantle. Therefore, the Shioli ejecta boulders are of crustal origin, including the olivine minerals present in them. Our results have important implications for the origin of olivine in the Shioli crater boulders being investigated by the SLIM mission.

Evaluating load-bearing and hypervelocity impact shielding capabilities of face-centered cubic lattice core sandwich panels

In the present paper, a comparative study on load-bearing as well as hypervelocity impact shielding performance of sandwich panels with face-centered cubic (FCC) lattice core is numerically performed in order to evaluate their competency in satellite structure applications. To this end, 5A06 aluminum alloy FCC and FCCz beside cube and octahedron lattice structures with similar areal densities were investigated. Whipple shield structure of same material and areal density was also studied in order to be compared to lattice structure in protection field. The present study simulates hypervelocity impact of a spherical projectile with 2 mm diameter, represents the space debris, collides with the structures at the velocity range of 2–6 km/s. Numerical simulation model was validated by performed experimental study. Authors were inspired by cube and FCCz topologies to propose a novel lattice structure could provide outstanding shielding and load-bearing capabilities in comparison to the other structures studied in this research. Furthermore, the detailed effects of projectile impact location on the protection performance were investigated and the mentioned item was found to have considerable influence on the structure shielding performance.

The “suevite” conundrum, Part 2: Re‐examining the type locality at the Ries impact structure, Germany

AbstractOne of the most common types of allochthonous impactite produced in hypervelocity impact events is impact breccia that contains melt particles. In numerous terrestrial hypervelocity impact structures such melt‐bearing breccias have been termed “suevite,” after the type locality at the Ries impact structure, Germany. Despite its widespread occurrence, the origin, emplacement, and classification of suevite remains debated. In this contribution, we re‐examine the nature and origin of suevite at the Ries impact structure. The results of new field and laboratory investigations, when combined and synthesized with results from previous studies, lead to a multi‐stage model for the origin and emplacement of allochthonous impactites during the Ries impact event. Following the creation of a transient cavity the so‐called Bunte Breccia and “megablocks” were emplaced via ballistic sedimentation and subsequent radial flow during the excavation stage to form a continuous ejecta blanket. At the end of the excavation stage, a mixture of melt and lithic fragments formed a lining to the transient cavity and it is this material that later became the crater, dike, and outer suevite (OS) units. The crater suevite represents the material from the displaced zone of the transient cavity that was transported and mixed but never left the cavity. The emplacement of dike suevite occurred during the modification stage as the crater suevite was intruded into fractures in the underlying crater floor. The OS and rare impact melt rocks overlying the ballistic (Bunte Breccia) ejecta deposits were emplaced as outwards‐directed ground‐hugging flows largely during the modification stage of crater formation. The OS flows varied both spatially and temporally in terms of the flow characteristics, from being dominated by solid particles and gas (cf. pyroclastic density currents) to a mixture of solid particles, liquid (impact melt), and minor gases (i.e., particulate impact melt‐rich flows). These particulate impact melt‐rich flows dominated by far. Minor “fallback” of material from an ejecta plume is evidenced by accretionary lapilli in the Nördlingen 1973 core. In summary, allochthonous impactites at the Ries impact structure are not unusual but are consistent with observations from other terrestrial and planetary craters, where melt‐rich impactites overly ballistic ejecta deposits both outside and inside crater rims and where melt‐rich impactites occur in crater interiors.

Production of high velocity micron-sized ice particles using the NASA Ames Vertical Gun Range for application to missions to icy moons.

The Ames Vertical Gun Range (AVGR) is a hypervelocity impact facility hosting a variable angle, two-stage, light-gas gun that can accelerate projectiles up to 7 km s−1. We have used the AVGR to produce impacts into supercooled (73–89 K) synthetic seawater ice targets inside a large impact chamber, whose pressure is 0.3 to 0.7 Torr.We report on the effective novel use of stainless steel meshes (49 μm, 100 μm, 149 μm, and 500 μm) to filter the ejecta plume for the ice grains of a desired size and demonstrate that reproducible temperature, speed, and particle size distribution can be achieved.The resulting ejecta plume of micrometer-sized ice particles (micro grains) from these impacts provides a method to simulate spacecraft encounters with ice particles found in the plumes of the outer Solar System, especially Enceladus. Image analysis of ejecta plume impacts onto aluminum (Al) foil enabled us to determine the ice particle diameter range. We find that the particles in the ejecta plume have speeds from 0.2 to 2 km s−1 and temperatures from 102 to 113 K (−171 to −160 °C). Furthermore, 61–97% by numberof the ice grains have equivalent diameter between 2.5 and 20 μm, that is, in the range 1 μm ≤ radii ≤10 μm, the upper size constrained by Cassini, i.e., ∼2 μm to 50 μm. Overall, the AVGR provides a high-fidelity simulation of ice micro grains impacting spacecraft surfaces and sample-collecting systems. This may be useful in the design, testing, and data analysis of future missions to Enceladus, Europa, and other icy moons.

A detailed chemical study of the extreme velocity stars in the galaxy

ABSTRACT Two decades on, the study of hypervelocity stars is still in its infancy. These stars can provide novel constraints on the total mass of the Galaxy and its dark matter distribution. However how these stars are accelerated to such high velocities is unclear. Various proposed production mechanisms for these stars can be distinguished using chemo-dynamic tagging. The advent of Gaia and other large surveys have provided hundreds of candidate hyper velocity objects to target for ground-based high-resolution follow-up observations. We conduct high-resolution spectroscopic follow-up observations of 16 candidate late-type hyper velocity stars using the Apache Point Observatory and the McDonald Observatory. We derive atmospheric parameters and chemical abundances for these stars. We measure up to 22 elements, including the following nucleosynthetic families: $\alpha$ (Mg, Si, Ca, and Ti), light/odd-Z (Na, Al, V, Cu, and Sc), Fe-peak (Fe, Cr, Mn, Co, Ni, and Zn), and neutron capture (Sr, Y, Zr, Ba, La, Nd, and Eu). Our kinematic analysis shows one candidate is unbound, two are marginally bound, and the remainder are bound to the Galaxy. Finally, for the three unbound or marginally bound stars, we perform orbit integration to locate possible globular cluster or dwarf galaxy progenitors. We do not find any likely candidate systems for these stars and conclude that the unbound stars are likely from the the stellar halo, in agreement with the chemical results. The remaining bound stars are all chemically consistent with the stellar halo as well.

Piezoelectric energy harvesting from the atomic oxygen hypervelocity impact in low Earth orbit

Atomic oxygen (AO) in low Earth orbit (LEO) can cause severe progressive damage to spacecraft orbiting at hypervelocities over 7 km/s; therefore, all space-graded materials need to be qualified for protection against these high energy impacts. Instead of treating AO as a threat, can we use these atomic impacts, which have enough energy to cause material failure, to generate power? Despite its potential, no attempt has yet been made to utilize the hypervelocity impact energy of AO. Thus, we propose a piezoelectric energy harvesting method through the hypervelocity AO impact in LEO. In this study, energy harvesting with various configurations was experimentally demonstrated using a conventional lead zirconate titanate (PZT) ceramic plate under oxygen plasma exposure to simulate AO impact. The average output power density was 4 W/m2 under 1.43 × 1016 atoms/cm2s effective AO flux conditions. Our study provides a new method for generating energy in a space environment with limited energy sources.

Dynamic mechanical response and constitutive model of (Ti37.31Zr22.75Be26.39Al4.55Cu9)94Co6 high-entropy bulk metallic glass

In this work, the mechanical response and fracture characteristics of (Ti37.31Zr22.75Be26.39Al4.55Cu9)94Co6 high-entropy bulk metallic glass (HE-BMG) were investigated in detail over a wide range of strain rates (10−4–105 s−1). The HE-BMG exhibited a negative strain rate sensitivity under uniaxial compression, with the strength showing more significant rate dependence under dynamic conditions. The shear band behavior translated from the dominance of multiple shear bands propagations under quasi-static compression to the rapid propagation of a single shear band to form cracks under dynamic compression. Under dynamic loading, the shearing velocity increased along an arc-shaped displacement path, and the local stress state on the shear fracture surface shifted from compressive-shear to tensile-shear, accompanied by changes in fracture morphologies. The spall strength of HE-BMG decreased as flyer impact speed increased, while the long-term dependence of spall strength on strain rate may be positive. With the increase of impact speed, the main microstructural features of the spalling surface translated from flat regions accompanied by dimples to cup-cone structures. Furthermore, the complete parameters of the Johnson–Holmquist II (JH-2) model for HE-BMG were obtained based on experimental data. Numerical simulations of planar impact, penetration, and hypervelocity impact are in good agreement with experimental results, demonstrating the validity of the JH-2 model parameters. The current work has important guiding value for the application of HE-BMG in space debris protection.

Impact-induced deformation away from the impact point on small asteroids

Abstract We investigated the propagation of energy and momentum inside a small gravitational aggregate asteroid following a hyper-velocity impact, comparable to NASA’s Double Asteroid Redirection Test on asteroid Dimorphos. We show that the impact energy damps rapidly inside different kinds of granular structures, unable to reach the antipodal hemisphere of the impact. However, global reshaping of the asteroid after the formation of a sizeable (&amp;gt;1/3 of target size) crater causes meter-range displacement of boulders on the antipodal hemisphere due to mass rearrangement to achieve a new equilibrium shape. As a result, a surface depression opposite to the crater is formed, which may produce some surface refreshment. The boulder mass ejection following the synthetic DART-like impact is estimated to be at least $0.1\, {{\%}}$ of the mass of the Dimorphos-like target, in agreement with recent detections of boulders ejected from the actual DART impact.

Origami multi-layer space shield for cylindrical space structure

The multidisciplinary space environment, encompassing orbital debris, cosmic radiation, and solar radiative heat, poses significant risks to spacecraft and astronauts, necessitating efficient and effective shielding solutions. A multi-layer shield with wide spacing has been proven to be an effective way to shield the spacecraft from space debris impact; however, due to the limited volume of the payload fairing, it was not feasible to apply a multi-layer shield to the spacecraft fuselage. Through the origami design, the shield maintains a compact form during launch and subsequently expands in outer space to enhance protection. Through geometric analysis, it has been confirmed that the deployable multi-layer space shield can occupy less space than conventional space shield structures while expanding into wider shield intervals and multiple layers. Through hypervelocity impact experiments, it was confirmed that as the bumper spacing of the multi-layer space shield expands, its ballistic performance becomes superior to conventional space structures. The deployable multi-layer space shield can reduce not only hypervelocity impacts but also solar radiative heat using the same mechanism as multi-layer insulation. Through cosmic radiation dose analysis, it has been confirmed that the multi-layer space shield is effective in cosmic radiation shielding compared to conventional space structures.