Hypervelocity Research Articles

V-type Asteroids as the Origin of Mesosiderites

We present the results of a campaign of hypervelocity impact experiments on natural mesosiderite targets, using representative main asteroid belt impact speeds. The objective is to document further the surface evolution of iron-rich asteroids. In contrast with iron meteorites, we demonstrate the fragile behavior of mesosiderite at impact since experiments result in both cratering and catastrophic disruption. The behavior of metal-rich asteroids at impact is thus highly influenced by the original ratio of metal/silicate. A visible to near-infrared spectral analysis shows that the pyroxene silicate signature of impacted mesosiderites, or their ejecta, is fully preserved. Our results thus rule out a mesosiderite hypothesis for the very nature of M/X-type asteroids including (16) Psyche, despite a small fraction of its surface possibly being covered by mesosiderite-like materials. Finally, we address the question of whether mesosiderites and howardite–eucrite–diogenite (HED) meteorites are genetically linked to (4) Vesta or other differentiated asteroids in the main belt based on their spectral similarity.

Effects of projectile parameters on the momentum transfer and projectile melting during hypervelocity impact

The effects of projectile/target impedance matching and projectile shape on energy, momentum transfer and projectile melting during collisions are investigated by numerical simulation. By comparing the computation results with the experimental results, the correctness of the calculation and the statistical method of momentum transfer coefficient is verified. Different shapes of aluminum, copper and heavy tungsten alloy projectiles striking aluminum, basalt, and pumice target for impacts up to 10 km/s are simulated. The influence mechanism of the shape of the projectile and projectile/target density on the momentum transfer was obtained. With an increase in projectile density and length-diameter ratio, the energy transfer time between the projectile and targets is prolonged. The projectile decelerates slowly, resulting in a larger cratering depth. The energy consumed by the projectile in the excavation stage increased, resulting in lower mass-velocity of ejecta and momentum transfer coefficient. The numerical simulation results demonstrated that for different projectile/target combinations, the higher the wave impedance of the projectile, the higher the initial phase transition velocity and the smaller the mass of phase transition. The results can provide theoretical guidance for kinetic impactor design and material selection.

The damage characteristics and formation mechanism of ultrahigh strength 7055 aluminum alloy under hypervelocity impact

This paper studies the damage morphology evolution of ultrahigh strength 7055 aluminum alloy plate under the hypervelocity impact of aluminum projectile, and analyzes the formation mechanism of crater morphology at different impact velocities. It is found that the impact crater evolves from spherical crown shape to spherical-conical composite shape, and eventually transforms into hemispherical shape with the increase of impact velocity. The evolution of crater shape is highly associated with the ratio of steady-state shock pressure and the strength of the alloy. The variation of crater diameter as a function of impact velocity follows the hypothesis of hemispherical theory, while the crater depth shows a great deviation due to the formation of conical region at the crater bottom and spall fracture at the back of the target. It is demonstrated that the formation of conical crater is related to the poor resistance to shear localization of 7055 aluminum alloy due to its low strain hardening capacity under dynamic loading. Hence, adiabatic shear bands are generated and evolve into shear cracks, thereby causing the formation of conical region at the crater bottom. It is suggested that the resistance to shear localization should be highly considered for the design, evaluation and selection of protection materials for spacecraft.

Analysis of hypervelocity-impacted thin films for space applications

Exposure to the harsh space environment and hypervelocity impacts from micrometeoroids and small orbital debris can affect space operations through long-term degradation of spacecraft materials, surfaces, or systems. Multi-layer insulation (MLI) and coated polyimide films are spacecraft materials commonly found on the external surfaces of spacecraft for thermal control and protection. Characterizing the damage to these exposed materials with in situ and laboratory measurements can better inform spacecraft designers and operators in understanding and mitigating surface or system degradation. In this paper, we examine flown Hubble Space Telescope (HST) Equipment Bay 5 MLI and coated polyimide hypervelocity ground tested articles to characterize hypervelocity impact damage. Impact feature cavities are inspected to identify damage, which can validate long-term degradation models, improve thermal management systems, or improve accuracy of damage predictions. An overview of the impact characterization using optical microscopy, narrow-band spectroscopy, and Scanning Election Microscopy/Energy Dispersive X-ray (SEM/EDX) of the two materials is presented. Observations of robustness in the space environment, as well as a detailed assessment of cratering and penetration statistics for the space-exposed sample, are also discussed.

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.

Fluid–solid coupled simulation of hypervelocity impact and plasma formation

Previous theoretical and computational studies on hypervelocity impact have mainly focused on the dynamic response of the solid materials that constitute the projectile and the target, while the surrounding environment is often assumed to be a vacuum. In this paper, we consider impact events that occur in a fluid (e.g., gas) medium, and present a computational model that includes the dynamics, thermodynamics, and ionization of the surrounding fluid material. The model couples the compressible Navier–Stokes equations with the Saha equations to predict the onset and extent of ionization in the surrounding fluid. An extended level set method with two signed distance functions is employed to track the three material interfaces between the projectile, the target, and the ambient fluid. This method accommodates the large deformation, contact, and separation of the interfaces, while avoiding spurious overlapping of different material subdomains. The advective fluxes across material interfaces are computed by constructing and solving bimaterial Riemann problems, thereby taking into account the discontinuities in both state variables (e.g., density) and thermodynamic relations. The computational model is first verified for an infinite ideal plasma and a one-dimensional three-material impact problem. Next, the model is employed to analyze the impact of a tantalum rod projectile onto a soda lime glass (SLG) target in an argon gas environment. In different analyses, the impact velocity is varied between 3 and 6km/s, and the radius of the projectile is varied between 2.5 and 10mm. Each analysis starts with a steady-state fluid dynamics simulation that generates the shock-dominated hypersonic flow around the projectile. This flow field is then used as an initial condition to start the fluid–solid coupled impact simulation. The predicted maximum temperature and pressure within the SLG target agree reasonably well with published experimental data for a similar material (fused quartz). Within the ambient gas, the impact-generated shock wave is found to be stronger than the initial bow shock in front of the projectile. Behind this shock wave, a region of high pressure and temperature forms in the early stage of the impact, mainly due to the hypersonic compression of the fluid between the projectile and the target. The temperature within this region is significantly higher than the peak temperature in the solid materials. For impact velocities higher than 4km/s, ionization is predicted. This finding indicates that the ambient gas may be a nontrivial contributor to the plasma formed in terrestrial and atmospheric hypervelocity impact events.

Dependence of impact regime boundaries on the initial temperatures of projectiles and targets

Towards higher impact velocities, ballistic events are increasingly determined by the material temperatures. Related effects might range from moderate thermal softening to full phase transition. In particular, it is of great interest to quantify the conditions for incipient or full melting of metals during impact interactions, which result in a transition from still strength-affected to hydrodynamic material behavior. In this work, we investigate to which extent the respective melting thresholds are also dependent on the initial, and generally elevated, temperatures of projectiles and targets before impact. This is studied through the application of a model developed recently by the authors to characterize the transition regime between high-velocity and hypervelocity impact, for which the melting thresholds of materials were used as the defining quantities. The obtained results are expected to be of general interest for ballistic application cases where projectiles or targets are preheated. Such conditions might result, for example, from aerodynamic forces acting onto a projectile during atmospheric flight, explosive shaped-charge-jet formation or armor exposure to environmental conditions. The performed analyses also broaden the scientific understanding of the relevance of temperature in penetration events, generally known since the 1960s, but often not considered thoroughly in impact studies.

Collisional particle-in-cell investigations of electromagnetic pulses in hypervelocity impact plasmas

A collisional, 2D discontinuous Galerkin particle-in-cell (DG-PIC) code is developed to analyze electromagnetic pulses (EMPs) generated from hypervelocity impact plasmas. The discontinuous Galerkin scheme is used to solve the 2D transverse electric Maxwell’s equations while the particle-in-cell scheme is used to model charged species dynamics. Two models for Coulomb collisions are tested: a small-angle “particle-moment” model and a general Langevin equation model. Both collisionless and collisional simulations are able to reliably reproduce EMP generation due to charge separation within the bulk and the resulting electrostatic oscillations that occur. Both collision models cause a decrease in the frequency of the EMPs that are formed; however, this decrease is not significant enough to explain the discrepancy between experiments and simulations in previous literature. Despite this, Coulomb collisions can be significant in the physics of the plasma behind EMP generation for hypervelocity impacts, particularly in increased heating within the plasma. Overall, although Coulomb collisions are highly influential in the temperature of the plasma, they are not important in the EMP generated and its threat to spacecraft.

ALEGRA: Finite element modeling for shock hydrodynamics and multiphysics

ALEGRA is a multiphysics finite-element shock hydrodynamics code, under development at Sandia National Laboratories since 1990. Fully coupled multiphysics capabilities include transient magnetics, magnetohydrodynamics, electromechanics, and radiation transport. ALEGRA is used to study hypervelocity impact, pulsed power devices, and radiation effects. The breadth of physics represented in ALEGRA is outlined here, along with simulated results for a selected hypervelocity impact experiment.

Evaluation of hypervelocity impact of micrometeoroids and orbital debris on next-generation space solar cells

This paper discusses the hypervelocity impacts of micrometeoroids and orbital debris (MMODs) on inverted metamorphic triple-junction (IMM3J) and perovskite solar cells, which are much thinner than conventional triple-junction (3J) solar cells. We experimentally found that IMM3J solar cells can suffer from short-circuit faults due to the hypervelocity impacts of MMODs, unlike conventional 3J cells, and determined the projectile diameters and velocities that could cause them using a model proposed by Burt. No short-circuit mode was identified in perovskite solar cells, but they had open-circuit faults several days after the hypervelocity impact experiment, which are possibly attributed to the decomposition of the perovskite crystal by moisture in the air due to the broken seal.

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.

Meeting the challenges of hypervelocity impact testing at 10 km/s

The ability to evaluate the response of spacecraft hardware to the impacts of orbital debris at velocities of interest, e.g., 9 to 11 km/s, has been an elusive goal of the hypervelocity impact community. This velocity range is greater than the capability of two-stage, light-gas guns traditionally used to test spacecraft shields, structures, and thermal protection systems. To meet the need for test capabilities at these higher velocities, the University of Dayton Research Institute (UDRI) developed a three-stage, light-gas gun and used it to launch Nylon, aluminum, aluminum oxide, and stainless steel spheres to velocities up to 10 km/s. The development of the three-stage, light-gas gun, a reliable functioning sabot, and a method of discarding the sabot after its use posed significant design and operational challenges. This paper describes: (1) the three-stage, light-gas gun; (2) a unique, one-piece sabot design required to withstand the extreme accelerations and loads imposed on the spheres and sabots during their launch, and (3) a novel method of discarding the sabot after its use. It concludes with the presentation of the results of two tests performed on spacecraft hardware at impact velocities of 9.23 and 9.90 km/s.

Experimental Evidence for Shear‐Induced Melting and Generation of Stishovite in Granite at Low (<18 GPa) Shock Pressure

AbstractKnowledge of the shock behavior of planetary materials is essential to interpret shock metamorphism documented in rocks at hypervelocity impact structures on Earth, in meteorites, and in samples retrieved in space missions. Although our understanding of shock metamorphism has improved considerably within the last decades, the effects of friction and plastic deformation on shock metamorphism of complex, polycrystalline, non‐porous rocks are poorly constrained. Here, we report on shock‐recovery experiments in which natural granite was dynamically compressed to 0.5–18 GPa by singular, hemispherically decaying shock fronts. We then combine petrographic observations of shocked samples that retained their pre‐impact stratigraphy with distributions of peak pressures, temperatures, and volumetric strain rates obtained from numerical modeling to systematically investigate progressive shock metamorphism of granite. We find that the progressive shock metamorphism of granite observed here is mainly consistent with current classification schemes. However, we also find that intense shear deformation during shock compression and release causes the formation of highly localized melt veins at peak pressures as low as 6 GPa, which is an order of magnitude lower than currently thought. We also find that melt veins formed in quartz grains compressed to >10–12 GPa contain the high‐pressure silica polymorph stishovite. Our results illustrate the significance of shear and plastic deformation during hypervelocity impact and bear on our understanding of how melt veins containing high‐pressure polymorphs form in moderately shocked terrestrial impactites or meteorites.

Evaluating UHMWPE-stuffed aluminium foam sandwich panels for protecting spacecraft against micrometeoroid and orbital debris impact

Robotic spacecraft shielding for protection against micrometeoroid impact is typically provided by existing structural panels, thermal insulation blankets, or reinforced component containers. Here the performance of an open cell aluminium foam core sandwich panel with intermediate ultra-high molecular weight polyethylene (UHMWPE) stuffing under hypervelocity impact of spherical aluminium projectiles was evaluated. Providing comparable structural and thermal performance as honeycomb sandwich panels, foam core sandwich panels have demonstrated improved impact shielding behaviour in existing studies. The inclusion of UHMWPE stuffing is found, through experimental testing and a comprehensive numerical study, to increase the shielding capability of foam core sandwich panels (40–80% increase in critical projectile diameter) for a modest weight penalty (25%). Compared to conventional aluminium honeycomb sandwich panels with equivalent weight, the improvement in shielding performance is >100%.

Experimental validation of hydrazine reaction model through hypervelocity impact tests

The impact of debris on a satellite can result in a catastrophic event that not only destroys the spacecraft but it can also generate additional debris in space threatening the sustainability of space activities. Therefore, the design of spacecraft and its critical components require some understanding of the potential damage that can be inflicted by such event. For hydrazine fuel tank located outside the spacecraft, it is important to evaluate the conditions that may lead to its explosion in case of impact.This study aims at investigating through experimental tests, the temperature and pressure range for which hydrazine reacts under hypervelocity impact. The investigated tank conditions are representative of the temperature and pressure typically encountered for a satellite at the end of operational life i.e. with some residual remaining hydrazine in the tank. The main challenge of the project is related to the complexity and the hazard of the handling hydrazine. A specific test configuration and process have been developed for the safety of the operators and the surrounding environment. An ultra-fast valve was designed to isolate the target chamber right after the crossing of the projectile and before any hydrazine vapor comes back towards the gas-gun. The process prevents any direct contact of the laboratory personal with hydrazine. Four instrumented tests have been performed on small container impacted by stainless steel ball of 3 mm diameter at 6 km/s. A hydrazine reaction triggered by the impact has been detected on two tests with the highest temperature. In one case, the released energy has led to a catastrophic failure of the reservoir. These results are valuable for the calibration of a hydrazine thermochemical reaction model of satellite reservoir impact behavior even though the ignition process is not clearly established yet.

Simulating hypervelocity impacts into rubble pile structures for planetary defense

Kinetic impactors are one of the most mature technologies for planetary defense and this technique was tested for the first time by NASA's Double Asteroid Redirection Test (DART) mission. The material and physical properties of the asteroid are very important in understanding the efficacy of a kinetic impactor. To constrain how the local topography of an impactor alters the response to the hypervelocity impact of a kinetic impactor, we used the adaptive smoothed particle hydrodynamics code, Spheral++, to impact plates into a rubble pile asteroid. By varying both the impact location and the strength between the boulders and regolith of the formed asteroid, we find that variations in the rubble pile contributes approximately 10% uncertainty to the resulting momentum enhancement in regolith dominated impacts. We further demonstrate that the craters produced from the impacts into the rubble pile are wide, shallow, and show deviations from symmetry due to the presence of boulders on the surface near the impact site. These simulations help us constrain the potential outcomes that may occur from a hypervelocity kinetic impact in a planetary defense scenario.

Preliminary study of radio frequency waves in hypervelocity impact plasma

Orbital debris and meteoroids can cause mechanical and electrical anomalies by impacting spacecraft. Although mechanical damage tends to occur only from particles with masses >10−3g, electrical damage can be a result of hypervelocity (> 10 km/s) impacts (HVI) even with smaller particles. In HVI, the projectile speed exceeds the speed of sound in the material and has enough energy to create plasma by ionizing the material near the surface, which can then emit radio frequency (RF) waves.In this paper, we conduct a preliminary study on the characteristics of impact-generated RF emission with the ultimate goal of building an RF predictive model for risk assessment of HVI electrical effects that can damage spacecraft. First, we introduce wavelet analysis as a method for denoising and quantifying the total RF signal energy. An appropriate mother wavelet and the number of decomposition levels are selected using a synthetic signal. Second, the total energy of the RF emission is calculated using Parseval's theorem. Results suggest that the total RF signal energy is proportional to the energy flux of the impactor. Finally, spectrograms of the RF emission are analyzed to characterize features that can be used in the future to predict impacts that can cause electrical damage to satellites.

Impact melt rocks from the Late Paleocene Hiawatha impact structure, northwest Greenland

AbstractImpact melt rocks formed during hypervelocity impact events are ideal for studying impact structures. Here, we describe impact melt rock samples collected proximal to the 31 km wide 58 Ma Hiawatha impact structure, northwest Greenland, which is completely covered by the Greenland Ice Sheet. The melt rocks contain diagnostic shock indicators (e.g., planar deformation features [PDF] in quartz and shocked zircon) and form three groups based on melt textures and chemistry: (i) hypocrystalline, (ii) glassy, and (iii) carbonate‐based melt rocks. The exposed foreland directly in front of the structure consists of metasedimentary successions and igneous plutons; however, the carbonate‐based impactites indicate a mixed target sequence with a significant carbonate‐rich component. Well‐preserved organic material in some melt rocks indicates that North Greenland at the time of impact was host to abundant organic material, likely a dense high‐latitude temperate forest. Geochemical signatures of platinum‐group elements in selected samples indicate an extraterrestrial component and support previous identification of a highly fractionated iron impactor in glaciofluvial sand. Our results illustrate the possibility to study impact structures hidden beneath a thick ice sheet based on transported samples and this opens a new avenue for identifying other potential impact craters in Greenland and Antarctica.

High Frictional Coated Multi-Layer Ballistic Fabrics for High Velocity and Hypervelocity Impact Protection

Increasing the inter-fiber friction of ballistic fabrics is crucial for improving their impact shielding performance. Shear thickening fluid (STF) impregnation is commonly used to improve inter-fiber friction, but it has several fundamental shortcomings. Polymer coating, with its superior properties, can be an ideal material for increasing the friction coefficient of fabrics. Our study aimed to evaluate the effectiveness of the coating process in enhancing the energy absorption mechanism within and among the fabric layers. Additionally, we investigated the capability of a multi-layer coated fabric system for hypervelocity impact shielding and spall liners. Our findings demonstrated the effectiveness of the coating process in improving the ballistic limit of the fabric system. Coated fabrics showed a 19.6% and 23.4% increase in specific energy absorption compared to pristine fabrics. We conducted hypervelocity impact experiments with impact velocities between 1.9 km/s to 2.1 km/s using a triple bumper system. The front bumper generated a debris cloud, the back bumper comprised the coated fabrics, and the third bumper acted as a witness plate. We compared the area of impact on the witness plate and the penetration area to estimate the efficiency of the coated fabrics. Our results showed that the coated fabrics had a higher area of impact with lower intensity of damage and a decrease in the penetration area compared to pristine fabrics with similar areal densities, indicating excellent impact shielding performance.

Design, fabrication, and hypervelocity impact testing of screen-printed flexible micrometeoroid and orbital debris impact sensors for long-duration spacecraft health monitoring

Micrometeoroid and orbital debris (MMOD) are a key risk for spacecraft damage that could compromise missions. Detecting and evaluating MMOD damage is therefore a crucial component in the health monitoring of spacecraft, especially for long duration, deep space expeditions. In this work, we developed a passive sensor system fabricated from conductive metal ink screen-printed on flexible Kapton, using roll-to-roll manufacturing suitable for low-cost fabrication of large areas of sensors, as a MMOD sensor for a spacecraft shield. The sensor is integrated into a low density, two-wall Whipple shield comprising of thin aluminum sheets sandwiching a polyimide foam. The shield with the sensors were tested with hypervelocity impacts at approximately 7 km/s using different particle diameters. Data collected from the sensors were successfully used to determine the impact size, impact location, and predict the impact energy of the damage.