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.

Experimental investigation of spectral evolution in flash radiation by hypervelocity impact on aluminum plates

In this study,a series of hypervelocity impact tests were carried out based on a two-stage light gas gun,and the sequence spectrum and radiation evolution data of the impact products under different impact conditions were obtained.The diameter of the projectile is 3-5 mm,the impact velocity is 3.13-6.58 km/s,and the chamber pressure is 0.56-990 Pa.The spectrum of ejected debris cloud in the 250-310 nm band were obtained using a transient spectral measurement system and a multi-channel radiometer measurement system.The test results reveal that the flash radiation intensity increases as a power function with the kinetic energy of the impact.Furthermore,the peak value of the line spectrum decreases as the chamber vacuum degree increases,while the radiation width gradually expands.The line spectrum in the spectral characterization curve corresponds to the ejected debris clouds splitting phase,which does not produce significant line spectrum during material fragmentation and is dominated by the continuum spectrum produced by blackbody radiation.There will appear one or three characteristic peaks in the flash radiation time curve,the first and second peaks correspond to the penetration phase and the third peak corresponds to the expansion phase of the ejected debris clouds on the time scale,the first and second peaks are more sensitive to the chamber vacuum degree,and when the pressure is higher than 99 Pa,the first and second characteristic peaks will disappear.The radiant heat attenuation of the flash under different impact conditions is significantly different,the attenuation exponent has a power function relationship with the impact velocity and the chamber vacuum degree,while the attenuation exponent has a linear relationship with the diameter of the projectile,the specific expression of the attenuation exponent is obtained by fitting.The findings from this research can serve as a valuable reference for remote diagnostic technologies based on flash radiation characteristics.

Experimental and numerical study of hypervelocity impact damage on composite overwrapped pressure vessels

Ground-based tests are important for studying hypervelocity impact(HVI)damage to spacecraft pressure vessels in the orbital debris environment.We analyzed the damage to composite overwrapped pressure vessels(COPVs)in the HVI tests and classified the damage into non-catastrophic damage and catastrophic damage.We proposed a numerical simulation method to further study non-catastrophic damage and revealed the characteristics and mechanisms of non-catastrophic damage affected by impact conditions and internal pressures.The fragments of the catastrophically damaged COPVs were collected after the tests.The crack distribution and propagation process of the catastrophic ruptures of the COPVs were analyzed.Our findings contribute to understanding the damage characteristics and mechanisms of COPVs by HVIs.

Modeling on the shock wave in spheres hypervelocity impact on flat plates

In hypervelocity impacts of projectiles into thin flat targets,shock initiation and interaction dominate the responses of projectiles and targets,and especially dominate the features of the debris cloud.To estimate the geometric features of the wave front during the first complete propagation in the sphericalprojectile,the Geometric Propagation Model(GPM)is built in this paper to describe the geometry of the shock wave front,which proposes an ellipse contour as a function of time and equivalent speed.The GPM identifies the geometric features of the wave front as a function of time and impact velocity successfully.Combined with the GPM and SPH simulation,the shock pressure distribution and attenuation in the spherical-projectile have been obtained.Meanwhile,the attenuation of shock pressure and speed are presented as a function of impact velocity,respectively,and a method for obtaining the equivalent speed of the shock wave is proposed by the GPM.The GPM may be applicable to hypervelocity events involving any monolithic materials as long as the equivalent speed could be supplied from numerical simulation.The GPM proposed in this paper and the corresponding shock wave analysis provide a new insight into the processes of the quantitative analysis of the initiation of the debris cloud.

Characteristics structure analysis on debris cloud in the hypervelocity impact of disk projectile on thin plate

In this paper,the gauge points setting is introduced in the SPH simulation to analyze the debris cloud structure generated by the hypervelocity impact of disk projectile on thin plate.Compared with the experiments,more detailed information of the debris cloud structure can be classified from the numerical simulation.However,due to the solitary dispersion and overlap display of the particles in the SPH simulation,accurate comparison between numerical and experimental results is difficult to be performed.To track the velocity and spatial distribution of the particles in the debris cloud induced from disk and plate,gauge points are locally set in the single-layer profile in the SPH model.By analyzing the gauge points’spatial coordinate and velocity,the location and velocity of characteristic points in the debris cloud are determined.The boundary of debris cloud is achieved,as well as the fragments distribution outside the main structure of debris cloud.

Preliminary Study on Diagnostic Techniques for Transient Plasma Generated by Hypervelocity Impact

A fast-sweep Langmuir probe （FSLP） diagnostic system was designed and applied to obtain the electron temperature fluctuations of a transient plasma. The diagnostic system consists of a single Langmuir probe driven by a high frequency sinusoidal voltage. The current-voltage I- V characteristics can be recorded by sweeping the voltage and measuring the current with an appropriate circuit. This new instrument is based on a dual channel circuit that compensates for stray capacitance. The current and voltage spectra were acquired from the probe synchronously by a digital oscilloscope. The aim of this work was to apply the FSLP diagnostic system to a time- dependent plasma generated by a hypervelocity impact between the LY12 Aluminum projectile and LY12 Aluminum target.

Effect of compressibility on the hypervelocity penetration

We further consider the effect of rod strength by employing the compressible penetration model to study the effect of compressibility on hypervelocity penetration.Meanwhile, we define different instances of penetration efficiency in various modified models and compare these penetration efficiencies to identify the effects of different factors in the compressible model. To systematically discuss the effect of compressibility in different metallic rod-target combinations, we construct three cases, i.e., the penetrations by the more compressible rod into the less compressible target, rod into the analogously compressible target, and the less compressible rod into the more compressible target. The effects of volumetric strain, internal energy, and strength on the penetration efficiency are analyzed simultaneously. It indicates that the compressibility of the rod and target increases the pressure at the rod/target interface. The more compressible rod/target has larger volumetric strain and higher internal energy. Both the larger volumetric strain and higher strength enhance the penetration or anti-penetration ability. On the other hand, the higher internal energy weakens the penetration or anti-penetration ability. The two trends conflict, but the volumetric strain dominates in the variation of the penetration efficiency, which would not approach the hydrodynamic limit if the rod and target are not analogously compressible. However, if the compressibility of the rod and target is analogous, it has little effect on the penetration efficiency.

Grain refinement process of pure iron target under hypervelocity impact

The structure of ultrafine grain is formed at the crater bottom of pure iron target under hypervelocity impact. The microstructures of different layers at the crater bottom were characterized by optical microscopy （OM）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The cross-section observation was performed to reveal the grain refinement process driven by plastic deformation. Firstly, low energy dislocation structures （LEDS） such as dense dislocation walls （DDWs） and dislocation tangles （DTs） refine the original grains and form intersecting lamellar structures. With increasing strain, DDWs and DTs transform into subboundaries with small misorientations to separate lamellar structure to cells. Subboundaries are converted to high misorientation grain boundaries, so ultrafine grains are formed. The formation of ultrafine grains was discussed in the dynamic recrystallization process due to the large strain and strain rate induced by spherical shock wave.

A simplified approximate model of compressible hypervelocity penetration

A simplified approximate model considering rod/target material's compressibility is proposed for hypervelocity penetration.We study the effect of shockwaves on hypervelocity penetration whenever the compressibility of the rod is much larger,analogously,and much less than that of the target,respectively.The results show that the effect of shockwaves is insignificant up to 12 km/s,so the shockwave is neglected in the present approximate model.The Murnaghan equation of state is adopted to simulate the material behaviors in penetration and its validity is proved.The approximate model is finally reduced to an equation depending only on the penetration velocity and a simple approximate solution is achieved.The solution of the approximate model is in agreement with the result of the complete compressible model.In addition,the effect of shockwaves on hypervelocity penetration is shown to weaken material's compressibility and reduce the interface pressure of the rod/target,and thus the striking/protective performance of the rod/target is weakened,respectively.We also conduct an error analysis of the interface pressure and penetration efficiency.With a velocity change of 1.6 times the initial sound speed for the rod or target,the error of the approximate model is very small.For metallic rod-target combinations,the approximate model is applicable even at an impact velocity of 12 km/s.

Analysis of the stress wave and rarefaction wave produced by hypervelocity impact of sphere onto thin plate

Shock wave is emitted into the plate and sphere when a sphere hypervelocity impacts onto a thin plate.The fragmentation and phase change of the material caused by the propagation and unloading of shock wave could result in the formation of debris cloud eventually.Propagation models are deduced based on one-dimensional shock wave theory and the geometry of sphere,which uses elliptic equations(corresponding to ellipsoid equations in physical space)to describe the propagation of shock wave and the rarefaction wave.The“Effective thickness”is defined as the critical plate thickness that ensures the rarefaction wave overtake the shock wave at the back of the sphere.The“Effective thickness”is directly related to the form of the debris cloud.The relation of the“Effective thickness”and the“Optimum thickness”is also discussed.The impacts of Al spheres onto Al plates are simulated within SPH to verify the propagation models and associated theories.The results show that the wave fronts predicted by the propagation models are closer to the simulation result at higher impact velocity.The curvatures of the wave fronts decrease with the increase of impact velocities.The predicted“Effective thickness”is consistent with the simulation results.The analysis about the shock wave propagation and unloading in this paper can provide a new sight and inspiration for the quantitative study of hypervelocity impact and space debris protection.

Research and development on hypervelocity impact protection using Whipple shield:An overview

Whipple shield,a dual-wall system,as well as its improved structures,is widely applied to defend the hypervelocity impact of space debris(projectile).This paper reviews the studies about the mechanism and process of protection against hypervelocity impacts using Whipple shield.Ground-based experiment and numerical simulation for hypervelocity impact and protection are introduced briefly.Three steps of the Whipple shield protection are discussed in order,including the interaction between the projectile and bumper,the movement and diffusion of the debris cloud,and the interaction between the debris cloud and rear plate.Potential improvements of the protection performance focusing on these three steps are presented.Representative works in the last decade are mentioned specifically.Some prospects and suggestions for future studies are put forward.

Spectral measurements of hypervelocity flow in an expansion tunnel

Atmospheric reentry vehicles and planetary probes fly through the atmosphere at hypervelocity speed. At such speed, there is a significant proportion of heat load to the vehicle surface due to radiative heating. Accurate prediction needs a good knowledge of the radiation spectrum properties. In this paper, a high-speed camera and spectrograph coupled to an intensified charge-coupled device have bee n impleme nted to inv estigate the rad i at io n flow over a semi-cylinder model. The experiments were carried out in the JF16 expansi on timnel with secondary shock velocity of 7.9 km·s^-1. Results show that the emissio n spectrum comprises several atomic lines and molecular band systems. We give detailed data of the radiation spectrum, shock shape, shock detached distance and radiation intensity varying with space and wavelength. This valuable experimental dataset will be helpful to validate computational fluid dynamics codes and radiation models, which equates to increased prediction accuracy of radiation heating. Also, some suggestions for spectral measurement in hypervelocity flow field were list in the end.

Experimental Study and Numerical Simulation of Hypervelocity Projectile Impact on Double-Wall Structure

Tests of hypervelocity projectile impact on double-wall structure were performed with the front wall ranging from 0.5 mm to 2.0 mm thick and different impact velocities. Smooth particle hydrodynamics (SPH) code in LS-DYNA was employed for the simulation of hypervelocity impact on the double-wall structure. By using elementary shock wave theory, the experimental results above are analyzed. The analysis can provide an explanation for the penetration mechanism of hypervelocity projectile impact on double-wall structure about the effect of front wall thickness and impact velocity..

Sweep Langmuir Probe and Triple Probe Diagnostics for Transient Plasma Produced by Hypervelocity Impact

Two techniques are applied to diagnose characteristic parameters of plasma created by hypervelocity impact, such as electron temperature and electron density. The first technique is a sweep Langmuir probe （SLP）, which is a new apparatus based on a dual channel circuit that can compensate for stray capacitance and obtain a good synchronicity, so that electrostatic turbulence with a good temporal resolution can be acquired. The second technique is a triple Langmuir probe （TLP）, which is an electrostatic triple Langmuir probe diagnostic system, in which no voltage and frequency sweep is required. This technique allows to measure electron temperature, electron density as a function of time. Moreover, the triple Langmuir probe diagnostic system allows the direct display of electron temperature and semidirect display of electron density by an appropriate display system, the system permits us to eliminate almost all data processing procedures. SLP and TLP were applied to obtain fluctuations of the characteristic parameters of plasma generated by hypervelocity impact. As an example of their application to time-dependent plasma measure- ment, the electron temperature and electron density of plasmas were acquired in hypervelocity impact experiments. Characteristic parameters of plasma generated by hypervelocity impact were compared by the two kinds of diagnostic techniques mentioned above.

Debris cloud structure and hazardous fragments distribution under hypervelocity yaw impact

This study investigates how the debris cloud structure and hazardous fragment distribution vary with attack angle by simulating a circular cylinder projectile hypervelocity impinging on a thin plate using the finite element-smoothed particle hydrodynamics(FE-SPH)adaptive method.Based on the comparison and analysis of the experimental and simulation results,the FE-SPH adaptive method was applied to address the hypervelocity yaw impact problem,and the variation law of the debris cloud structure with the attack angle was obtained.The screening criterion of the hazardous fragment at yaw impact is given by analyzing the debris formation obtained by the FE-SPH adaptive method,and the distribution characteristics of hazardous fragments and their relationship with the attack angle are given.Moreover,the velocity space was used to evaluate the distribution range and damage capability of asymmetric hazardous fragments.The maximum velocity angle was extended from fully symmetrical working conditions to asymmetrical cases to describe the asymmetrical debris cloud distribution range.In this range,the energy density was calculated to quantitatively analyze how much damage hazardous fragments inflict on the rear plate.The results showed that the number of hazardous fragments generated by the case near the 35°attack angle was the largest,the distribution range was the smallest,and the energy density was the largest.These results suggest that in this case,debris cloud generated by the impact had the strongest damage to the rear plate.

Experimental Study of Hypervelocity Impact on Multi-Shock Structure

Hypervelocity impact tests on multi-shock shields are carried out in order to develop space structures (against) space debris impacts. Sheets of LY12 aluminum were used as bumpers. The total thickness of shield structure, which consists of several sheets with various thickness, is 3.0 mm or 2.0 mm. Results of the tests show that the type 0.5 mm+0.5 mm+0.5 mm+0.5 mm is a better choice of spacecraft shield structure.

EXPERIMENTAL INVESTIGATIONS OF HYPERVELOCITY IMPACT ONTO ALUMINIUM DUAL-PLATE STRUCTURE

Dual-plate structure is very effective in the protection of space vehicle from hypervelocity im- pact.The experiments of A1 projectile impacting A1 dual targets at the velocity ranging over 2.5—7.0 km/s were systematically conducted.The damage effects were examined,including the perforation of the shield, the development of debris cloud and the general damage characteristics of the subplate.Many valuable experi- mental data and phenomena have been obtained

Experimental and analytical assessment of the hypervelocity impact damage of GLAss fiber REinforced aluminum

This article addresses the response of GLAss fiber REinforced aluminum to hypervelocity impacts of micrometeoroid analogs at impact velocities of 7 km/s and beyond.In relation,the damage modes of different GLAss fiber REinforced aluminum configurations have been exemplified.The GLAss fiber REinforced aluminum configurations comprised six to twelve variably thick aluminum layers and up to four plies of glass fiber reinforced epoxy per composite laminate.Hypervelocity impact experiments have been conducted with the help of a two-stage light-gas gun,wherein aluminum-and stainless steel projectiles were launched at velocities up to 7.15 km/s.Visual inspection of the damage area suggested the dissipation of impact energy in elastic-plastic deformation,petalling,delamination,debonding,tensile failure of fibers,and pyrolysis of epoxy.A prevailing damage mode was not apparent albeit.The quasi-isotropic ply orientation of S2-glass/FM94-epoxy laminates promoted the interference of shockand rarefaction waves and suppressed the damage area of GLAss fiber REinforced aluminum.To discriminate between the impact performance of different GLAss fiber REinforced aluminum configurations,the energy dissipated in different damage modes of GLAss fiber REinforced aluminum has been assessed quantitatively.In terms of normalized energy,the cross-ply GLAss fiber REinforced aluminum dissipated higher energy in petal formation than in other primary damage modes.The normalized petalling energy was found to decline with the increase of impact energy.The outcomes of this study will help to optimize the GLAss fiber REinforced aluminum laminate,which will be employed as a bumper shield to prevent the fatal damage and the unzipping of a spacecraft pressure bulkhead.

Evidence in Oman for Mantle Excavating Hypervelocity Impact at the Cenomanian-Turonian Boundary?

Speculation that elliptical to circular segments of surface exposed lithospheric mantle belts might mark rims of large terrestrial impact basins suggests that the ophiolite rimmed Sulu Sea, Loyalty and Yucatan basins may have resulted from middle Miocene, late Eocene and K-Pg boundary mantle excavating hypervelocity impacts on Earth(Olds, 2019). The Semail ophiolite suggests such a circular rim segment with a ~250 km radius of curvature implying an originally ~500 km diameter impact basin before subsequent deformation/destruction at plate boundaries. Presently the Arabian plate is being actively consumed at the Makran subduction zone(Penney et al., 2017) which evidently will result in subduction of the Gulf of Oman and suturing of the adjacent Semail ophiolite in the near geological future. For large impact basins on the rocky planets, O’Keefe and Ahrens(1993) estimate maximum excavation depth to be roughly 5% of final crater diameter. In this case maximum ejecta source depths of ~25 km are implied, a number roughly comparable with observed thicknesses of crust plus mantle sections for the Semail ophiolite(Aldega et al., 2017) and depths of burial due to over-thrusting(obduction) implied by the exhumed metamorphic sole(Cowan et al., 2014). Hacker et al.(1996) and Roberts et al.(2016) place peak metamorphism timing of the Semail metamorphic sole within uncertainty of the C-T Boundary at 94 Ma. Study of possible correlation of peak obduction timing with end-Cenomanian global extinction plus anoxic events(Wan et al., 2003) and C-T boundary impact ejecta plus tsunami deposits(Monteiro et al., 2001) may be warranted.

Satellite breakup behaviors and model under the hypervelocity impact and explosion:A review

The primary causes of satellite breakups are hypervelocity impact and explosion,the research on satellite breakup can be used not only to evaluate the influence of breakup event on the space environment,but also to trace whether the satellite has been deliberately attacked.It is of great significance in both civil and military aspects.The study of satellite breakup behaviors and model is reviewed to summarize the research progress and insufficiency in recent decades,including the satellite breakup experiment,measurement and characterization of fragments,distribution characteristics of breakup fragments,satellite breakup model,etc.The classical studies are introduced in detail,and the limitations of the current research are pointed out.According to the current research results,the contemporary challenges and future directions for satellite breakup study are presented.The research on satellite breakup is developing in two directions:the miniaturization of satellite size and the complexity of satellite component.The study on satellite breakup needs to be explored and deepened on improving the experimental launch speed,expanding the model application range and breakup revealing the results under combined effect of impact and explosion.