Iron Projectiles Research Articles

Microscopic impactor debris at Kamil Crater (Egypt): The origin of the Fe-Ni oxide spherules

Kamil crater (Egypt) is a natural laboratory for the study of processes and products associated with the impacts of small iron projectiles on the Earth’s crust. In particular, because of the distinctive composition of the impactor (an ungrouped Ni-rich ataxite) and the target (Cretaceous sandstones and minor wackes) it offers a unique opportunity to study impactor–target physical–chemical interactions. Continuing the study of impact melt ejecta, we investigated the mineralogy and geochemistry of 25 Fe-Ni spherules - representative of a suite of 135 - recovered from the soil around the crater. Samples were collected during our 2010 geophysical expedition and investigated by combining scanning electron microscope imaging, electron probe microanalyzer and Raman spectroscopy analyses. Spherules range in size from 100 to 500 µm and show a variety of dendritic textures and mineral compositions dominated by Fe-Ni oxides of the wüstite – bunsenite and magnetite – trevorite series or Fe-Ni metal. All these features indicate quenching of high temperature (1600–1500 °C) oxide or metal liquid droplets under varying oxidizing conditions. A geochemical affinity with the iron impactor recorded by the Fe, Co, Ni ratios in the constituent phases (average Ni/Co element ratio of 25.1 ± 7.6; average Ni/(Ni + Fe) molar ratio of 0.21 ± 0.13), combined with target contamination (i.e., the ubiquitous occurrence of Si and Al from trace to minor amounts), document their origin as impact melt spherules formed through the physical and chemical interaction between metal projectile and silicate target melts and air. We propose a petrogenetic model that envisions formation as liquid droplet residues of immiscible projectile in a mixed silicate melt and their subsequent separation as individual spherules by stripping during hypervelocity ejection. We also argue that this model applies to all impact events produced by small iron projectiles and that such individual Fe-Ni oxide and metal spherules should be common impact products, despite little documentation in the literature. Our detailed mineralogical and geochemical characterization will facilitate their distinction from other, similar spherules of different origin (cosmic spherules, ablation spherules) often encountered in the geologic record.

Comparing HZETRN, SHIELD, FLUKA and GEANT transport codes

For the first time, the American (NASA) and Russian (ROSCOSMOS) space radiation transport codes, HZETRN and SHIELD respectively, are directly compared to each other. Calculations are presented for Galactic Cosmic Ray (GCR) minimum Hydrogen, Oxygen and Iron projectiles incident on a uniform Aluminum cylinder of varying thickness. Comparisons are made for the flux spectra of neutrons, light ions (Z≤ 2), heavy ions (Z> 2) and pions emitted from the back of the Aluminum cylinder. In order to provide more benchmark comparisons, some calculations with the GEANT and FLUKA transport codes are also shown.

Double differential neutron yields from thick targets used in space applications

In March 2016, secondary neutron production from thick-target shielding experiments were conducted at the National Aeronautics and Space Administration’s (NASA) Space Radiation Laboratory at Brookhaven National Laboratory. Ion beams of proton, helium, and iron projectiles were aimed at aluminum targets with areal densities of 20, 40, and 60 g/cm2 . The ion beams were extracted at energies of 400 and 800 AMeV and neutron yields were measured with liquid scintillators at 10°, 30°, 45°, 60°, 80°, and 135° off the beam axis. A second 60 g/cm2 aluminum target was placed 3.5 m downstream from the middle of front target to study backscattered neutrons. Double differential thick-target neutron yields for various combinations of projectile, projectile energy, target material, target thickness, and detector location were produced using the time-of-flight technique. These measurements will help NASA perform uncertainty analyses on their transport codes and contribute to shielding design studies for future space applications.

Estimation of hypervelocity impact parameters from measurements of optical flash

When meteoroids and orbital debris hit satellites or surfaces of other objects in space, an optical flash is generated. Measuring properties of this impact flash can reveal several important properties of the impact phenomenon. In this paper, we present results from hypervelocity impact tests that were carried out at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. Spherical iron projectiles were shot at targets comprising tungsten, copper, spacecraft solar cells, solar panel substrate and optical solar reflectors. The impactors had masses ranging from 35 pg to 0.15 fg and speeds ranging from 2.8 km/s to 67 km/s. The impact flash generated was measured using a photomultiplier tube and scaling laws were generated to study the dependence of observed luminosity on the mass and velocity of the impactor. Efforts to determine the mass and velocity exponents independently were successful for all targets except solar cells. The mass exponent was found to lie in the range between 0.38 and 0.64 for various targets, which is significantly lower than the value of 1 often assumed in literature. Observations made from different angles were compared and the difference in the optical yields was found to be insignificant. The rise time of the integrated signal was found to have a negative correlation with the velocity of the impactor only for particles with speed greater than 8 km/s, which is contrary to what was observed in previous research. The correlation is however weak, with an R2 value of 0.026 and could not be reproduced using a matched filter approach. A support vector regression based scheme was developed for estimating the velocity of the impactor, using temporal characteristics of the optical flash. The algorithm was able to estimate the velocity with a mean estimation error of 6.56 km/s.

Naval Crossfire: A Comparative Analysis of Iron Projectiles from Mid-18th to Early 19th Centuries European Warships

The ordnance of early Modern main maritime powers (i.e. Great Britain, France, and Spain) played an important role in conflicts for supremacy of the seas. Therefore, it was subjected to various innovation processes, in order to improve their efficiency. This study presents the characterization results of an array of iron projectiles recovered from the following sites: 1) the sloop-of-war HMS Swift (1763-1770), 2) the Spanish ship Triunfante (1756-1795), 3) the French ship Bucentaure (1804-1805), and 4) the site Deltebre I (1813). Based on data obtained using Optical Microscopy (OM), Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray Spectrometry (EDXRS), a comparative analysis was performed, in order to clarify the technological differences and similarities that were present in the projectiles used by the mentioned ships.

Theory and experiments characterizing hypervelocity impact plasmas on biased spacecraft materials

Space weather including solar activity and background plasma sets up spacecraft conditions that can magnify the threat from hypervelocity impacts. Hypervelocity impactors include both meteoroids, traveling between 11 and 72 km/s, and orbital debris, with typical impact speeds of 10 km/s. When an impactor encounters a spacecraft, its kinetic energy is converted over a very short timescale into energy of vaporization and ionization, resulting in a small, dense plasma. This plasma can produce radio frequency (RF) emission, causing electrical anomalies within the spacecraft. In order to study this phenomenon, we conducted ground-based experiments to study hypervelocity impact plasmas using a Van de Graaff dust accelerator. Iron projectiles ranging from 10−16 g to 10−11 g were fired at speeds of up to 70 km/s into a variety of target materials under a range of surface charging conditions representative of space weather effects. Impact plasmas associated with bare metal targets as well as spacecraft materials were studied. Plasma expansion models were developed to determine the composition and temperature of the impact plasma, shedding light on the plasma dynamics that can lead to spacecraft electrical anomalies. The dependence of these plasma properties on target material, impact speed, and surface charge was analyzed. Our work includes three major results. First, the initial temperature of the impact plasma is at least an order of magnitude lower than previously reported, providing conditions more favorable for sustained RF emission. Second, the composition of impact plasmas from glass targets, unlike that of impact plasmas from tungsten, has low dependence on impact speed, indicating a charge production mechanism that is significant down to orbital debris speeds. Finally, negative ion formation has a strong dependence on target material. These new results can inform the design and operation of spacecraft in order to mitigate future impact-related space weather anomalies and failures.

Influence on Launching Velocity by the Figure and Material Characteristic of Projectiles

A solid metal plate is often used as the projectile in reconnection electromagnetic launcher. Yet, the performance is not optimum. In this paper, analysis is made about the laws of influence on magnetic field distribution of driving coils by using projectiles with different figures and materials. Further analysis is made about the influence on launching velocity of the aforementioned factors. A single-stage reconnection electromagnetic launcher is made. Experiments are carried out separately on latticed projectiles, hollow projectiles, aluminum projectiles, iron projectiles, and copper projectiles. Some significant conclusions are drawn. Under the same condition, hollow projectiles achieve the highest velocity, while latticed projectiles have a weaker shielding effect upon magnetic field. The magnetic permeability and electric conductivity of material have a great influence upon launching velocity. Based on magnetic domain theory, qualitative analysis is made about the causation of magnetic hysteresis loss, classical eddy current loss, and abnormal loss. As the loss under high-frequency alternating magnetic field increases rapidly, ferromagnetic materials are not suitable here. The electric conductivity of projectiles, as well as the thickness and the density, makes sense to launching velocity. As the frequency grows higher in pulsed magnetic field, the influence from thickness and electric conductivity of projectiles becomes weaker. Therefore, hollow projectiles made up of aluminum material which has a higher electric conductivity and a lower density will be the best choice.

Residual temperature measurements of light flash under hypervelocity impact

Experimental and theoretical results for light flash temperatures are presented for impacts on soda-lime glass by iron projectiles. The experiments were performed with a 2 MV Van de Graaff, where iron dust particles (0.14–0.63 μm in diameter) impacted soda-lime glass at a velocity range of 5–20 km s −1. Theoretical calculations were based on the assumption of the Mie–Gruneisen equation of state (EoS) with different values for the Gruneisen coefficient and hydrodynamic behaviour (no strength effects were considered). Within the scatter of experimental data, results suggest a constant value for the average light flash temperature of approximately 2600 K independent of iron dust impact velocity. Although theoretical calculations are limited by the use of the Mie–Gruneisen EoS up to the point of incipient vaporisation of the target material, relatively good agreement with experiments is observed. This agreement suggests that the observed constant temperature may be due to material phase change from incipient to complete vaporisation over the range of velocities considered.

Oblique hypervelocity impacts: Implication for the analysis of material retrieved after exposure to space

In the past few years, a wide variety of surfaces have been brought back to Earth after being exposed to the space particulate environment. The impact features found on this material can give clues to the characteristics of the impacting man-made debris and meteoroids. Many investigations have been carried out to deduce projectile parameters (size, shape, and velocity vector) from the morphology of impact features and their origin from the analysis of projectile remnants inside craters formed. However, there are still ambiguities in the interpretation of these results. Recently, the post-flight analysis of solar arrays retrieved from the hubble space telescope (HST) showed the lack of data concerning the interpretation of many impact features. In the present study, we have examined especially the distinctive features of craters caused by particles at oblique incidence. These craters represent more than one third of impacts with a size between 5 μm and 1 mm observed on the European Retrievable Carrier (EuReCa) and HST solar arrays. Interpretation difficulties of this kind of impacts on solar cells led to hypervelocity impacts test onto pure silica targets performed with iron projectiles at different incidence angles and different velocity ranges. They were made in order to find a possible link between the incidence angle of a projectile, the impact velocity, and the parameters, which could be deduced from the analysis of the crater and projectile remnants. A detailed survey of impacts features formed was done for each couple angle velocity. High-resolution observations show an evolution of the crater morphology and circularity with the increasing angles of incidence and velocity, and some changes in the projectile remnants amount, appearance, and position are also noted.

Fragmentation studies of relativistic iron ions using plastic nuclear track detectors

We measured fluence and fragmentation of high-energy (1 or 5 A GeV) 56Fe ions accelerated at the Alternating Gradient Synchrotron or at the NASA Space Radiation Laboratory (Brookhaven National Laboratory, NY, USA) using solid-state CR-39 nuclear track detectors. Different targets (polyethylene, PMMA, C, Al, Pb) were used to produce a large spectrum of charged fragments. CR-39 plastics were exposed both in front and behind the shielding block (thickness ranging from 5 to 30 g/cm 2) at a normal incidence and low fluence. The radiation dose deposited by surviving Fe ions and charged fragments was measured behind the shield using an ionization chamber. The distribution of the measured track size was exploited to distinguish the primary 56Fe ions tracks from the lighter fragments. Measurements of projectile’s fluence in front of the shield were used to determine the dose per incident particle behind the block. Simultaneous measurements of primary 56Fe ion tracks in front and behind the shield were used to evaluate the fraction of surviving iron projectiles and the total charge-changing fragmentation cross-section. These physical measurements will be used to characterize the beam used in parallel biological experiments.

Extraction and microanalysis of cosmic dust captured during sample return missions: laboratory simulations

Particles of cometary and asteroidal origin collected at source using dedicated capture cell technologies will be returned to Earth within the next 8 years. Furthermore, coincidental capture of interplanetary dust particles will occur on the exposed surfaces of the Genesis spacecraft. Laboratory simulations using both light-gas-gun and Van de Graaff accelerators have impacted dust analogues at velocities ranging from 5 km s −1 to ca. 72 km s −1 into comparable silicon and aerogel targets. Analysis of the impacts on silicon has shown complete spallation of impact residues for silicate projectiles of 38–53 μm in diameter, however craters formed by 1 μm iron projectiles show that near-intact residues can be preserved. An olivine grain embedded in aerogel has been characterized in situ using Raman micro-spectroscopy. Monte Carlo simulations and laboratory experiments have shown that analytical scanning electron microscopy can also be used to characterize embedded grains. Development of a novel particle extraction methodology using a 266 nm UV laser micro-dissection system has resulted in the recovery of an olivine grain. The extracted particle was then “cleaned up” using focused ion beam (FIB) milling to remove excess aerogel that was fused on the grain surface.

Numerical simulation of grazing impacts from micron sized particles on the XMM-newton mirrors

This paper presents the results of numerical simulations of micron-sized particles hypervelocity impacts on the XMM telescope mirror surfaces at grazing angles. The scope of the study was to demonstrate the possibility that very high energy peaks detected by the Charge Coupled Devices (CCDs) placed at the end of the mirror surfaces were caused by micrometeoroid impacts. First simulated were tests performed with the dust accelerator of Max Planck Institut fur Kernphysik (Heidelberg, Germany) at impact velocities around 5 km/s and impact angles between 1 and 5 degrees from the mirror surface plane. The results showed the projectile leaving the target plastically deformed but not fragmented with an exit angle much smaller than the entry one, thus confirming the experimental evidence that some material travelling after the impact close to the target surface reached the location of CCDs. Additional simulations with iron projectiles were performed at increasing impact angles up to 45° from the mirror surface plane. They showed that the amount of material leaving after impact nearly parallel to the mirror surface progressively diminishes due to the onset of projectile fragmentation and scattering, but some material is still found even for high impact angles. This effect is probably due to the high density of the gold coating layer of the XMM mirror, as it was not observed in analogous simulations with a softer aluminium coating. In order to better approximate the conditions of a real natural meteoroid impact, simulations at I -degree incidence and velocities up to 30 km/s were performed with aluminium projectiles, whose density is closer to the expected values for meteoroids in space. The results showed that the velocity increase induces more projectile erosion phenomena in the contact zone with the target, further reducing the exit angle. Above 20 km/s the projectile exit path is practically parallel to the mirror surface, thus supporting the hypothesis that a micrometeoroid impacting at grazing angle on the mirror surface can find its way up to the XMM CCDs focal plane.

Time of flight mass spectra of ions in plasmas produced by hypervelocity impacts of organic and mineralogical microparticles on a cosmic dust analyser

The ionic plasma produced by a hypervelocity particle impact can be analysed to determine compositional informa- tion for the original particle by using a time-of-flight mass spectrometer. Such methods have been adopted on interplanetary dust detectors to perform in-situ analyses of encountered grains, for example, the Cassini Cosmic Dust Analyser (CDA). In order to more fully understand the data returned by such instruments, it is necessary to study their response to impacts in the laboratory. Accordingly, data are shown here for the mass spectra of ionic plasmas, produced through the acceleration of microparticles via a 2 MV van de Graa accelerator and their impact on a dimensionally correct CDA model with a rhodium target. The microparticle dusts examined have three dierent chemical compositions: metal (iron), organic (polypyrrole and polystyrene latex) and mineral (aluminosilicate clay). These microparticles have mean diameters in the range 0.1 to 1.6 m and their velocities range from 1-50 km s 1 . They thus cover a wide range of compositions, sizes and speeds expected for dust particles encountered by spacecraft in the Solar System. The advent of new low-density, microparticles with highly controllable attributes (composition, size) has enabled a number of new investigations in this area. The key is the use of a conducting poly- mer, either as the particle itself or as a thin overlayer on organic (or inorganic) core particles. This conductive coating permits ecient electrostatic charging and acceleration. Here, we examine how the projectile's chemical composition influences the ionic plasma produced after the hypervelocity impact. This study thus extends our understanding of impact plasma formation and detection. The ionization yield normalized to particle mass was found to depend on impact speed to the power (3.4 0.1) for iron and (2.9 0.1) for polypyrrole coated polystyrene and aluminosilicate clay. The ioization signal rise time was found to fall for all projectile materials from a few microseconds at low impact speeds (3 km s 1 ) to a few tenths of a microsecond at higher speeds (approximately 16 km s 1 for aluminosilicate particles and approximately 28 km s 1 for iron and polystyrene particles). At speeds greater than these the rise time was a constant few tenths of a microsecond independent of impact speed. The mass resolution of the time of flight spectrometer was found to be non-linear at high masses above 100 amu. It wasm=m= 5f orm= 1 amu and 40 for m= 200 amu. However, although at high masses most mass peaks had the resolution quoted, there were also occasional much narrower mass peaks observed, suggesting that at 250 to 280 amum=m= 80 to 100. The lower resolutions may be due to closely spaced mass peak signals eectively merging into one observed peak due to the (greater but still finite) resolution found for the isolated mass peaks. Complex mass spectra have been reproducibly obtained from a number of dierent projectiles that display many charged molecular fragments with masses up to 250 amu and with periodicities of 12-14 amu. These new studies reveal an extremely strong dependence of the time-of-flight mass spectra on the impact speed, particularly at low velocities (1-20 km s 1 ). In some impact velocity regimes it is possible to distinguish time-of-flight spectra originating from organic microparticles from those obtained from iron microparticles. However, such discrimination was not possible at high impact speeds, nor was it possible to distinguish between the time-of-flight spectra obtained for aluminosilicate particles from those obtained for iron projectiles.

A new energy source for organic synthesis in Europa's surface ice

Colored regions on Jupiter's satellite Europa and other icy bodies in the outer solar system may be contaminated by organic macromolecular solid material that is produced when surface ices are exposed to electrical energy. Hypervelocity meteorite impacts and fracture may release tidal and tectonic stresses in icy crusts in the form of electrical discharges, which provide the energy for in situ synthesis of the organic solids. We report for the first time here on measurements of electrical discharge, light emission, and magnetic phenomena in hypervelocity impacts into ice with small iron projectiles having velocities ∼5 km s−1. In these experiments, part of the impacting projectile's kinetic energy is converted into electrical potential, while the mechanical disruption of the impact also causes the release of stress energy as light, heat, and electrical and magnetic fields as secondary emissions. These new energy sources described here suggest that the dark material in the area of impact craters may be solid phase, complex organic material called tholin, generated from the energy of the impacts. The morphology of Europa's impact craters is suggestive of fluidized colored material welling up from the fracture zone, probably during crater formation, but possibly later. Large pools of liquid water might persist under the meteorite crater for thousands of years [Thomson and Sagan, 1992], with the potential for prebiotic chemistry to take place at an accelerated rate due to energy pumped in from the secondary emissions.

Hydrocode and microstructural analysis of explosively formed penetrators

A comparison of residual microstructural features in tantalum, iron, and copper explosively-formed projectiles (EFP's) utilizing optical and transmission electron microscopy (TEM) was undertaken and these observations correlated with corresponding microhardness maps measured on the recovered EFP half sections. These microstructural comparisons and residual microhardness maps were then used to validate AUTODYN-2D hydrocode simulations of residual yield stress profiles and the geometrical parameters measured from the recovered EFP's. Both Johnson-Cook and Zerilli-Armstrong constitutive relations were applied and compared in these simulations which also examined the initiation parameters on EFP evolution. Calculated plastic strain and temperature contour plots were also correlated with observed microstructures and the microhardness maps.

Comparison of residual microstructures associated with impact craters in fcc stainless steel and bcc iron targets: the microtwin versus microband issue

Deformation microtwins characteristic of Neumann bands dominate the residual microstructures beyond a dynamic recrystallization and highly deformed regime below the crater wall of impact craters in polycrystalline bcc iron targets impacted by 3.2 mm diameter iron projectiles at velocities ranging from 0.5 to 3.8 km s −1. Corresponding impact craters in polycrystalline fcc 304L stainless steel targets impacted by 3.2 mm diameter stainless steel projectiles at velocities ranging from 0.5 to 3.9 km s −1 were observed to have a more limited dynamic recrystallization zone at the crater wall followed by a highly deformed transition into a region of mostly microtwins, but with some intermixing of grains containing microbands.

Fragmentation cross section measurements of iron projectiles using CR-39 plastic nuclear track detectors

For long term space missions in which larger radiation doses are accumulated it is necessary to improve the precision of models predicting the space radiation environment. Different models are available to determine the flux of cosmic ray heavy ions behind shielding material. The accuracy of these predictions depends on the knowledge of the fragmentation cross sections, especially at energies of several hundred MeV/nucleon, where the particle flux is at a maximum and especially for those particles with high LET, i.e. iron nuclei. We have measured fragmentation cross sections of 56Fe projectiles at beam energies of 700 and 1700 A MeV using experimental set-ups with plastic nuclear track detectors. In this paper we describe the experimental technique to study the fragmentation reactions of 56Fe projectiles using CR-39 plastic nuclear track detectors. Results for different targets are presented.

Use of combined light flash and plasma measurements to study hypervelocity impact processes

We present new measurements concerning generation of light flash during hypervelocity impacts. We use iron particles (10 −13 to 10 −17 kg) with velocities over the range 1 to 42 km/s impacting semi-infinite targets (aluminium and molybdenum). The main results of previous work in the field are found to be reproduced with some slight deviations. For iron projectiles with given mass and velocity the energy of the flash (normalized to mass) is proportional to velocity to the power of 3.5 for aluminium targets and 3.9 for molybdenum targets. The duration of the flash is of order 1 microsecond. Simultaneous measurements of the generation of impact plasma do not change this. The onset of plasma generation of the bulk target material does not affect the total light flash energy. We discuss the duration of the flash compared to a simple calculation of temperature in the target and plasma vs time.

Metal-oxide-silicon capacitor detectors for measuring micrometeoroid and space-debris flux

Capacitor-type micrometeoroid flux detectors have been fabricated and tested. The detectors were of the metaloxide-silicon type and were formed using standard silicon technology developed for fabricating microelectronic devices and circuits. The detectors were tested using an electrostatic accelerator and carbonyl iron projectiles ranging in size from 0.3 to 5.0 /ion in diameter (1 X 10~13 to 5 X 10~10 g) with velocities from 1 to 20 km/s. The detector operation was found to be reliable if the bias voltage was held above a threshold value that is necessary for a significant capacitor discharge. Variations of the bias voltage above the bias threshold did not appear to affect the detector sensitivity. An empirical relationship has been developed relating the sensitivity of the detectors to the detector thickness (dielectric plus top electrode) and the projectile diameter, velocity, and angle of impact. The mechanism responsible for the capacitor discharge appears to be the creation of charge carriers, followed by cascade ionization in the dielectric, caused by an impacting projectile. Once triggered, the discharge is then powered by the charge stored in the capacitor, which forms a plasma (spark) that causes a portion of the top metal electrode to vaporize, creating an open circuit at the impact site (i.e., the discharge self-extinguishes), which then allows the capacitor to recharge. The detector area lost as a result of impact damage is dependent on the discharge energy and is negligible for most applications.

Hypervelocity impact simulation experiments on LDEF°-foils

A variety of space environmental effects can be studied on many experiments having been exposed on the LDEF-satellite. Among others the thermal blankets of the Ultra-Heavy Cosmic Ray Nuclei Experiment (“UHCRE”, Exp. A0178) displayed many micrometeoroid / space debris impact features. In an effort to understand their nature and characteristics, an experimental impact simulation program has been carried out. UHCRE-spare foils have been impacted by glass, aluminium, and iron projectiles with masses ranging from about 30 nanograms up to several milligrams. Impact velocities range between about 3 km/s and 13 km/s. Characteristic impact craters and perforation holes have been produced. Their sizes and morphologies have been related with respective projectile impact parameters. “Halo zones” around perforation holes, as they had been observed in the exposed LDEF-foils, have also been obtained experimentally. They were found to be delamination effects within the foil layers caused by the propagation of impact shock waves.