Hypervelocity Particle Research Articles

Estimating the impact parameters of cosmic dust particles using a piezoelectric lead zirconate titanate detector

A cosmic dust detector for installation on a satellite is currently being developed using piezoelectric lead zirconate titanate (PZT), which can possess both functions of the collector and the transducer. The characteristics of the PZT detector have been studied by bombarding it with hypervelocity particles supplied by a Van de Graaff accelerator. The front surface of the detector used in this study was covered with a white paint to reduce any increase in the temperature due to the solar radiation. There was a linear relationship between the rise time of the signal produced by the detector and the particle's velocities, which were above 10 km/s on impact. This implies that individual particle velocities on impact can be inferred through the empirical formula derived from the data obtained from the PZT detector.

Hypervelocity capture of particles in aerogel: Dependence on aerogel properties

Capture of high-speed (hypervelocity) particles in aerogel at ambient temperatures of 175–763 K is reported. This extends previous work which has mostly focussed on conducting experiments at ambient laboratory temperatures, even though aerogels are intended for use in cosmic dust capture cells in space environments which may experience a range of temperatures (e.g., the NASA Stardust mission which collected dust at 1.81 AU and putative Mars atmospheric sampling missions). No significant change in track length (normalised to impactor size) was found over the range 175–600 K, although at 763 K a significant reduction (30%) was found. By contrast, entrance hole diameter remained constant only up to 400 K, above this sudden changes of up to 50% were observed. Experiments were also carried out at normal laboratory temperature using a wide range of aerogel densities and particle sizes. It was found that track length normalised to particle size varies inversely with aerogel density. This is a power law dependence and not linear as previously reported, with longer tracks at lower densities. Glass projectiles (up to 100 μm size) were found to undergo a variety of degrees of damage during capture. In addition to the well known acquisition of a coating (partial or complete) of molten aerogel the mechanical damage includes pitting and meridian fractures. Larger (500 μm diameter) stainless steel spheres also showed damage during capture. In this case melting and ablation occurs, suggesting surficial temperatures during impact in excess of 1400 °C. The response of the aerogel itself to passage of particles through it is reported. The presence of fan-like fractures around the tracks is attributed to cone cracking similar to that in glasses of normal density, with the difference that here it is a repetitive process as the particles pass through the aerogel.

Laser mass spectrometric detection of extraterrestrial aromatic molecules: Mini-review and examination of pulsed heating effects

Laser mass spectrometry is a powerful tool for the sensitive, selective, and spatially resolved analysis of organic compounds in extraterrestrial materials. Using microprobe two-step laser mass spectrometry (muL(2)MS), we have explored the organic composition of many different exogenous materials, including meteorites, interplanetary dust particles, and interstellar ice analogs, gaining significant insight into the nature of extraterrestrial materials. Recently, we applied muL(2)MS to analyze the effect of heating caused by hypervelocity particle capture in aerogel, which was used on the NASA Stardust Mission to capture comet particles. We show that this material exhibits complex organic molecules upon sudden heating. Similar pulsed heating of carbonaceous materials is shown to produce an artifactual fullerene signal. We review the use of muL(2)MS to investigate extraterrestrial materials, and we discuss its recent application to characterize the effect of pulsed heating on samples of interest.

Characterization of prompt flash signatures using high-speed broadband diode detectors

Abstract Impact flash is a brief, intense flash of light released when a target is impacted by a hypervelocity particle. It is caused by emissions from a jet of shocked material which is thrown from the impact site. Impact flash phenomenology has been known for decades, and is now being considered for applications where remote diagnostics are required to observe and diagnose impacts on satellites and space craft where micrometeoroid and orbital debris impacts are common. Additionally, this phenomena and remote diagnostics are under consideration for missile defense applications. Currently, optical signatures created from hypervelocity impact can be utilized as the basis for detectors (spectrometers, pyrometers), which characterize the material composition and temperature. More recent interest has focused on study of hypervelocity impact generated debris and the physics of the associated rapidly expanding and cooling multiphase debris cloud. To establish this capability technically in the laboratory, we have conducted a series of experiments on a two-stage light gas gun at impact velocities ranging from 6 to 19 km/s, which is representative for light emissions resulting from hypervelocity impacts in space. At these high impact velocities jetting is no longer the dominant mechanism for observed impact flash signatures. The focus of this work is to develop fast, inexpensive photo-diodes for use as a reliable prompt flash, and late time radiating debris cloud diagnostic to: (a) characterize material behavior in the shocked and expanding state when feasible; (b) ascertain scaling of luminosity with impact velocity; (c) determine the temperature of the impact flash resulting from radiating emissions when multiple silicon diodes are used in conjunction with narrow band pass filtering at specific wavelengths as a pyrometer. The results of these experiments are discussed in detail using both a metallic target, such as aluminum, and an organic material such as Composition-B explosive.

SPH SIMULATIONS OF HYPERVELOCITY IMPACT OF AL SPHERES ON MULTI-PLATE STRUCTURES

A series of numerical simulations using SPH (Smoothed Particle Hydrodynamics) method were carried out to study the hypervelocity impact of aluminum spheres on multi-plate structures. Both the morphologic characteristics of debris clouds and the damage of intermediate plates were investigated. The possible damage effects of debris cloud threat on back wall were also described qualitatively. Results showed that, comparing with single plate or double-plate structures, the multi-plate structure has higher resistance capacity to the impact from hypervelocity particles. Hence the multi-plate shield structure has a better shielding performance with a reduction in weight of the structure. It provides a promising alternative to the traditional shield in the spacecraft shield design.

Measurement of incident position of hypervelocity particles on piezoelectric lead zirconate titanate detector

A cosmic dust detector for use onboard a satellite is currently being developed by using piezoelectric lead zirconate titanate (PZT). The characteristics of the PZT detector have been studied by bombarding it with hypervelocity iron (Fe) particles supplied by a Van de Graaff accelerator. One central electrode and four peripheral electrodes were placed on the front surface of the PZT detector to measure the impact positions of the incident Fe particles. It was demonstrated that the point of impact on the PZT detector could be identified by using information on the time at which the first peak of the output signal obtained from each electrode appeared.

Low-charge detector for the monitoring of hyper-velocity micron-sized dust particles

A new low-noise beam detector was developed, assembled and tested for the Heidelberg dust accelerator facility. The detector was used to determine in situ the charge, speed and mass of individual dust grains flying through a highly shielded metal cylinder with a length of 200 mm and integrated with a charge-sensitive amplifier Amptek model A250F/NF. Micron-sized latex and iron particles were fired at speeds between 5 and 50 km s−1. The detector characterizes dust particles with a primary charge of 1 fC, a speed of 20 km s−1 and a size of 0.1 µm with a signal-to-noise ratio of 6. The noise of the integrated detector system is typically 0.15 fC (950 electrons) in a bandwidth from 2 kHz to 10 MHz. The new detector allows the control and selection of particles either with a lower surface potential (low-conductive surfaces of polyaniline-coated polystyrene particles), or smaller grains with very small primary charges (sub-micron-sized grains with speeds above 10 km s−1).

Hydrodynamical and radiative transfer modeling of meteoroid impacts into Saturn's rings

In a small hypervelocity impact, superheated gas and particles glow brightly with thermal emission for a brief time interval at short wavelengths; this phenomenon is referred to as an impact flash. Over the past decade, impact flashes have been observed on the Moon and in the laboratory in both the IR and visible portions of the spectrum. These phenomena have been used to constrain impactor parameters, such as impact size, velocity and composition. With the arrival of the Cassini spacecraft at Saturn, we embarked on a study of impact flashes in Saturn's rings. We present results on the feasibility of observing impact flashes and therefore estimating the flux of meteoroids impacting Saturn's rings using Cassini's Ultraviolet Imaging Spectrograph (UVIS). Our modeling effort is two-fold. We start by simulating impacts using the CTH hydrodynamical code. Impacts involve an icy ring particle and a serpentine meteoroid, modeled with the ANEOS equation of state. The objects are centimeters to meters in diameter and collide at 30 to 50 km s −1. We then use the resulting temperatures and densities of the impact plumes in a radiative transfer calculation. We calculate bound–free, free–free, electron scattering and negative ion opacities along a line-of-sight through the center of each impact plume. Our model has shown that impact flashes will not be seen with the UVIS because (1) the plumes are optically thick when their central temperatures are high, with photosphere temperatures too cool to emit observable UV flux and (2) when the plumes become optically thin, even the hottest region of the plume is too cool to observe in the UV. This corroborates the lack of UVIS impact flash detections to date. Impact flashes are not likely to be seen by other Cassini instruments because of the short lifetimes of the plumes.

Numerical Simulation of Shaped Charges Using the SPH Solver: Jet Formation and Target Penetration

The SPH (Smoothed Particle Hydrodynamics) solver of the AUTODYN-3D was utilized to demonstrate a remarkable numerical simulation of shaped charges, specifically the process of jet formation and target penetration. A shaped charge consists of an explosive, a case and a conical liner. The Euler solver has been generally utilized for the simulation of the liner collapse process. Though the axi-symmetric modeling of the liner usually is selected, the actual jet formation process is never so idealistic. When we choose options consistent with live fire experiments, the SPH solver produces a more accurate solution over the Euler approach. The SPH method is capable of dealing with problems, including the free surface, deformable boundaries, moving interface and extremely large deformation. Calculated hypervelocity particles using the SPH method precisely represented the actual observed jet formation profiles of shaped charge characteristics. Accurate representations of the jet velocities, a velocity gradient with the tip traveling much faster than the trail and phase changes of the liner material were demonstrated. Using the calculated jet particles from the SPH method, the penetration process was simulated. The calculation was very time-consuming and the results did not conform to the traditional theories of the penetration. We have been investigating this discrepancy.

A method for producing gradient density aerogel

The Stardust Mission used gradient density aerogel as the hypervelocity particle capture medium in both the cometary and interstellar collection grids. The development and production of these materials was performed exclusively for this mission as a means of improving the efficiency of the collection process. The density of an aerogel can be dictated by controlling the ratio of the condensable silica to that of the solvent used in the aerogel precursor solution. A density gradient was established by gradually mixing the precursor solution for low density aerogel into the precursor solution for high density aerogel and continuously pumping the resultant mixture into a mold. The aerogel designed for the capture of cometary particles had a density gradient ranging from 10 mg/cm3 to 50 mg/cm3 across the 3 cm profile of each block. Whereas those designed for the capture of interstellar grains had a gradient ranging from 10 mg/cm3 to 20 mg/cm3 across a 1 cm profile. Since various physical properties, e.g., refractive index, thermal conductivity, acoustic impedance, dielectric constant, are correlated to the density, they also vary with the density. This method of establishing a density gradient in aerogel can be used to produce other material gradients, e.g., gradient oxide, gradient dopant, in any sol–gel based material.

In-situ Fe XANES of extraterrestrial grains trapped in aerogel collectors: An analytical test for the interpretation of Stardust samples analyses

On 15 January 2006, the NASA Stardust Capsule Sample Return came back to Earth with its load of cometary and contemporary interstellar grains trapped in aerogel collectors. These cometary grains are the first samples of known parent body and their study in the laboratory will give new clues on the nature of the cometary materials. Using Synchrotron X-ray Microscopy (SXRM), some analogues of Stardust's samples were analysed. The aim was to develop an analytical protocol and to study the effects of the slowing down of hypervelocity particles into aerogel on the physical and chemical properties of the collected grains. Our samples originate either from the NASA Orbital Debris Collection Experiment (ODCE) deployed outside the MIR station, or from light gas gun shots of Allende meteorite grains into aerogel at velocities of 6 km/s. They consist of grains trapped in pieces of aerogel, a few hundreds of microns large. Using synchrotron X-ray microbeam, micro-fluorescence mappings and X-ray absorption near-edge structure (XANES) spectra were performed, bringing information on elemental analysis, repartition and speciation of Fe in our samples. In particular, the XANES studies obtained at the iron K-edge show that iron is present in different oxidation states in the samples, rather in a ferric form at the track entrance while rather in a ferrous form at the end of the track as well as in the final grain. The tests performed on the Allende meteorite dust grains for which the Fe 2+/Fe 3+ ratio is a priori known, tend to show that the final particle presents the same oxidation state as the initial incident one, a very encouraging clue for the validity of the future interpretation of Stardust samples analyses.

Aerogel: Space exploration applications

The unique physical properties of aerogel have proven to be enabling to a variety of both flight and proposed space exploration missions. The extremely low density and highly porous nature of aerogel makes it suitable for stopping high velocity particles, as a highly efficient thermal barrier, and as a porous medium for the containment of cryogenic fluids. The use of silica aerogel as a hypervelocity particle capture and return media for the Stardust Mission has drawn the attention of many in the space exploration community. Aerogel is currently being used as the thermal insulation material in the 2003 Mars Exploration Rovers. The SCIM (Sample Collection for the Investigation of Mars) and the STEP (Satellite Test of the Equivalence Principle) Missions are both proposed space exploration missions, in which, the use of aerogel is critical to their overall design and success. Composite materials comprised of silica aerogel and oxide powders are under development for use in a new generation of thermoelectric devices that are planned for use in many future space exploration mission designs. Work is currently ongoing in the development and production of non-silicate and composite aerogels to extend the range of useful applications envisioned for aerogel in future space exploration projects.

2013 SPH法によるShaped Chargeの数値シミュレーション : ジェット生成とターゲット侵徹(S04-2 FEM/メッシュフリー法/粒子法とその関連技術(2),S04 FEM/メッシュフリー法/粒子法とその関連技術)

The SPH solver of the AUTODYN-3D was applied to the numerical simulation of shaped charges. The hypervelocity particles of SPH precisely represented the profiles of shaped charges, including the jet velocity, the velocity gradient and the elastic-plastic phase changes of the liner material. Using the calculated jet particles, the target penetration process was simulated. The results of the calculation were time-consuming and some parameters did not conform with the traditional theory of the penetration.

Damage behaviour of metallic materials caused by subsonic to hypervelocity particle impact

The aim of this paper is to investigate fundamental damage behaviour of metallic materials such as aluminium, mild steel and titanium, which typically have different crystal structures, by the single impact from low velocity to hypervelocity. An ordinary gas gun unit was used up to an velocity of 200 ms −1 and a two-stage light gas gun unit was used from 300 to 5500 ms −1 in this study. Impact tests by a WC ball were performed on the three metallic materials at various impact velocities and at normal angle. Indentation shapes on a cross-sectional surface and the ratios of crater diameter and depth to the diameter of the WC ball were examined. Three modes were recognized in indentation configurations independent of the type of materials. Average contact pressure, which was obtained by the impact energy divided by indentation volume, showed not only a mechanical property of the target material during the impact process but also fracture strength of the projectile. A single particle impact test at a shallow impact angle and at a hypervelocity showed large material removal in spite of its single impact and intimated the difference in mechanisms of the material removal between subsonic and hypervelocity impacts.

Evaluation of mineralogical alteration of micrometeoroid analog materials captured in aerogel

Silica aerogel has been used as a capturing medium for micrometeoroids and space debris. Several previous investigations suggest that aerogel could capture hypervelocity particles macroscopically intact. However, it has not been fully evaluated whether retrieved grains retain their pristine mineralogy. This study attempts to evaluate the intact survivability of high-speed projectiles in aerogel using impact experiments. Such experiments are essential for rigorous examination or further scientific discussion on the samples of on-going and future sample return missions in which aerogels are/will be used as capturing media. We fired two kinds of micrometeoroid analog materials into aerogel with a two-stage light gas gun (2–4 km/s), serpentine and cronstedtite, which are commonly found in CM/CI, and CM chondrites, respectively. As these hydrated minerals are broken down into anhydrous ones at relatively low temperatures, it is suitable for the evaluation of thermal alteration during the capturing process. The retrieved residues were examined with SEM/EDS, Synchrotron Radiation-XRD, and TEM/EDS. The SR-XRD analysis revealed that most of the volumes of residues are mineralogically unaltered. TEM observations show that one serpentine grain shot at 4 km/s has an unaltered crystalline part inside, an amorphous layer, and the outermost molten aerogel layer. One cronstedtite grain shot at 3 km/s, also examined by TEM, was found to have an unaltered interior as well as a vesiculated silicate melt layer. Image analysis revealed both mineral grains reduced their volume down to 10% of the original on average. These results suggest that it is possible to capture serpentine and cronstedtite particles mineralogically intact with the aerogel, at least in the interior of each particle, below 4 km/s, in spite of their large volume loss.

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.

低速から超音速の固体粒子衝突による材料の変形挙動

低速から超音速の固体粒子衝突による材料の変形挙動

Small hypervelocity particles captured in aerogel collectors: Location, extraction, handling and storage

Abstract— It has now been about a decade since the first demonstrations that hypervelocity particles could be captured, partially intact, in aerogel collectors. But the initial promise of a bonanza of partially‐intact extraterrestrial particles, collected in space, has yet to materialize. One of the difficulties that investigators have encountered is that the location, extraction, handling and analysis of very small (10 μm and less) grains, which constitute the vast majority of the captured particles, is challenging and burdensome. Furthermore, current extraction techniques tend to be destructive over large areas of the collectors. Here we describe our efforts to alleviate some of these difficulties. We have learned how to rapidly and efficiently locate captured particles in aerogel collectors, using an automated microscopic scanning system originally developed for experimental nuclear astrophysics. We have learned how to precisely excavate small access tunnels and trenches using an automated micromanipulator and glass microneedles as tools. These excavations are only destructive to the collector in a very small area—this feature may be particularly important for excavations in the precious Stardust collectors. Using actuatable silicon microtweezers, we have learned how to extract and store “naked” particles—essentially free of aerogel—as small as 3 μm in size. We have also developed a technique for extracting particles, along with their terminal tracks, still embedded in small cubical aerogel blocks. We have developed a novel method for storing very small particles in etched nuclear tracks. We have applied these techniques to the extraction and storage of grains captured in aerogel collectors (Particle Impact Experiment, Orbital Debris Collector Experiment, Comet‐99) in low Earth orbit.

Soft capture of earth-orbiting hypervelocity particles with aerogel

The Orbital Debris Collection (ODC) experiment exposed ∼ 0.6 m 2 of SiO 2- based aerogel (0.02 g/cm 3) for 18 months on the US Docking Module of the Mir space station. Post-flight inspection revealed hundreds of millimeter-sized hypervelocity features, ranging from deep penetration tracks to rather shallow pits. Intermediate morphologies suggest that deep tracks and shallow pits are the end members of a morphological continuum that seems controlled by impact velocity. Some 163 particles were recovered from the termini of deep tracks. Scanning (SEM) and Transmission Electron Microscopy (TEM) suggest that shock and thermal alterations are minimal and that individual phases and their textures are well preserved. SEM investigations combined with Energy Dispersive X-Ray Spectroscopy (EDS) reveal a wide variety of natural and man-made particle types, akin to those from other space-exposed surfaces. Very shallow aerogel depressions contain human-waste products. The transparent pits, ∼ 20% of all hypervelocity features, contain no residues detectable with SEM-EDS methods, suggesting that the utility of aerogel to soft capture hypervelocity impactors is velocity-limited. This velocity threshold is estimated at ∼ 18–20 km/s for the ODC aerogel.

New monopulse plasma generation and acceleration facility for surface treatment

The Fachgebiet Raumfahrttechnik is working on the field of hypervelocity particle accelerators based on the electrothermal and the electromagnetic principle. All these accelerators generate a hypervelocity plasma pulse that also can be used for surface treatment and modification of metals and alloys. The facilities and pulsed power sources used up to now, however, are not adapted nor optimized for the special needs of the surface treatment application. Therefore, an entire new system was designed, built and taken into operation. Besides the mere realization of all technical requirements and aspects, a major objective was the development of a user friendly industrial-like demonstrator facility. Based on the experience of pulsed power system design and surface treatment application, we implemented the mono-pulse technique using the latest developments by ABB in the field of semiconductor switches and diodes. The pulsed power supply consists of two 25 kJ modules with high power thyristors and self-blocking diodes that generate a single half-wave current pulse of up to 200 kA with a length of about 50 /spl mu/s. The paper describes the overall system with special emphasis on the pulsed power modules. The proper functioning of the electrical system was documented in extensive check-out tests. Finally, first surface modification experiments were conducted with the new facility to show its capability in this field.