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This study focuses on the numerical analysis of large meteoroids during their entry into Earth atmosphere. For this purpose, two entries of meteoroids have been computed: the Chelyabinsk event that occurred in 2013, and a meteor, which felt in the Atlantic Ocean in February 2016, the Saint-Valentine day. For both meteoroids, several points along their re-entry trajectory have been calculation. Computations have been then performed using a non-equilibrium Navier-Stokes solver to determine the temperatures and the composition of the mixture around the meteoroids, as well as the convective heating. Then, the SPARK line-by-line radiation code has been selected to post-process the CFD results for predicting the radiative heating. It has to be noted that SPARK capabilities have been recently extended via an updated database capable of reproducing VUV molecular radiation. The spectra obtained for the St Valentine meteoroid, highlight the strong contribution of molecular VUV radiation at high altitude. Then, comparisons have been carried out between the radiative heating calculated using engineering correlations and the CFD/radiation computations at the different altitudes. The comparison put in evidence the lack of reliability of usual stagnation point correlations particularly at low altitude and high level of stagnation pressure. Finally, the last part of this work focuses on the meteoroid demise. Firstly, a qualitative analysis of the thermal response of the meteoroid accounting for the available elements convective and radiative blockage have been conducted. In a last step, an estimate of the material opacity for the incoming radiation wavelength range has been performed based on the available literature on silica materials. A scenario for the meteoroid demise is then proposed, supported by the outcome of this work. [ABSTRACT FROM AUTHOR]

Every time the Earth is impacted by celestial bodies of various sizes, some produce bright meteors known as fireballs. This study utilizes observational data from USG (U.S. Government) sensors. From 871 fireball data (as of July 30, 2021), we selected 249 events accompanied by pre-impact velocity information. Using the available velocity information and calculated total impact energy, we have calculated the impact velocity, photometric mass, radius (assuming a density value that complies with the P.E. criteria), and an estimate of the absolute magnitude of the parent body outside the atmosphere. Based on the cumulative number of events with the absolute magnitude of the parent body equal to or lower than H0, the fireball flux is 8 fireballs event per year over the Earth's whole surface for H ≤ 31.5 which is equivalent with D ≥ 3 meters across the Earth's surface. Our simple power-law model for predicting the number of meteoroids as the parent body for fireballs event with absolute magnitude < H0, corresponds to the cumulative number of a sub-class of small Near-Earth asteroids (NEAs) with orbits similar to the Earth's known as Arjuna. [ABSTRACT FROM AUTHOR]

A problem of two bodies separating in the atmosphere during supersonic flight was studied using multigrid method of modeling dynamics. Two main configurations were taken into consideration. When two fragments were initially located on the line perpendicular to the direction of the flight, they separated from each other symmetrically and acquired the same absolute value of lateral velocity. When fragments were initially located one behind another with a certain distance between them, collimation effect was observed with the lagging fragment moving into the near wake area of the leading body. A series of consequential collisions of bodies occurred with the distance between fragments decreasing over time in the case of inelastic impact. Eventually the system transitioned to the state of the joint flight of two bodies one directly behind the other. Over time numerical disturbances lead to the break of symmetry with fragments sliding against each other and then separating in lateral direction. The separation velocity of the leading body was significantly higher for this configuration. The joint flight of two bodies behind each other was found to be unstable unless the lagging fragment had smaller size than leading body. [ABSTRACT FROM AUTHOR]

Observations of the mesospheric Ni layer have been performed by lidar in January-March 2018 at Kuehlungsborn/Germany (54°N, 12°E). These soundings provide only the second Ni data set after initial observations by Collins et al. at Chatanika/Alaska (65°N, 147°W)[1]. We utilized for the first time a transition from the low-lying excited Ni(3D) state at 341 nm. For all soundings, nightly mean peak densities varied between ~280 cm−3 and 450 cm3, which is a factor of ~40 less than previously reported for Chatanika [1]. The observed Ni abundance is especially important if compared with the abundance of other metals like Fe, and with their respective abundances in evaporating meteoroids, which form the source of the metal layer in the upper mesosphere. Here, we present exemplarily a sounding from January 8, 2018. Beside the Ni raw data and density profiles we show a temperature profile as measured simultaneously be the co-located RMR lidar and the temperature variation due to gravity waves and tides. [ABSTRACT FROM AUTHOR]

In this work, the physical parameters of near Earth objects (NEO) are studied. The search for parent bodies of low-activity small meteor showers – k-Cygnids, δ-Cancrids, and Virginids are performed among asteroids that could be faded comets. For kCygnids by all the catalogues of meteor orbits 2 asteroids are selected – 153311 2001MG1, 385343 2002LV, whose orbits provide from 90% to 100% compliance with meteoroids’ orbits of a shower. The 2012LL9 is only selected by 3 catalogues of meteor orbits. By catalogue of Astronomical Institute of the Czech Academy of Sciences other asteroids – 2002JY8 and 2005LP40 – are selected. As a result of analyzing 14800 NEO from the Apollo group, in this work near-Earth objects closely genetically related to the existing meteor showers are determined. 2002LV and 2001MG1 asteroids are the closest to the Kappa-Cygnids by orbital elements. 2014RS17, 2006BF56, 2001YB5 asteroids are the closest to the Delta-Cancrids by orbital elements. 2008VL14, 2006UF17, 2010VF, 2000DO1, 2010CF55, 2010TN55, 2007EJ88, 481482 2007CA19 asteroids are the closest to the Virginids by orbital elements. The genetic criterion definition methods were used in the analysis. The analysis of near-Earth objects (NEO), i.e. small celestial bodies crossing the Earth’s orbit, whose number exceeds 15 thousand, is important in terms of asteroid threats. These objects have highly elliptical orbits (HEO) with distances at perigee lower than 1.3 AU. NEO could be comet nuclei that had lost the icy component under the influence of solar radiation. The major part of NEO formed in the main belt, and they are mainly stony and iron. To search for a parent body of an observed meteor shower are used similarity D-criteria. The minimum value for D indicates a high degree of similarity between orbits of 2 small bodies. [ABSTRACT FROM AUTHOR]

An algorithm for solving adjoint aerodynamic and ballistic problems is proposed to investigate a flight of a system of bodies in the atmosphere, taking into account their relative movement and rotation. The algorithm is used to study the separation of two identical bodies of rectangular shape with the account of rotation. Rotation leads to the separation of the bodies not only under the acting pushing aerodynamic force, but also under additional lateral force due to the angle of attack of the bodies. The separation velocity of two rotating meteor fragments may increase up to three times comparing to the calculations where it is assumed that bodies do not rotate. This study was carried out in order to estimate the influence of various factors on the separation velocity of meteoroid fragments after destruction of a parent body and the change of their trajectories after fragmentation. [ABSTRACT FROM AUTHOR]

The Mini-EUSO telescope, approved by ASI (Italian Space Agency) and Roscosmos (Russian Space Agency) as long-term program of space experiments to be launched on the Progress spacecraft during the Expedition 60/61 in 2019, will be placed on a nadir-facing, UV transparent window on the ISS Russian Zvezda module looking down on Earth. As one of the JEM-EUSO collaboration missions, its first objective is to observe UV light produced by UHECR (Ultra High Energy Cosmic Ray) events from upper atmosphere (~ 400 km altitude), moreover, from this point of view, Mini-EUSO will perform, for the first time, high-resolution mapping of night-earth UV (300 - 400 nm) emission, focusing on terrestrial background sources, TLEs (Transient Luminous Events), bioluminescence, meteoroids burning in atmosphere, search for SQM (Strange Quark Matter) signals, as well as detecting and mapping space debris. The integration of the instrument, currently underway at the University of Rome Tor Vergata, is at an advanced stage in order to be compliant with a launch opportunity in June 2019. The on ground test results will be presented. [ABSTRACT FROM AUTHOR]

The model of atmospheric fragmentation of large meteoroids to the cloud of fragments is proposed. The comparison with similar models used in the literature is made. The approximate analytical solution of meteor physics equations is obtained for the mass loss of the disrupted meteoroid, the energy deposition and for the light curve normalized to the maximum brightness. This solution is applied to modelling of interaction of the Chelyabinsk meteoroid with the atmosphere. The influence of uncertainty of initial parameters of the meteoroid on characteristics of its interaction with the atmosphere is estimated. Comparison of the analytical solution with the observational data is made. [ABSTRACT FROM AUTHOR]

This paper is concerned with mathematical model for numerical simulation of meteoroid dynamics. The simulations of bolide ballistics are carried out via hard sphere approximation. System of differential equations for movement and heat transfer is solved in Lagrange variables via Runge-Kutta methods. The drag force of atmospheric air is computed via Henderson formula, valid for wide ranges of Reynolds and Mach numbers. The parameters of surrounding gas are obtained from standard atmosphere model. The impact pressure is computed taking into account entropy jump through bow head shockwave and consequent isentropic deceleration of the flow in the vicinity of streamlined sphere. Meteoroid fragmentation is modeled as sequential division of parent body into two parts using random weighting coeficient for parent mass. The condition for fragmentation event occur when the hemisphere-averaged value of impact pressure exceeds the threshold of relative body strength, which nonlinearly depends on ration of initial meteoroid mass to current mass of considered fragment. To compute trajectory divergence for newly-formed splinters we introduce the repulsive force, dependent on impact pressure, cross sectional areas of mutually repulsing bodies and distances between them. The set of mathematical models is implemented as the program complex. Preliminary computational results show that fragmentation altitude, terminal velocities and maximum splinter masses are in good agreement with corresponding observations and measurements. [ABSTRACT FROM AUTHOR]

We present a study on statistical approach to estimate initial meteoroid shape of the Sutter's Mill meteorite, aiming to fit lognormal, Weibull and Grady statistical mass distributions to the recovered fragments. We show a good correspondence of the selected distribution functions to the experimental data, with the best fit obtained with exponential cumulative distribution function (as a special case ofWeibull distribution). This allows us to implement a novel technique for meteoroid pre-entry shape estimation, based on the detailed data on surviving meteorite fragments recovered on the ground. In total, all the available 77 fragments of the Sutter's Mill meteorite were analyzed. This recovered fragment set is proved statistically complete. From the results obtained in this study, we suggest that only one major fragmentation event occurred during the atmospheric passage of the Sutter's Mill meteoroid. The scaling analysis reveals an elongated pre-fragmentation shape of the meteoroid, being an average between the known estimates for the shapes of the asteroids Castalia, Gaspra and Ausonia. [ABSTRACT FROM AUTHOR]

It has been known that space debris or meteoroid impact damage can have significant effects on spacecraft. Experimental test has been conducted up to 7 km/s, and numerical simulations are performed at higher velocities. Studies on the hypervelocity impact onto single plate, double spaced plates (Whipple shield), and multiple plates (MS shield) have been performed and ballistic limit curves (BLCs) are proposed. Last 15 years SPH (Smoothed Particle Hydrodynamics) has been applied to the hypervelocity impact problems because of cost of test and numerical efficiency especially in the hypervelocity impact regime. Although most of the simulations captured the debris shape well, somehow they do not seem to match well with the empirical ballistic limit curves. We have recently developed a new axisymmetric SPH hydrocode. In order to assess the confidence that should be placed in such simulations we simulated the hypervelocity impacts on aluminum Whipple shields and compared with the empirical BLCs. The SPH simulations indicated an improved accuracy compared with the previously published SPH simulation results. Other effort we put was using different types of equation of state, however no further improvement was achieved. [ABSTRACT FROM AUTHOR]

In-situ cosmic dust instruments and measurements played a critical role in the emergence of the field of dusty plasmas. The major breakthroughs included the discovery of β-meteoroids, interstellar dust particles within the solar system, Jovian stream particles, and the detection and analysis of Enceladus's plumes. The science goals of cosmic dust research require the measurements of the charge, the spatial, size and velocity distributions, and the chemical and isotopic compositions of individual dust particles. In-situ dust instrument technology has improved significantly in the last decade. Modern dust instruments with high sensitivity can detect submicron-sized particles even at low impact velocities. Innovative ion optics methods deliver high mass resolution, m/dm>100, for chemical and isotopic analysis. The accurate trajectory measurement of cosmic dust is made possible even for submicron-sized grains using the Dust Trajectory Sensor (DTS). This article is a brief review of the current capabilities of modern dust instruments, future challenges and opportunities in cosmic dust research. [ABSTRACT FROM AUTHOR]

There is significant evidence that some fraction of meteoric bodies is destroyed in the atmosphere. The evolution of the fragment cloud depends on a large number of factors, among them: the meteoroidSˇs altitude and velocity at the moment of breakup, fragments sizes and properties of a body material. The interaction of shock waves forming in front of the fragments may lead to both an increase and decrease of the midsection area of the fragment cloud [1], [2]. In this work, we consider the inter action of the fragments in a supersonic flow. The configuration properties of two spherical bodies of different radii are considered. Via numerical simulations, we calculate the pressure distribution in the flow around the two bodies for different relative positions. We construct the functions of the coefficients of transverse and drag forces from the angle between the central line of the two bodies and the flow direction for different distances between the two fragments. We find the conditions for the collimation effect, i.e., fragment involving into the wake of the leading (usually, the largest) fragment. We systematize the simulation results for drag and forces and infer the basic aerodynamic properties of the meteoroid fragments. Moreover, in the work dynamics of two spherical fragments in a supersonic stream is defined on the basis of numerical calculations. The aerodynamic properties are accurately expressed in a dynamic picture. Besides, it is obtained, that fragments connect and move as a unit due to aerodynamic interaction. [ABSTRACT FROM AUTHOR]

The novel structure of metallic foams is of interest in the design of next-generation debris shields as it introduces physical mechanisms that are advantageous to hypervelocity impact shielding (e.g. increased fragmentation/melt/vaporization, energy dissipation, etc.). Preliminary investigations have shown improved shielding capability over traditional spacecraft primary structures. In this paper, the results of a current hypervelocity impact test program on metallic open-cell foam core sandwich panels are reported. A preliminary ballistic limit equation has been derived from the experimental results, and is presented in a form suitable for implementation in risk assessment software codes. [ABSTRACT FROM AUTHOR]

In the framework of ground-based science campaign dedicated to the encounter with Rosetta spacecraft, the mineralogies of the asteroids (21) Lutetia and (2867) Steins were investigated. Near-infrared (NIR) spectra of the asteroid in the 0.8–2.5 μm spectral range have been obtained with SpeX/IRTF in remote-observing mode from Meudon, France, and Cambridge, MA, in March, April and December 2006 and in January and March 2007. A χ2 test using meteorite spectra from the RELAB database was performed in order to find the best fit of complete visible+infrared (VNIR) spectra of Lutetia. To constrain the possible composition of Steins’ surface, we constructed a simple mixing model using a linear (areal) mix of three components obtained from the RELAB database. A space-weathering model was applied to the aubrite ALH-78113 spectrum. In the case of (21) Lutetia we find a clear spectral variation (slope), and a good correspondence between spectral variations and rotational phase. The surface mixing model places Steins in a subdivision of the E-type class with objects like Angelina, Eger, and Nereus, a group not sampled by the current collection of aubrite meteorites. [ABSTRACT FROM AUTHOR]

The conventional spacecraft meteoroids and orbital debris shielding system is the Whipple shield. In general there is a threshold velocity that is just sufficient to shatter the projectile for each system consisting of a projectile and bumper. This velocity is known as the fragmentation onset velocity. To determine the fragmentation onset velocity experimentally, a number of experiments have been conducted with different projectile/bumper configuration. The numerical simulations of fragmentation onset velocity of different material projectile hypervelocity impacts on bumpers with different combination of impact velocities and bumper-thicker-to-projectile-diameter ratios (t/D) have been performed using the SPH technique of AUTODYN. The spherical projectile materials are aluminum, steel and copper. All bumper material is aluminum alloy 6061-T6. The simulation velocities were in the range of 1 km/s∼7 km/s. The ratios of t/D were varied from 0.01 to 0.8. The material model contains Mie-Gruneisen (shock) equation of state, Steinberg-Guinan strength model, principal tensile stress failure model and Grady fragmentation failure model. The simulation results are given and compared with the experimental results. The simulation results are consistent very well with the experimental results. The effects of t/D and material shock impedance etc. on fragmentation onset velocity have been given in Figures and equations. [ABSTRACT FROM AUTHOR]

Impacting at hypervelocity, an asteroid struck the Earth approximately 65 million years ago in the Yucatan Peninsula area. This triggered the extinction of almost 70% of the species of life on Earth including the dinosaurs. Other impacts prior to this one have caused even greater extinctions. Preventing collisions with the Earth by hypervelocity asteroids, meteoroids, and comets is the most important immediate space challenge facing human civilization. This is the Impact Imperative. We now believe that while there are about 2000 earth orbit crossing rocks greater than 1 kilometer in diameter, there may be as many as 200,000 or more objects in the 100 m size range. Can anything be done about this fundamental existence question facing our civilization? The answer is a resounding yes! By using an intelligent combination of Earth and space based sensors coupled with an infra-structure of high-energy laser stations and other secondary mitigation options, we can deflect inbound asteroids, meteoroids, and comets and prevent them from striking the Earth. This can be accomplished by irradiating the surface of an inbound rock with sufficiently intense pulses so that ablation occurs. This ablation acts as a small rocket incrementally changing the shape of the rock's orbit around the Sun. One-kilometer size rocks can be moved sufficiently in about a month while smaller rocks may be moved in a shorter time span. We recommend that space objectives be immediately reprioritized to start us moving quickly towards an infrastructure that will support a multiple option defense capability. While lasers should be the primary approach initially, all mitigation options depend on robust early warning, detection, and tracking resources to find objects sufficiently prior to Earth orbit passage in time to allow mitigation. Infrastructure options should include ground, LEO, GEO, Lunar, and libration point laser and sensor stations for providing early warning, tracking, and deflection... [ABSTRACT FROM AUTHOR]

Drag coefficients of meteoroids have been investigated in various flow regimes. Some new simple approximations for the drag coefficient and convective heat transfer coefficient of the meteoroid are proposed. Analytic solutions of the meteoroid drag equation were obtained using these approximations. Some numerical solutions with all variable coefficients have also been obtained. The comparison of solutions with constant and variable coefficients shows significant differences, depending on the size of meteoroid. [ABSTRACT FROM AUTHOR]

The use of time-domain reflectometry (TDR) has been proposed to determine fault position and/or density along electrodynamic tether (EDT) systems. Future EDT missions are desired to be long duration (from several months to years); hence, these missions can expect possibly significant performance degradation due to breaches in tether insulating material caused by hazards such as micrometeoroids. A TDR system provides one possible method for measuring EDT fault build-up as a function of time, allowing researchers to understand and model the degradation characteristics and to design EDT systems to survive expected levels. In addition, including a TDR system as part of long-duration EDT missions would facilitate real-time tracking of the expected performance degradation and health state of the tether. The TDR technique has long been an effective tool for determining the location of loads and faults along common transmission lines (TLs) such as coaxial cables. Also sometimes known as pulse reflectometry, TDR works by sending an impulse down a TL and recording the reflected energy as a function of time. Measurement of the reflected TDR waveform provides insight into the physical structure of the TL and any loads, i.e., faults, along its length. In addition, the delay between launched and reflected signals determines the location of the load or fault. [ABSTRACT FROM AUTHOR]

This paper examines interactions of single and multi-strand tethers with the meteoroid and orbital debris complex in low Earth orbit (LEO). The techniques by which a tether owner/operator may establish baseline estimates of on-orbit lifetime or sever rates using the publicly available NASA ORDEM96 engineering model of the orbital debris environment and the NASA SSP-30425 and SP-8013 models of the meteoroid complex are explored. The concepts of cross-sectional area and surface area flux are explained, with examples, to illustrate for the engineer the method of calculating impact rates of each debris component on the tether. The tether and composite material impact effects literature is then reviewed, and applied to an estimation of tether sever rates, given the previously calculated impact rates. Single and multi-strand tethers are examined to formulate the probability of tether failure in the event of an impact. [ABSTRACT FROM AUTHOR]