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Matthew J. Genge - One of the best experts on this subject based on the ideXlab platform.

  • Micrometeorites: Insights into the flux, sources and Atmospheric Entry of extraterrestrial dust at Earth
    Planetary and Space Science, 2020
    Co-Authors: Matthew J. Genge, Matthias Van Ginneken, M. D. Suttle
    Abstract:

    Abstract Micrometeorites (MMs) provide constraints on the flux and sources of extraterrestrial dust falling on Earth as well as recording the processes occurring during Atmospheric Entry. Collections of micrometeorites have been recovered from a wide variety of environments including Antarctic moraine, rock traps, ice and snow and on roof tops in urban areas. Studies of the mineralogy and composition of MMs suggest that most particles (>98%) >50 ​μm in diameter have asteroidal sources, whilst ~50% of particles smaller than 50 ​μm are likely to be derived from comets. The relative abundance of S(IV)-type asteroid materials, similar to ordinary chondrites increases with size, although C-type asteroidal materials, similar to carbonaceous chondrites dominate over all. Although MMs provide excellent evidence on the nature and abundance of extraterrestrial dust at the Earth’s orbit they are not without bias and uncertainty. Mineralogical and compositional change during Atmospheric Entry makes the exact nature of their precursors uncertain complicating evaluation of source beyond basic classes of material. This is particularly true at larger sizes when complete melting to form cosmic spherules occurs, however, unmelted MMs >50 ​μm in size are also often thermally altered. Mixing with Atmospheric oxygen and mass fractionation by evaporation furthermore complicates the use of oxygen isotope compositions in identifying parent bodies. All MM collections are suggested to exhibit biases owing to: (1) collection method, (2) terrestrial weathering, (3) terrestrial contamination, and (4) erosion and deposition by terrestrial surface processes. Even in the least biased collections, those collected by dedicated melting of Antarctic snow, erosive loss of material is suggested here to make fluxes uncertain by factors of up to ~2. The abundance of asteroid-derived MMs observed in collections contradicts models of the orbital evolution of interplanetary dust to Earth, which suggests >70% should be provided by comets.

  • Vesicle dynamics during the Atmospheric Entry heating of cosmic spherules
    Meteoritics & Planetary Science, 2016
    Co-Authors: Matthew J. Genge
    Abstract:

    Cosmic spherules are unique igneous objects that form by melting due to gas drag heating during Atmospheric Entry heating. Vesicles are an important component of many cosmic spherules since they suggest their precursors had finite volatile contents. Vesicle abundances in spherules decrease through the series porphyritic, glassy, barred, to cryptocrystalline spherules. Anomalous hollow spherules, with large off-centre vesicles occur in both porphyritic and glassy spheres. Numerical simulation of the dynamic behaviour of vesicles during Atmospheric flight is presented that indicates vesicles rapidly migrate due to deceleration and separate from non-porphyritic particles. Modest rotation rates of tens of radians s-1 are, however, sufficient to impede loss of vesicles and may explain the presence of small solitary vesicles in barred, cryptocrystalline and glassy spherules. Rapid rotation at spin rates of several thousand radians s-1 are required to concentrate vesicles at the rotational axis and leads to rapid growth by coalescence and either separation or retention depending on the orientation of the rotational axis. Complex rapid rotations that concentrate vesicles in the core of particles are proposed as a mechanism for the formation of hollow spherules. High vesicle contents in porphyritic spherules suggest volatile-rich precursors, however, calculation of volatile retention indicates these have lost >99.9% of volatiles to degassing prior to melting. The formation of hollow spherules, by rapid spin, necessarily implies pre-Atmospheric rotations of several thousand radians s-1. These particles are suggested to represent immature dust, recently released from parent bodies, in which rotations have not been slowed by magnetic damping

  • the origins of i type spherules and the Atmospheric Entry of iron micrometeoroids
    Meteoritics & Planetary Science, 2016
    Co-Authors: Matthew J. Genge
    Abstract:

    The Earth's extraterrestrial dust flux includes a wide variety of dust particles that include FeNi metallic grains. During their Atmospheric Entry iron micrometeoroids melt and oxidize to form cosmic spherules termed I-type spherules. These particles are chemically resistant and readily collected by magnetic separation and are thus the most likely micrometeorites to be recovered from modern and ancient sediments. Understanding their behavior during Atmospheric Entry is crucial in constraining their abundance relative to other particle types and the nature of the zodiacal dust population at 1 AU. This article presents numerical simulations of the Atmospheric Entry heating of iron meteoroids to investigate the abundance and nature of these materials. The results indicate that iron micrometeoroids experience peak temperatures 300–800 K higher than silicate particles explaining the rarity of unmelted iron particles which can only be present at sizes of <50 μm. The lower evaporation rates of liquid iron oxide leads to greater survival of iron particles compared with silicates, which enhances their abundance among micrometeorites by a factor of 2. The abundance of I-types is shown to be broadly consistent with the abundance and size of metal in ordinary chondrites and the current day flux of ordinary chondrite-derived MMs arriving at Earth. Furthermore, carbonaceous asteroids and cometary dust are suggested to make negligible contributions to the I-type spherule flux. Events involving such objects, therefore, cannot be recognized from I-type spherule abundances in the geological record.

  • The origins of I-type spherules and the Atmospheric Entry of iron micrometeoroids
    Meteoritics & Planetary Science, 2016
    Co-Authors: Matthew J. Genge
    Abstract:

    The Earth's extraterrestrial dust flux includes a wide variety of dust particles that include FeNi metallic grains. During their Atmospheric Entry iron micrometeoroids melt and oxidize to form cosmic spherules termed I-type spherules. These particles are chemically resistant and readily collected by magnetic separation and are thus the most likely micrometeorites to be recovered from modern and ancient sediments. Understanding their behavior during Atmospheric Entry is crucial in constraining their abundance relative to other particle types and the nature of the zodiacal dust population at 1 AU. This article presents numerical simulations of the Atmospheric Entry heating of iron meteoroids to investigate the abundance and nature of these materials. The results indicate that iron micrometeoroids experience peak temperatures 300–800 K higher than silicate particles explaining the rarity of unmelted iron particles which can only be present at sizes of

Timothy J. Mcintyre - One of the best experts on this subject based on the ideXlab platform.

  • Simulating Gas Giant Atmospheric Entry Using Helium and Neon Test Gas Substitutions
    Journal of Spacecraft and Rockets, 2019
    Co-Authors: Christopher M. James, Richard G. Morgan, David Gildfind, Steven Lewis, Timothy J. Mcintyre
    Abstract:

    Flight into the gas giant planets involves Atmospheric Entry velocities between 20 and 50  km/s, which are mostly beyond the capabilities of current ground testing facilities that make use of test ...

  • Radiative Heat flux Measurements for Titan Atmospheric Entry Condition in a Superorbital Expansion Tunnel
    30th International Symposium on Shock Waves 1, 2017
    Co-Authors: Hadas Porat, Richard G. Morgan, Timothy J. Mcintyre
    Abstract:

    Entry into the atmosphere of Titan, a moon of Saturn, was studied using the X2 superorbital expansion tunnel. For Titan Atmospheric Entry conditions, the radiative heat transfer is expected to be significant even at what is considered to be a relatively low shock speed of 6.5 km/s. To further our understanding of superorbital flows, the experiments presented hereafter use newly developed radiation gauges to measure the radiative heatflux and emission spectroscopy to provide quantitative information about the radiating species in the shock layer for a Titan Atmospheric Entry condition. The radiative heatflux for a Titan 6.5 km/s Entry condition was successfully measured by newly developed CNT-Rad radiation gauges. Radiative heatflux measurements were made using cylindrical and hemispherical models, confirming that scaling the shock standoff has successfully resulted in comparable radiative heatflux measurements. The spectral distribution and radiative intensity was also measured for the cylindrical model along the stagnation streamline. The results show that CN violet bands are dominating the spectra and can be analysed to allow a temperature analysis to further characterise the flow.

  • Emission Spectroscopy of a Mach Disk at Titan Atmospheric Entry Conditions
    29th International Symposium on Shock Waves 1, 2015
    Co-Authors: Hadas Porat, Fabian Zander, Richard G. Morgan, Timothy J. Mcintyre
    Abstract:

    The prediction of heat transfer is important for Atmospheric Entry applications, as it guides the design of a spacecraft thermal protection system (TPS). The radiative heat transfer processes encountered by a spacecraft upon Atmospheric Entry are more complex in nature than the convective heat transfer and therefore more challenging to predict accurately, resulting in the use of large safety factors.

  • Vacuum ultraviolet and ultraviolet emission spectroscopy measurements for Titan and Mars Atmospheric Entry conditions
    44th AIAA Thermophysics Conference, 2013
    Co-Authors: Hadas Porat, Richard G. Morgan, Umar A. Sheikh, Troy N. Eichmann, Timothy J. Mcintyre
    Abstract:

    Vacuum Ultraviolet (VUV) emission spectroscopy radiation measurements were conducted for Titan and Mars Atmospheric Entry conditions using the Centre for Hypersonics X2 expansion tube. The VUV measurements were taken while viewing downstream through the shock layer of a scaled model. UV-Visible emission spectroscopy measurements were conducted in parallel, viewing the shock layer through a side window. The spectra was dominated by the CN violet molecular bands and the main atomic lines identified were C, N and Al. For a Titan 8.5km/s condition, sample of the calibrated spectra for the VUV is presented and discussed, alongside uncalibrated continues spectra from the VUV through to the UV-Visable.

Guy Libourel - One of the best experts on this subject based on the ideXlab platform.

  • Effects of Atmospheric Entry heating on the noble gas and nitrogen content of micrometeorites
    Earth and Planetary Science Letters, 2013
    Co-Authors: Evelyn Fûri, Guy Libourel, Alice Aléon-toppani, Bernard Marty, Laurent Zimmermann
    Abstract:

    Fragments of the carbonaceous chondrite Orgueil were subjected to pulse-heating sequences in order to simulate the heating conditions experienced by micrometeorites (MMs) upon Entry into Earthʼs atmosphere. By increasing the experimental run times from 2 to 120 s at a fixed temperature of 1350 °C, the different textures of natural MMs (from non-vesicular fine-grained particles to melted cosmic spherules) were reproduced, and the noble gas (He, Ne, Ar) and nitrogen abundances and isotope ratios of the MM analogues were subsequently determined by CO2 laser extraction-static mass spectrometry analysis. The starting material shows a heterogeneous He–Ne–Ar–N signature, consistent with the mineralogical heterogeneity of CI chondrites and the inhomogeneous distribution of various noble gas and nitrogen components among meteoritic minerals. Nonetheless, our experiments demonstrate that moderately to strongly heated Orgueil fragments retain only a few percent of their initial noble gas and nitrogen inventories, indicating that Atmospheric Entry heating results in extensive degassing of meteoritic dust particles. The evolution of the noble gas and nitrogen isotope ratios may, in part, be explained by equilibration with the atmosphere; however, the decreasing δ15N values may also indicate preferential degradation of a 15N-rich component by thermal processing of chondritic matter. Furthermore, the efficient loss of helium and cosmogenic neon during heating will lead to an underestimate of the 3He and 21Ne exposure ages of MMs, as well as to large uncertainties for cosmic dust accretion rates derived from extraterrestrial 3He abundances in deep-sea sediments or polar ice cores. While the relative proportions of infalling cometary and asteroidal dust on Earth are unknown, the contribution of noble gases, nitrogen, and water from cosmic dust to the terrestrial volatile inventory appears negligible.

  • Factors controlling compositions of cosmic spinels: application to Atmospheric Entry conditions of meteoritic materials
    Geochimica et Cosmochimica Acta, 2003
    Co-Authors: Alice Toppani, Guy Libourel
    Abstract:

    Abstract During their deceleration through the Earth's atmosphere, meteoritic materials, i.e., interplanetary dust particles, micrometeorites and meteorites, experience thermal shocks which may alter their pristine mineralogy, texture or chemical characteristics. Among these changes, one of the most ubiquitous is the formation of spinels resulting from partial melting and subsequent crystallization of the meteoritic material. These “cosmic spinels” differ from terrestrial spinels by their high Ni and Fe3+ contents and show large variations in composition. In order to better understand the factors controlling their chemistry, pulse-heating experiments simulating Atmospheric Entry of extraterrestrial objects were carried out using Orgueil samples as proxies of meteoritic material. Covering a large range of experimental conditions (temperature 500°C We also show that, due to their fast crystallization kinetics, cosmic spinels can record through their composition, i.e., Al2O3 contents and FeO/Fe2O3 ratio, the diverse conditions of the atmosphere crossed by the extraterrestrial object during its fall towards the Earth's surface. Chemistry of cosmic spinels is thus a powerful tool for constraining the Entry conditions in the Earth's atmosphere of any extraterrestrial object, including altitude of deceleration, Entry angle and incident velocity. These in turn, may provide valuable information on the origin of the extraterrestrial material.

  • experimental simulation of Atmospheric Entry of micrometeorites
    Meteoritics & Planetary Science, 2001
    Co-Authors: Alice Toppani, Guy Libourel, Cecile Engrand, M. Maurette
    Abstract:

    — Depending on their velocity, Entry angle and mass, micrometeorites suffer different degrees of heating during their deceleration in the Earth's atmosphere, leading, in most cases, to significant textural, mineralogical and chemical modifications. One of these modifications is the formation of a magnetite shell around most micrometeorites, which until now could not be reproduced, neither theoretically nor experimentally. The present study was designed to better understand the Entry heating effects on micrometeorites and especially the formation of the magnetite shell. Fragments of the Murchison and Orgueil meteorites were used as analogue material in flash-heating experiments performed in a high-temperature furnace; effects of temperature, heating duration, and oxygen fugacity were investigated. These experiments were able to reproduce most of the micrometeorites textures, from the vesicular fine-grained micrometeorites to the totally melted cosmic spherules. For the first time, the formation of a magnetite shell could be observed on micrometeorite analogues. We suggest that the most plausible mechanism for the formation of this shell is a peripheral partial melting with subsequent magnetite crystallization at the surface of the micrometeorite. Furthermore, with this study, it is possible to estimate the Atmospheric Entry conditions of micrometeorites, such as the peak temperature and the duration of flash-heating.

Domenico Tescione - One of the best experts on this subject based on the ideXlab platform.

  • Optimum design of ablative thermal protection systems for Atmospheric Entry vehicles
    Applied Thermal Engineering, 2017
    Co-Authors: Aniello Riccio, Francesco Raimondo, Andrea Sellitto, Valerio Carandente, Roberto Scigliano, Domenico Tescione
    Abstract:

    Abstract The Thermal Protection System (TPS) provides spacecrafts entering the atmosphere with the thermal insulation from the aerothermodynamic heating. The design of such a subsystem is very critical, considering that its damage can lead to a catastrophic failure of the whole Entry system, in particular if ablative materials are considered. In order to design an ablative TPS, in fact, a reliable numerical procedure, able to compute surface recession rate, pyrolysis and internal temperature histories under severe heating conditions, is necessary. Indeed, the TPS needs to be sized to effectively shield the spacecraft from the high heat fluxes acting during the Atmospheric Entry phase. At the same time, its weight has to be the minimum value able to guarantee a suitable protection. This article aims to describe an optimization procedure for the design of ablative heat shields. In particular, in the present work, the numerical method is applied to the ablative TPS of the hypersonic reEntry capsule Stardust.

Xiuqiang Jiang - One of the best experts on this subject based on the ideXlab platform.

  • high dimensional uncertainty quantification for mars Atmospheric Entry using adaptive generalized polynomial chaos
    Aerospace Science and Technology, 2020
    Co-Authors: Xiuqiang Jiang, Roberto Furfaro, Zhenbo Wang
    Abstract:

    Abstract The probabilistic uncertainties in Mars Atmospheric Entry degrade the Entry guidance performance. The propagation law of high-dimensional uncertainty during Mars Atmospheric Entry is still an open problem that should be investigated. The current work aims to examine the uncertainty propagation during Mars Atmospheric Entry due to uncertain initial state and model parameters, with introducing the generalized polynomial chaos method into Mars Atmospheric Entry dynamics simulations. For more efficient and accurate, generalized polynomial chaos is modified through spectral decomposition and random space decomposition. First, stochastic dynamics are modeled and transformed into equivalent deterministic dynamics in a higher-dimensional space and are updated adaptively when the statistic characteristic of the system state changes greatly. Second, the random space is decomposed when the relative error in variance becomes larger than the predefined threshold. In each random sub-domain, the updated generalized polynomial chaos is employed. Finally, the adaptive generalized polynomial chaos is used to quantify the uncertainty propagation in Mars Atmospheric Entry dynamics. Comparison studies are also performed with traditional generalized polynomial chaos and Monte-Carlo simulations. The influence levels and the evolution profiles of the initial and parametric uncertainties are revealed through numerical simulations.

  • Mars Atmospheric Entry trajectory optimization via particle swarm optimization and Gauss pseudo-spectral method:
    Proceedings of the Institution of Mechanical Engineers Part G: Journal of Aerospace Engineering, 2015
    Co-Authors: Xiuqiang Jiang
    Abstract:

    In this paper, a hybrid optimization strategy using particle swarm optimization and Gauss pseudo-spectral method is proposed to generate the optimal Entry trajectory of Mars pin-point landing mission. This hybrid optimization strategy merges global optimization with local optimization. Coarse optimization is first conducted to provide a global relative suitable initial guess for subsequent local accurate optimization, which can greatly improve optimization efficiency and robustness and produce the optimal Mars Atmospheric Entry trajectory from the present position to the designed terminal state satisfying the path constraints. The validity of the hybrid optimization strategy developed in this paper is confirmed by computer simulation in the presence of aerodynamics uncertainties.

  • review and prospect of guidance and control for mars Atmospheric Entry
    Progress in Aerospace Sciences, 2014
    Co-Authors: Xiuqiang Jiang
    Abstract:

    Abstract The Mars Atmospheric Entry phase plays a vital role in the whole Mars exploration mission-cycle. It largely determines the success of the entire Mars mission. In order to achieve a pin-point Mars landing, advanced Entry guidance and control is essential. This paper systematically summarizes the past development and current state-of-art of Mars Entry guidance and control technologies. More specifically, the Mars Entry process and main technical challenges are first introduced. Second, the guidance and control technologies adopted in the past successful Mars landing mission are reviewed in detail. Next, current state-of-art and recent developments of guidance and control for Mars Atmospheric Entry are summarized at length. The advantages and disadvantages of the various existing methods are analyzed. Lastly, supposing future Mars pin-point landing missions as the potential project application goals, a more comprehensive outlook and prospect for the next-generation Mars Entry guidance and control technologies are described.