Size scaling of crater size, ejecta mass, and momentum enhancement due to hypervelocity impacts into 2024-T4 and 2024-T351 aluminum

2019 ◽  
Author(s):  
James D. Walker ◽  
Sidney Chocron ◽  
Donald J. Grosch
Keyword(s):  
Hypervelocity Impacts ◽  
Size Scaling ◽  
Crater Size ◽  
Informed Decisions ◽  
Celestial Bodies ◽  
Comet Nuclei ◽  
The Impact

Abstract Momentum enhancement occurs when impactors strike objects at hypervelocities due to the formation of crater ejecta whose departure from the impact body impart more momentum to the impacted body. In previous work the momentum enhancement caused when metals, rock, and pumice were impacted have been examined [1-7]. Momentum enhancement is quantified by β, which is the ratio of the resulting target momentum by the impactor momentum. By quantifying momentum enhancement it is possible to make informed decisions about the use of hypervelocity impactors to deflect celestial bodies such as asteroids or comet nuclei.

scholarly journals Self-Secondaries Formed by Cold Spot Craters on the Moon

2021 ◽  
Vol 13 (6) ◽  
pp. 1087
Author(s):  
Yiren Chang ◽  
Zhiyong Xiao ◽  
Yang Liu ◽  
Jun Cui
Keyword(s):  
Systematic Investigation ◽  
Impact Craters ◽  
Spatial Density ◽  
Cold Spot ◽  
The Moon ◽  
Potential Threat ◽  
Frequency Distributions ◽  
Crater Size ◽  
The Impact ◽  
Density Pattern

Self-secondaries are a population of background secondaries, and they have been observed on top of impact melt and ballistically emplaced ejecta deposits on various planetary bodies. Self-secondaries are formed by impacts of sub-vertically launched ejecta, but the launch mechanism is not confirmed. The potential threat of self-secondaries to the theoretical and applicable reliability of crater chronology has been noted, but not constrained. Hitherto discovered self-secondaries were located around complex impact craters, but their potential existence around simple craters has not been discovered. Here we report the first discovery of self-secondaries around lunar cold spot craters, which are an extremely young population of simple craters formed within the past ~1 million years on the Moon. Self-secondaries are widespread on layers of cascading flow-like ejecta deposits around cold spot craters. The spatial density of self-secondaries dwarfs that of potential primary craters. The spatial distribution of self-secondaries is highly heterogeneous across the ejecta deposits. With respect to the impactor trajectory that formed cold spot craters, self-secondaries formed at the downrange of the ejecta deposits have the largest spatial density, while those at the uprange have the smallest density. This density pattern holds for all cold spot craters that were formed by non-vertical impacts, but self-secondaries do not exhibit other systematic density variations at different radial distances or at other azimuths with respect to the impactor trajectory. Among known mechanics of ejecting materials to the exterior of impact craters, impact spallation is the most likely scenario to account for the required large ejection velocities and angles to form self-secondaries. The production population of self-secondaries is estimated based on the highly diverse crater size-frequency distributions across the ejecta deposits of cold spot craters. For a better understanding of the impact history on the Moon, a systematic investigation for the effect of self-secondaries on lunar crater chronology is required.

Modeling Hypervelocity Impacts Using Smoothed Particle Hydrodynamics

2018 ◽  
Author(s):  
M. Ganser ◽  
B. van der Linden ◽  
C. G. Giannopapa
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Large Deformations ◽  
Hypervelocity Impact ◽  
Density Fluctuations ◽  
Computational Domain ◽  
Simulation Tool ◽  
Hypervelocity Impacts ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
The Impact

Hypervelocity impacts occur in outer space where debris and micrometeorites with a velocity of 2 km/s endanger spacecraft and satellites. A proper shield design, e.g. a laminated structure, is necessary to increase the protection capabilities. High velocities result in massive damages. The resulting large deformations can hardly be tackled with mesh based discretization methods. Smoothed Particle Hydrodynamics (SPH), a Lagrangian meshless scheme, can resolve large topological changes whereas it still follows the continuous formulation. Derived by variational principles, SPH is able to capture large density fluctuations associated with hypervelocity impacts correctly. Although the impact region is locally limited, a much bigger domain has to be discretized because of strong outgoing pressure waves. A truncation of the computational domain is preferable to save computational power, but this leads to artificial reflections which influence the real physics. In this paper, hypervelocity impact (HVI) is modelled by means of basic conservation assumptions leading to the Euler equations of fluid dynamics accompanied by the Mie-Grueneisen equation of state. The newly developed simulation tool SPHlab presented in this work utilizes the discretization method smoothed particle hydrodynamics (SPH) to capture large deformations. The model is validated through a number of test cases. Different approaches are presented for non-reflecting boundaries in order to tackle artificial reflections on a computational truncated domain. To simulate an HVI, the leading continuous equations are derived and the simulation tool SPHlab is developed. The method of characteristics allows to define proper boundary fluxes by removing the inwards travelling information. One- and two-dimensional model problems are examined which show excellent absorption behaviour. An hypervelocity impact into a laminated shield is simulated and analysed and a simple damage model is introduced to model a spallation failure mode.

Analysis of hypervelocity impacts: The tungsten case

2021 ◽  
Author(s):  
A Fraile ◽  
Prashant Dwivedi ◽  
Giovanni Bonny ◽  
Tomas Polcar
Keyword(s):  
Kinetic Energy ◽  
Interatomic Potential ◽  
Detailed Examination ◽  
Penetration Process ◽  
Damage Initiation ◽  
Crater Size ◽  
Crater Volume ◽  
Parallel Molecular Dynamics ◽  
Dynamics Simulations ◽  
The Impact

Abstract The atomistic mechanisms of damage initiation during high velocity (v up to 9 km/s, kinetic energies up to 200 keV) impacts of W projectiles on a W surface have been investigated using parallel molecular-dynamics simulations involving large samples (up to 40 million atoms). Various aspects of the impact at high velocities, where the projectile and part of the target materials undergo massive plastic deformation, breakup, melting, and vaporization, are analyzed. Different stages of the penetration process have been identified through a detailed examination of implantation, crater size and volume, sputtered atoms, and dislocations created by the impacts. The crater volume increases linearly with the kinetic energy for a given impactor; and the total dislocation length increases with the kinetic energy but depends itself on the size of the impactor. Furthermore, the total dislocation length is less dependent of the fine details of the interatomic potential. The results are rationalized based on the physical properties of bcc W.

Dust impact detections by a set of Faraday cups in the lunar environments

2020 ◽  
Author(s):  
Oleksii Kononov ◽  
Jiří Pavlů ◽  
Libor Nouzák ◽  
Jana Šafránková ◽  
Zdeněk Němeček ◽  
...  
Keyword(s):  
Solar Wind ◽  
Sampling Rate ◽  
Identification Algorithm ◽  
Impact Pulse ◽  
Ion Energy ◽  
Ion Energy Distribution ◽  
Hypervelocity Impacts ◽  
Dust Detection ◽  
The Impact ◽  
Novel Design

<p>The Bright Monitor of the Solar Wind (BMSW) for the Luna-Resurs-1 mission is an instrument designed for high-time (30 ms) resolution measurements of moments of the ion energy distribution by Faraday cups in the solar wind and in a plasma environment at altitudes between 65 and 150 km above the lunar surface. Previous studies performed by a similar instrument located on-board the Spektr-R spacecraft demonstrated a possibility to detect hypervelocity impacts of dust grains by such instruments Our analysis shows that the main problem of the reliable detection of dust impacts using such types of instruments is their sampling rate. In the paper, we present a novel design of a set of FCs that improves the ability of the dust detection using a simple identification algorithm that can store data with a higher sampling rate around the impact pulse. Moreover, we discuss a calibration of the detectors and their front-end electronics using the dust accelerator in order to find a relation between impact parameters and pulse heights.</p>

Seasonal variation of Mercury's exosphere deduced from MESSENGER data and simulation study

2020 ◽  
Author(s):  
Yudai Suzuki ◽  
Kazuo Yoshioka ◽  
Go Murakami ◽  
Ichiro Yoshikawa
Keyword(s):  
Seasonal Variation ◽  
Solar Radiation ◽  
Radiation Pressure ◽  
Seasonal Variability ◽  
Solar Radiation Pressure ◽  
Space Environment ◽  
Generation Process ◽  
Surface Transport ◽  
Celestial Bodies ◽  
The Impact

<p>Celestial bodies with surface-bound exosphere are valuable because we can directly see the interaction between the bodies and space environment to which they are exposed. This interaction is especially expected to be clearly observed around Mercury. This research aims to clarify the generation process of neutral sodium exosphere, through the comparison between the data from MASCS onboard MESSENGER spacecraft and 3-D model calculation considering generation, transportation and dissipation processes.</p><p>First, seasonal variability of the amount of sodium exosphere is analyzed for each local time (LT) using MASCS data. Previous research has shown that the amount of sodium above LT12 reaches a maximum at aphelion, and it is found that this maximum is seen only above LT12. In addition, two hypotheses proposed by the research: the increase in the surface sodium density of the dayside due to fast rotation of terminator, and the expansion of exosphere owing to weaker radiation pressure, were turned out to be inconsistent with seasonal variability above LT06 and the results of test particle calculations.</p><p>Following these results, in order to understand the key process of the seasonal variation of the amount of sodium especially around LT12, 3-D sodium exosphere model including release from the surface, transport due to gravity and solar radiation pressure, and dissipation due to ionization caused by solar radiation is constructed. The results from numerical calculation is consistent with the observations by MASCS in terms of the vertical profile and the seasonal variability above LT06 and LT18, but the maximum at aphelion above LT12 could not be reproduced. Then, when the existence of the impact of comet dust stream is assumed as a local and short-term sodium source, the model with impact of 10<sup>8</sup>kg comets per Mercury year could reproduce observations.</p><p>Using the model constructed in this study, the sodium distribution which would be observed by MSASI onboard MIO spacecraft is predicted. The comparison between the calculation and observation by MSASI will provide us new insights into the interaction between the celestial bodies and space environment.</p><p>In this presentation, we will summarize the results of comparison between observations by MASCS and 3-D Monte Carlo simulation about the seasonal variability of Mercury’s sodium exosphere.</p>

Ejecta Size and Crater Size of Pure Aluminum in Hypervelocity Impacts

2017 ◽  
Vol 2017 (0) ◽  
pp. OS0418
Author(s):  
Masahiro NISHIDA ◽  
Yushiro MOZAKI ◽  
Hiroki TANAKA ◽  
Hiroyuki YAMADA
Keyword(s):  
Pure Aluminum ◽  
Hypervelocity Impacts ◽  
Crater Size

scholarly journals OPEN SCIENCE: Where are we? How did we get here? Where to we go from here?

2018 ◽  
Author(s):  
Maryrose Franko
Keyword(s):  
Open Data ◽  
Open Science ◽  
Data Formats ◽  
Informed Decisions ◽  
Scientific Innovation ◽  
Readable Form ◽  
Machine Readable ◽  
The Impact ◽  
Machine Readable Form

The mission of nonprofit funders dictates that research resulting from our funding be freely accessed by our patients and families to help make informed decisions about care, and by our boards and donors to be able to evaluate the impact of our funding. But it is equally critical to our mission that data resulting from our support be published in a machine-readable form and available in easily accessible and open data formats to enable reuse by other researchers. In addition, as technology evolves the need and the ability to share to all research outputs must evolve with it. Only then can the impact of the research be multiplied - increasing the potential for significant and far-reaching advances and scientific innovation.

scholarly journals Risk quantification for SARS-CoV-2 infection through airborne transmission in university settings

2021 ◽  
Author(s):  
Mythri Ambatipudi ◽  
Paola Carrillo Gonzalez ◽  
Kazi Tasnim ◽  
Jordan T. Daigle ◽  
Taisa Kulyk ◽  
...  
Keyword(s):  
Exchange Rate ◽  
Web Application ◽  
Quantitative Model ◽  
Infection Risk ◽  
Filtration Efficiency ◽  
Air Exchange Rate ◽  
Informed Decisions ◽  
University Spaces ◽  
The Impact ◽  
Air Exchange

ABSTRACTThe COVID-19 pandemic has significantly impacted learning as many institutions switched to remote or hybrid instruction. An in-depth assessment of the risk of infection that takes into account environmental setting and mitigation strategies is needed to make safe and informed decisions regarding reopening university spaces. A quantitative model of infection probability that accounts for space-specific parameters is presented to enable assessment of the risk in reopening university spaces at given densities. The model uses local positivity rate, room capacity, mask filtration efficiency, air exchange rate, room volume, and time spent in the space as parameters to calculate infection probabilities in teaching spaces, dining halls, dorms, and shared bathrooms. The model readily calculates infection probabilities in various university spaces, with mask filtration efficiency and air exchange rate being among the dominant variables. When applied to university spaces, this model demonstrated that, under specific conditions that are feasible to implement, in-person classes could be held in large lecture halls with an infection risk over the semester < 1%. Meal pick-ups from dining halls and the use of shared bathrooms in residential dormitories among small groups of students could also be accomplished with low risk. The results of applying this model to spaces at Harvard University (Cambridge and Allston campuses) and Stanford University are reported. Finally, a user-friendly web application was developed using this model to calculate infection probability following input of space-specific variables. The successful development of a quantitative model and its implementation through a web application may facilitate accurate assessments of infection risk in university spaces. In light of the impact of the COVID-19 pandemic on universities, this tool could provide crucial insight to students, faculty, and university officials in making informed decisions.

scholarly journals Evaluative tools in impact investing: Three case studies on the use of theories of change

2018 ◽  
Vol 6 (2) ◽  
Author(s):  
Noel B. Verrinder ◽  
Kagiso Zwane ◽  
Debby Nixon ◽  
Sara Vaca
Keyword(s):  
Environmental Change ◽  
Case Studies ◽  
Impact Investing ◽  
Informed Decisions ◽  
Evaluation Community ◽  
The World ◽  
Social And Environmental Change ◽  
Theories Of Change ◽  
The Impact

Impact investing is becoming one of the largest forces in driving social and environmental change globally. However, how one defines, measures and communicates this impact is not well defined or consistently implemented. This can prevent investors from making well-informed decisions and allows for ‘impact washing’. The evaluation community has many tools that could be adapted and used in the world of impact investing. Theories of change allow for the better communication of impact, identification of indicators to be measured and critical interrogation of logic. The attributes of theories of change could assist in steering the growing force of impact investing towards gathering more investment and achieving greater impact. This paper is exploratory and examines the development and use of theories of change as a tool for impact investing and seeks to identify the benefits of the tool. We qualitatively review three case studies of organisations that have implemented theories of change and identify common key themes. We find that theories of change are a useful tool for the communication of impact, identification of indicators to be measured and for the critical interrogation of logic. However, theories of change do not provide a panacea to the impact challenge; the need to rigorously measure impact is not fulfilled by merely identifying what needs to be measured. Regardless, the use of theories of change adds an advantage in a space where others have not gone to the same length to show their commitment to driving change.

scholarly journals Sustainability of Steel Office Buildings

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3723
Author(s):  
Filip Broniewicz ◽  
Miroslaw Broniewicz
Keyword(s):  
Sustainable Development ◽  
Social Impact ◽  
Office Buildings ◽  
Office Building ◽  
Sustainable Construction ◽  
Sustainable Buildings ◽  
Steel Construction ◽  
Informed Decisions ◽  
The Impact ◽  
Design And Construction

Sustainable construction is an important part of sustainable development because of its contribution to the economy as well as the environmental and social impact of buildings on our lives. Steel is one of the most basic materials, both in the structures and for the finishes. It enables efficiency, durability, and recyclability, especially for office buildings. All these features of steel show its sustainable potential. Consumers are becoming increasingly concerned about the environment. They need to be able to make informed decisions about the impact of their actions. This publication is aimed at setting out key themes for the design and construction of sustainable buildings. Examples of office building environmental analyses are presented to illustrate how this is being achieved in steel construction.

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