scholarly journals Triggering Comet-Like Activity of Main Belt Comets

2015 ◽  
Vol 10 (S318) ◽  
pp. 135-141
Author(s):  
N. Haghighipour ◽  
T. I. Maindl ◽  
C. Schäfer ◽  
R. Speith ◽  
R. Dvorak
Keyword(s):  
Impact Angle ◽  
Material Strength ◽  
Main Belt ◽  
Water Ice ◽  
New Class ◽  
Energy Impact ◽  
Particle Hydrodynamics ◽  
Fracture Models ◽  
The Impact

AbstractMain Belt Comets (MBCs) have attracted a great deal of interest since their identification as a new class of bodies by Hsieh and Jewitt in 2006. Much of this interest is due to the implication that MBC activity is driven by the sublimation of volatile material (presumed to be water-ice) presenting these bodies as probable candidates for the delivery of a significant fraction of Earth's water. Results of the studies of the dynamics of MBCs suggest that these objects might have formed in-situ as the remnants of the break-up of large icy asteroids. Simulations also show that collisions among MBCs and small objects could have played an important role in triggering the cometary activity of these bodies. Such collisions might have exposed sub-surface water-ice which sublimated and created thin atmospheres and tails around MBCs. In order to drive the effort of understanding the nature of the activation of MBCs, we have investigated these collision processes by simulating the impacts in detail using a smooth particle hydrodynamics (SPH) approach that includes material strength and fracture models. We have carried out simulations for a range of impact velocities and angles, allowing m-sized impactors to erode enough of an MBC's surface to expose volatiles and trigger its activation. Impact velocities were varied between 0.5 km/s and 5.3 km/s, and the projectile radius was chosen to be 1 m. As expected, we observe significantly different crater depths depending on the impact energy, impact angle, and MBC's material strength. Results show that for all values of impact velocity and angle, crater depths are only a few meters, implying that if the activity of MBCs is due to the sublimation of water-ice, ice has to exist in no deeper than a few meters from the surface. We present details of our simulations and discuss the implications of their results.

scholarly journals Binary asteroid (31) Euphrosyne: ice-rich and nearly spherical

2020 ◽  
Vol 641 ◽  
pp. A80
Author(s):  
B. Yang ◽  
J. Hanuš ◽  
B. Carry ◽  
P. Vernazza ◽  
M. Brož ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Family Formation ◽  
Large Fraction ◽  
Imaging Study ◽  
Spherical Shape ◽  
Hydrostatic Equilibrium ◽  
Main Belt ◽  
Binary Asteroid ◽  
Water Ice ◽  
The Impact

Aims. Asteroid (31) Euphrosyne is one of the biggest objects in the asteroid main belt and it is also the largest member of its namesake family. The Euphrosyne family occupies a highly inclined region in the outer main belt and contains a remarkably large number of members, which is interpreted as an outcome of a disruptive cratering event. Methods. The goals of this adaptive-optics imaging study are threefold: to characterize the shape of Euphrosyne, to constrain its density, and to search for the large craters that may be associated with the family formation event. Results. We obtained disk-resolved images of Euphrosyne using SPHERE/ZIMPOL at the ESO 8.2 m VLT as part of our large program (ID: 199.C-0074, PI: Vernazza). We reconstructed its 3D shape via the ADAM shape modeling algorithm based on the SPHERE images and the available light curves of this asteroid. We analyzed the dynamics of the satellite with the Genoid meta-heuristic algorithm. Finally, we studied the shape of Euphrosyne using hydrostatic equilibrium models. Conclusions. Our SPHERE observations show that Euphrosyne has a nearly spherical shape with the sphericity index of 0.9888 and its surface lacks large impact craters. Euphrosyne’s diameter is 268 ± 6 km, making it one of the top ten largest main belt asteroids. We detected a satellite of Euphrosyne – S/2019 (31) 1 – that is about 4 km across, on a circular orbit. The mass determined from the orbit of the satellite together with the volume computed from the shape model imply a density of 1665 ± 242 kg m−3, suggesting that Euphrosyne probably contains a large fraction of water ice in its interior. We find that the spherical shape of Euphrosyne is a result of the reaccumulation process following the impact, as in the case of (10) Hygiea. However, our shape analysis reveals that, contrary to Hygiea, the axis ratios of Euphrosyne significantly differ from those suggested by fluid hydrostatic equilibrium following reaccumulation.

scholarly journals Mesospheric dust and its secondary effects as observed by the ESPRIT payload

2009 ◽  
Vol 27 (3) ◽  
pp. 1119-1128 ◽  
Author(s):  
O. Havnes ◽  
L. H. Surdal ◽  
C. R. Philbrick
Keyword(s):  
Charge Density ◽  
Lower Layer ◽  
Bound Water ◽  
Impact Angle ◽  
Dust Particles ◽  
Height Range ◽  
Dust Layer ◽  
Water Ice ◽  
Dust Charge ◽  
The Impact

Abstract. The dust detector on the ESPRIT rocket detected two extended dust/aerosol layers during the launch on 1 July 2006. The lower layer at height ~81.5–83 km coincided with a strong NLC and PMSE layer. The maximum dust charge density was ~−3.5×109 e m−3 and the dust layer was characterized by a few strong dust layers where the dust charge density at the upper edges changed by factors 2–3 over a distance of ≲10 m, while the same change at their lower edges were much more gradual. The upper edge of this layer is also sharp, with a change in the probe current from zero to IDC=−10−11 A over ~10 m, while the same change at the low edge occurs over ~500 m. The second dust layer at ~85–92 km was in the height range of a comparatively weak PMSE layer and the maximum dust charge density was ~−108 e m−3. This demonstrates that PMSE can be formed even if the ratio of the dust charge density to the electron density P=NdZd /n_e≲0.01. In spite of the dust detector being constructed to reduce possible secondary charging effects from dust impacts, it was found that they were clearly present during the passage through both layers. The measured secondary charging effects confirm recent results that dust in the NLC and PMSE layers can be very effective in producing secondary charges with up to ~50 to 100 electron charges being rubbed off by one impacting large dust particle, if the impact angle is θi≳20–35°. This again lends support to the suggested model for NLC and PMSE dust particles (Havnes and Næsheim, 2007) as a loosely bound water-ice clump interspersed with a considerable number of sub-nanometer-sized meteoric smoke particles, possibly also contaminated with meteoric atomic species.

Analysis of surface-erosion mechanism due to impacts of freely rotating angular particles using smoothed particle hydrodynamics erosion model

2017 ◽  
Vol 231 (12) ◽  
pp. 1537-1551 ◽  
Author(s):  
Xiangwei Dong ◽  
Zengliang Li ◽  
Qi Zhang ◽  
Wei Zeng ◽  
G.R. Liu
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Impact Angle ◽  
Surface Erosion ◽  
Free Rotation ◽  
Erosion Model ◽  
Erosion Mechanism ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
The Impact ◽  
Angular Particles

The free rotation of an angular particle during its impact on ductile surfaces is an important factor that influences the erosion mechanism. However, the phenomenon cannot be easily revealed experimentally because the incident conditions cannot be accurately controlled. In this study, a novel erosion model based on smoothed particle hydrodynamics method is proposed to simulate single and multiple impacts of particles with specified angularities on a ductile surface. The model can simulate a particle having free rotation during the impact process and initial rotation prior to the impact. The results show that the impact angle and initial orientation significantly affect the tumbling behavior, which determines the erosion mechanism. Moreover, the initial rotation is investigated by assigning an initial angular velocity to the particle at the onset of impact. The proposed smoothed particle hydrodynamics erosion model is proven to be a promising complementary method that supports experimental techniques. This study provides insight for understanding the fundamental mechanisms of surface erosion due to angular particles.

scholarly journals Numerical Simulation of Impact Behavior of Ceramic Coatings Using Smoothed Particle Hydrodynamics Method

2020 ◽  
pp. 1-25
Author(s):  
Jian Zhang ◽  
Zhe Lu ◽  
Sugrim Sagar ◽  
Hyunhee Choi ◽  
Heesung Park ◽  
...  
Keyword(s):  
Spherical Particle ◽  
Smoothed Particle Hydrodynamics ◽  
Coating Layer ◽  
Ceramic Coatings ◽  
Impact Angle ◽  
Impact Behavior ◽  
Sph Method ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
The Impact

Abstract In this work, the impact behavior of an alumina spherical particle on alumina coating is modeled using the smoothed particle hydrodynamics (SPH) method. The effects of impact angle (0°, 30°, and 60°) and velocity (100 m/s, 200 m/s, and 300 m/s) on the morphology changes of the impact pit and impacting particle, and their associated stress and energy are investigated. The results show that the combination of impact angle of 0° and velocity of 300 m/s produces the highest penetration depth and largest stress and deformation in the coating layer, while the combination of 100 m/s & 60° causes the minimum damage to the coating layer. This is because the penetration depth is determined by the vertical velocity component difference between the impacting particle and the coating layer, but irrelevant to the horizontal component. The total energy of the coating layer increases with the time, while the internal energy increases with the time after some peak values, which is due to energy transmission from the spherical particle to the coating layer and the stress shock waves. The energy transmission from impacting particle to coating layer increases with the increasing particle velocity, and decreases with the increasing inclined angle. The simulated impact pit morphology is qualitatively similar to the experimental observation. This work demonstrates that the SPH method is useful to analyze the impact behavior of ceramic coatings.

Rigid-Object Water-Entry Impact Dynamics: Finite-Element/Smoothed Particle Hydrodynamics Modeling and Experimental Validation

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Ravi Challa ◽  
Solomon C. Yim ◽  
V. G. Idichandy ◽  
C. P. Vendhan
Keyword(s):  
Finite Element ◽  
Smoothed Particle Hydrodynamics ◽  
Material Strength ◽  
Water Impact ◽  
Numerical Predictions ◽  
Wide Range ◽  
Particle Hydrodynamics ◽  
Drop Tests ◽  
Smoothed Particle ◽  
The Impact

A numerical study on the dynamic response of a generic rigid water-landing object (WLO) during water impact is presented in this paper. The effect of this impact is often prominent in the design phase of the re-entry project to determine the maximum force for material strength determination to ensure structural and equipment integrity, human safety and comfort. The predictive capability of the explicit finite-element (FE) arbitrary Lagrangian-Eulerian (ALE) and smoothed particle hydrodynamics (SPH) methods of a state-of-the-art nonlinear dynamic finite-element code for simulation of coupled dynamic fluid structure interaction (FSI) responses of the splashdown event of a WLO were evaluated. The numerical predictions are first validated with experimental data for maximum impact accelerations and then used to supplement experimental drop tests to establish trends over a wide range of conditions including variations in vertical velocity, entry angle, and object weight. The numerical results show that the fully coupled FSI models can capture the water-impact response accurately for all range of drop tests considered, and the impact acceleration varies practically linearly with increase in drop height. In view of the good comparison between the experimental and numerical simulations, both models can readily be employed for parametric studies and for studying the prototype splashdown under more realistic field conditions in the oceans.

scholarly journals The impact of focused ion beam induced damage on scanning spreading resistance microscopy measurements

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Komal Pandey ◽  
Kristof Paredis ◽  
Thomas Hantschel ◽  
Chris Drijbooms ◽  
Wilfried Vandervorst
Keyword(s):  
Focused Ion Beam ◽  
Ion Beam ◽  
Three Dimensional ◽  
Region Of Interest ◽  
Amorphous Region ◽  
Impact Angle ◽  
Spreading Resistance ◽  
Energy Impact ◽  
The Impact ◽  
Dopant Deactivation

Abstract Scanning Spreading Resistance Microscopy is a well-established technique for obtaining quantitative two- and three-dimensional carrier profiles in semiconductor devices with sub-nm spatial resolution. However, for sub-100 nm devices, the use of focused ion beam becomes inevitable for exposing the region of interest on a sample cross section. In this work, we investigate the impact of the focused ion beam milling on spreading resistance analysis and we show that the electrical effect of the focused ion beam extends far beyond the amorphous region and depends on the dopant concentration, ion beam energy, impact angle, and current density. For example, for dopant concentrations between 1.0 × 1020 and 1.5 × 1016 cm−3 we observe dopant deactivation at least between 23 and 175 nm for a glancing 30 keV ion beam. Further, we show that dopant deactivation is caused by defect diffusion during milling and is not directly impacted by the presence of Gallium in the sample. Later, we also discuss potential ways to mitigate these effects.

High-Energy Impact Certification of Aero Structures: Experiments and Numerical Simulations

2015 ◽  
Vol 237 ◽  
pp. 233-238
Author(s):  
Grzegorz Socha ◽  
Sebastian Szałkowski ◽  
Andrzej Zbrowski
Keyword(s):  
Numerical Simulations ◽  
Impact Resistance ◽  
Experimental Tests ◽  
High Energy ◽  
Sustainable Technologies ◽  
Impact Tests ◽  
Energy Impact ◽  
Particle Hydrodynamics ◽  
Real Objects ◽  
The Impact

The article presents the test results obtained from the “Research methods and systems for the investigation on impact resistance of elements of aero structures and land vehicles aimed at the assessment of passenger safety” R&D project that was jointly executed by the Institute of Aviation, the Institute for Sustainable Technologies – National Research Institute, and the PZL Mielec. The main objective of the project was to perform impact tests of the windscreen and the vertical stabilizer of the PZL M28 Skytruck. The experimental tests were conducted for real objects in full scale. The investigations were carried out using an original 250 mm pneumatic gun. Apart from the impact tests, the project was also focused on numerical simulations of impacts employing the Finite Element Method (test object modelling) and the Smoothed Particle Hydrodynamics methods (the model of the gelatine projectile). The authors compare the results of experimental tests and numerical simulations. They present the differences in the results obtained and analyse the reasons behind these discrepancies, and based on the analysis, they conclude that the main cause for them is the simplified mathematical model describing the behaviour of the material subjected to dynamic loads, which was used in numerical simulations.

Finite-Element and Smoothed Particle Hydrodynamics Modeling of Rigid-Object Water-Entry Impact Dynamics and Validation With Experimental Results

2010 ◽  
Author(s):  
Ravi Challa ◽  
Solomon Yim ◽  
V. G. Idichandy ◽  
C. P. Vendhan
Keyword(s):  
Finite Element ◽  
Smoothed Particle Hydrodynamics ◽  
Material Strength ◽  
Water Impact ◽  
Numerical Predictions ◽  
Wide Range ◽  
Particle Hydrodynamics ◽  
Drop Tests ◽  
Smoothed Particle ◽  
The Impact

A numerical study on the dynamic response of a generic rigid water-landing object (WLO) during water impact is presented in this paper. The effect of this impact is often prominent in the design phase of the re-entry project, to determine the maximum force it is subjected to, for material strength determination to ensure structural and equipment integrity, human safety and comfort. The predictive capability of the explicit finite-element arbitrary Lagrangian-Eulerian (ALE) and smoothed particle hydrodynamics (SPH) methods of a state-of-the-art nonlinear dynamic finite-element code for simulation of coupled dynamic fluid structure interaction (FSI) responses of the splashdown event of a WLO were evaluated. The numerical predictions are first validated with experimental data for the maximum impact accelerations and then used to supplement experimental drop tests to establish trends over a wide range of conditions including variations in vertical velocity, entry angle and object weight. The results show that the fully coupled FSI models can capture the water-impact response accurately for all range of drop tests considered and the impact accelerations are practically linearly with the increase in the height of the drop. The reliability of the maximum impact accelerations was calibrated with approximate classical von Karman and Wagner closed-form solutions.

scholarly journals Toward understanding the origin of asteroid geometries

2018 ◽  
Vol 620 ◽  
pp. A167 ◽  
Author(s):  
K. Sugiura ◽  
H. Kobayashi ◽  
S. Inutsuka
Keyword(s):  
Major Axis ◽  
Impact Angle ◽  
Equal Mass ◽  
Low Velocity ◽  
Irregular Shapes ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Model Of Friction ◽  
Self Gravity ◽  
The Impact

More than a half of the asteroids in the main belt have irregular shapes with ratios of the minor to major axis lengths of less than 0.6. One of the mechanisms that create such shapes is collisions between asteroids. The relationship between the shapes of collisional outcomes and impact conditions such as impact velocities may provide information on the collisional environments and its evolutionary stages when those asteroids are created. In this study, we perform numerical simulations of collisional destruction of asteroids with radii 50 km and subsequent gravitational reaccumulation using smoothed-particle hydrodynamics for elastic dynamics with self-gravity, a model of rock fractures, and a model of friction in completely damaged rock. We systematically vary the impact velocity from 50 to 400 m s−1 and the impact angle from 5° to 45°. We investigate shapes of the largest remnants resulting from collisional simulations. As a result, various shapes (bilobed, spherical, flat, elongated, and hemispherical shapes) are formed through equal-mass and low-velocity (50−400 m s−1) impacts. We clarify a range of the impact angle and velocity to form each shape. Our results indicate that irregular shapes, especially flat shapes, of asteroids with diameters larger than 80 km are likely to be formed through similar-mass and low-velocity impacts, which are likely to occur in the primordial environment prior to the formation of Jupiter.

scholarly journals Dynamics, Origin, and Activation of Main Belt Comets

2009 ◽  
Vol 5 (S263) ◽  
pp. 207-214 ◽  
Author(s):  
Nader Haghighipour
Keyword(s):  
Numerical Modeling ◽  
Surface Water ◽  
Outer Part ◽  
Asteroid Belt ◽  
Activation Mechanism ◽  
Main Belt ◽  
Water Ice ◽  
Numerical Studies ◽  
Cometary Activity

AbstractThe discovery of Main Belt Comets (MBCs) has raised many questions regarding the origin and activation mechanism of these objects. Results of a study of the dynamics of these bodies suggest that MBCs were formed in-situ as the remnants of the break-up of large icy asteroids. Simulations show that similar to the asteroids in the main belt, MBCs with orbital eccentricities smaller than 0.2 and inclinations lower than 25° have stable orbits implying that many MBCs with initially larger eccentricities and inclinations might have been scattered to other regions of the asteroid belt. Among scattered MBCs, approximately 20% reach the region of terrestrial planets where they might have contributed to the accumulation of water on Earth. Simulations also show that collisions among MBCs and small objects could have played an important role in triggering the cometary activity of these bodies. Such collisions might have exposed sub-surface water ice which sublimated and created thin atmospheres and tails around MBCs. This paper discusses the results of numerical studies of the dynamics of MBCs and their implications for the origin of these objects. The results of a large numerical modeling of the collisions of m-sized bodies with km-sized asteroids in the outer part of the asteroid belt are also presented and the viability of the collision-triggering activation scenario is discussed.

Sign in / Sign up

Export Citation Format

Share Document