The Experts below are selected from a list of 22149 Experts worldwide ranked by ideXlab platform
Tong Zhou - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic performance of Lunar Surface nuclear power system with heat sink temperature change in a rotational period
Applied Thermal Engineering, 2018Co-Authors: Senqing Fan, Tong ZhouAbstract:Abstract The thermodynamic performance of the Lunar Surface nuclear power system with Free-Piston Stirling Engines (FPSE) was analyzed based on the energy conservation of the system. The heat sink temperature was assumed to follow the sine function law. The cold side temperature of the FPSE was changing with time in a rotational period and would be increased with the increase of the heat sink temperature. The thermodynamic performance of the power system was changing with lower thermal efficiency and high amount of exhaust heat rejection, during the day time with heat sink temperature higher than 200 K. During the dark time, the power system could be kept as a steady state with higher thermal efficiency and less amount of exhaust heat rejection. The energy storage option could be required, if the electrical power output was expected to meet the grid. The highest thermal efficiency could be increased from 0.21 to 0.235, if the area of the heat rejection system was increased from 120 m2 to 180 m2, since the cold side temperature of the PFSE could be decreased. Larger area of the heat rejection system could increase the specific area but has the advantage of lightweight for the power system.
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thermodynamic analysis and optimization of a stirling cycle for Lunar Surface nuclear power system
Applied Thermal Engineering, 2017Co-Authors: Senqing Fan, Tong ZhouAbstract:Abstract A model for the description of the thermal efficiency of a Lunar Surface nuclear reactor power system with eight free piston Stirling engines to generate nominal electrical power of 100 kWe was developed. The heat loss of the hot heat pipes, finite rate heat transfer, regenerative heat loss, finite regeneration process time and conductive thermal bridging losses were considered. The results showed that the thermal efficiency increased and then decreased with the hot side temperature increase. The highest thermal efficiency was about 0.29 under the condition of the effectiveness of the regenerator being 0.9 and compression ratio being 2. Higher cold side temperature had bad effect on the thermal efficiency but could reduce the size of the heat rejection system. When the cold side temperature was designed as 500 K, the lowest power system mass of 6.6 ton could be obtained. Enhanced heat transfer of the heat exchangers would increase the thermal efficiency but higher values of the nominal convection heat transfer coefficient of the heat exchangers would lead to a negligible thermal efficiency increase. The results obtained here may provide a new ideal to design Lunar Surface nuclear powered Stirling cycle.
A R Poppe - One of the best experts on this subject based on the ideXlab platform.
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artemis observations of solar wind proton scattering off the Lunar Surface
Journal of Geophysical Research, 2018Co-Authors: A R Poppe, J S Halekas, Charles Lue, J P McfaddenAbstract:We study the scattering of solar wind protons off the Lunar Surface, using ion observations collected over 6 years by the ARTEMIS satellites at the Moon. We show the average scattered proton energy spectra, directional scattering distributions, and scattering efficiency, for different solar wind incidence angles and impact speeds. We find that the protons have a scattering distribution that is similar to existing empirical models for scattered hydrogen energetic neutral atoms, with a peak in the backward direction (toward the Sun). We provide a revised model for the scattered proton energy spectrum. We evaluate the positive to neutral charge state ratio by comparing the proton spectrum with existing models for scattered hydrogen. The positive to neutral ratio increases with increasing exit speed from the Surface but decreases with increasing impact speed. Combined, these counteracting effects result in a scattering efficiency that decreases from ~0.5% at 300 km/s solar wind speed to ~0.3% at 600 km/s solar wind speed.
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anisotropic solar wind sputtering of the Lunar Surface induced by crustal magnetic anomalies
Geophysical Research Letters, 2014Co-Authors: A R Poppe, J S Halekas, M Sarantos, G T Delory, Y SaitoAbstract:The Lunar exosphere is generated by several processes each of which generates neutral distributions with different spatial and temporal variability. Solar wind sputtering of the Lunar Surface is a major process for many regolith-derived species and typically generates neutral distributions with a cosine dependence on solar zenith angle. Complicating this picture are remanent crustal magnetic anomalies on the Lunar Surface, which decelerate and partially reflect the solar wind before it strikes the Surface. We use Kaguya maps of solar wind reflection efficiencies, Lunar Prospector maps of crustal field strengths, and published neutral sputtering yields to calculate anisotropic solar wind sputtering maps. We feed these maps to a Monte Carlo neutral exospheric model to explore three-dimensional exospheric anisotropies and find that significant anisotropies should be present in the neutral exosphere depending on selenographic location and solar wind conditions. Better understanding of solar wind/crustal anomaly interactions could potentially improve our results.
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negative potentials above the day side Lunar Surface in the terrestrial plasma sheet evidence of non monotonic potentials
Geophysical Research Letters, 2011Co-Authors: M Horanyi, A R Poppe, J S HalekasAbstract:[1] The Lunar Prospector (LP) Electron Reflectometer (ER) instrument conducted a series of measurements of the Lunar Surface potential in a variety of conditions. Occasionally, when the Moon was exposed to the terrestrial plasma sheet and in daylight, large, unexpected negative potentials (∼−500 V) were measured. In this paper, we compare LP ER measurements with one-dimensional particle-in-cell simulations of the potential above the Lunar Surface when the Moon is exposed to both solar UV radiation and the terrestrial plasma sheet. The simulations show that large negative potentials will be measured by LP ER due to the presence of stable, non-monotonic potentials. Implications of these measurements to other airless bodies in the solar system are also discussed.
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simulations of the photoelectron sheath and dust levitation on the Lunar Surface
Journal of Geophysical Research, 2010Co-Authors: A R Poppe, M HoranyiAbstract:[1] The Lunar Surface represents a complex plasma environment due to the presence of solar ultraviolet (UV) radiation, the incoming solar wind flux and charged, levitated micron- and sub-micron sized dust particles. Photoemission due to solar UV radiation dominates the charging environment, creating a photoelectron sheath above the Lunar Surface. To further investigate the dusty plasma environment on the Surface of the Moon, a one-dimensional particle-in-cell (PIC) code has been designed specifically for the Lunar Surface. The code has been validated against analytic solutions for photoelectron sheaths with basic photoelectron energy distributions. Simulations have focused on the role of the emitted photoelectron energy distribution and solar UV variability in determining the sheath profile. Additionally, the charging and levitation of test dust particles in the photoelectron sheath are studied. Limits on the maximum size and height of levitated dust grains are also presented.
M Horanyi - One of the best experts on this subject based on the ideXlab platform.
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impacts of fast meteoroids and a plasma dust cloud over the Lunar Surface
Jetp Letters, 2017Co-Authors: S I Popel, A P Golub, L M Zelenyi, M HoranyiAbstract:The possibility of the formation of a plasma–dust cloud in the exosphere of the Moon owing to impacts of meteoroids on the Lunar Surface is discussed. Attention is focused on dust particles at large altitudes of ~10–100 km at which measurements were performed within the NASA LADEE mission. It has been shown that a melted material ejected from the Lunar Surface owing to the impacts of meteoroids plays an important role in the formation of the plasma–dust cloud. Drops of the melted material acquire velocities in the range between the first and second cosmic velocities for the Moon and can undergo finite motion around it. Rising over the Lunar Surface, liquid drops are solidified and acquire electric charges, in particular, owing to their interaction with electrons and ions of the solar wind, as well as with solar radiation. It has been shown that the number density of dust particles in the plasma–dust cloud present in the exosphere of the Moon is ≲10−8 cm−3, which is in agreement with the LADEE measurements.
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laboratory investigation of Lunar Surface electric potentials in magnetic anomaly regions
Geophysical Research Letters, 2015Co-Authors: Carollee Howes, X Wang, Jan Deca, M HoranyiAbstract:To gain insight into Lunar Surface charging in the magnetic anomaly regions, we present the results of laboratory experiments with a flowing plasma engulfing a magnetic dipole field above an insulating Surface. When the dipole moment is perpendicular to the Surface, large positive potentials (close to ion flow energies in eV) are measured on the Surface in the dipole lobe regions, charged by the unmagnetized ions while the electrons are magnetically excluded. The potential decreases exponentially with distance from the Surface on the ion (flow) Debye length scale. The Surface potentials become much smaller when the dipole moment is parallel to the Surface, likely due to collisionality. We discuss the implications of our laboratory results for the Lunar Surface charging in the magnetic anomaly regions, suggesting that the Surface potential may be much higher than the generally expected several volts positive due to photoemission.
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negative potentials above the day side Lunar Surface in the terrestrial plasma sheet evidence of non monotonic potentials
Geophysical Research Letters, 2011Co-Authors: M Horanyi, A R Poppe, J S HalekasAbstract:[1] The Lunar Prospector (LP) Electron Reflectometer (ER) instrument conducted a series of measurements of the Lunar Surface potential in a variety of conditions. Occasionally, when the Moon was exposed to the terrestrial plasma sheet and in daylight, large, unexpected negative potentials (∼−500 V) were measured. In this paper, we compare LP ER measurements with one-dimensional particle-in-cell simulations of the potential above the Lunar Surface when the Moon is exposed to both solar UV radiation and the terrestrial plasma sheet. The simulations show that large negative potentials will be measured by LP ER due to the presence of stable, non-monotonic potentials. Implications of these measurements to other airless bodies in the solar system are also discussed.
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simulations of the photoelectron sheath and dust levitation on the Lunar Surface
Journal of Geophysical Research, 2010Co-Authors: A R Poppe, M HoranyiAbstract:[1] The Lunar Surface represents a complex plasma environment due to the presence of solar ultraviolet (UV) radiation, the incoming solar wind flux and charged, levitated micron- and sub-micron sized dust particles. Photoemission due to solar UV radiation dominates the charging environment, creating a photoelectron sheath above the Lunar Surface. To further investigate the dusty plasma environment on the Surface of the Moon, a one-dimensional particle-in-cell (PIC) code has been designed specifically for the Lunar Surface. The code has been validated against analytic solutions for photoelectron sheaths with basic photoelectron energy distributions. Simulations have focused on the role of the emitted photoelectron energy distribution and solar UV variability in determining the sheath profile. Additionally, the charging and levitation of test dust particles in the photoelectron sheath are studied. Limits on the maximum size and height of levitated dust grains are also presented.
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Lunar Surface dust dynamics and regolith mechanics
Reviews of Geophysics, 2007Co-Authors: M Horanyi, J E Colwell, Susan N Batiste, Scott Robertson, Stein StureAbstract:[1] The Lunar Surface is characterized by a collisionally evolved regolith resulting from meteoroid bombardment. This Lunar soil consists of highly angular particles in a broad, approximately power law size distribution, with impact-generated glasses. The regolith becomes densified and difficult to excavate when subjected to Lunar quakes or, eventually, manned and unmanned activity on the Surface. Solar radiation and the solar wind produce a plasma sheath near the Lunar Surface. Lunar grains acquire charge in this environment and can exhibit unusual behavior, including levitation and transport across the Surface because of electric fields in the plasma sheath. The fine component of the Lunar regolith contributes to the operational and health hazards posed to planned Lunar expeditions. In this paper we discuss the mechanical response of the regolith to anticipated exploration activities and review the plasma environment near the Lunar Surface and the observations, models, and dynamics of charged Lunar dust.
M Santosh - One of the best experts on this subject based on the ideXlab platform.
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Lunar Surface mineralogy using hyperspectral data implications for primordial crust in the earth moon system
Geoscience frontiers, 2017Co-Authors: V Sivakumar, R Neelakantan, M SantoshAbstract:Mineralogy of the Lunar Surface provides important clues for understanding the composition and evolution of the primordial crust in the Earth–Moon system. The primary rock forming minerals on the Moon such as pyroxene, olivine and plagioclase are potential tools to evaluate the Lunar Magma Ocean (LMO) hypothesis. Here we use the data from Moon Mineralogy Mapper (M3) onboard the Chandrayaan-1 project of India, which provides Visible/Near Infra Red (NIR) spectral data (hyperspectral data) of the Lunar Surface to gain insights on the Surface mineralogy. Band shaping and spectral profiling methods are used for identifying minerals in five sites: the Moscoviense basin, Orientale basin, Apollo basin, Wegener crater-highland, and Hertzsprung basin. The common presence of plagioclase in these sites is in conformity with the anorthositic composition of the Lunar crust. Pyroxenes, olivine and Fe-Mg-spinel from the sample sites indicate the presence of gabbroic and basaltic components. The compositional difference in pyroxenes suggests magmatic differentiation on the Lunar Surface. Olivine contains OH/H2O band, indicating hydrous phase in the primordial magmas.
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Lunar Surface mineralogy using hyperspectral data: Implications for primordial crust in the Earth–Moon system
Elsevier, 2017Co-Authors: V Sivakumar, R Neelakantan, M SantoshAbstract:Mineralogy of the Lunar Surface provides important clues for understanding the composition and evolution of the primordial crust in the Earth–Moon system. The primary rock forming minerals on the Moon such as pyroxene, olivine and plagioclase are potential tools to evaluate the Lunar Magma Ocean (LMO) hypothesis. Here we use the data from Moon Mineralogy Mapper (M3) onboard the Chandrayaan-1 project of India, which provides Visible/Near Infra Red (NIR) spectral data (hyperspectral data) of the Lunar Surface to gain insights on the Surface mineralogy. Band shaping and spectral profiling methods are used for identifying minerals in five sites: the Moscoviense basin, Orientale basin, Apollo basin, Wegener crater-highland, and Hertzsprung basin. The common presence of plagioclase in these sites is in conformity with the anorthositic composition of the Lunar crust. Pyroxenes, olivine and Fe-Mg-spinel from the sample sites indicate the presence of gabbroic and basaltic components. The compositional difference in pyroxenes suggests magmatic differentiation on the Lunar Surface. Olivine contains OH/H2O band, indicating hydrous phase in the primordial magmas
Senqing Fan - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic performance of Lunar Surface nuclear power system with heat sink temperature change in a rotational period
Applied Thermal Engineering, 2018Co-Authors: Senqing Fan, Tong ZhouAbstract:Abstract The thermodynamic performance of the Lunar Surface nuclear power system with Free-Piston Stirling Engines (FPSE) was analyzed based on the energy conservation of the system. The heat sink temperature was assumed to follow the sine function law. The cold side temperature of the FPSE was changing with time in a rotational period and would be increased with the increase of the heat sink temperature. The thermodynamic performance of the power system was changing with lower thermal efficiency and high amount of exhaust heat rejection, during the day time with heat sink temperature higher than 200 K. During the dark time, the power system could be kept as a steady state with higher thermal efficiency and less amount of exhaust heat rejection. The energy storage option could be required, if the electrical power output was expected to meet the grid. The highest thermal efficiency could be increased from 0.21 to 0.235, if the area of the heat rejection system was increased from 120 m2 to 180 m2, since the cold side temperature of the PFSE could be decreased. Larger area of the heat rejection system could increase the specific area but has the advantage of lightweight for the power system.
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thermodynamic analysis and optimization of a stirling cycle for Lunar Surface nuclear power system
Applied Thermal Engineering, 2017Co-Authors: Senqing Fan, Tong ZhouAbstract:Abstract A model for the description of the thermal efficiency of a Lunar Surface nuclear reactor power system with eight free piston Stirling engines to generate nominal electrical power of 100 kWe was developed. The heat loss of the hot heat pipes, finite rate heat transfer, regenerative heat loss, finite regeneration process time and conductive thermal bridging losses were considered. The results showed that the thermal efficiency increased and then decreased with the hot side temperature increase. The highest thermal efficiency was about 0.29 under the condition of the effectiveness of the regenerator being 0.9 and compression ratio being 2. Higher cold side temperature had bad effect on the thermal efficiency but could reduce the size of the heat rejection system. When the cold side temperature was designed as 500 K, the lowest power system mass of 6.6 ton could be obtained. Enhanced heat transfer of the heat exchangers would increase the thermal efficiency but higher values of the nominal convection heat transfer coefficient of the heat exchangers would lead to a negligible thermal efficiency increase. The results obtained here may provide a new ideal to design Lunar Surface nuclear powered Stirling cycle.
