Research on the recovery of the lunar gravity from simulant orbit perturbation data

2009 ◽  
Author(s):  
K. Zeng ◽  
J. C. Li ◽  
Y. Fang
Keyword(s):  
Lunar Gravity ◽  
Orbit Perturbation ◽  
Perturbation Data

Saturn's E, G and F rings: modulated by the plasma sheet

1984 ◽  
Vol 75 ◽  
pp. 597
Author(s):  
E. Grün ◽  
G.E. Morfill ◽  
T.V. Johnson ◽  
G.H. Schwehm
Keyword(s):  
Solar Wind ◽  
Direct Contact ◽  
Transport Processes ◽  
Time Variable ◽  
Dust Particles ◽  
Spatial Diffusion ◽  
Drag Forces ◽  
Orbit Perturbation ◽  
Time Variations ◽  
F Ring

ABSTRACTSaturn's broad E ring, the narrow G ring and the structured and apparently time variable F ring(s), contain many micron and sub-micron sized particles, which make up the “visible” component. These rings (or ring systems) are in direct contact with magnetospheric plasma. Fluctuations in the plasma density and/or mean energy, due to magnetospheric and solar wind processes, may induce stochastic charge variations on the dust particles, which in turn lead to an orbit perturbation and spatial diffusion. It is suggested that the extent of the E ring and the braided, kinky structure of certain portions of the F rings as well as possible time variations are a result of plasma induced electromagnetic perturbations and drag forces. The G ring, in this scenario, requires some form of shepherding and should be akin to the F ring in structure. Sputtering of micron-sized dust particles in the E ring by magnetospheric ions yields lifetimes of 102to 104years. This effect as well as the plasma induced transport processes require an active source for the E ring, probably Enceladus.

scholarly journals Additive Manufacturing Under Lunar Gravity and Microgravity

2021 ◽  
Vol 33 (2) ◽  
Author(s):  
B. Reitz ◽  
C. Lotz ◽  
N. Gerdes ◽  
S. Linke ◽  
E. Olsen ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Spare Parts ◽  
Manufacturing Processes ◽  
Complex Structures ◽  
Lunar Gravity ◽  
Limited Extent ◽  
Test Environment ◽  
Manufacturing Tests ◽  
Laser Experiments ◽  
Materials Used

AbstractMankind is setting to colonize space, for which the manufacturing of habitats, tools, spare parts and other infrastructure is required. Commercial manufacturing processes are already well engineered under standard conditions on Earth, which means under Earth’s gravity and atmosphere. Based on the literature review, additive manufacturing under lunar and other space gravitational conditions have only been researched to a very limited extent. Especially, additive manufacturing offers many advantages, as it can produce complex structures while saving resources. The materials used do not have to be taken along on the mission, they can even be mined and processed on-site. The Einstein-Elevator offers a unique test environment for experiments under different gravitational conditions. Laser experiments on selectively melting regolith simulant are successfully conducted under lunar gravity and microgravity. The created samples are characterized in terms of their geometry, mass and porosity. These experiments are the first additive manufacturing tests under lunar gravity worldwide.

Trajectory Design in the Sun-Earth-Moon System Using Lunar Gravity Assists

1998 ◽  
Vol 35 (2) ◽  
pp. 191-198 ◽  
Author(s):  
Roby S. Wilson ◽  
Kathleen C. Howell
Keyword(s):  
Trajectory Design ◽  
The Sun ◽  
Lunar Gravity ◽  
Moon System ◽  
Gravity Assists

Ligand Field-Spin Orbit Energy Levels in the d4 and d6 Electron Configurations of Octahedral and Tetrahedral Symmetry

1974 ◽  
Vol 29 (1) ◽  
pp. 31-41 ◽  
Author(s):  
E. König ◽  
S. Kremer
Keyword(s):  
Strong Field ◽  
Energy Levels ◽  
Coulomb Repulsion ◽  
Orbit Interaction ◽  
Complete Agreement ◽  
Ligand Field ◽  
Spin Orbit ◽  
Tetrahedral Symmetry ◽  
Spin Orbit Interaction ◽  
Orbit Perturbation

The complete ligand field -Coulomb repulsion -spin orbit interaction matrices have been derived for the d4 and d6 electron configurations within octahedral (Oh) and tetrahedral (Td) symmetry. The calculations were perform ed in both the weak-field and strong-field coupling schemes and complete agreement of the results was achieved. The energy matrices are parametrically dependent on ligand field (Dq), Coulomb repulsion (B, C) and spin-orbit interaction (ζ). Correct energy diagrams are presentend which display the splittings by spin-orbit perturbation as well as the effect of configuration mixing. Applications to the interpretation of optical spectral data, to the detailed behavior at the crossover of ground terms, and to complete studies in magnetism are pointed out.

A method to determine regional lunar gravity fields from earth-based satellite tracking data

2005 ◽  
Vol 53 (13) ◽  
pp. 1331-1340 ◽  
Author(s):  
S. Goossens ◽  
P.N.A.M. Visser ◽  
B.A.C. Ambrosius
Keyword(s):  
Satellite Tracking ◽  
Tracking Data ◽  
Lunar Gravity ◽  
Gravity Fields

Work in Reduced-Gravity Environments

1969 ◽  
Vol 11 (5) ◽  
pp. 433-439 ◽  
Author(s):  
E. C. Wortz
Keyword(s):  
Human Performance ◽  
Research Data ◽  
Lunar Gravity ◽  
Reduced Gravity

Research data on human performance in weightless and lunar-gravity environment are considered on a single continuum of reduced traction. Apparent contradictions in the effects of reduced gravity on tasks requiring the use of the upper torso and those requiring locomotion are resolved. It is concluded that reduced traction systematically reduces the efficiency of work in all reduced-gravity conditions.

Speech Waveform Perturbation Analysis

1986 ◽  
Vol 29 (1) ◽  
pp. 50-64 ◽  
Author(s):  
Anders G. Askenfelt ◽  
Britta Hammarberg
Keyword(s):  
Relative Frequency ◽  
Clinical Applications ◽  
Rate Of Change ◽  
Frequency Of Occurrence ◽  
Pitch Period ◽  
Acoustic Measures ◽  
Before And After ◽  
Perturbation Data ◽  
Acoustic Measure ◽  
Pathological Voice

The performance of seven acoustic measures of cycle-to-cycle variations (perturbations) in the speech waveform was compared. All measures were calculated automatically and applied on running speech. Three of the measures refer to the frequency of occurrence and severity of waveform perturbations in special selected parts of the speech, identified by means of the rate of change in the fundamental frequency. Three other measures refer to statistical properties of the distribution of the relative frequency differences between adjacent pitch periods. One perturbation measure refers to the percentage of consecutive pitch period differences with alternating signs. The acoustic measures were tested on tape recorded speech samples from 41 voice patients, before and after successful therapy. Scattergrams of acoustic waveform perturbation data versus an average of perceived deviant voice qualities, as rated by voice clinicians, are presented. The perturbation measures were compared with regard to the acoustic-perceptual correlation and their ability to discriminate between normal and pathological voice status. The standard deviation of the distribution of the relative frequency differences was suggested as the most useful acoustic measure of waveform perturbations for clinical applications.

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