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Results for “LUNAR GRAVITATION”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Central peaks in Mercurian craters - Comparisons to the moon

A key question in cratering studies continues to be the mode of formation of central structures. Studies of central peaks, the smallest and simplest central features found in impact structures, could provide clues to the formational mechanisms of the entire morphologic sequence of central features. The present investigation is concerned with a systematic examination of central peaks in fresh Mercurian craters, and a comparison of Mercurian and lunar central peak morphometry and morphology. It is found that the central peak diameter/rim diameter relation on Mercury is indistinguishable from the lunar case. The gravitational field strength of the planet, therefore, does not appear to be the dominant force controlling central peak formation. Of the presently proposed processes for central peak formation, dynamic rebound best fits current observations.

Hale, W.↗
NASA NTRS1994

Conversion Of Classical Orbital Elements

OSMEAN is sophisticated program that converts between osculating and mean classical orbital elements. Enables engineer to exploit advantages of each approach for design and planning or orbital trajectories and maneuvers. Converts mean elements to osculating elements or vice-versa. Conversion based on mathematical modeling of all first-order aspherical terrestrial, lunar, and solar gravitational perturbations plus second-order aspherical term based on second-degree central-body zonal perturbation. Written in FORTRAN 77.

Guinn, Joseph R.↗
NASA NTRS1961

A Comparison of Theory and Observation of the Echo I Satellite

Observations of the Echo I balloon satellite have been compared with a theory including the following perturbing effects: (1) solar radiation pressure; (2) lunar and solar gravitation; (3) second, third, and fourth harmonics of the earth's gravitational potential; and (4) atmospheric drag. With a set of orbital elements at the 26th day of the lifetime of the satellite, it was possible to match the observational data to 180 days with root mean square residuals as follows: Delta-a = 17.9 km, Delta-e = 0.0021, Delta-i = 0.0177 deg., Delta-omega = 1.1231 deg., Delta-Omega = 0.4821 deg., Delta-perigee height = 7.50 km. No differential correction has been applied as yet. Values of atmospheric density between 1500 and 930 km, assuming neutral drag effects only, have been inferred from the orbital data. The connection between solar activity and drag is also examined. As the Echo I perigee height continues to oscillate between 900 and 1500 km, more valuable orbital data will be obtained and atmospheric properties will be deduced. Further refinements in the mathematical model, especially in a time-dependent model atmosphere, should bring a substantial reduction in the residuals of the observations.

Bryant, R. W.↗
NASA NTRS1999

Optimization of Insertion Cost for Transfer Trajectories to Libration Point Orbits

The objective of this work is the development of efficient techniques to optimize the cost associated with transfer trajectories to libration point orbits in the Sun-Earth-Moon four body problem, that may include lunar gravity assists. Initially, dynamical systems theory is used to determine invariant manifolds associated with the desired libration point orbit. These manifolds are employed to produce an initial approximation to the transfer trajectory. Specific trajectory requirements such as, transfer injection constraints, inclusion of phasing loops, and targeting of a specified state on the manifold are then incorporated into the design of the transfer trajectory. A two level differential corrections process is used to produce a fully continuous trajectory that satisfies the design constraints, and includes appropriate lunar and solar gravitational models. Based on this methodology, and using the manifold structure from dynamical systems theory, a technique is presented to optimize the cost associated with insertion onto a specified libration point orbit.

Howell, K. C.↗
NASA NTRSDate not supplied

Autonomous Burn Targeting for a Lunar Sortie Staged From a Near-Rectilinear Halo Orbit

NASA is planning manned lunar landings starting in the mid 2020s as part of its Artemis program. These lunar sortie missions will be staged from a Near-Rectilinear Halo Orbit (NRHO), with a requirement for the lander to autonomously determine the timing and targets for multiple burns so that it can navigate its way back to the staging vehicle in the NRHO. The lander mission profile transitions through multiple gravitational regimes, at times influenced equally by 3rd bodies (Earth and Sun) as much as by the Moon, while at other times the lander is primarily influenced by lunar gravitation. These different gravitational regimes pose challenges to guidance and targeting logic. The present work describes options for autonomous logic for each of several major maneuvers of the lunar sortie, including numerical techniques to incorporate the effect of 3rd bodies. Throughout the development there is an emphasis on simplicity and computational efficiency.

NRHO↗
NASA NTRS1991

Terrestrial mantle siderophiles and the lunar impact record

Results of an analytical fit to the lunar cratering record are shown to be in good agreement with geochemical estimates of the meteoritic component mixed into the lunar crust. Upon a gravitational scaling to the earth consistent with the statistical probability that earth impactors were more massive than lunar ones, an estimate is obtained of 1.5 x 10 to the 22nd kg of material accumulated by the earth begining 4.4 Gyr ago. This is in excellent agreement with estimates of postcore-formation meteoritic input derived from geochemical considerations of the abundances of highly siderophile elements in the terrestrial mantle. Approximate agreement is therefore established between the lunar cratering record scaling and both lunar and terrestrial geochemical constraints.

Chyba, Christopher F.↗
NASA NTRS2023

Constraining the Structure under Lunar Impact Basins with Gravity

The lunar gravity field is used to estimate and constrain the depth of mass anomalies under 19 major lunar impact basins. We use radial gravitational spectra, consisting of accelerations computed either per spherical harmonic degree or cumulatively, at surface locations to obtain the distribution of the gravity signal with spherical harmonic degree and, by implication, to the likely depth below the surface. The results provide estimates for the maximum likely depths of the primary component to the mass anomalies under 19 basins. We find that the maximum depths of the primary source of mascon gravity on the lunar nearside are deeper than the depths for those on the farside when South Pole–Aitken (SPA) is excluded. All basin mass anomalies on the lunar nearside are in the mantle. The maximum depth of the primary source of the mass anomalies is 200 km beneath the surface. The upper 20 km under all basins is largely devoid of anomalies, reflecting predominantly mixing and relaxation associated with impact melt combined with ejecta fallback, as well as homogenization associated with post-basin formation impact bombardment. Except for SPA, all basin anomalies merge with the deep interior at ∼150 km or below, indicating the depth penetration of disruption of the density structure of the lunar interior associated with impact bombardment.

Lunar gravitational field↗
NASA NTRS1974

Bibliography

Bibliographical listing of recently published work pertaining to 15 subject areas of lunar research, with brief abstracts for each item listed. Subject areas covered include: motion of the moon in space, dynamics of the earth-moon system, and lunar astronautics; librations; shape and gravitational field; internal structure, thermal and stress history; chemical composition; lunar exosphere; lunar coordinates and mapping of the moon; physical structure of the lunar surface; photometry of the moon; thermal emission of the lunar surface; electromagnetic properties; exploration of the moon by spacecraft.

Kopal, Z.↗
NASA NTRS1969

The gravitational field of the moon

Lunar structure and evolution based on satellite measurements of mass distribution, radius moments of inertia, gravity anomalies and topographic irregularities

Kaula, W. M.↗
NASA NTRS1981

Electromagnetic-gravitational energy systems

Two methods are considered to 'tap' the earth's rotational energy. This ancient 'collapsed gravitational energy' exceeds the earth-lunar binding energy. One involves an orbiting 'electromagnetic-gravitational' coupling system whereby the earth's rotation, with its nonuniform mass distribution, first uses gravity to add orbital energy to a satellite, similar to a planetary 'flyby'. The second stage involves enhanced satellite 'drag' as current-carrying coils withdraw the added orbital energy as they pass through the earth's nonuniform magnetic field. A second more direct method couples the earth's rotational motion using conducting wires moving through the noncorotating part (ionospheric current systems) of the geomagnetic field. These methods, although not immediately feasible, are considerably more efficient than using pure gravitational coupling to earth-moon tides.

Schatten, K. H.↗
NASA NTRS1972

Photogrammetry and altimetry. Part A: Apollo 16 laser altimeter

The laser altimeter measures precise altitudes of the command and service module above the lunar surface and can function either with the metric (mapping) camera or independently. In the camera mode, the laser altimeter ranges at each exposure time, which varies between 20 and 28 sec (i.e., 30 to 43 km on the lunar surface). In the independent mode, the laser altimeter ranges every 20 sec. These altitude data and the spacecraft attitudes that are derived from simultaneous stellar photography are used to constrain the photogrammetric reduction of the lunar surface photographs when cartographic products are generated. In addition, the altimeter measurements alone provide broad-scale topographic relief around the entire circumference of the moon. These data are useful in investigating the selenodetic figure of the moon and may provide information regarding gravitational anomalies on the lunar far side.

Wollenhaupt, W. R.↗