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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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Nonperiodic motions near long-period librations about equilateral points of restricted three-body problem
Librational motion analysis for elliptical restricted three-body problem
Stability of rotating liquid mass /e.g. earth/, following Jeans treatment of Jacobi ellipsoidal equilibrium configurations
Higher order perturbations of elements in three- body problem determined using methods of Krylov- Bogoliubov and Poincare
Canonical elements for variables of Levi-Civita regularizing binary collisions in restricted three-body problem, noting existence of periodic orbits
Motion in ternary stellar system consisting of central body and close and distant companions
Invariant curves dissolution and nonapplicability of third integrals explained examining perturbation values and initial conditions and resonance phenomena
Three-dimensional structure of solar plasma flow generated by solar flares, noting geometric factors in geomagnetic storm intensity decrease
Bounded isoenergetic displacement of periodic orbits in restricted circular three-body problem
Hansen planetary theory representing position of disturbed planet as deviation in time and space from position of fictitious planet with Keplerian motion
The various source mechanisms for celestial gamma rays are reviewed. The gamma-ray data are examined as a source of information about the processes and source locations for the production of charged particle cosmic rays, galactic structure, explosive nucleosynthesis in supernovae, regions of confinement for cosmic rays, regions where matter-antimatter annihilation occurs, and the general condition in cosmological space both in the past and present. Topics include gamma rays from pi mesons by nuclear interactions, nuclear and supernovae lines, diffuse emission and discrete sources, interstellar absorption and detection of gamma rays, and others. A brief view of the available gamma-ray detection systems and techniques is presented.
New ephemerides of Jupiter's Galilean Satelites are produced from an analysis of CCD astrometric data, Voyager-mission optical navigation images, mutual event observations, photographic plates, and eclipse timing obeservations.
The Earth, Mars, Sun, Jupiter system allows for a sensitive.
NASA has embarked on a program of.
Of the three major groups of comets approaching the Sun to between 6 and 12 solar radii and discovered with the coronagraphs on board SOHO, we investigate the Marsden and Kracht groups.We call these comets ''sunskirters'' to distinguish them from the Kreutz system sungrazers. Our objective is to understand the origin, history, and orbital evolution of the two groups.
We have updated the orbits of the small inner Saturnian satellites using additional Cassini imaging observations through 2007 March. Statistically significant changes from previously published values appear in the eccentricities and inclinations of Pan and Daphnis, but only small changes have been found in the estimated orbits of the other satellites. We have also improved our knowledge of the masses of Janus and Epimetheus as a result of their close encounter observed in early 2006.
We present the Superparticle Model/Algorithm for Collisions in Kuiper belts and debris disks (SMACK), a new method for simultaneously modeling, in 3-D, the collisional and dynamical evolution of planetesimals in a debris disk with planets. SMACK can simulate azimuthal asymmetries and how these asymmetries evolve over time. We show that SMACK is stable to numerical viscosity and numerical heating over 10(exp 7) yr, and that it can reproduce analytic models of disk evolution. We use SMACK to model the evolution of a debris ring containing a planet on an eccentric orbit. Differential precession creates a spiral structure as the ring evolves, but collisions subsequently break up the spiral, leaving a narrower eccentric ring.
The long-term stability of the narrow F Ring core has been hard to understand. Instead of acting as "shepherds", Prometheus and Pandora together stir the vast preponderance of the region into a chaotic state, consistent with the orbits of newly discovered objects like S/2004S6. We show how a comb of very narrow radial locations of high stability in semimajor axis is embedded within this otherwise chaotic region. The stability of these semimajor axes relies fundamentally on the unusual combination of rapid apse precession and long synodic period which characterizes the region. This situation allows stable "antiresonances" to fall on or very close to traditional Lindblad resonances which, under more common circumstances, are destabilizing. We present numerical integrations of tens of thousands of test particles over tens of thousands of Prometheus orbits that map out the effect. The stable antiresonance zones are most stable in a subset of the region where Prometheus first-order resonances are least cluttered by Pandora resonances. This region of optimum stability is paradoxically closer to Prometheus than a location more representative of "torque balance", helping explain a longstanding paradox. One stable zone corresponds closely to the currently observed semimajor axis of the F Ring core. While the model helps explain the stability of the narrow F Ring core, it does not explain why the F Ring material all shares a common apse longitude; we speculate that collisional damping at the preferred semimajor axis (not included in the current simulations) may provide that final step. Essentially, we find that the F Ring core is not confined by a combination of Prometheus and Pandora, but a combination of Prometheus and precession.