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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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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Prospects for gravitational wave and ultra-light dark matter detection with binary resonances beyond the secular approximation

Precision observations of orbital systems have recently emerged as a promising new means of detecting gravitational waves and ultra-light dark matter, offering sensitivity in new regimes with significant discovery potential. These searches rely critically on precise modeling of the dynamical effects of these signals on the observed system; however, previous analyses have mainly only relied on the secularly-averaged part of the response. We introduce here a fundamentally different approach that allows for a fully time-resolved description of the effects of oscillatory metric perturbations on orbital dynamics. We find that gravitational waves and ultra-light dark matter can induce large oscillations in the orbital parameters of realistic binaries, enhancing the sensitivity to such signals by orders of magnitude compared to previous estimates.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1973

Further comments on the application of the method of averaging to the study of the rotational motions of a triaxial rigid body, part 3

Variational equations were applied to the case of a rapidly spinning triaxial body moving in an elliptic orbit, in which the orbital plane is regressing at a constant rate. The explicit differential equations obtained in this application were integrated by the method of averaging to develop secular analytical expressions, which, to first-order in a small parameter, describe the complete space motions of the rigid body under the influence of nonresonant gravity-gradient perturbations. The effects of aerodynamic torque on the rotational motion of an orbiting satellite are studied, as another example of the application of the variational equations derived and the method of averaging.

Liu, J. J. F.↗
NASA NTRS1973

Poincare-Lighthill and linear-time-scales methods for linear perturbation problems.

For a class of multidimensional linear perturbation problems of considerable significance in applications, the Poincare-Lighthill technique is shown to give first-order expansion terms which grow unbounded relative to the leading term (secular behavior), while the method of linear time scales leads to well-behaved expansion terms. A solvable example is introduced for comparison with the exact solution.

Klimas, A.↗
NASA NTRS1980

Uncertainty in ring current parameters due to the quiet magnetic field variability at mid-latitudes

At midlatitudes the presence of Sq variation is a problem, as variability of Sq currents may produce magnetic perturbations comparable to the magnetic effects of the partial ring current on comparable time scales. The paper reports the results of an empirical determination of the quiet magnetic field, which includes the Sq variation and secular variation at 27 midlatitude magnetic observatories for the 1967-1968 period. The main concern is with the consequences of the quiet field uncertainty in terms of using midlatitude magnetic data to quantify the size and location of the magnetic disturbances caused by substorms and the ring current. Attention is given to investigating the error associated with the empirical model used. It is shown how the uncertainty can be reduced by examining the changes occurring in some interval of time.

Clauer, C. R.↗
NASA NTRS1978

Incompressible fluid ellipsoids in halos. I - The second-harmonic oscillations of the Maclaurin spheroids

The structure and stability of Maclaurin spheroids embedded in rigid uniform-density oblate spheroidal halos are determined by the tensor virial-equation method. These spheroid-halo systems can be thought of as crude fluid analogs of disk galaxies with halos. The halos are assumed to have the same center, the same axis of symmetry, and the same equatorial radius as the Maclaurin spheroids. Only halos with lower eccentricity than the Maclaurin spheroids are considered. The dynamic instability of the toroidal (barlike) modes is suppressed when m, the ratio of the halo mass to Maclaurin spheroid mass, is greater than 3 pi/8 for spherical halos and when m is greater than 1/2 for halos congruent to the Maclaurin spheroids. Intermediate halo flattenings yield intermediate critical m-values. On the other hand, a neutral point of the toroidal modes in the rotating and inertial frames occurs for all m and for all allowed halo flattenings. Growth rates for secular instability beyond the neutral point are calculated, and the eigenfrequencies of all second-harmonic modes are given for select cases. The Ostriker-Peebles (1973) conjecture concerning the stability of disk galaxies against barlike perturbations appears to be incorrect.

Durisen, R. H.↗
NASA NTRS2022

Adiabatic Evolution Due to the Conservative Scalar Self-force During Orbital Resonances

We calculate the scalar self-force experienced by a scalar point-charge orbiting a Kerr black holealongrθ-resonant geodesics. We use the self-force to calculate the averaged rate of change of thecharge’s orbital energy⟨ ̇E⟩, angular momentum⟨ ̇Lz⟩, and Carter constant⟨ ̇Q⟩, which togethercapture the leading-order adiabatic, secular evolution of the point-charge. Away from resonances,only the dissipative (time antisymmetric) components of the self-force contribute to⟨ ̇E⟩,⟨ ̇Lz⟩, and⟨ ̇Q⟩. We demonstrate, using a new numerical code, that duringrθresonances conservative (timesymmetric) scalar perturbations also contribute to⟨ ̇Q⟩and, thus, help drive the adiabatic evolutionof the orbit. Furthermore, we observe that the relative impact of these conservative contributionsto⟨ ̇Q⟩is particularly strong for eccentric 2:3 resonances. These results provide the first conclusivenumerical evidence that conservative scalar perturbations of Kerr spacetime are nonintegrable duringrθresonances.

Zachary Nasipak↗
DOE OSTI2021

A Tidal Origin for a Three-body Resonance in Kepler-221

Over the course of the last two decades, traditional models of planet formation have been repeatedly challenged by the emerging census of extrasolar planets. Key among them is the orbital architecture problem: while standard models of orbital migration predict resonant orbits for short-period objects, most planets do not appear to lie in orbital resonances. Here, we show that the four-planet system Kepler-221, not previously recognized to have active orbital resonances, has a three-body commensurability relation unique within the Kepler sample. Using a suite of numerical experiments as well as a perturbative analysis, we demonstrate that this system likely began as a resonant chain and proceeded to undergo large-scale divergence away from resonance, under the action of tidal dissipation. Our results further indicate that obliquity tides, driven by a secular spin–orbit resonance and mutual inclination, are an excellent candidate for driving this orbital divergence, and that the high tidal luminosity may also explain the anomalous size of planet b, which lies within the Fulton radius gap.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1999

Does Turbulence in the Iron Convection Zone Cause the Massive Outbursts of Eta Carinae?

Taken at face value, the observed properties of the central object in Eta-Car suggest a very massive, hot main-sequence star, only slightly evolved. If this is so, the star's extraordinarily high steady rate of mass loss must dynamically perturb its outer envelope down to the iron convection zone, where the kinetic energy associated with turbulent convection can be directly fed into mass ejection. Runaway mass loss, triggered by either internal (pulsational, rotational) or external (tidal) forcing, would produce a secular oscillation of the outer envelope. In either case, the oscillation is potentially able to account for the observed approximately 5 yr cycles of visual outbursts in Eta-Car, including the giant eruption of 1843.

Stothers, Richard B.↗
NASA NTRS1990

The inclusion of higher degree and order gravity terms in the design of a repeat ground track orbit

Mean Orbit Elements can be chosen such that a desired ground track repeat criteria is obtained when propagating with the secular effects of a central body gravity field. If the proper initial conditions are chosen that correspond to these Mean Elements, the orbit can also be propagated with the full gravity field and form another ground track repeat pattern. Further, if the effects of other perturbative forces are compensated for, such that the ground track remains near this pattern, the central body effects can again be considered repetitive. The process of arriving at these conclusions, along with the supporting numerical simulations, are presented.

Vincent, Mark A.↗
NASA NTRS2004

Chemistry and Transport in a Multi-Dimensional Model

Our work has two primary scientific goals, the interannual variability (IAV) of stratospheric ozone and the hydrological cycle of the upper troposphere and lower stratosphere. Our efforts are aimed at integrating new information obtained by spacecraft and aircraft measurements to achieve a better understanding of the chemical and dynamical processes that are needed for realistic evaluations of human impact on the global environment. A primary motivation for studying the ozone layer is to separate the anthropogenic perturbations of the ozone layer from natural variability. Using the recently available merged ozone data (MOD), we have carried out an empirical orthogonal function EOF) study of the temporal and spatial patterns of the IAV of total column ozone in the tropics. The outstanding problem about water in the stratosphere is its secular increase in the last few decades. The Caltech/PL multi-dimensional chemical transport model (CTM) photochemical model is used to simulate the processes that control the water vapor and its isotopic composition in the stratosphere. Datasets we will use for comparison with model results include those obtained by the Total Ozone Mapping Spectrometer (TOMS), the Solar Backscatter Ultraviolet (SBUV and SBUV/2), Stratosphere Aerosol and Gas Experiment (SAGE I and II), the Halogen Occultation Experiment (HALOE), the Atmospheric Trace Molecular Spectroscopy (ATMOS) and those soon to be obtained by the Cirrus Regional Study of Tropical Anvils and Cirrus Layers Florida Area Cirrus Experiment (CRYSTAL-FACE) mission. The focus of the investigations is the exchange between the stratosphere and the troposphere, and between the troposphere and the biosphere.

Yung, Yuk L.↗
NASA NTRS2008

Lunar Frozen Orbits

Based upon the derivation of the equations of frozen orbits about the Earth, an analytical formulation is presented for lunar frozen orbits (LFO) in a wide altitude range. Global examination is made of combinations of inclination, semimajor axis, and eccentricity to zero out the mean eccentricity and argument of periapsis drift. Included in this development are the effects of both the lunar gravity potential and third body perturbations. Unlike the Earth frozen orbits, with the major perturbation due to the uniform 52 through J5 gravity terms, lunar frozen orbits are restricted by the distribution of the lunar mascons. With accurate modeling, they exhibit a predictive pattern that drives the overall mission design. In addition to a derivation for analytical expressions, a fill1 numerical simulation is used for verification and examination of secular drift from all third body effects. This presentation addresses a selection of usable lunar orbits that reduce or eliminate the need for stationkeeping while maintaining usable science or communication/navigation orbit parameters.

Folta, David↗
NASA NTRSDate not supplied

Perturbations, TTVs & the (Un)reliability of Ephemerides of Kepler Planets

Fractional uncertainties quoted for orbital periods of the vast majority of planet candidates listed in recent Kepler catalogs are $<10^{-5}$, with values $\sim 10^{-6}$ (corresponding to 2 minutes per 4 years) being typical. These small uncertainties suggest ephemeris predictions for most Kepler planets are robust for decades to come. Tabulated periods list formal uncertainties in the mean times between midpoints of successive transits during the time interval in which transits were observed. However, transit timing variations (TTVs) produce errors in estimates of some planets’ orbital periods that need to be accounted for in certain dynamical investigations and ephemeris predictions. Periodic TTVs with timescales short compared to the interval of Kepler observations largely average out and do not produce significant errors in estimates of orbital periods. TTVs with timescales comparable to the interval of Kepler observations have been fit for dozens of Kepler planet candidates to estimate long-term average orbital periods (Holczer et al. 2016, ApJS 225, 9), and more detailed dynamical models have been used to estimate long-term average periods of a small number of well-studied planets. Most Kepler planets that show large TTVs are near mean-motion orbital resonances with other planets. The largest effect for planets moderately close to two-body resonances are due to rotation of the forced eccentricity vector by resonant perturbations; the timescale for this precession is typically short, so the variations tend to average out. Libration of planets locked in resonances typically occurs on timescales longer than the Kepler baseline, but few Kepler planets appear to be resonantly-locked. The more general but smaller (during the era of Kepler observations) effect is caused by secular precession of the planets' free eccentricities usually has a period much longer than the baseline of the Kepler observations, so it is not accounted for in estimates of mean periods or uncertainties. This precession causes a discrepancy between Kepler era mean orbital period and long-term mean orbital period can exist even for planets having TTVs that are too small to be observable during the epoch of Kepler observations.

Kepler↗
NASA NTRS2010

Transforming Mean and Osculating Elements Using Numerical Methods

Mean element propagation of perturbed two body orbits has as its mathematical basis averaging theory of nonlinear dynamical systems. Averaged mean elements define the long-term evolution characteristics of an orbit. Using averaging theory, a near identity transformation can be found that transforms the mean elements back to the osculating elements that contain short period terms in addition to the secular and long period mean elements. The ability to perform the conversion is necessary so that orbit design conducted in mean elements can be converted back into osculating results. In the present work, this near identity transformation is found using the Fast Fourier Transform. An efficient method is found that is capable of recovering the osculating elements to first order

averaging↗
NASA NTRS1975

The motions of Phobos and Deimos from Mariner 9 TV data

Orbit elements for the two Martian satellites Phobos and Deimos have been determined from 80 television photographs of the satellites taken by the imaging system of the Mariner 9 spacecraft. Phobos was found to be within 60 km of its positions predicted by recently published ephemeris theories which include a secular acceleration term in the longitude. This tends to corroborate the existence of a secular acceleration in the longitude of Phobos. Deimos was found to be within 100 km of its position predicted from earth-based observations. Comparison of the satellite's orbits determined from Mariner 9 data are made to these same ephemeric theories which are based on recent processing of earth-based observations. In addition, the magnitude of periodic perturbations to the satellite orbits due to Mars' gravity field and solar gravity are discussed and a 110 km long period perturbation in the longitude of Deimos is identified.

Born, G. H.↗
NASA NTRS1988

A second-order analytic analysis for frozen orbits

An analytical method for studying characteristics of frozen orbits using mean orbital elements is presented. By removing some of the approximations of Brouwer and Kosai (1959) and using the method of integration by parts, an analytic solution is obtained accurate to the second order in the sense of expansion of the perturbing potential of an aspherical approximation. The solution applies to orbits at and near the critical inclination as well as to frozen orbits and, of course, to unfrozen orbits. The analysis reveals that a frozen orbit can be interpreted as an orbit in which movements of the long-periodic part of the rate of change of periapsis cancels the secular part exactly at any time.

Tang, Charles C. H.↗
NASA NTRS1998

On the Origin of Chaos in the Asteroid Belt

We consider the effect of gravitational perturbations from Jupiter on the dynamics of asteroids, when Jupiter is itself perturbed by Saturn. The presence of Saturn introduces a number of additional frequencies into Jupiters orbit. These frequencies in turn produce chaos in narrow regions on either side of the chaotic zones associated with the mean motion resonances between the asteroids and Jupiter. The resonant arguments of these three-body resonances contain the longitudes of Jupiter and the asteroid together with either the secular frequency 9-6, or the longitude of Saturn. Resonances involving the longitude of Saturn are analogs of the Laplace resonance in the Jovian satellite system. We show that many three-body resonances involving the longitude of Saturn are chaotic. We give simple expressions for the width of the chaotic region and the associated Lyapunov time. In some cases the chaos can produce a diffusive growth in the 4 eccentricity of the asteroid that leads to ejection of the asteroid on times shorter than the age of the solar system. We give simple estimates for the diffusion time. Finally, we present the results of numerical integrations testing the theory.

Murray, N.↗
NASA NTRS1976

A mechanism for inducing climatic variations through ozone destruction: Screening of galactic cosmic rays by solar and terrestrial magnetic fields

A perturbation analysis, allowing for temperature and opacity feedbacks, is developed to calculate depletions in the O3 abundance and reductions of stratospheric solar heating that result from increases in NOx concentration. A pair of perturbation coefficients give the reduction in O3 and temperature through the stratosphere for a specified NOx increase. This type of analysis illustrates the tendency for various levels to self-heal when a perturbation occurs. Physical arguments indicate that the expected sign of the climatic effect is correct, with colder surface temperatures produced by reduced magnetic shielding. In addition, four qualitative reasons are suggested for thinking that significant ozone reductions by cosmic ray influxes will lead to an increased terrestrial albedo from stratospheric condensation. In this view, long-term (approximately 10,000 years) climatic changes have resulted from secular geomagnetic variations while shorter (approximately 100 years) excursions are related to changes in solar activity.

Chamberlain, J. W.↗