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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
NASA NTRS1938

On some reciprocal relations in the theory of nonstationary flows

In the theory of nonstationary flows about airfoils, the "indicial lift" function ksub1(s) of Wagner and the "alternating lift" function c(k) of Theodorsen have fundamental significance. This paper reports on some interesting relations of the nature of Fourier transforms that exist between these functions. General problems in transient flows about airfoils may be given a unified broad treatment when these functions are employed. Certain approximate results also are reported which are of notable simplicity, and an analogy with transient electrical flows is drawn.

Garrick, I E↗
NASA NTRS1965

Cosmology without general relativity

Idealizations in cosmology with special theory of relativity - partitioned universe, microcosmic model, and similarity to Newtonian cosmology

RELATIVITY THEORY↗
NASA NTRS1982

Misconceptions in recent papers on special relativity and absolute space theories

Several recent papers which purport to substantiate or negate arguments in favor of certain theories of absolute space have been based on fallacious principles. This paper discusses three related instances, indicating where misconceptions have arisen. It is established, contrary to popular belief, that the classical Lorentz ether theory accounts for all the experimental evidence which supports the special theory of relativity. It is demonstrated that the ether theory predicts the null results obtained from pulsar timing and Moessbauer experiments. It is concluded that a measurement of the one-way velocity of light has physical meaning within the context of the Lorentz theory, and it is argued that an adequately designed experiment to measure the one-way velocity of light should be attempted.

Torr, D. G.↗
NASA NTRS1971

Boundary layer transition: A review of theory, experiment and related phenomena

The overall problem of boundary layer flow transition is reviewed. Evidence indicates a need for new, basic physical hypotheses in classical fluid mechanics math models based on the Navier-Stokes equations. The Navier-Stokes equations are challenged as inadequate for the investigation of fluid transition, since they are based on several assumptions which should be expected to alter significantly the stability characteristics of the resulting math model. Strong prima facie evidence is presented to this effect.

Kistler, E. L.↗
NASA NTRS1972

The octahedral shear strain theory and its relation to biaxial cumulative fatigue damage.

The octahedral shear strain range concept is used in analyzing multiaxial fatigue damage. Limited test data from a two-step loading sequence show that the loading effect is still pronounced in the multiaxial case and that the relation between damage and cycle ratio is nonlinear. Among uniaxial cumulative damage concepts, the modified multiaxial double linear damage rule seems to show the most favorable experimental results.

Zamrik, S. Y.↗
NASA NTRS1977

Review of magnetospheric boundary layer phenomena and relations to current theories

Recent observations on the magnetopause and boundary layer are reviewed. A region with magnetosheath-like plasma is found in an entry layer inside the magnetopause, at least partly on closed field lines. There is no enhanced flow near the magnetopause, in contrast to what would be expected on the basis of reconnection theories. Inside the magnetopause there is a boundary layer, which must be polarized. Parallel electric fields and currents are involved, thus invalidating the mapping of the electric field along magnetic field lines. Access to the entry layer must be impulsive or diffusive in nature.

Heikkila, W. J.↗
NASA NTRS1989

A physical model for earthquakes. III - Thermodynamical approach and its relation to nonclassical theories

An earthquake theory based on fundamental thermodynamical considerations was developed using two principles. The first principle is that physical systems, including fault systems, tend toward a state of minimal Helmholtz free energy, which corresponds to static equilibrium. The second postulate is that, if the system is not at minimal free energy, thermodynamic forces arise which drive the system back toward a minimum. According to this theory, the propagation of a fracture, or the formation of a slip on a frictional surface, are manifestations of the physics which attempt to return the system to minimal free energy. It is shown that the process of return to minimal free energy by the system corresponds to the production of entropy, thereby rendering the process irreversible.

Rundle, John B.↗
NASA NTRS1989

Gravitational consequences of modern field theories

Some gravitational consequences of certain extensions of Einstein's general theory of relativity are discussed. These theories are not alternative theories of gravity in the usual sense. It is assumed that general relativity is the appropriate description of all gravitational phenomena which were observed to date.

Horowitz, Gary T.↗
NASA NTRS1976

The Laplace relation and the masses of Uranus' satellites

It is noted that the mean motions of Uranus' satellites Miranda, Ariel, and Umbriel exhibit nearly the same commensurability as that observed among the three inner Galilean satellites of Jupiter, which is referred to as the Laplace relation. The theory of the Laplace relation among the Uranian satellites is completed by generating terms due to the first-order portions of the disturbing functions, using a generalization of Souillart's approach for the Galilean satellites. The theory is compared with past observations of Miranda's mean motion to obtain an upper limit on the product of the masses of Ariel and Umbriel. This mass limit is examined in terms of implied density and albedo constraints for comparison with the bulk properties of other solar-system bodies. The results suggest that if Ariel and Umbriel both have the same geometric albedo and density, then Ariel's radius would have to be less than about 1200 km and Umbriel's, less than about 800 km.

Greenberg, R.↗
NASA NTRS1964

Astrorelativity

Extension of special relativity to transformations for variable mass systems, & relativistic perturbation theory for satellite orbits

VARIABLE MASS SYSTEM↗
NASA NTRS1980

Primer vector theory applied to the linear relative-motion equations

Prime vector theory is used in analyzing a set of linear relative-motion equations - the Clohessy-Wiltshire (C/W) equations - to determine the criteria and necessary conditions for an optimal N-impulse trajectory. The analysis develops the analytical criteria for improving a solution by: (1) moving any dependent or independent variable in the initial and/or final orbit, and (2) adding intermediate impulses. If these criteria are violated, the theory establishes a sufficient number of analytical equations. The subsequent satisfaction of these equations will result in the optimal position vectors and times of an N-impulse trajectory. The solution is examined for the specific boundary conditions of: (1) fixed-end conditions, two impulse, and time-open transfer; (2) an orbit-to-orbit transfer; and (3) a generalized renezvous problem.

Jezewski, D.↗
NASA NTRS1989

Reciprocal relations for transmission coefficients - Theory and application

The authors present a rigorous proof of certain intuitively plausible reciprocal relations for time harmonic plane-wave transmission and reflection at the interface between a fluid and an anisotropic elastic solid. Precise forms of the reciprocity relations for the transmission coefficients and for the transmitted energy fluxes are derived, based on the reciprocity theorem of elastodynamics. It is shown that the reciprocity relations can be used in conjunction with measured values of peak amplitudes for transmission through a slab of the solid (water-solid-water) to obtain the water-solid coefficients. Experiments were performed for a slab of a unidirectional fiber-reinforced composite. Good agreement of the experimentally measured transmission coefficients with theoretical values was obtained.

Qu, Jianmin↗
NASA NTRS1981

The visual surface brightness relation and the absolute magnitudes of RR Lyrae stars. I - Theory

A theoretical relation analogous to the Barnes-Evans relation between stellar surface brightness and V-R color is derived which is applicable to the temperatures and gravities appropriate to RR Lyrae stars. Values of the visual surface brightness and V-R colors are calculated for model stellar atmospheres with effective temperatures between 6000 and 8000 K, log surface gravities from 2.2 to 3.5, and A/H anbundance ratios from -0.5 to -3.0. The resulting relation is found to be in reasonable agreement with the empirical relation of Barnes, Evans and Moffet (1978), with, however, small sensitivities to gravity and metal abundance. The relation may be used to derive stellar angular diameters from (V,R) photometry and to derive radii, distances, and absolute magnitudes for variable stars when combined with a radial velocity curve. The accuracies of the radii and distances (within 10%) and absolute magnitudes (within 0.25 magnitudes) compare favorably with those of the Baade-Wesselink method currently in use.

Manduca, A.↗
NASA NTRS1993

Lunar LIGO: A new concept in gravitational wave astronomy

For three decades, physicists have been in search of an elusive phenomenon predicted by Einstein's general theory of relativity; gravitational radiation. These weak vibrations of spacetime have, thus far, eluded conclusive Earth-based detection due in part to insufficient detector sensitivity and noise isolation. The detection of gravitational waves is crucial for two reasons. It would provide further evidence for the validity of Einstein's theory of relativity, the presently accepted theory of gravitation. Furthermore, the ability to identify the location of a source of a detected gravitational wave event would yield a radical new type of astronomy based on non-electromagnetic emissions. We continue our study of a lunar-based system which can provide an important complement to Earth-based analysis because it is completely independent of the geophysical sources of noise on Earth, while providing an Earth-Moon baseline for pin-pointing burst sources in the Universe. We also propose for the first time that a simplified version of the LIGO beam detector optical system, which we will call LLIGO (Lunar LIGO), could be emplaced on the Moon as part of NASA's robotic lander program now under study (Artemis). The Earth-based investigation has two major programs underway. Both involve large interferometer-type gravitational wave antennas.

Lafave, Norman↗