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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 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

The effect of centrifugal distortion on CO2-laser frequencies

Values of the coefficient H for the appropriate carbon-dioxide laser levels are estimated on the basis of theoretical considerations. The values are compared with data obtained by Petersen et al. (1973). It is found that very small perturbations become important as the accuracy of the CO2-laser frequencies increases, especially for lines far away from the band center. Careful experimental frequency measurements are mandatory in the high J region if an accuracy of the order of 10 kHz is desired.

Menzies, R. T.↗
NASA NTRS1974

Influence of thermal distortion on the anomalous behavior of a gravity gradient satellite

Consideration of the problem of determining the influence of solar heating on the low-frequency dynamic stability of a gravity-gradient satellite. The scope of the effort includes the development of a computer program that uses a quasi-static approach for describing a satellite's unsteady orbital motion. The essential feature of the quasi-static approach is that the satellite's long, slender booms reach their thermal equilibrium position solely as a result of thermal bending without consideration of the dynamic effects of boom vibration. A nonlinear analytical model and a corresponding computer program have been developed to study the effect of absorptivity, sun angle, and hinge stiffness on the stability of a satellite's motion.

Goldman, R. L.↗
NASA NTRS1974

Evidence from charged particle studies for the distortion of the Jovian magnetosphere

Consideration of the relationship between the rotation of Jupiter's magnetic field and time variations in the intensity of approximately 6- to 30-MeV electrons observed by the University of Chicago experiment on Pioneer 10 in the outer regions of Jupiter's magnetosphere (R greater than 20 Jupiter radii). For R equal to or greater than 40 Jupiter radii the authors' observations are found to be consistent with rigid corotation of the magnetosphere with Jupiter. For R equal to or greater than 40 Jupiter radii, significant deviations from rigid corotation appear with the observed phase of the intensity variations leading the phase expected for rigid corotation on the inbound pass and lagging on the outbound pass. From a different point of view it is found that the time delay between the observed times of intensity minimums and the times expected on the basis of a rigid 9 hour 55 minute period for the intensity variations increased steadily while Pioneer 10 was within the magnetosphere and had reached approximately a ten hour time difference when the spacecraft left the magnetosphere at R approximately equal to 98 Jupiter radii outbound.

Mckibben, R. B.↗
NASA NTRS1975

The effect of ring distortions on buckling of blunt conical shells

A rigorous analytical study of cones stiffened by many thin-gage, open-section rings is presented. The results are compared with data previously obtained from uniform pressure tests of the Viking mission flight aeroshell and of the Viking structural prototype aeroshells. A conventional analysis, in which the rings are modeled as discrete rigid cross sections, is shown to lead to large, unconservative strength predictions. A more sophisticated technique of modeling the rings as shell branches leads to much more realistic strength predictions and more accurately predicts the failure modes. It is also shown that if a small initial imperfection proportional to the shape of the buckling mode is assumed, the critical buckling modes from analysis and test are in agreement. However, the reduction in buckling strength from the perfect-shell predictions is small.

Heard, W. L., Jr.↗
NASA NTRS1975

Instability of a gravity gradient satellite due to thermal distortion

A nonlinear analytical model and a corresponding computer program were developed to study the influence of solar heating on the anomalous low frequency, orbital instability of the Naval Research Laboratory's gravity gradient satellite 164. The model's formulation was based on a quasi-static approach in which deflections of the satellite's booms were determined in terms of thermally induced bending without consideration of boom vibration. Calculations, which were made for variations in absorptivity, sun angle, thermal lag, and hinge stiffness, demonstrated that, within the confines of a relatively narrow stability criteria, the quasi-static model of NRL 164 not only becomes unstable, but, in a number of cases, responses were computed that closely resembled flight data.

Goldman, R. L.↗
NASA NTRS1975

Lateral distortions of electromagnetic cascades in emulsion chambers

Electromagnetic cascades in a lead-emulsion chamber have been studied to determine the effect of air gaps on the upstream sides of the emulsions. Such air gaps cause a change in the form of the radial distribution of electron tracks, making cascades appear older and giving incorrect energy estimates. The number of tracks remaining within a radius r was found to vary as exp(-g/G), where g is the gap thickness. The characteristic gap thickness in mm is G = 3.04 + 1.30 ln (Err per GeV per sq mm) where E is the energy of the initiating gamma ray. Use of this relation provides a significant correction to cascade-energy estimates and allows one to calculate the effect of different gap thicknesses on the energy threshold for visual detection of cascades.

Porter, L. G.↗