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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 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Radio wave propagation experiments to probe the ionosphere

Ionospheric bias corrections associated with radio tracking of spacecraft depend on the following measuring techniques for integrated electron content: (1) Faraday rotation measurements from an earth synchronous satellite; (2) ranging measurements at two frequencies; and (3) group and phase velocity measurements obtained from tracking data. The extraction of the integrated electron content directly from tracking data is achieved by comparison of range-rate measurements based on Doppler shift with differentiated range measurements based on tone delay. This method is most desirable because the measured corrections pertain directly to the spacecraft whose orbit is being determined and can be used in near earth as well as deep space tracking data.

Schmid, P. E.↗
NASA NTRS1972

Separation and communications geometry analysis for a Jupiter entry probe from a Pioneer spacecraft

The separation and communications geometry analysis is presented which shows that it is possible to target a Jupiter entry probe from a Pioneer spin-stabilized vehicle to desired entry conditions and maintain a continuous line-of-sight communications link while the probe descends to a pressure of 10 bars within the atmosphere. Such a targeting is possible with either the deflected probe mode or with the deflected bus mode. For the nominal mission studied, an 800 day trip in 1978 with the Pioneer type spacecraft flying by a 1.3 R(J), it was possible to achieve entries near zero angle of attack at about -25 deg relative entry flight path angle. Because of the constraint on the deflection maneuver for the deflected probe mode, the deflection and phasing velocity requirements are much larger for this mode. The geometry parameters, look angles, ranges and range rates, provided by this analysis permit the design of a functional communications system for the bus and probe. Avoiding a high trapped radiation belt hazard at Jupiter by flying the bus by at 6 R(J), however, requires using a despun antenna on the flyby bus.

Tindle, E. L.↗
NASA NTRS1971

Measurement of the propagating waves on Yagi-Uda array.

Measurement of the characteristics of the propagating waves on an array of identical wires. Experimental data showed that propagating waves could be supported on the structure without significant attenuation for two frequency bands. The central frequency of the higher passband was about three times higher tha n that of the lower passband. All propagating waves were slow waves. Phase velocities were varied from 0.99 to 0.25 of the free-space velocity. The k-beta diagrams of the waves were obtained and were found to be in good agreement with theory.

Cubley, H. D.↗
NASA NTRS1971

Numerical solution for propagation of coupled longitudinal and transverse waves normal to the applied magnetic field in a three-fluid medium.

The solution was obtained without approximating the dispersion relation. This was made possible by the use of a computer method for carrying out the extremely large number of algebraic manipulations involved. The three-fluid model employed accounts for the interaction of the electron, ion, and neutral species. The solution for the e-folding distance describes the damping characteristics of each wave mode. Each of the e-folding solutions corresponds to one of the phase velocity solutions.

Mcclendon, R. W.↗
NASA NTRS1972

Traveling ionospheric disturbance as a diagnostic tool for thermospheric dynamics.

Evaluation of observational results of traveling ionospheric disturbances. The experiment continuously monitors the wave polarization of signals transmitted by the geostationary satellite ATS 3. One year of single-station data has been compiled for synoptic study. When observed at three stations, in addition to the period of the wave, the horizontal phase velocity can be determined. An attempt has been made to link the experimentally determined ionospheric parameters with the neutral atmospheric parameters by using a crude theory. The result suggests that a better theory should be developed, so that the diagnosis of these thermospheric parameters can be made by making traveling disturbance observations. In doing so, many previously ignored factors should be reexamined, especially the effect produced by high thermospheric winds.

Yeh, K. C.↗
NASA NTRS1971

Air-coupled seismic waves at long range from Apollo launchings.

Microphones and seismographs were co-located in arrays on Skidaway Island, Georgia, for the launchings of Apollo 13 and 14, 374 km to the south. Simultaneous acoustic and seismic waves were recorded for both events at times appropriate to the arrival of the acoustic waves from the source. The acoustic signal is relatively broadband compared to the nearly monochromatic seismic signal; the seismic signal is much more continuous than the more pulse-like acoustic signal; ground loading from the pressure variations of the acoustic waves is shown to be too small to account for the seismic waves; and the measured phase velocities of both acoustic and seismic waves across the local instrument arrays differ by less than 6 per cent and possibly 3 per cent if experimental error is included. It is concluded that the seismic waves are generated by resonant coupling to the acoustic waves along some 10 km of path on Skidaway Island.

Donn, W. L.↗
NASA NTRS1972

Universal instability associated with the plasmapause and its role in geomagnetic micropulsations.

The observed close correlation between the plasmapause and micropulsations is explained on the basis of a universal instability model. Both theoretical and experimental studies of a nonhomogeneous magnetoplasma indicate that a steep plasma density gradient at the plasmapause is likely the origin of the universal instability in the magnetosphere. Drift waves excited at the plasmapause may be unstable in the direction of the electron drift and propagate eastward nearly perpendicularly to the magnetic field. The drift waves, however, tend to convert very quickly to ion sound or Alfven waves with a much larger phase velocity parallel to the magnetic field. This may be a possible source mechanism for rather regular geomagnetic micropulsations, and specific mechanisms are identified for the long- and short-period cases.

Kikuchi, H.↗
NASA NTRS1973

Ultrasonic calibration device

Device is an instrument for producing known changes in both acoustic absorption and phase velocity. Calibration signal arises from actual change of acoustic parameters, not from electrical simulation. Instrument is able to simulate changes in sensitivity enhancement achieved by use of ultrasonic resonators, which cannot be achieved using electrical calibration techniques.

Heyman, J. S.↗
NASA NTRS1972

Convective amplification of Type 1 irregularities in the equatorial electrojet

Wave propagation and refraction of Type 1 irregularities in the equatorial electrojet were investigated. Quantitative calculation of wave refraction in a model electrojet showed that the direction of wave refraction must change sign at one altitude. Waves propagating with the electrons rotate their wave vectors upwards in the upper electrojet and downwards in the lower electrojet during the day, and vice versa at night. Furthermore, the altitude region of largest linear growth rate is also the one with the weakest refraction rate. Consequently, computations of the ray-path integrated wave growth shows that this region would dominate the backscatter spectrum from the electrojet if linear theory were valid, and it is further noted that the maximum amplitude wave should have phase velocities exceeding the ion acoustic speed. It was concluded that propagation alone, without inclusion of nonlinear effects, cannot explain backscatter observations of a constant Doppler frequency shift given by the ion acoustic speed.

Lee, K.↗
NASA NTRS1972

Microwave dual frequency propagation experiment using the Mariner Venus Mercury probe.

The Mariner Venus Mercury spacecraft (MVM) will be launched in a multiple planet flyby orbit. A coherent dual frequency down link operating at 2.3 and 8.4 GHz will be used to measure the dispersive nature of the transmission medium. Radio tracking will produce Doppler and range information at both 2.3 and 8.4 GHz so that the dispersive group and phase velocity perturbations of the medium can be measured. Interpretation of the dispersive results will yield information about the neutral and ionized atmospheres of Venus and Mercury, the interplanetary media, the solar wind, and corona.

Levy, G. S.↗
NASA NTRS1973

Spatial resonance in the ionosphere.

When the phase velocity of an internal gravity wave equals the natural drift of an ionization irregularity, then a spatial resonance results. If the ionization irregularity has been produced by the gravity wave then it is possible to obtain simple quantitative relations to describe this effect. They indicate this spatial resonance will only occur when the horizontal electric field is westward (i.e., at night), and for tropospherically launched waves it will only affect the ionization at the valley of the equatorial electron density profile.

Beer, T.↗
NASA NTRS1973

Convective amplification of type I irregularities in the equatorial electrojet.

Wave propagation and refraction of 'type I' irregularities in the equatorial electrojet are investigated. Quantitative calculation of wave refraction in a model electrojet shows that the direction of wave refraction must change sign at one altitude. Waves propagating with the electrons rotate their wave vectors upward in the upper electrojet and downward in the lower electrojet during the day, and vice versa at night. Furthermore, the altitude region of largest linear growth rate is also the one with the weakest refraction rate. Consequently, computations of the ray-path integrated wave growth show that this region would dominate the backscatter spectrum from the electrojet if linear theory were valid, and it is further noted that the maximum amplitude wave should have phase velocities exceeding the ion acoustic speed. It is therefore concluded that propagation alone, without inclusion of nonlinear effects, cannot explain backscatter observations of a constant Doppler frequency shift given by the ion acoustic speed.

Lee, K.↗
NASA NTRS1973

Responses to rotating linear acceleration vectors considered in relation to a model of the otolith organs

Human subjects were exposed to a linear acceleration vector that rotated in the transverse plane of the skull without angular counterrotation. Lateral eye movements showed a sinusoidal change in slow phase velocity and an asymmetry or bias in the same direction as vector rotation. A model is developed that attributes the oculomotor response to otolithic mechanisms. It is suggested that the bias component is the manifestation of torsion of the statoconial plaque relative to the base of the utricular macula and that the sinusoidal component represents the translational oscillation of the statoconia. The model subsumes a hypothetical neural mechanism which allows x- and y-axis accelerations to be resolved. Derivation of equations of motion for the statoconial plaque in torsion and translation, which take into account forces acting in shear and normal to the macula, yield estimates of bias and sinusoidal components that are in qualitative agreement with the diverse experimental findings.

Benson, A. J.↗
NASA NTRS1973

Use of Steinhausen's model for describing periodic Coriolis star nystagmus

Phase lag, maximal slow phase velocity, and beat frequency were measured in periodic Coriolis star nystagmus. The results have been described by Steinhausen's model of the semicircular canal system. Estimates of the biophysical constants have been obtained. It is concluded that this model is a good functional approximation for describing, and also for interpreting, the behavior of the system.

Valentinuzzi, M.↗
NASA NTRS1973

Studies of irregularities in motion of vibroshock type mechanisms

Reciprocating motion mechanisms, in which a mass with large gaps can be driven with almost uniform speed, are investigated. A single-mass system with dry friction, the motion of which is restricted by two stops, is examined. The system is put into motion by kinematic disturbances through a flexible link. Periodic modes of movement, under conditions in which the disturbance arises from two impacts on the mass (from the right and left stops) are examined. Primary attention was given to irregularities in the course of the mass. The shock interaction of the mass with the stop was accounted for by the shock speed restoration coefficient R. The shock-frequency characteristics of the free shock vibrations were determined. Expressions were obtained which define the transitional process. The phase and velocity of several succeeding shocks were determined. After taking account of the conditions of the steady mode of movement, velocities and phases in the steady mode of movement were obtained.

Mateyshka, S. Y.↗
NASA NTRS1974

The longitudinal movement of stratospheric ozone waves as determined by satellite

The Nimbus III Infrared Interferometer Spectrometer sensor provides several thousand total ozone data points over the entire globe each day. A time-longitudinal distribution of total ozone for 60 deg S is shown. A selection of this latitude makes it possible to compare the data with radiance values computed by Fritz (1970). Hemispheric differences in longitudinal progression during June 1969 are discussed together with group- and phase-velocities of ozone 'waves.'

Reiter, E. R.↗
NASA NTRS1974

A transmission oscillator ultrasonic spectrometer

A continuous wave ultrasonic instrument capable of measuring very small changes in acoustic attenuation and phase velocity is described. This transmission oscillator ultrasonic spectrometer (TOUS) exhibits high sensitivity because it oscillates marginally. In spite of this high sensitivity, the TOUS system is relatively simple, compact, and inexpensive. These features suggest that the TOUS is suitable not only for precise laboratory measurements of the physical properties of materials, but also for field applications in nondestructive testing.

Conradi, M. S.↗
NASA NTRS1974

Hydraulic concentration of magnetic fields in the solar photosphere. II - Bernoulli effect

The magnetic filaments in the solar photosphere are subject to vigorous kneading and massaging by the convective turbulence at, and beneath, the visible surface. It is shown that the Bernoulli effect of the consequent surging of fluid up and down along the filaments is a major factor in concentrating the magnetic pressure of the filament (the mean square field). The mean field is also increased if the phase velocity of the external massaging exceeds the Alfven speed within the filament. The net observational magnetic result of the surging, then, depends upon the response of the observing instrument, and whether it essentially observes the mean field, the rms field, or whether there are saturation effects. It is suggested that the chromospheric mottles (spicules) seen in H alpha are in fact the intense magnetic filaments that carry most of the magnetic flux across the photospheric boundary of the sun.

Parker, E. N.↗