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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 1,009 records · Page 56

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NASA NTRS1984

The view from the Shuttle Orbiter - Observing the oceans from manned space flights

Examples of earth-looking hand-held photography and orbital sensor imagery of ocean features and phenomena in the framework of the Space Shuttle Earth Observations Project are presented. These include images of a floating substance in Capricorn Channel off northeastern Queensland, Australia; atolls in the central Maldive Islands; a spiral eddy and probable oil slick in the Caribbean Sea north of Aruba; and spiral eddies recorded in sun glint over the Mozambique Channel. It is concluded that the observation of the world's oceans during Shuttle missions with the trained eyes of the crewmen and documentation with hand-held photography add a significant dimension to the remote sensing of the ocean.

Kaltenbach, J. L.↗

NASA NTRS1986

The phase relationship between gyrophase-bunched ions and MHD-like waves

Recent calculations and computer simulations of the right-hand resonant ion beam instability have indicated that gyrophase-bunched ion distributions may be generated as a first step in the disruption of field-aligned beams. Theory predicts a distinct phase angle relationship between the gyrovelocity of the phase-bunched ions and the wave magnetic field. In this paper, observations of such a relationship between gyrophase-bunched ions and MHD-like waves upstream from the earth's bow shock are presented. The observed phases are in accord with the theoretical predictions of the right-hand resonant ion beam instability.

Fuselier, S. A.↗

NASA NTRS1986

Computer simulations of electromagnetic cool ion beam instabilities

Electromagnetic ion beam instabilities driven by cool ion beams at propagation parallel or antiparallel to a uniform magnetic field are studied using computer simulations. The elements of linear theory applicable to electromagnetic ion beam instabilities and the simulations derived from a one-dimensional hybrid computer code are described. The quasi-linear regime of the right-hand resonant ion beam instability, and the gyrophase bunching of the nonlinear regime of the right-hand resonant and nonresonant instabilities are examined. It is detected that in the quasi-linear regime the instability saturation is due to a reduction in the beam core relative drift speed and an increase in the perpendicular-to-parallel beam temperature; in the nonlinear regime the instabilities saturate when half the initial beam drift kinetic energy density is converted to fluctuating magnetic field energy density.

Gary, S. P.↗

NASA NTRS1985

Recent advancements in telepresence technology development

This paper describes recent developments at JPL aimed at enhancing the operator's awareness of the remote task he or she is controlling in space teleoperation. The first development is related to the use of force-reflecting or bilateral manual control in weightless condition. The second development is related to integrated graphics displays of force and torque information originating from a remote robot hand. The third development is related to a distributed computational system in teleoperation organized in two groups: one integrated with a remote robot arm and hand, and another integrated with the control station. This computational system carries out interactive automation functions.

Corker, K.↗

NASA NTRS1987

Duplex Wrench

Special tool enables one worker to do two-worker job. Wrench holds two nuts in place while third nut, coaxial with others, turned. Developed for tightening delicate couplings on gas-supply panel. Single operator restrains coupling pressure cap and connector body nut with one hand. Other hand free to tighten coupling nut with torque wrench.

Canada, C. N.↗

NASA NTRS1987

Designing Rectangular RHCP Microstrip Antennas

RHCP, Right-Handed, Circularly Polarized Microstrip Antenna program, aids in design of rectangular microstrip-antenna element, given desired frequency of operation and characteristics of substrate. Begins design calculations on basis of square element with linear polarization. Effective dielectric constant and changes in electrical length due to fringing at edges of radiating element taken into account. Coaxial feed inset with 50 ohms input impedance. Placement of feed such that two orthonormal modes produced in antenna cavity, right- or left-handed circular polarization obtained. Written in FORTRAN 77.

Davidson, Shayla E.↗

NASA NTRS1986

The influence of scattering particles morphology on the characteristics of lidar signals

The characteristics of light scattering by a separate spherical particle are used as a priori information when interpreting the data on laser sounding of atmospheric aerosols. Analogously, it is necessary to have a priori information on the characteristics of light scattering by a single crystals in order to restitute the microstructure of crystal formation in the atmosphere. In contrast to the aerosol particles the crystals are of different shapes. On the one hand, this complicates the solution of electrodynamic problems on light scattering by such crystals. On the other hand, if obtaining such a solution is possible, one can determine the morphology of scattering particles accoring to the sounding data and this enables additonal information to be obtained on such meteorological parameters as temperature, pressure, and humidity. Using the geometric-wave approach the problem of scattering of plane electromagnetic wave on convex polyhedrons of arbitrary form was solved. As a result, the expressions were obtained for electric field components of perpendicular and parallel polarizations scattered in any given direction.

Zuev, V. E.↗

NASA NTRS1986

A combined Raman lidar for low tropospheric studies

One of the main goals of laser sensing of the atmosphere was the development of techniques and facilities for remote determination of atmospheric meteorological and optical parameters. Of lidar techniques known at present the Raman-lidar technique occupies a specific place. On the one hand Raman lidar returns due to scattering on different molecular species are very simple for interpretation and for extracting the information on the atmospheric parameters sought, but, on the other hand, the performance of these techniques in a lidar facility is overburdened with some serious technical difficulties due to extremely low cross sections of Raman effect. Some results of investigations into this problem is presented which enables the construction of a combined Raman lidar capable of acquiring simultaneously the profiles of atmospheric temperature, humidity, and some optical characteristics in the ground atmospheric layer up to 1 km height. The operation of this system is briefly discussed.

Arshinov, Y. F.↗

NASA NTRS1986

A model of the spatial and temporal variation of the Uranus thermal structure

Seasonal variability of the temperature structure of Uranus is modeled for all latitudes in the .0004 to 2 bar pressure range in anticipation of the Voyager encounter in January 1986. Atmospheric heating in the model results on the one hand from an internal heat source and, on the other hand, from absorption of solar energy by methane and by non-conservative aerosols located between the 0.5 and 2 bar levels. Various cases for the behavior of the internal heat flux are investigated, such as constant with latitude or constrained to yield a time-averaged thermal emission independent of latitude. Meridional transport of heat in the stably stratified atmosphere is not taken into account. The results indicate that the Voyager encounter time, very small north-south temperature asymmetry should be expected. Moreover, the northern hemisphere, although not illuminated, should emit as much energy (within one percent) as the southern hemisphere at this date. At a given latitude, extreme temperatures are reached at the equinoxes. At the poles, seasonal amplitudes of about 10 K in the upper stratosphere and 6 K at the 0.6 bar level are predicted, and the variation with time of the emission to space is found to be at most 20 percent. The atmosphere of Uranus appears to be characterized by very long radiative response times (mainly due to its cold temperature) which inhibit the large seasonal variations that one could otherwise expect in view of the high obliquity of the planet and its long orbital period.

Bezard, B.↗

NASA NTRS1987

Power flow as a complement to statistical energy analysis and finite element analysis

Present methods of analysis of the structural response and the structure-borne transmission of vibrational energy use either finite element (FE) techniques or statistical energy analysis (SEA) methods. The FE methods are a very useful tool at low frequencies where the number of resonances involved in the analysis is rather small. On the other hand SEA methods can predict with acceptable accuracy the response and energy transmission between coupled structures at relatively high frequencies where the structural modal density is high and a statistical approach is the appropriate solution. In the mid-frequency range, a relatively large number of resonances exist which make finite element method too costly. On the other hand SEA methods can only predict an average level form. In this mid-frequency range a possible alternative is to use power flow techniques, where the input and flow of vibrational energy to excited and coupled structural components can be expressed in terms of input and transfer mobilities. This power flow technique can be extended from low to high frequencies and this can be integrated with established FE models at low frequencies and SEA models at high frequencies to form a verification of the method. This method of structural analysis using power flo and mobility methods, and its integration with SEA and FE analysis is applied to the case of two thin beams joined together at right angles.

Cuschieri, J. M.↗

NASA NTRS1987

Digital data from shuttle photography: The effects of platform variables

Two major criticisms of using Shuttle hand held photography as an Earth science sensor are that it is nondigital, nonquantitative and that it has inconsistent platform characteristics, e.g., variable look angles, especially as compared to remote sensing satellites such as LANDSAT and SPOT. However, these criticisms are assumptions and have not been systematically investigated. The spectral effects of off-nadir views of hand held photography from the Shuttle and their role in interpretation of lava flow morphology on the island of Hawaii are studied. Digitization of photography at JSC and use of LIPS image analysis software in obtaining data is discussed. Preliminary interpretative results of one flow are given. Most of the time was spent in developing procedures and overcoming equipment problems. Preliminary data are satisfactory for detailed analysis.

Davis, Bruce E.↗

NASA NTRS1986

Planetary fast neutral emission and effects on solar wind - A cometary exosphere analog

Ion-neutral charge exchange reactions occurring in planetary magnetospheres produce a copious supply of fast neutrals in the form of high-speed magnetospheric neutral winds. Theoretical models of such processes and their subsequent effects on the solar wind are investigated. Source strengths for emission from earth's ring current (10 to the 25th - 10 to the 26th/s), Jupiter's Io plasma torus (1-2 x 10 to the 28th/s), and both the Dione-Tethys torus and the Titan hydrogen torus (10 to the 26th - 10 to the 27th/s) of Saturn are evaluated. The effects of an extensive atomic nitrogen cloud surrounding the orbit of Titan are also considered in connection with the Saturnian aurora. Reionization and pickup of sulfur atoms in the circumplanetary region of Jupiter lead to a small mass-loading effect on the solar wind velocity (less than 10 percent); however, the heat input is substantial, resulting in a large increase in the effective ion temperature (not less than 100 percent). The pickup ion model is also applied tot the generation of electromagnetic ion cyclotron waves in the local neighborhood of the central body. The model suggests the preferential excitation of left-hand-polarized waves in regions where the solar wind-magnetic field angle is large (outer sheath) and right-hand waves in regions where the angle is small (near-tail).

Barbosa, D. D.↗

NASA NTRS1986

DE 1 observations of harmonic auroral kilometric radiation

The plasma wave instrument on board the DE 1 spacecraft has observed several intervals of auroral kilometric radiation during which harmonic structure is clearly present. The paper presents evidence, some of which is based on unique capabilities of the DE instrument, which argues strongly that the harmonic structures are natural rather than instrumental in origin. The harmonic emissions occur infrequently, but when present may persist for intervals of up to an hour. The emissions are relatively narrow band and consist of a relatively weak fundamental accompanied by an even weaker second harmonic. The ratio of power in the fundamental band to the power in the harmonic ranges from 10 to 100. In all cases, polarization data indicate that the fundamental is a left-hand ordinary (L-O) mode emission while the harmonic is right-hand extraordinary (R-X) mode. These observations are consistent with predictions based on the cyclotron maser mechanism.

Mellott, M. M.↗

NASA NTRS1987

Electromagnetic ion beam instabilities - Growth at cyclotron harmonic wave numbers

The linear theory of electromagnetic ion beam instabilities for arbitrary angles of propagation is studied, with an emphasis on the conditions necessary to generate unstable modes at low harmonics of the ion cyclotron resonance condition. The present results extend the analysis of Smith et al. (1985). That paper considered only the plasma parameters at a time during which harmonic wave modes were observed in the earth's foreshock. The parameters of that paper are used as the basis of parametric variations here to establish the range of beam properties which may give rise to observable harmonic spectra. It is shown that the growth rates of both left-hand and right-hand cyclotron harmonic instabilities are enhanced by an increase in the beam temperature anisotropy and/or the beam speed. Decreases in the beam density and/or the core-ion beta reduce the overall growth of the cyclotron harmonic instabilities but favor the growth of these modes over the growth of the nonresonant instability and thereby enhance the observability of the harmonics.

Smith, Charles W.↗

NASA NTRS1987

The electromagnetic ion cyclotron beam anisotropy instability

Electromagnetic instabilities driven by an anisotropic, relatively cool ion beam are studied for the case in which both the beam and the instabilities propagate parallel or antiparallel to a uniform magnetic field. At modest beam-core relative drift speeds, sufficiently large perpendicular-to-parallel beam temperature ratios and sufficiently large plasma beta, the mode of fastest growth rate is the ion cyclotron beam anisotropy instability. Because the right-hand polarized waves observed upstream of slow shocks in the earth's magnetotail can lead to the appropriate beam anisotropy, the ion cyclotron instability may be present and account for the left-hand polarized magnetic waves observed there. Also, because of its relatively low phase speed, the ion cyclotron beam anisotropy instability may provide the scattering necessary for ion Fermi acceleration at slow shocks of sufficiently high plasma beta.

Peter Gary, S.↗

NASA NTRS1986

The pultrusion process for structures on advanced aerospace transportation systems

The pultrusion process, which has the potential for use in the manufacture of structures for aerospace hardware, is described. In this process, reinforcing fibers are pulled continuously through a resin system for wetting and subsequently through a heated die for polymerization. By using this process, fabrication of very long lengths of high strength, lightweight structures with consistently high quality for aerospace applications is possible. The more conventional processes involve hand lay-up, vacuum bagging, autoclaving or oven curing techniques such that lengths of structural elements produced are limited by the lengths of autoclaves or curing ovens. Several types of developmental structural elements are described in which fiberglass, aramid, graphite, and hybrid fiber systems have been used as reinforcements in an epoxy matrix and their flexural properties compared. Reinforcement fibers having tailor-made orientations which achieve tailor-made strength in the pultrusions are described. The potential aerospace applications for the pultruded products are described with advantages cited over conventional hand lay-up methods.

Wilson, Maywood L.↗

NASA NTRS1987

Magnetic elliptical polarization of Schumann resonances

Measurements of orthogonal, horizontal components of the magnetic field in the ELF range obtained during September 1985 show that the Schumann resonance eigenfrequencies determined separately for the north-south and east-west magnetic components differ by as much as 0.5 Hz, suggesting that the underlying magnetic signal is not linearly polarized at such times. The high degree of magnetic ellipticity found suggests that the side multiplets of the Schumann resonances corresponding to azimuthally inhomogeneous normal modes are strongly excited in the highly asymmetric earth-ionosphere cavity. The dominant sense of polarization over the measurement passband is found to be right-handed during local daylight hours, and to be left-handed during local nighttime hours.

Sentman, D. D.↗

NASA NTRS1988

Handheld Controller For Robotic End Effector

Controller provides both position and force feedback. Hand grip houses controller. End-effector force and position fed back to operator's hand through rotation of trigger and rocking of trigger guard.

Jau, Bruno M.↗