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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 559 records · Page 31

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NASA NTRS1981

A comparison of the radio data and model calculations of Jupiter's synchrotron radiation. I - The high energy electron distribution in Jupiter's inner magnetosphere. II - East-west asymmetry in the radiation belts as a function of Jovian longitude

A comparison has been made between detailed model calculations of Jupiter's synchrotron radiation and the radio data at wavelengths of 6, 21, and 50 cm. The calculations were performed for a Jovian longitude of 200 deg and were based on the multipole field configurations as derived from the Pioneer data. The electron distribution in the inner magnetosphere was derived as a function of energy, pitch angle, and spatial coordinates. In addition, the hot region or east-west asymmetry in the radiation belts is investigated. It is suggested that this asymmetry is due to the combined effect of an overabundance of electrons at jovicentric longitudes of 240-360 deg and the existence of a dusk-to-dawn directed electric field over the inner magnetosphere generated by the wind system in the upper atmosphere.

De Pater, I.↗

NASA NTRS1983

Circuitry for Angle Measurements

Angle resolver pulsed and read under microprocessor control. Pulse generator excites resolver windings with dual slope pulse. System sequentially reads sine and cosine windings. Microprocessor determines angle through which resolver shaft turned from reference angle. Suitable applications include rate tables, antenna direction controllers, and machine tools.

Currie, J. R.↗

NASA NTRS1985

Tethers Open New Space Options

The fundamentals of tether action are discussed with focus on the forces acting on tethered masses and a tethered satellite system being developed for deployment from the space shuttle is examined. The static, dynamic, and electric properties of the tether can be exploited for use in the long term observation of phenomena of the lower troposphere; as a space based wind tunnel; to generate high electrodynamic power; to provide desirable gravity for the space station; to dock orbit transfer vehicles with the space station; and to form a constellation of space platforms tied to the space station. Italy is responsible for building and integrating the satellite. NASA is involved in building the deployer and integrating the tethered satellite system with the space shuttle.

Bekey, I.↗

NASA NTRS1985

Relationship between scattered power and correlation time in VHF radar signals

Equations describing the wave number spectra of wind shear-generated turbulent velocities and refractive index irregularities are discussed, and relations between radar echo power and signal correlation time are derived. If the radar backscatter wavelength is within the inertial subrange of the spectrum, a positive correlation between the scattered power and the signal correlation time is expected. For radar Bragg wavelengths within the dissipative subrange of turbulence, the correlation between scattered power and signal correlation time will be negative as usually expected in turbulence.

Royrvik, O.↗

NASA NTRS1985

A rotating superconducting solenoid for 100 kWh energy storage

Two concentric superconducting solenoids, one rotating, the other stationary are analyzed for energy storage in space. Energy is transferred from the rotating mass through a shaft coupled to a motor-generator. The inner windings interact with the magnetic field of the outer solenoid to cancel the centrifugal and self-field forces of the flywheel rim. Current is induced in the inner solenoid thus requiring no separate power supply, while the current in the outer solenoid must vary with the angular velocity of the flywheel. The effect of the gap and scaling laws are developed. The efficiency in energy per unit mass is marginally attractive.

Waynert, J.↗

NASA NTRS1985

Composite statistical method for modeling wind gusts for aircraft simulation

This paper discusses the application of three statistical methods in combination to model wind gusts for use in aircraft flight simulation. The approach combines principal components analysis, time series analysis and probability distribution model to analyze and simulate wind gust components. Comparisons are given between wind gust components generated by the model and components measured onboard an aircraft.

Schiess, J. R.↗

NASA NTRS1986

Quantitative determination of engine water ingestion

This paper describes a novel non-intrusive optical technique for determination of liquid mass flux in a droplet laden airstream. The technique was developed for quantitative determination of engine water ingestion resulting from heavy rain or wheel spray. Independent measurements of the liquid water content (LWC) of the droplet laden aircraft and of the droplet velocities were made at the simulated nacelle inlet plane for the liquid mass flux determination. The liquid water content was measured by illuminating and photographing the droplets contained within a thin slice of the flow field by means of a sheet of light from a pulsed YAG laser. A fluorescent dye introduced in the water greatly improved the droplet image definition. The droplet velocities were determined from double exposed photographs of the moving droplet field. The technique was initially applied to a steady spray generated in a wind tunnel. It was found that although the spray was initially steady, the aerodynamic breakup process was inherently unsteady. This resulted in a wide variation of the instantaneous liquid water content of the droplet laden airstream. The standard deviation of ten separate LWC measurements was 31 percent of the average. However, the liquid mass flux calculated from the average LWC and droplet velocities came within 10 percent of the known water ingestion rate.

Parikh, P.↗

NASA NTRS1986

General circulation model simulations of superrotation in slowly rotating atmospheres - Implications for Venus

The results of three-dimensional general circulation model experiments simulating the earth atmosphere with planetary rotation rates between 1 and 1/64th times the earth's and diurnally averaged thermal forcing are used to evaluate Venus atmospheric superrotation theories invoking the upward transport of angular momentum from the solid planet by the zonal mean circulation. While the theories predict that superrotation is a common feature of slowly rotating planetary atmospheres, suggesting that superrotation should appear in the present, slowly rotating cases, the steady state circulations are noted to include only weak globally averaged superrotation, consistent with previously reported results from lower resolution models. The thermally driven equator-to-pole circulation rapidly generates zonal mean winds during spinup, near the planetary surface, precluding vertical angular momentum transport and suppressing further superrotation development.

Covey, C.↗

NASA NTRS1986

Quantitative determination of engine water ingestion

A nonintrusive optical technique is described for determination of liquid mass flux in a droplet laden airstream. The techniques were developed for quantitative determination of engine water ingestion resulting from heavy rain or wheel spray. Independent measurements of the liquid water content (LWC) of the droplet laden airstream and of the droplet velocities were made at the stimulated nacelle inlet plane for the liquid mass flux determination. The LWC was measured by illuminating and photographing the droplets contained within a thin slice of the flow field by means of a sheet of light from a pulsed laser. A fluorescent dye introduced in the water enchanced the droplet image definition. The droplet velocities were determined from double exposed photographs of the moving droplet field. The technique was initially applied to a steady spray generated in a wind tunnel. It was found that although the spray was initially steady, the aerodynamic breakup process was inherently unsteady. This resulted in a wide variation of the instantaneous LWC of the droplet laden airstream. The standard deviation of ten separate LWC measurements was 31% of the average. However, the liquid mass flux calculated from the average LWC and droplet velocities came within 10% of the known water ingestion rate.

Parikh, P.↗

NASA NTRS1989

A candidate concept for display of forward-looking wind shear information

A concept is proposed which integrates forward-look wind shear information with airplane performance capabilities to predict future airplane energy state as a function of range. The information could be displayed to a crew either in terms of energy height or airspeed deviations. The anticipated benefits of the proposed display information concept are: (1) a wind shear hazard product that scales directly to the performance impact on the airplane and that has intuitive meaning to flight crews; (2) a reduction in flight crew workload by automatic processing of relevant hazard parameters; and (3) a continuous display of predicted airplane energy state if the approach is continued. Such a display may be used to improve pilot situational awareness or improve pilot confidence in wind shear alerts generated by other systems. The display is described and the algorithms necessary for implementation in a simulation system are provided.

Hinton, David A.↗

NASA NTRS1991

Io's volcanic and sublimation atmospheres

Fully 3D axisymmetric gasdynamic equations simulating SO2 and H2S frost sublimation and SO2 dayside and nightside volcanic atmospheres on Io are numerically solved, using a time-explicit finite-volume formulation. Both the sublimation and volcanic atmospheres generate horizontal supersonic winds away from the subsolar point or the volcanic vent. While the sublimation atmosphere is primarily driven by horizontal pressure gradients determined by surface temperatures, the volcanic atmosphere is driven by pressure gradients that are determined by the source rate. Sublimation and condensation produce patterns of surface deposits which are characteristic of the two types of atmospheres. The volcanic model is quantitatively consistent with Voyager observations of ring deposits.

Moreno, Miguel A.↗

NASA NTRS1990

Stratospheric chemistry and transport

A Chemical Tracer Model (CTM) that can use wind field data generated by the General Circulation Model (GCM) is developed to implement chemistry in the three dimensional GCM of the middle atmosphere. Initially, chemical tracers with simple first order losses such as N2O are used. Successive models are to incorporate more complex ozone chemistry.

Prather, Michael↗

NASA NTRS1990

Bearingless rotor aeromechanical stability measurements and correlations using nonlinear aerodynamics

The aeromechanical stability of a 1/8th Froude scaled bearingless rotor model was investigated experimentally in a wind tunnel. Both shaft-fixed and shaft-free conditions were examined to study the aeroelastic stability of a bearingless rotor without the incorporation of auxiliary dampers. This wind tunnel investigation generated a set of stability data for four different advance ratios, and a wide range of collective pitch settings. Theoretical analysis was performed using the newly developed University of Maryland Advanced Rotorcraft Code (UMARC). For analysis, the blade is modeled as an elastic beam undergoing flap bending, lag bending, elastic twist, and axial deformation. Blade response is calculated using a finite element method in time. Nonlinear aerodynamic effects are included by using a semiempirical stall modeling. The linearized periodic rotor perturbation equations in the nonrotating frame are solved for stability roots using Floquet transition matrix theory, as well as constant coefficient approximation. The predicted results are compared with the experimental data.

Wang, James M.↗

NASA NTRS1993

Magnetic Direct-Current-Measuring Circuits

Two circuits measure large direct currents in main conductors by use of magnetic fields produced by currents in glassy metal toroidal ferromagnetic cores surrounding main conductors. In both circuits, direct currents to be measured deduced from transient voltages generated in multiturn windings by transitions between magnetic fields produced by measured currents and saturation magnetic fields of cores.

Sullender, Craig C.↗

NASA NTRS1993

Behavior of vortices generated by an advancing ejecta curtain in theory, in the laboratory, and on Mars

Several papers assess the interaction between an atmosphere and advancing ejecta to assess possible atmospheric processes affecting ejecta emplacement. Ejecta travel through an atmosphere in two modes: larger ejecta blocks follow ballistic trajectories unhindered by the atmosphere; finer ejecta are entrained in a turbulent basal cloud, which develops as the advancing ejecta curtain generates strong atmospheric winds. Laboratory experiments reveal that this cloud of fine ejecta produce ramparts, flow lobes, or radial scouring that superposes larger ballistic ejecta emplaced earlier. Martian, Venusian, and terrestrial ejecta facies can be interpreted in terms of processes observed in the laboratory with appropriate first-order corrections for scaling. A continuum model of the atmospheric flow around an advancing inclined plate simulated and reproduced some of the complex flow patterns observed in front and at the top of the curtain. Here we consider improvements to the model to compare quantitatively the approximate position of ejecta deposition (i.e., run-out distance) with laboratory experiments and Martian ejecta facies.

Barnouin, O. S.↗

NASA NTRS1994

Wall interaction effects for a full-scale helicopter rotor in the NASA Ames 80- by 120-foot wind tunnel

A full-scale helicopter rotor test was conducted in the NASA Ames 80- by 120-Foot Wind Tunnel with a four-bladed S-76 rotor system. This wind tunnel test generated a unique and extensive data base covering a wide range of rotor shaft angles-of-attack and rotor thrust conditions from 0 to 100 knots. Three configurations were tested: (1) empty tunnel; (2) test stand body (fuselage) and support system; and (3) fuselage and support system with rotor installed. Empty tunnel wall pressure data are evaluated as a function of tunnel speed to understand the baseline characteristics. Aerodynamic interaction effects between the fuselage and the walls of the tunnel are investigated by comparing wall, ceiling, and floor pressures for various tunnel velocities and fuselage angles-of-attack. Aerodynamic interaction effects between the rotor and the walls of the tunnel are also investigated by comparing wall, ceiling, and floor pressures for various rotor shaft angles, rotor thrust conditions, and tunnel velocities. Empty tunnel wall pressure data show good repeatability and are not affected by tunnel speed. In addition, the tunnel wall pressure profiles are not affected by the presence of the fuselage apart from a pressure shift. Results do not indicate that the tunnel wall pressure profiles are affected by the presence of the rotor. Significant changes in the wall, ceiling, and floor pressure profiles occur with changing tunnel speeds for constant rotor thrust and shaft angle conditions. Significant changes were also observed when varying rotor thrust or rotor shaft angle-of-attack. Other results indicate that dynamic rotor loads and blade motion are influenced by the presence of the tunnel walls at very low tunnel velocity and, together with the wall pressure data, provide a good indication of flow breakdown.

Shinoda, Patrick M.↗

NASA NTRS1993

Correlated variations of UV and radio emissions during an outstanding Jovian auroral event

An exceptional Jovian aurora was detected in the FUV on December 21, 1990, by means of Vilspa and Goddard Space Flight Center (GFSC) International Ultraviolet Explorer (IUE) observations. This event included intensification by a factor of three between December 20 and 21, leading to the brightest aurora identified in the IUE data analyzed, and, in the north, to a shift of the emission peak towards larger longitudes. The Jovian radio emission simultaneously recorded at decameter wavelengths in Nancay also exhibits significant changes, from a weak and short-duration emission on December 20 to a very intense one, lasting several hours, on December 21. Confirmation of this intense radio event is also found in the observations at the University of Florida on December 21. The emissions are identified as right-handed Io-independent 'A' (or 'non Io-A') components from the northern hemisphere. The radio source region deduced from the Nancay observations lies, for both days, close to the UV peak emission, exhibiting in particular a similar shift of the source region toward larger longitudes from one day to the next. A significant broadening of the radio source was also observed and it is shown that on both days, the extent of the radio source closely followed the longitude range for which the UV brightness exceeds a given threshold. The correlated variations, both in intensity and longitude, strongly suggest that a common cause triggered the variation of the UV and radio emissions during this exceptional event. On one hand, the variation of the UV aurora could possibly be interpreted according to the Prange and Elkhamsi (1991) model of diffuse multicomponent auroral precipitation (electron and ion): it would arise from an increase in the precipitation rate of ions together with an inward shift of their precipitation locus from L approximately equal 10 to L approximately equal 6. On the other hand, the analysis of Ulysses observations in the upstream solar wind suggests that a significant disturbance in the solar wind, involving the generation of an interplanetary shock and the presence of a CME have interacted with the Jovian magnetosphere at about the time of the auroral event. Both arguments suggest that we may have observed for the first time a magnetic storm-type interaction in an outer planet magnetosphere, affecting simultaneously several auroral processes. Conversely, the observed relationship between the level of UV auroral activity and the detection of decameter emission (DAM), if it were a typical feature, might argue in favour of a more direct and permanent association between the auroral processes leading to UV and radio aurorae, possibly related to 'discrete-arc'-like activity and electron precipitation.

Prange, R.↗

NASA NTRS1994

A Remarkable Auroral Event on Jupiter Observed in the Ultraviolet with the Hubble Space Telescope

Two sets of ultraviolet images of the Jovian north aurora were obtained with the Faint Object Camera on board the Hubble Space Telescope. The first series shows an intense discrete arc in near corotation with the planet. The maximum apparent molecular hydrogen emission rate corresponds to an electron precipitation of approximately 1 watt per square meter, which is about 30,000 times larger than the solar heating by extreme ultraviolet radiation. Such a particle heating rate of the auroral upper atmosphere of Jupiter should cause a large transient temperature increase and generate strong thermospheric winds. Twenty hours after initial observations, the discrete arc had decreased in brightness by more than one order of magnitude. The time scale and magnitude of the change in the ultraviolet aurora leads us to suggest that the discrete Jovian auroral precipitation is related to large-scale variations in the current system as is the case of for Earth's discrete aurorae.

Gerard, J. C.↗