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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Discussion of flight experiments with an entry research vehicle

The focus of interest is the maneuvering flight of advanced entry vehicles operating at altitudes above 50 km and at velocities of 5 to 8 km/s. Information resulting in more accurate aerodynamic analysis is sought and measurement techniques that appear to be applicable are identified. Measurements discussed include: shock layer or boundary layer profiles of velocity, temperature, species mass fractions, and other gas properties associated with aerodynamic heating; surface energy transfer process; nonequilibrium flow processes and pressure distribution; separated, vortic leeside flow of nonequilibrium fluid; boundary layer transition on highly swept configurations; and shock and surface slip and gas/surface interaction. Further study should focus on evolving measurement techniques, installation requirements, and on identification of the portions of flights where successful results seem probable.

Potter, J. L.↗
NASA NTRS1985

Measurements of energy distribution and wall temperature in flowing hydrogen microwave plasma systems

An electrothermal propulsion concept utilizing a microwave plasma system as the mechanism to convert electromagnetic energy into translational energy of the flowing gas is being investigated. A calorimetric experimental system has been designed and built enclosing the microwave plasma system to accurately determine the net energy transferred to the flowing gas. For a flow rate of 8900 micromoles/sec, a pressure of 7.4 torr, and an absorbed power level of 80 W, an energy transfer efficiency of 50 percent has been measured. A heat transfer model that characterizes the energy transfer processes in the plasma is developed. A wall temperature for the plasma system is calculated.

Chapman, R.↗
NASA NTRS1985

Three-dimensional radiative transfer using a Fourier-transform matrix-operator method

The three-dimensional equation of transfer for a scattering medium with planar geometry is solved by using a spatial Fourier transform and extending matrix-operator techniques developed previously for the one-dimensional equation. Doubling and adding algorithms were derived by means of an interaction principle for computing the Fourier-transformed radiation field. The resulting expressions fully describe the radiative transfer process in a scattering medium, inhomogeneous in the x-, y- and z-directions, illuminated from above by an arbitrarily general intensity field and bounded from below by a surface with completely general reflection properties.

Martonchik, J. V.↗
NASA NTRS1986

Spatial distributions of magnetic field fluctuations in the dayside magnetosheath

In a study that tests the hypothesis that magnetosheath magnetic fields are disturbed on plasma streamlines which are connected to the quasi-parallel bow shock, magnetometer observations from the ISEE 2 and IMP 8 spacecraft are used to investigate the dayside spatial distributions of fluctuating magnetosheath fields for different interplanetary field orientations. The results suggest that although other sources such as Kelvin-Helmholtz instabilities and flux transfer processes probably contribute to the fluctuations in the magnetosheath field, the quasi-parallel shock source is an important contributor in the dayside region.

Luhmann, J. G.↗
NASA NTRS1986

Polarization photometer to measure bidirectional reflectance factor R(55 deg, 0 deg, 55 deg, 180 deg) of leaves

A polarization photometer has been developed for rapidly determining the bidirectional, polarized, and diffuse light-scattering properties of individual leavs illuminated and measured 'in vivo' at an angle of 55 deg (approximately Brewster's angle) in six wavelength bands in the visible and near-IR wavelength regions. The optical performance and data quality of the system are evaluated to estimate the magnitude of the variation in the data attributable to the instrument system and to measurement procedures. The potential to discriminate between three species of oak is demonstrated using data acquired by the polarization photometer. The instrument is being used to increase understanding of the radiation transfer process in plant canopies and specifically to determine how agronomic information of the physical and chemical processes in leaves, plants, and plant canopies is expressed in these light-scattering properties.

Vanderbilt, V. C.↗
NASA NTRS1986

Fast fluctuations of soft X-rays from active regions

A selection of short lived small soft X-ray bursts is studied using data from the Hard X-ray Imaging Spectrometer (HXIS), and the results are compared with the data from the Hard X-Ray Burst Spectrometer (HXRBS) with a view to understanding conditions at the onset of flares. Short-lived events provide an opportunity to study the radiation from the primary energy transfer process without confusion from the slowly-varying thermal X-ray emission which characterizes the decay of a large flare. The fast decay of the soft X-rays, only a few tens of seconds, suggests that they occur in the dense chromosphere. The results indicate that the short events may be signatures of several different phenomena, depending on their characteristics. Some events occur in association with reverse-drift type III bursts and simultaneous flaring elsewhere on the Sun, thus suggesting dumping of particles accelerated at a remote site. Some events have hard X-ray bursts and normal type III bursts associated with them, while others have neither. The latter events place strong constraints on the nonthermal electron population present.

Simnett, G. F.↗
NASA NTRS1984

Applications of aerospace technology

The objective of the Research Triangle Institute Technology Transfer Team is to assist NASA in achieving widespread utilization of aerospace technology in terrestrial applications. Widespread utilization implies that the application of NASA technology is to benefit a significant sector of the economy and population of the Nation. This objective is best attained by stimulating the introduction of new or improved commercially available devices incorporating aerospace technology. A methodology is presented for the team's activities as an active transfer agent linking NASA Field Centers, industry associations, user groups, and the medical community. This methodology is designed to: (1) identify priority technology requirements in industry and medicine, (2) identify applicable NASA technology that represents an opportunity for a successful solution and commercial product, (3) obtain the early participation of industry in the transfer process, and (4) successfully develop a new product based on NASA technology.

Rouse, Doris J.↗
NASA NTRS1987

Effect of structure on current and potential distributions in porous electrode

Porous electrodes generally contain constricted macropores and localized micropores. The effects of the macropore constrictions on the resistance of a capillary were studied and an analytical model was developed for predicting the current distribution in a constricted macropore which directly includes constriction effects and does not require an empirical tortuosity parameter. The current and concentration distributions in localized micropores were also investigated and it was shown that the microporous area is fully accessible to charge and mass transfer processes. From these analyses it was concluded that the micropores primarily affect the kinetics of the interfacial processes by contributing to the interfacial area, while the macropores impose ohmic and mass transport limitations through the volume of the porous electrode.

Lanzi, Oscar↗
NASA NTRS1986

The accretion disk limit cycle mechanism in GK Persei

The accretion disk thermal instability (limit cycle) mechanism for dwarf novalike outbursts is applied to the old nova GK Per in order to find values of the input parameters which reproduce the observed outbursts and to constrain the physics associated with the disk and the mass transfer process. It is found that models in which the dimensionless viscosity parameter has the value of 0.003 in the cold phase and 0.015 in the hot phase reproduce the observed spacing and duration of the eruptions. The calculated light curves at V and 1750 A are close to those observed during recent eruptions of GK Per if the interstellar reddening E(B-V) to this system is roughly 0.3.

Cannizzo, J. K.↗
NASA NTRS1987

Navier Stokes solution of the flowfield over ice accretion shapes

The numerical simulation of flow about ice accretion shapes has been accomplished by solving the Navier-Stokes equations using MacCormack's explicit finite difference scheme. The computations were performed on a CRAY-XMP computer. The influence of turbulence is taken into account by means of an algebraic eddy-viscosity model. In order to optimize the grid spacing and to achieve near orthogonality at the surface of the complex ice shapes, a hyperbolic grid generation scheme is utilized. Particular attention is given to the heat transfer process for which good agreement between the numerical and experimental results is achieved. In addition, liquid water droplet trajectories are coupled within the flowfield along with the resulting collection efficiencies using a parabolized Navier-Stokes formulation.

Scott, J. N.↗
NASA NTRS1986

Heat and mass transfer in flames

Heat- and mass-transfer processes in turbulent diffusion flames are discussed, considering turbulent mixing and the structure of single-phase flames, drop processes in spray flames, and nonluminous and luminous flame radiation. Interactions between turbulence and other phenomena are emphasized, concentrating on past work of the author and his associates. The conserved-scalar formalism, along with the laminar-flamelet approximation, is shown to provide reasonable estimates of the structure of gas flames, with modest levels of empiricism. Extending this approach to spray flames has highlighted the importance of drop/turbulence interactions; e.g., turbulent dispersion of drops, modification of turbulence by drops, etc. Stochastic methods being developed to treat these phenomena are yielding encouraging results.

Faeth, G. M.↗
NASA NTRS1986

An experimental study using flow visualization on the effect of an acoustic field on heat transfer from spheres

The physical mechanisms responsible for the heat transfer process in a thermal-acoustic field were investigated using the technique of holographic interferometry for flow visualization. Experimental results were obtained with sound pressure levels in the range of 120 to 150 decibels, relative to a pressure of 0.0002 dynes/sq cm. Steady state laminar flow was observed when the vibrational Reynolds number was below 400; separated flow was observed when it was above 400. In the presence of a horizontal sound field, the data indicate that the relation between the vibrational Nusselt number, Nu(v) and the vibrational Reynolds number, Re(v) is given by Nu(v) = Re(v) exp 0.22. In the presence of a vertical sound field, the corresponding relation is Nu(v) = Re(v) exp 0.15.

Leung, W. W.↗
NASA NTRS1987

Experimental study of laminar boundary layer receptivity to a traveling pressure field

Study is made of the production of Tollmien-Schlichting (T-S) waves within a Blasius boundary layer by an externally-imposed, two-dimensional, pressure field of a particular type. The field is that due to flow past a relatively small cylinder aligned parallel to the test plate and normal to the flow. The cylinder was carried on a circular path about an axis located well above the plate and such that the closest approach of the cylinder to the layer was several times the layer thickness or cylinder diameter. The turbulent wake did not, therefore, directly perturb the layer. Through adjustment of the circumferential velocity, the pressure field was swept along a certain region of the plate with controllable speed. Both the pressure field and the layer response are described in detail. It is shown that the production of T-S waves was sharply maximal for the case of circumferential speed near that of freely-propagating T-S waves, and that the coupling efficiency was extremely high for this case of resonance. The relevance of this energy transfer process to T-S wave production by the unsteady pressure fields resulting from wind tunnel wall turbulent boundary layers for both subsonic and supersonic flow is mentioned.

Kendall, James M.↗
NASA NTRS1988

Study of toluene rotary fluid management device and shear flow condenser performance for a space-based organic Rankine power system

Management of two-phase fluid and control of the heat transfer process in microgravity is a technical challenge that must be addressed for an orbital Organic Rankine Cycle (ORC) application. A test program was performed in 1-g that satisfactorily demonstrated the two-phase management capability of the rotating fluid management device (RFMD) and shear-flow condenser. Operational tests of the RFMD and shear flow condenser in adverse gravity orientations, confirmed that the centrifugal forces in the RFMD and the shear forces in the condenser were capable of overcoming gravity forces. In a microgravity environment, these same forces would not have to compete against gravity and would therefore be dominant. The specific test program covered the required operating range of the Space Station Solar Dynamic Rankine Cycle power system. Review of the test data verified that: fluid was pumped from the RFMD in all attitudes; subcooled states in the condenser were achieved; condensate was pushed uphill against gravity; and noncondensible gases were swept through the condenser.

Havens, Vance↗
NASA NTRS1987

Charge exchange avalanche at the cometopause

A sharp transition from a solar wind proton dominated flow to a plasma population primarily consisting of relatively cold cometary heavy ions has been observed at a cometocentric distance of about 160,000 km by the VEGA and GIOTTO missions. This boundary (the cometopause) was thought to be related to charge transfer processes, but its location and thickness are inconsistent with conventionally estimated ion - neutral coupling boundaries. In this paper a two-fluid model is used to investigate the major physical processes at the cometopause. By adopting observed comet Halley parameters the model is able to reproduce the location and the thickness of this charge exchange boundary.

Gombosi, Tamas I.↗
NASA NTRS1987

Technology advancements for the U.S. manned Space Station - An overview

The structure and methodology of the Johnson Space Center (JSC) advanced development program is described. An overview of the program is given, and the technology transfer process to other disciplines is described. The test bed and flight experiment programs are described, as is the technology assessment which was performed at the end of the Phase B program. The technology program within each discipline is summarized, and the coordination and integration of the JSC program with the activities of other NASA centers and with work package contractors are discussed.

Simon, William E.↗
NASA NTRS1988

Aerodynamic investigation by infrared imaging

Infrared imaging systems can be used to measure temperatures of actively heated bodies immersed in an airstream. This monitoring of the convective heat transfer process, provides also information about the interaction between the body and the flow. The concept appeals to Nusselt/Reynolds numbers relations in order to produce data of interest from surface temperatures. Two test cases are presented and reference is made to analytical results: the mapping of a laminar jet and the temperature distribution along a constant power heated flat plate in laminar boundary layer regime. Although this research is currently focused on low speed aerodynamics, the extension to high speed aerodynamics, where the body undergoes frictional heating is of interest in this context, too.

Roberts, A. Sidney, Jr.↗
NASA NTRS1988

Specular, diffuse and polarized imagery of an oat canopy

Light, polarized by specular reflection, has been found to be an important part of the light scattered by several measured plant canopies. The authors investigate for one canopy the relative importance of specularly reflected sunlight, specularly reflected light from other sources including skylight, and diffusely upwelling light. Polarization images are used to gain increased understanding of the radiation transfer process in a plant canopy. Analysis of the results suggests that properly analyzed polarized remotely sensed data, acquired under specific atmospheric conditions by a specially designed sensor, potentially provide measures of physiological and morphological states of plants in a canopy.

Vanderbilt, Vern C.↗