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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 937 records · Page 52
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Axially grooved heat pipes - 1976

This paper summarizes the 'state-of-the-art' of axially grooved heat pipes. Applications are identified and the related heat pipe design and performance are defined. Recent developments in the analysis, design and fabrication of axially grooved hardware are also discussed. A mathematical model which predicts the hydrodynamic behavior and accounts for liquid recession, liquid/vapor shear interaction and 1-g puddle flow is also presented. Performance data for various fluids in the 100-500 K range is compared to predictions from the Groove Analysis Program (GAP). Finally, a simplified closed form solution which accounts for gravity effects, self-priming and composite pumping by the grooves as well as all of the hydrodynamic losses is also discussed.

Brennan, P. J.↗
NASA NTRS1977

Axially grooved heat pipe study

A technology evaluation study on axially grooved heat pipes is presented. The state-of-the-art is reviewed and present and future requirements are identified. Analytical models, the Groove Analysis Program (GAP) and a closed form solution, were developed to facilitate parametric performance evaluations. GAP provides a numerical solution of the differential equations which govern the hydrodynamic flow. The model accounts for liquid recession, liquid/vapor shear interaction, puddle flow as well as laminar and turbulent vapor flow conditions. The closed form solution was developed to reduce computation time and complexity in parametric evaluations. It is applicable to laminar and ideal charge conditions, liquid/vapor shear interaction, and an empirical liquid flow factor which accounts for groove geometry and liquid recession effects. The validity of the closed form solution is verified by comparison with GAP predictions and measured data.

Source record↗
NASA NTRS1978

Activities of the US Geological Survey in Applications of Remote Sensing in the Chesapeake Bay Region

The application of remote sensing in the Chesapeake Bay region has been a central concern of three project activities of the U.S. Geological Survey: two are developmental, and one is operational. The two developmental activities were experiments in land-use and land-cover inventory and change detection using remotely sensed data from aircraft and from the LANDSAT and Skylab satellites. One of these is CARETS (Central Atlantic Regional Ecological Test Site). The other developmental task is the Census Cities Experiment in Urban Change Detection. The present major concern is an operational land-use and land-cover data-analysis program, including a supporting geographical information system.

Wray, J. R.↗
NASA NTRS1977

Thermal radiation analysis system (TRASYS 2), programmer's manual

TRASYS, the Thermal Radiation Analysis System, is a digital computer software system with a generalized capability to solve the radiation-related aspects of thermal analysis problems. When used in conjunction with a generalized thermal analysis program such as the Systems Improved Numerical Differencing Analyzer (SINDA) program, any thermal problem that can be expressed in terms of a lumped parameter, radiation conductor thermal network can be solved. The function of TRASYS is twofold. It provides: 1) Internode radiation interchange data; 2) Incident and absorbed heat rate data from environmental radiant heat sources. Data of both types are provided in a format directly usable by the thermal analyzer programs.

Connor, R. J.↗
NASA NTRS1978

Modifications to the accuracy assessment analysis routine SPATL to produce an output file

The SPATL is an analysis program in the Accuracy Assessment Software System which makes comparisons between ground truth information and dot labeling for an individual segment. In order to facilitate the aggregation cf this information, SPATL was modified to produce a disk output file containing the necessary information about each segment.

Carnes, J. G.↗
NASA NTRS1978

Low-cycle fatigue of thermal-barrier coatings at 982 deg C

The low-cycle fatigue lives of ZrO2-NiCrAlY and Al2O3-ZrO2-NiCrAlY thermal-barrier coatings in air at 982 C were determined from cyclic flexural tests of coated TAZ-8A strips. Strains were computed as a function of specimen displacements from a nonlinear, three-dimensional stress analysis program. Fatigue resistances of thermal-barrier coatings applied to the strips were compared with those of uncoated and NiCrAlY-coated strips. The results indicate that ZrO2 is about four times greater in fatigue life than TAZ-8A at 982 C, that ZrO2 would probably retain that fatigue strength up to 1316 C, and that adding an outer coat of Al2O3 to ZrO2 is neither beneficial nor detrimental to fatigue resistance.

Kaufman, A.↗
NASA NTRS1978

The prediction of lightning-induced voltages on metallic and composite aircraft

Various government agencies have put forth effort to enable the prediction of what lightning current will do to aircraft avionic systems. Ongoing and future efforts of predicting avionic voltages and currents caused by electromagnetic fields external to the aircraft are illustrated. The Intrasystem Analysis Program (IAP) was put to use to predict lightning-induced voltages on avionic systems. Presently funded programs are investigating the modification nonmetallic composite materials will cause to the metallic IAP program predictions. The various factors involved in designing prediction techniques are discussed.

Birken, J.↗
NASA NTRS1979

A maximum likelihood convolutional decoder model vs experimental data comparison

This article describes the comparison of a maximum likelihood convolutional decoder (MCD) prediction model and the actual performance of the MCD at the Madrid Deep Space Station. The MCD prediction model is used to develop a subroutine that has been utilized by the Telemetry Analysis Program (TAP) to compute the MCD bit error rate for a given signal-to-noise ratio. The results indicate that that the TAP can predict quite well compared to the experimental measurements. An optimal modulation index also can be found through TAP.

Chen, R. Y.↗
NASA NTRS1979

A theoretical study of heterojunction and graded band gap type solar cells

The work performed concentrated on including multisun effects, high temperature effects, and electron irradiation effects into the computer analysis program for heterojunction and graded bandgap solar cells. These objectives were accomplished and the program is now available for such calculations.

Chiang, J. P. C.↗
NASA NTRS1979

Spacecraft charging results for the DSCS-3 satellite

Spacecraft charging results are presented for the DSCS-3 satellite for a severe geomagnetic substorm. Spacecraft charging results were obtained by the use of the electrostatic charging analysis program (ESCAP). The ESCAP computer code which can determine both the transient or steady state differential charging potentials was an engineering design tool that utilized a circuit theory approach to spacecraft charging. Using the ESCAP code, the steady state (static) differential potentials of the outer spacecraft surfaces and metallic structure were obtained for the DSCS-3 satellite when under the influence of a severe geomagnetic substorm during the local midnight-to-dawn quadrant of its geosynchronous orbital path. The results indicated that, in the steady state, most of the DSCS-3 outer surface materials will not achieve differential potentials large enough to produce an electrostatic discharge.

Massaro, M. J.↗
NASA NTRS1979

Analysis of the Effects of Impurities in Silicon

A solar cell fabrication and analysis program was conducted to determine the effects on the resultant solar cell efficiency of impurities intentionally incorporated into silicon. The program employed flight quality technologies and quality assurance to assure that variations in cell performance were due to the impurities incorporated in the silicon. The initial verification runs have resulted in an average AM0 cell efficiency of 12.8% at 25 C.

Wohlgemuth, J. H.↗
NASA NTRS1979

A dc model for power switching transistors suitable for computer-aided design and analysis

A model for bipolar junction power switching transistors whose parameters can be readily obtained by the circuit design engineer, and which can be conveniently incorporated into standard computer-based circuit analysis programs is presented. This formulation results from measurements which may be made with standard laboratory equipment. Measurement procedures, as well as a comparison between actual and computed results, are presented.

Wilson, P. M.↗
NASA NTRS1979

Effects of diffusion factor, aspect ratio and solidity on overall performance of 14 compressor middle stages

A series of high hub tip radius ratio compressor stages representative of the middle and latter stages of axial flow compressors is discussed. The effects of aspect ratio, diffusion factor, and solidity on rotor and stage performance are determined. Fourteen middle stages are tested to study the effects on performance of varying both diffusion through the rotor and stator blades and blade aspect ratio. The design parameters in the streamline analysis program, the blade geometry program, and the blade coordinate program are presented.

Britsch, W. R.↗
NASA NTRS1979

Analysis of the Effects of Impurities in Silicon

A solar cell fabrication and analysis program to determine the effects on the resultant solar cell efficiency of impurities incorporated into silicon is conducted. Flight quality technologies and quality assurance are employed to assure that variations in cell performance are due to the impurities incorporated in the silicon. The type and level of impurity doping in each test lot is given and the mechanism responsible for the degradation of cell performance is identified and correlated to the doped impurities.

Wohlgemuth, J. H.↗
NASA NTRS1979

The effect of fuel sprays on emissions from a gas turbine combustor

A research gas turbine combustor which allows for independent control of drop size, fuel/air ratio, air inlet temperature, pressure, reference velocity, and residence time has been used to study the influence of fuel spray characteristics on primary zone emissions. Local concentrations of oxides of nitrogen, carbon monoxide and unburned hydrocarbons at various locations in the flow, local gas temperature, gas velocity, and the turbulence intensity (measured with laser velocimetry) are obtained. A comprehensive data analysis program to compute the local fuel/air ratio and the sum of the mole fractions of the species present confirms the validity of the emissions data. Increasing drop size is correlated with an increase in unburned hydrocarbons, while increasing residence time is associated with sharp decreases in hydrocarbons and carbon monoxide and an increase in oxides of nitrogen.

Nicholls, J. A.↗
NASA NTRS1979

Diagnostics of wear in aeronautical systems

The use of appropriate diagnostic tools for aircraft oil wetted components is reviewed, noting that it can reduce direct operating costs through reduced unscheduled maintenance, particularly in helicopter engine and transmission systems where bearing failures are a significant cost factor. Engine and transmission wear modes are described, and diagnostic methods for oil and wet particle analysis, the spectrometric oil analysis program, chip detectors, ferrography, in-line oil monitor and radioactive isotope tagging are discussed, noting that they are effective over a limited range of particle sizes but compliment each other if used in parallel. Fine filtration can potentially increase time between overhauls, but reduces the effectiveness of conventional oil monitoring techniques so that alternative diagnostic techniques must be used. It is concluded that the development of a diagnostic system should be parallel and integral with the development of a mechanical system.

Wedeven, L. D.↗
NASA NTRS1980

Predicting crack propagation

Flaw growth under load is predicted in two dimensions with Advanced Crack Propagation Predictive Analysis Program (FLAGR04). FLAGR04 accommodates variety of cracks, crack transitions, stress gradients, changes in material properties, and Willenberg retardation. Program is written in FORTRAN IV for batch execution and is available for CDC and IBM machines.

Hu, T.↗