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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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Device suitable for molecular epitaxial formation of semiconductor components. Improved electrostatic lens system uses cylindrical mirror as central element between two tubular lenses. Abberations introduced by mirror tend to cancel those introduced by tubular lenses. Result is order-of-magnitude improvement in chromatic or spherical compensation.
Refinements in a 10 percent thick supercritical airfoil produced improvements in the overall drag characteristics at normal force coefficients from about 0.30 to 0.65 compared with earlier supercritical airfoils which were developed for a normal force coefficient of 0.7. The drag divergence Mach number of the improved supercritical airfoil (airfoil 26a) varied from approximately 0.82 at a normal force coefficient to of 0.30, to 0.78 at a normal force coefficient of 0.80 with no drag creep evident. Integrated section force and moment data, surface pressure distributions, and typical wake survey profiles are presented.
Several improvements and enhancements recently made to NASTRAN are described. Some of the more important features are: streamlined rigid formats; improved rigid formats; changes related to plotting; checking of required PARAM bulk data cards; checkpoint/restart capability; unsorted and sorted bulk data deck echo; automatic output of the DMAP source listing; elimination of link switching caused by use of utility modules; paging the NASTRAN output; processing of mixed record data blocks by INPUT2/OUTPUT2 modules; module execute flag included in the OSCAR listing; and use of the multiple XDMAP cards in the DMAP. It is concluded that these changes increase the usefulness of the program.
An integrated thermal-structural finite element approach for efficient coupling of thermal and structural analyses is presented. New thermal finite elements which yield exact nodal and element temperature for one dimensional linear steady state heat transfer problems are developed. A nodeless variable formulation is used to establish improved thermal finite elements for one dimensional nonlinear transient and two dimensional linear transient heat transfer problems. The thermal finite elements provide detailed temperature distributions without using additional element nodes and permit a common discretization with lower order congruent structural finite elements. The accuracy of the integrated approach is evaluated by comparisons with analytical solutions and conventional finite element thermal-structural analyses for a number of academic and more realistic problems. Results indicate that the approach provides a significant improvement in the accuracy and efficiency of thermal stress analysis for structures with complex temperature distributions.
Five chemically different resin systems with improved fire resistance properties were studied for a possible screenprinting ink application. Fire resistance is hereby defined as the cured ink possessing improvements in flammability, smoke emission, and thermal stability. The developed ink is for application to polyvinyl fluoride film. Only clear inks without pigments were considered. Five formulations were evaluated compared with KC4900 clear acrylic ink, which was used as a baseline. The tests used in the screening evaluation included viscosity, smoke and toxic gas emission, limiting oxygen index (LOI), and polyvinyl fluoride film (PVF) printability. A chlorofluorocarbon resin (FPC461) was selected for optimization studies. The parameters for optimization included screenprinting process performance, quality of coating, and flammability of screenprinted 0.051-mm (0.002-in.) white Tedlar. The quality of the screenprinted coating on Tedlar is dependent on viscosity, curing time, adhesion to polyvinyl fluoride film, drying time (both inscreen and as an applied film), and silk screen mesh material and porosity.
A directed principal component (PC) analysis and its transformation was applied to 7-channel thematic mapper simulator (TMS) data and 4-channel LANDSAT multispectral scanner system (MSS) data collected over the city of Lancaster, Pennsylvania, to create improved imagery for geometric control point selection for image to image registration. Nineteen temporally stable geometric control points, such as road interactions and bridges, were selected for a 236 sq km area. The control points were visible on both the TMS and MSS imagery. On the first attempt the corresponding image control points were selected on both data sets without using the principal components transformation. Many of the road intersection locations were visible but the actual road crossings could not be distinguished. As a result, mensuration errors using raw data exceeded the equivalent of two (79 x 79 m) pixels. The application of a guided principal components transformation yielded TMS and MSS single band images showing improved detail in the scene's urban and residential infrastructure. The PC transformed data sets were then utilized for the reselection of geometric control points. By shown greater detail, control points on both the TMS and MSS imagery could be located with greater precision using the PC transformed data.
An improved method for use of optimization techniques in transonic airfoil design is demonstrated. FLO6QNM incorporates a modified quasi-Newton optimization package, and is shown to be more reliable and efficient than the method developed previously at NASA-Ames, which used the COPES/CONMIN optimization program. The design codes are compared on a series of test cases with known solutions, and the effects of problem scaling, proximity of initial point to solution, and objective function precision are studied. In contrast to the older method, well-converged solutions are shown to be attainable in the context of engineering design using computational fluid dynamics tools, a new result. The improvements are due to better performance by the optimization routine and to the use of problem-adaptive finite difference step sizes for gradient evaluation.
The adherence between a ceramic thermal barrier coating and a metal bond coating is improved by ion sputtering a ceramic film on the bond cost. A ceramic thermal barrier coating is then plasma-sprayed onto this primer film. This improves the integrity and strength of the interface between the plasma-sprayed ceramic layer and metallic bond coat which insures stronger adherence between the metal and the ceramic.
An improved method for use of optimization techniques in transonic airfoil design is demonstrated. FLO6QNM incorporates a modified quasi-Newton optimization package, and is shown to be more reliable and efficient than the method developed previously at NASA-Ames, which used the COPES/CONMIN optimization problem. The design codes are compared on a series of test cases with known solutions, and the effects of problem scaling, proximity of initial point to solution, and objective function precision are studied. In contrast to the older method, well-converged solutions are shown to be attainable in the context of engineering design using computational fluid dynamics tools, a new result. The improvements are due to better performance by the optimization routine and to the use of problem-adaptive finite difference step sizes for gradient evaluation.
An improved condensation nucleus counter (CNC) for use in the stratosphere is described. The University of Minnesota CNC (UMCNC) has a sequential saturator and condenser and uses n-butyl alcohol as the working fluid. The use of a coaxial saturator flow, with aerosol in the center and filtered, alcohol-laden air around it, speeds the response of this instrument and improves its stability as pressure changes. The counting efficiency has been studied as a function of particle size and pressure. The UMCNC provides an accurate measure of submicron aerosol concentration as long as the number distribution is not dominated by sub-0.02 micron diameter aerosol. The response of the UMCNC is compared with that of other stratospheric condensation nucleus counters, and the results of a (near) comparison with a balloon-borne condensation nucleus counter are presented. The UMCNC has operated 14 times on a NASA U-2 aircraft at altitudes from 8 to 21.5 km.
Static analysis and a computer structural model for the large 64-m antenna pedestal are developed using the MSC version of the NASTRAN program. This improved pedestal model includes the launch areas and the actual pressure pattern of the oil under the hydrostatic bearing pad. The results obtained from the new improved model have indicated that the deflections due to pad loads are in good agreement with field measurements. The top surface deflection of the pedestal obtained from the NASTRAN model is used as an input to the oil film computer program to determine the minimum oil film thickness under the pad.
The proper combination of optical design with image plane processing, as in the mechanism of human vision, which allows to improve the performance of sensor array imaging systems for edge detection and location was examined. Two dimensional bandpass filtering during image formation, optimizes edge enhancement and minimizes data transmission. It permits control of the spatial imaging system response to tradeoff edge enhancement for sensitivity at low light levels. It is shown that most of the information, up to about 94%, is contained in the signal intensity transitions from which the location of edges is determined for raw primal sketches. Shading the lens transmittance to increase depth of field and using a hexagonal instead of square sensor array lattice to decrease sensitivity to edge orientation improves edge information about 10%.
An improved Charge Injection Device (CID) stellar tracking sensor and an operating sensor in a control/readout electronics board were developed. The sensor consists of a shift register scanned, 256x256 CID array organized for readout of 4x4 subarrays. The 4x4 subarrays can be positioned anywhere within the 256x256 array with a 2 pixel resolution. This allows continuous tracking of a number of stars simultaneously since nine pixels (3x3) centered on any star can always be read out. Organization and operation of this sensor and the improvements in design and semiconductor processing are described. A hermetic package incorporating an internal thermoelectric cooler assembled using low temperature solders was developed. The electronics board, which contains the sensor drivers, amplifiers, sample hold circuits, multiplexer, analog to digital converter, and the sensor temperature control circuits, is also described. Packaged sensors were evaluated for readout efficiency, spectral quantum efficiency, temporal noise, fixed pattern noise, and dark current. Eight sensors along with two tracker electronics boards were completed, evaluated, and delivered.
The Space Shuttle Orbiter Auxiliary Power Unit subsystem has operated successfully on three vehicles by meeting mission requirements and has proven the design for space operation. The current Auxiliary Power Unit (APU) operational life is limited to 12 missions and the APU turnaround between flights is longer than originally anticipated. The Improved APU objective is to increase life to 50 missions, reduce the three - APU subsystem vehicle weight by 140 lbs., and reduce turnaround time. The design changes incorporated into the Improved APU and the associated development testing are described.
A resin product useful as an adhesive, composite or casting resin is described as well as the process used in its preparation to improve its flexural strength mechanical property characteristics. Improved flexural strength is attained with little or no change in density, thermal stability or moisture resistance by chemically incorporating 1.2% to 10.6% by weight Co(3) ions in an epoxidized resin system.
Ion implantation techniques offering improved cell performance and reduced cost have been studied. These techniques include non-mass-analyzed phosphorus implantation, argon implantation gettering, and low temperature boron annealing. It is found that cells produced by non-mass-analyzed implantation perform as well as mass-analyzed controls, and that the cell performance is largely independent of process parameters. A study of argon implantation gettering shows no improvement over non-gettered controls. Results of low temperature boron annealing experiments are presented.
An experimental jet fuel with a -33 C freezing point was chilled in a wing tank simulator with superimposed fuel heating to improve low temperature flowability. Heating consisted of circulating a portion of the fuel to an external heat exchanger and returning the heated fuel to the tank. Flowability was determined by the mass percent of unpumpable fuel (holdup) left in the simulator upon withdrawal of fuel at the conclusion of testing. The study demonstrated that fuel heating is feasible and improves flowability as compared to that of baseline, unheated tests. Delayed heating with initiation when the fuel reaches a prescribed low temperature limit, showed promise of being more efficient than continuous heating. Regardless of the mode or rate of heating, complete flowability (zero holdup) could not be restored by fuel heating. The severe, extreme-day environment imposed by the test caused a very small amount of subfreezing fuel to be retained near the tank surfaces even at high rates of heating. Correlations of flowability established for unheated fuel tests also could be applied to the heated test results if based on boundary-layer temperature or a solid index (subfreezing point) characteristic of the fuel. Previously announced in STAR as N82-26483
A 'pathfinder' plan to improve Halley's Comet targeting accuracy of ESA's Giotto spacecraft is proposed, by which optical data and orbit information from Soviet VEGA spacecraft are used to produce an updated ephemeris for Halley's Comet. Two versions of the plan are described and the increased targeting accuracy is determined through a linear covariance analysis. In both versions of the plan, NASA Deep Space Net VLBI measurements of VEGA position are exchanged for information from VEGA about its optical pointing angle and Doppler and ranging measurements which are then transmitted to Giotto. In the covariance analysis of targeting accuracy, it is found that by using pathfinder the error in Giotto-Halley targeting can be reduced from 500 to within 100 km. It is predicted that pathfinder will thus substantially improve the amount of data that Giotto will gather from its fly-by of Halley's Comet March 14, 1986.