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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 NTRS1974

Study of process variables associated with manufacturing hermetically-sealed nickel-cadmium cells

A two year study of the major process variables associated with the manufacturing process for sealed, nickel-cadmium, areospace cells is summarized. Effort was directed toward identifying the major process variables associated with a manufacturing process, experimentally assessing each variable's effect, and imposing the necessary changes (optimization) and controls for the critical process variables to improve results and uniformity. A critical process variable associated with the sintered nickel plaque manufacturing process was identified as the manual forming operation. Critical process variables identified with the positive electrode impregnation/polarization process were impregnation solution temperature, free acid content, vacuum impregnation, and sintered plaque strength. Positive and negative electrodes were identified as a major source of carbonate contamination in sealed cells.

Miller, L.↗
NASA NTRS1975

A note on optimal filtering in the presence of unknown biases

This note considers some aspects of the optimal filtering problem for linear processes in the presence of unknown biases in the input and the observations. It is proved via duality that the optimal filtering problem in the presence of an input bias is equivalent to a certain optimal regulator problem incorporating integral feedback. The question of observability of the augmented system used in the state and bias estimation is answered by deriving necessary and sufficient conditions when bias is present (1) in the input, (2) in the observations and (3) both in the input and the observations.

Joshi, S. M.↗
NASA NTRS1975

Improved resource use decisions and actions through remote sensing

Operational uses of remote sensing for improving management decisions and actions concerning resource uses are considered in terms of first generation, or direct-action; and second generation or indirect, delayed-action applications. From among applications completed during 1974-75, seven case studies are offered in illustration of the many contrasts which can be drawn between first and second generation application studies. These include: (1) multi-agency river basin planning; (2) corridor assessment and route location for highway location together with improvement of county-level planning decisions; (3) improving timber management practices; (4) enforcement of new state statutes; (5) county-wide open space preservation; (6) land value reappraisal relative to property tax equalization; and (7) optimizing agri-business processing plant locations.

Hill-Rowley, R.↗
NASA NTRS1977

Ambiguity resolution for satellite Doppler positioning systems

A test for ambiguity resolution was derived which was the most powerful in the sense that it maximized the probability of a correct decision. When systematic error sources were properly included in the least squares reduction process to yield an optimal solution, the test reduced to choosing the solution which provided the smaller valuation of the least squares loss function. When systematic error sources were ignored in the least squares reduction, the most powerful test was a quadratic form comparison with the weighting matrix of the quadratic form obtained by computing the pseudo-inverse of a reduced rank square matrix. A formula is presented for computing the power of the most powerful test. A numerical example is included in which the power of the test is computed for a situation which may occur during an actual satellite aided search and rescue mission.

Argentiero, P. D.↗
NASA NTRS1979

Ambiguity resolution for satellite Doppler positioning systems

The implementation of satellite-based Doppler positioning systems frequently requires the recovery of transmitter position from a single pass of Doppler data. The least-squares approach to the problem yields conjugate solutions on either side of the satellite subtrack. It is important to develop a procedure for choosing the proper solution which is correct in a high percentage of cases. A test for ambiguity resolution which is the most powerful in the sense that it maximizes the probability of a correct decision is derived. When systematic error sources are properly included in the least-squares reduction process to yield an optimal solution the test reduces to choosing the solution which provides the smaller valuation of the least-squares loss function. When systematic error sources are ignored in the least-squares reduction, the most powerful test is a quadratic form comparison with the weighting matrix of the quadratic form obtained by computing the pseudoinverse of a reduced-rank square matrix. A formula for computing the power of the most powerful test is provided. Numerical examples are included in which the power of the test is computed for situations that are relevant to the design of a satellite-aided search and rescue system.

Argentiero, P.↗
NASA NTRS1979

High efficiency ultrathin silicon solar cells

This paper summarizes developments in ultrathin, (50 micron), silicon solar cells for high power-to-weight ratio space power systems. The fabrication technology developments included uniformly thinning oriented silicon slices, enhancement of internal reflection, optimizing high-temperature processes, surface texturing and back surface field enhancement. The best textured-surface ultrathin cells have achieved 14.3% AMO efficiency, while pilot-manufacturing quantities of smooth-surfaced cells have been fabricated with efficiencies of 12%. Data are presented on cell structure, fabrication collection efficiencies and optical properties.

Storti, G.↗
NASA NTRS1981

Discrimination of form in images corrupted by speckle

The problem investigated is that of a human observer having to distinguish between certain specified geometrical forms corrupted by speckle - an idealization of the problem of a scientist studying a synthetic aperture radar map. Specifically, the cases of two simple alternative forms and of two and four orientations of a simple form have been considered. A theoretical model is developed for the observer's decision process by analogy with optimal receiver theory, and the probability of a correct decision is related to form parameters like size, contrast, and looks. These calculations are verified by psychophysical experiments using computer-simulated pictures.

Korwar, V. N.↗
NASA NTRS1981

A Module Experimental Process System Development Unit (MEPSDU)

A cost effective process sequence and machinery for the production of flat plate photovoltaic modules are described. Cells were fabricated using the process sequence which was optimized, as was a lamination procedure. Insulator tapes and edge seal material were identified and tested. Encapsulation materials were evaluated.

Source record↗
NASA NTRS1981

Development of thin wraparound junction silicon solar cells

The state of the art technologies was applied to fabricate 50 micro thick 2x4 cm, coplanar back contact (CBC) solar cells with AMO efficiency above 12%. A requirement was that the cells have low solar absorptance. A wraparound junction (WAJ) with wraparound metallization was chosen. This WAJ approach avoided the need for very complex fixturing, especially during rotation of the cells for providing adequate contacts over dielectric edge layers. The contact adhesion to silicon was considered better than to an insulator. It is indicated that shunt resistance caused by poor WAJ diode quality, and series resistance from the WAJ contact, give good cell performance. The cells developed reached 14 percent AMO efficiency (at 25 C), with solar absorptance values of 0.73. Space/cell environmental tests were performed on these cells and the thin CSC cells performed well. The optimized design configuration and process sequence were used to make 50 deliverable CBC cells. These cells were all above 12 percent efficiency and had an average efficiency of -13 percent. Results of environmental tests (humidity-temperature, thermal shock, and contact adherence) are also given.

Ho, F.↗
NASA NTRS1982

Development of a large area space solar cell assembly

The development of a large area high efficiency solar cell assembly is described. The assembly consists of an ion implanted silicon solar cell and glass cover. The important attributes of fabrication are the use of a back surface field which is compatible with a back surface reflector, and integration of coverglass application and cell fabrications. Cell development experiments concerned optimization of ion implantation processing of 2 ohm-cm boron-doped silicon. Process parameters were selected based on these experiments and cells with area of 34.3 sq cm wre fabricated. The average AMO efficiency of the twenty-five best cells was 13.9% and the best bell had an efficiency of 14.4%. An important innovation in cell encapsulation was also developed. In this technique, the coverglass is applied before the cell is sawed to final size. The coverglass and cell are then sawed as a unit. In this way, the cost of the coverglass is reduced, since the tolerance on glass size is relaxed, and costly coverglass/cell alignment procedures are eliminated. Adhesive investigated were EVA, FEP-Teflon sheet and DC 93-500. Details of processing and results are reported.

Spitzer, M. B.↗
NASA NTRS1985

Objectives and first results of the NASA SETI Sky Survey field tests at Goldstone, California

The objectives and preliminary results of the initial field tests of the prototype hardware and software for the NASA SETI program are reviewed with emphasis on the Sky Survey component of the NASA search strategy. In particular, attention is given to field test instrumentation, sky pixelation, sky survey field tests, baseline tests, antenna control tests, and radio frequency interference survey. The test results and observational experience will be used to finalize the design of the SETI Sky Survey processing system and to optimize the observational strategy and procedures in time to begin a full-scale Microwave Observing Program in 1990.

Gulkis, S.↗
NASA NTRS1986

MAX '91: An advanced payload for the exploration of high energy processes on the active sun

The results of a NASA science working group established to study a follow-on to the Solar Maximum Mission are given. A complement of instruments is suggested, with the primary objective of studying the physics of energetic processes in cosmic plasmas by observing high-energy phenomena in solar flares. High-quality flare observations will be possible with these instruments during the next peak in solar activity expected to last from 1990 through at least 1995. The primary objective of MAX '91 is to study energetic processes in cosmic plasmas by observing high-energy phenomena in solar flares. These processes, which are of general astrophysical importance, include energy release, particle acceleration, and energy transport. Results from comprehensive observing programs conducted during the last solar cycle have demonstrated the great scientific potential of high-energy emissions for addressing these central physical processes. Consequently, a payload optimized for observations of high-energy solar flare phenomena is suggested for MAX '91. It consists of the following four specific instruments: (1) a Fourier-transform X-ray and gamma-ray imager covering the energy range from a few keV to 1 MeV with arcsecond spatial resolution; (2) a cooled germanium X-ray and gamma-ray spectrometer with keV spectral resolution covering the energy range from 10 keV to 50 MeV; (3) Bragg spectrometers with high spectral resolution at wavelengths between 1 and 9 angstrons; and (4) a soft X-ray, EUV, or UV imaging instrument with arcsecond spatial resolution.

Source record↗
NASA NTRS1988

The Sizing and Optimization Language, (SOL): Computer language for design problems

The Sizing and Optimization Language, (SOL), a new high level, special purpose computer language was developed to expedite application of numerical optimization to design problems and to make the process less error prone. SOL utilizes the ADS optimization software and provides a clear, concise syntax for describing an optimization problem, the OPTIMIZE description, which closely parallels the mathematical description of the problem. SOL offers language statements which can be used to model a design mathematically, with subroutines or code logic, and with existing FORTRAN routines. In addition, SOL provides error checking and clear output of the optimization results. Because of these language features, SOL is best suited to model and optimize a design concept when the model consits of mathematical expressions written in SOL. For such cases, SOL's unique syntax and error checking can be fully utilized. SOL is presently available for DEC VAX/VMS systems. A SOL package is available which includes the SOL compiler, runtime library routines, and a SOL reference manual.

Lucas, Stephen H.↗
NASA NTRS1989

Nutritional models for a Controlled Ecological Life Support System (CELSS): Linear mathematical modeling

The NASA Controlled Ecological Life Support System (CELSS) Program is involved in developing a biogenerative life support system that will supply food, air, and water to space crews on long-duration missions. An important part of this effort is in development of the knowledge and technological capability of producing and processing foods to provide optimal diets for space crews. This involves such interrelated factors as determination of the diet, based on knowledge of nutrient needs of humans and adjustments in those needs that may be required as a result of the conditions of long-duration space flight; determination of the optimal mixture of crops required to provide nutrients at levels that are sufficient but not excessive or toxic; and consideration of the critical issues of spacecraft space and power limitations, which impose a phytomass minimization requirement. The complex interactions among these factors are examined with the goal of supplying a diet that will satisfy human needs while minimizing the total phytomass requirement. The approach taken was to collect plant nutritional composition and phytomass production data, identify human nutritional needs and estimate the adjustments to the nutrient requirements likely to result from space flight, and then to generate mathematical models from these data.

Wade, Rose C.↗
NASA NTRS1989

Validation of the procedures

Validation strategies are described for procedures aimed at improving the rotor blade design process through a multidisciplinary optimization approach. Validation of the basic rotor environment prediction tools and the overall rotor design are discussed.

Mantay, Wayne R.↗
NASA NTRS1991

Development of silicon carbide semiconductor devices for high temperature applications

The semiconducting properties of electronic grade silicon carbide crystals, such as wide energy bandgap, make it particularly attractive for high temperature applications. Applications for high temperature electronic devices include instrumentation for engines under development, engine control and condition monitoring systems, and power conditioning and control systems for space platforms and satellites. Discrete prototype SiC devices were fabricated and tested at elevated temperatures. Grown p-n junction diodes demonstrated very good rectification characteristics at 870 K. A depletion-mode metal-oxide-semiconductor field-effect transistor was also successfully fabricated and tested at 770 K. While optimization of SiC fabrication processes remain, it is believed that SiC is an enabling high temperature electronic technology.

Matus, Lawrence G.↗
NASA NTRS1989

NASA Space Engineering Research Center for Utilization of Local Planetary Resources

Progress toward the goal of exploiting extraterrestrial resources for space missions is documented. Some areas of research included are as follows: Propellant and propulsion optimization; Automation of propellant processing with quantitative simulation; Ore reduction through chlorination and free radical production; Characterization of lunar ilmenite and its simulants; Carbothermal reduction of ilmenite with special reference to microgravity chemical reactor design; Gaseous carbonyl extraction and purification of ferrous metals; Overall energy management; and Information management for space processing.

Ramohalli, Kumar↗
NASA NTRS1992

PAYCOS, a multidisciplinary sizing code for hypersonic vehicles

PAYCOS is a computer code developed to rapidly perform concept sizing, concept evaluation, and associated trade studies for supersonic and hypersonic maneuvering vehicles. PAYCOS is a multidisciplinary analysis code that allows the engineer to determine the best geometric configuration for each design through parametric studies and mathematical optimization. This paper presents a general overview of the code, including a brief discussion of the approach used to develop it. The modular structure of the code is reviewed, and a brief discussion of each module is presented. Input data needed to run the code and output data supplied by it are discussed. The role of mathematical optimization in the solution process is discussed in some detail and examples of this process are presented. Finally, current modifications to the code are described along with potential future modifications and applications.

Edington, Larry↗