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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 1,261 records · Page 70
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Advances in traction drive technology

Traction drives are traced from early uses as main transmissions in automobiles at the turn of the century to modern, high-powered traction drives capable of transmitting hundreds of horsepower. Recent advances in technology are described which enable today's traction drive to be a serious candidate for off-highway vehicles and helicopter applications. Improvements in materials, traction fluids, design techniques, power loss and life prediction methods will be highlighted. Performance characteristics of the Nasvytis fixed-ratio drive are given. Promising future drive applications, such as helicopter main transmissions and servo-control positioning mechanisms are also addressed.

Loewenthal, S. H.↗
NASA NTRS1982

Thermoelectric conversion for space nuclear power

A lightweight, high performance nuclear reactor power system can offer significant advantages for many space missions. Conceptual design has been completed for the SP-100, a system which utilizes many thermoelectric converters and is capable of delivering 100 kilowatts of electrical power. A reference design, using thermoelectric materials with an average figure of merit of 0.001/K and a reactor heat pipe temperature of 1500 K, is presented which has a mass of 2280 kg not including contingency. The sensitivity of system mass to changes in the configuration and thermoelectric material properties are presented

Ewell, R.↗
NASA NTRS1983

Optimization of bonded joints

A procedure for minimizing the elastic shear stress concentration in adhesive lap joints is presented. The proposed method is based upon tapering the adherends to achieve smooth stiffness transitions and uniform shear stresses. Both single and double lap splices are considered, but numerical examples are restricted to the case of double lap joints. Nonisotropic materials and nonoptimum design limitations, such as minimum and maximum thickness adherends, load-line eccentricity, and peel stresses are treated, and typical results are presented.

Ojalvo, I. U.↗
NASA NTRS1984

Structures and mechanisms

Structures, materials, and mechanisms is one of the older technologies in the aerospace business. The Structures, Materials, and Mechanisms Panel was divided into the four basic categories that fit the overall responsibilities of the panel: materials, mechanisms, structural design, and analysis.

Purdy, D.↗
NASA NTRS1984

Skin-stiffener interface stresses in composite stiffened panels

A model and solution method for determining the normal and shear stresses in the interface between the skin and the stiffener attached flange were developed. An efficient, analytical solution procedure was developed and incorporated in a sizing code for stiffened panels. The analysis procedure described provides a means to study the effects of material and geometric design parameters on the interface stresses. These stresses include the normal stress, and the shear stresses in both the longitudinal and the transverse directions. The tendency toward skin/stiffener separation may therefore be minimized by choosing appropriate values for the design variables. The most important design variables include the relative bending stiffnesses of the skin and stiffener attached flange, the bending stiffness of the stiffener web, and the flange width. The longitudinal compressive loads in the flange and skin have significant effects on the interface stresses.

Wang, J. T. S.↗
NASA NTRS1983

Getting the current out

Progress of a photovoltaic (PV) device from a research concept to a competitive power-generation source requires an increasing concern with current collection. The initial metallization focus is usually on contact resistance, since a good ohmic contact is desirable for accurate device characterization measurements. As the device grows in size, sheet resistance losses become important and a metal grid is usually added to reduce the effective sheet resistance. Later, as size and conversion efficiency continue to increase, grid-line resistance and cell shadowing must be considered simultaneously, because grid-line resistance is inversely related to total grid-line area and cell shadowing is directly related. A PV cell grid design must consider the five power-loss phenomena mentioned above: sheet resistance, contact resistance, grid resistance, bus-bar resistance and cell shadowing. Although cost, reliability and usage are important factors in deciding upon the best metallization system, this paper will focus only upon grid-line design and substrate material problems for flat-plate solar arrays.

Burger, D. R.↗
NASA NTRS1984

Experiments on water/melt explosions, nature of products, and models of dispersal

Experiments were carried out in a steel pressure device using controlled amounts of water and thermite melt to examine the mechanical energy released on explosive mixing following the initial contact of the two materials. An experimental design was used to allow the direct calculation of the mechanical energy by the dynamic lift of the device as recorded both optically and physically. A large number of experiments were run to accurately determine the optimum mixture of water and melt for the conversion of thermal to mechanical energy. The maximum efficiency observed was about 12% at a water/thermite mass ratio of 0.50. These experiments are the basis for the development of models of hydroexplosions and melt fragmentation. Particles collected from the experimental products are similar in size and shape to pyroclasts produced by much larger hydrovolcanic explosions. Melt rupture at optimum ratios produces very fine particles whereas rupture at high or low water/melt ratios produces large melt fragments. Grain surface textures in the experimental products are also related to the water/melt ratio and the mechanism of explosive mixing. It is thus possible to have qualitative information about the nature of the explosion from the sizes and shapes of the fragments produced.

Sheridan, M. F.↗
NASA NTRS1985

Manufacturing and producibility technology

Activities of the manufacturing/producibility working group within the Advanced High-Pressure O2/H2 Technology Program are summarized. The objectives of the M/P working group are: to develop and evaluate process and manufacturing techniques for advanced propulsion hardware design and selected materials; and to optimize the producibility of (SSME) components and assemblies by improved performance, increased life, greater reliability, and/or reduced cost. The technologies being developed include: plasma arc, laser, and inertia welding; combustion chamber and turbine blade coatings; coating processes; high performance alloy electroforming; and process control technology.

Hankins, J. D.↗
NASA NTRS1985

Silicon solar cell efficiency improvement: Status and outlook

Efficiency and operating life is an economic attribute in silicon solar cells application. The efficiency improvements made during the 30 year existence of the silicon solar cells, from about 6% efficiency at the beginning to 19% in the most recent experimental cells is illustrated. In the more stationary periods, the effort was oriented towards improving radiation resistance and yields on the production lines, while, in other periods, the emphasis was on reaching new levels of efficiency through better cell design and improved material processing. First results were forthcoming from the recent efforts. Considerably more efficiency advancement in silicon solar cells is expected, and the anticipated attainment of efficiencies significantly above 20% is discussed. Major advances in material processing and in the resulting material perfection are required.

Wolf, M.↗
NASA NTRS1985

Evaluation of results of cell electrophoresis experiments on space shuttle STS-3 including pre-flight and post-flight laboratory experiments

The objectives of the red blood cell experiments were to provide a visual check on the electrophoretic process and especially electroosmotic flow in space as well as to provide test separations of non-degradable standard particles for comparison with the separations of the three viable cell types studied on the Apollo-Soyuz Test Project. Determination of the maximum concentrations of cells that can be separated in column electrophore was a significant goal. Two of the eight columns were available for red cell experiments, so two concentrations of human and rabbit RBC mixtures were used. The objectives of another experiment were to evaluate the reproducibility of microgravity electrophoretic separation of living kidney cells, to separate cells with highly viability despite two freeze-thaw cycles, and to optimize the physical conditions of cell separation. Owing to the uncertain heterogeneity of the starting material, the experimental design does not assess resolution in microgravity, but improved separability was sought in comparison to density-gradient electrophoresis or continuous-flow electrophoresis. Efforts were made to increase cell yield and cell viability and to assess reproducibility directly.

Todd, P. W.↗
NASA NTRS1986

Space solar cell research: Problems and potential

The value of a passive, maintenance-free, renewable energy source was apparent in the early days of the space program, and the silicon solar cell was pressed into service. Efficiencies of those early space solar arrays were low, and lifetimes shorter than hoped for, but within a decade significant advances had been made in both areas. Better performance was achieved through improvements in silicon single crystal material, better device designs, and a better understanding of the factors that affect the performance of a solar cell in space. Chief among the latter, particularly for the mid-to-high altitude (HEO) and geosynchronous (GEO) orbits, are the effects of the naturally occurring particulate radiation environment. Although not as broadly important to the photovoltaic community at large as increased efficiency, the topic of radiation damage is critically important to use of solar cells in space, and is a major component of the NASA research program in space photovoltaics. A brief overview of some of the opportunities and challenges for space photovoltaic applications is given, and some of the current research directed at achieving high efficiency and controlling radiation damage in space solar cells is discussed.

Flood, D. J.↗
NASA NTRS1987

Lightweight Monorail Transport System

Report proposes monorail transportation system for zero-gravity environment. System carries materials and parts between locations on space station. Includes tubular rails instead of open channels usually found in overhead conveyor systems. Since resistance to torque of closed tube greater than that of open channel for same amount of material, tubular monorail designed for higher loads or for greater spacing between support points.

Weir, Harold F.↗
NASA NTRS1987

Mixing Valve for Protein-Crystal Growth

Apparatus for growing protein and other crystals holds reactants in separate chambers, then allows them to combine at proper time. Openings in cylindrical rotary valve connect chambers to each other selectively through internal passages. O-ring and strip seals prevent leakage over valve surface. Caps on chambers seal them tightly but are removable for addition of reactants or withdrawal of reaction products. Made from various chemically inert materials, and chambers designed with capacities ranging from milliliters to liters. Easily automated.

Carter, Daniel C.↗
NASA NTRS1987

Na/beta-alumina/NaAlCl4, Cl2/C circulating cell

A study was made of a high specific energy battery based on a sodium negative electrode and a chlorine positive electrode with molten AlCl3-NaCl electrolyte and a solid beta alumina separator. The basic performance of a Na beta-alumina NaAlCl4, Cl2/C circulating cell at 200 C was demonstrated. This cell can be started at 150 C. The use of melting sodium chloroaluminate electrolyte overcomes some of the material problems associated with the high working temperatures of present molten salt systems, such as Na/S and LiAl/FeS, and retains the advantages of high energy density and relatively efficient electrode processes. Preliminary investigations were conducted on a sodium-chlorine static cell, material compability, electrode design, wetting, and theoretical calculations to assure a better chance of success before assembling a Na/Cl2 circulating cell. Mathematical models provide a theoretical explanation for the performance of the NaCl2 battery. The results of mathematical models match the experimental results very well. According to the result of the mathematical modeling, an output at 180 mA/sq cm and 3.2 V can be obtained with optimized cell design.

Cherng, Jing-Yih↗
NASA NTRS1988

Advanced composite airframe program: Today's technology

The Advanced Composite Airframe Program (ACAP) was undertaken to demonstrate the advantages of the application of advanced composite materials and structural design concepts to the airframe structure on helicopters designed to stringent military requirements. The primary goals of the program were the reduction of airframe production costs and airframe weight by 17 and 22 percent respectively. The ACAP effort consisted of a preliminary design phase, detail design, and design support testing, full-scale fabrication, laboratory testing, and a ground/flight test demonstration. Since the completion of the flight test demonstration programs follow-on efforts were initiated to more fully evaluate a variety of military characteristics of the composite airframe structures developed under the original ACAP advanced development contracts. An overview of the ACAP program is provided and some of the design features, design support testing, manufacturing approaches, and the results of the flight test evaluation, as well as, an overview of Militarization Test and Evaluation efforts are described.

Good, Danny E.↗
NASA NTRS1988

Ceramic bearings for use in gas turbine engines

Three decades of research by U.S. industry and government laboratories have produced a vast body of data related to the use of ceramic rolling element bearings and bearing components for aircraft gas turbine engines. Materials such as alumina, silicon carbide, titanium carbide, silicon nitride, and a crystallized glass ceramic have been investigated. Rolling-element endurance tests and analysis of full-complement bearings have been performed. Materials and bearing design methods have continuously improved over the years. This paper reviews a wide range of data and analyses with emphasis on how early NASA contributions as well as more recent data can enable the engineer or metallurgist to determine just where ceramic bearings are most applicable for gas turbines.

Zaretsky, Erwin V.↗
NASA NTRS1988

Radar Cross Section Studies/Compact Range Research

A summary is given of the achievements of NASA Grant NsG-1613 by Ohio State University from May 1, 1987 to April 30, 1988. The major topics covered are as follows: (1) electromagnetic scattering analysis; (2) indoor scattering measurement systems; (3) RCS control; (4) waveform processing techniques; (5) material scattering and design studies; (6) design and evaluation of design studies; and (7) antenna studies. Major progress has been made in each of these areas as verified by the numerous publications produced.

Burnside, W. D.↗
NASA NTRS1986

Plasticity analysis of wear phenomena as an aid in the development of abradable materials

Plastic deformation accompanying the wear process in fully dense and porous metals was studied in order to develop more abradable gas path seal material systems for turbine engine applications. The finite element method was used to model high-rate viscoplastic deformation in the vicinity of a moving contact. Techniques were developed for studying such deformation in both solid (fully dense) and porous metals. Results of the analysis were verified by comparison with experimental data obtained using a pendulum-type rub test apparatus and a pin-on-disk sliding wear tester. It was found that the near-surface plastic deformation in fully dense solids was different from that for porous materials because of the compressibility of the latter. Both types of materials exhibit deformation features which can be taken advantage of in the design of more abradable material systems.

Kennedy, F. E., Jr.↗