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At least 469 records · Page 26

All sources NASA NTRS DOE OSTI

NASA NTRS2013

Magnetostrictive Alternator

This innovation replaces the linear alternator presently used in Stirling engines with a continuous-gradient, impedance-matched, oscillating magnetostrictive transducer that eliminates all moving parts via compression, maintains high efficiency, costs less to manufacture, reduces mass, and eliminates the need for a bearing system. The key components of this new technology are the use of stacked magnetostrictive materials, such as Terfenol-D, under a biased magnetic and stress-induced compression, continuous-gradient impedance-matching material, coils, force-focusing metallic structure, and supports. The acoustic energy from the engine travels through an impedancematching layer that is physically connected to the magnetostrictive mass. Compression bolts keep the structure under compressive strain, allowing for the micron-scale compression of the magnetostrictive material and eliminating the need for bearings. The relatively large millimeter displacement of the pressure side of the impedance-matching material is reduced to micron motion, and undergoes stress amplification at the magnetostrictive interface. The alternating compression and expansion of the magnetostrictive material creates an alternating magnetic field that then induces an electric current in a coil that is wound around the stack. This produces electrical power from the acoustic pressure wave and, if the resonant frequency is tuned to match the engine, can replace the linear alternator that is commonly used.

Dyson, Rodger↗

NASA NTRS1976

Cost/benefit trade-offs for reducing the energy consumption of commercial air transportation (RECAT)

The RECAT study evaluated the opportunities for reducing the energy requirements of the U.S. domestic air passenger transport system through improved operational techniques, modified in-service aircraft, derivatives of current production models, or new aircraft using either current or advanced technology. Each of these fuel-conserving alternatives was investigated individually to test its potential for fuel conservation relative to a hypothetical baseline case in which current, in-production aircraft types are assumed to operate, without modification and with current operational techniques, into the future out to the year 2000. Consequently, while the RECAT results lend insight into the directions in which technology can best be pursued for improved air transport fuel economy, no single option studied in the RECAT program is indicative of a realistic future scenario.

Gobetz, F. W.↗

NASA NTRS1978

Baseline tests of the Kordesh hybrid passenger vehicle

Performance test results are presented for a four-passenger Austin A40 sedan that was converted to a heat-engine-alternator-and battery-powered hybrid. It is propelled by a conventional, gasoline-fueled, heat-engine-driven alternator and a traction pack powering a series-wound, 10 hp direct-current electric drive motor. The 16 hp gasoline engine drives the 7 kilowatt alternator, which provides electrical power to the drive motor or to the 96 volt traction battery through a rectifier. The propulsion battery consists of eight 12 volt batteries connected in series. The electric motor is coupled to a four-speed standard transmission, which drives the rear wheels. Power to the motor is controlled by a three-step foot throttle, which actuates relays that control armature current and field excitation. Conventional hydraulic brakes are used.

Soltis, R. F.↗

NASA NTRS2003

Alternating-pulse iontophoresis for targeted cutaneous anesthesia

In studies of sensory contributions to motor control, it may be advantageous to temporarily reduce the sensitivity of specific sensory systems. This article details a method for non-invasively inducing cutaneous anesthesia, leaving proprioceptive and motor functions intact. This method, called alternating-pulse iontophoresis, differs from conventional direct-current (DC) iontophoretic drug delivery in that adjacent drug delivery electrodes are stimulated out-of-phase. The total current delivered at any instant is then less than that produced during a comparable DC application, while the uniformity of drug delivery is expected to improve. Effective delivery of local anesthetics to the cutaneous foot soles by alternating-pulse iontophoresis was demonstrated using cutaneous pressure sensory threshold levels (STL's) assessed with Semmes-Weinstein monofilaments (arbitrary units of perceived force, or a.u.). Thirteen of 16 healthy subjects achieved a level of anesthesia greater than or equal to that normally associated with clinical peripheral sensory neuropathy. Average STL's measured prior to the anesthesia procedure were 4.00 a.u. ( approximately 10 mN). Immediately following the procedure, STL's were elevated to an average of 5.40 a.u. ( approximately 246 mN) and averaged 4.97 a.u. ( approximately 92 mN) after 50 min of standing. A number of research and clinical applications for this technique are suggested.

Non-NASA Center↗

NASA NTRS1976

Cost/benefit trade-offs for reducing the energy consumption of commercial air transportation (RECAT)

A study has been performed to evaluate the opportunities for reducing the energy requirements of the U.S. domestic air passenger transport system through improved operational techniques, modified in-service aircraft, derivatives of current production models, or new aircraft using either current or advanced technology. Each of the fuel-conserving alternatives has been investigated individually to test its potential for fuel conservation relative to a hypothetical baseline case in which current, in-production aircraft types are assumed to operate, without modification and with current operational techniques, into the future out to the year 2000.

Gobetz, F. W.↗

NASA NTRS2016

Miniature Biosensor with Health Risk Assessment Feedback

Heart rate (HR) monitoring is a medical requirement during exercise on the International Space Station (ISS), fitness tests, and extravehicular activity (EVA); however, NASA does not currently have the technology to consistently and accurately monitor HR and other physiological data during these activities. Performance of currently available HR monitor technologies is dependent on uninterrupted contact with the torso and are prone to data drop-out and motion artifact. Here, we seek an alternative to the chest strap and electrode based sensors currently in use on ISS today. This project aims to develop a high performance, robust earbud based biosensor with focused efforts on improved HR data quality during exercise or EVA. A health risk assessment algorithm will further advance the goals of autonomous crew health care for exploration missions.

Hanson, Andrea↗

NASA NTRS1975

A statistical model for telecommunication link design

An evaluation is conducted of the current telecommunication link design technique and a description is presented of an alternative method, called the probability distribution method (PDM), which is free of the disadvantages of the current technique while retaining its advantages. The PDM preserves the simplicity of the design control table (DCT) format. The use of the DCT as a management design control tool is continued. The telecommunication link margin probability density function used presents the probability of achieving any particular value of link performance. It is, therefore, possible to assess the performance risk and other tradeoffs.

Yuen, J. H.↗

NASA NTRS1966

Diaphragm spring gives clutch over-center toggle effect

Diaphragm spring clutch mechanism is used in testing the relative merits of eddy-current and hysteresis dampers. The dampers are alternately coupled to a single damping boom shaft. The floating clutch mechanism enables the inoperative damper to remain completely isolated from the damping boom shaft during test of the other damper.

Rosenberg, H. W.↗

NASA NTRS1972

Alternating method applied to edge and surface crack problems

The Schwarz-Neumann alternating method is employed to obtain stress intensity solutions to two crack problems of practical importance: a semi-infinite elastic plate containing an edge crack which is subjected to concentrated normal and tangential forces, and an elastic half space containing a semicircular surface crack which is subjected to uniform opening pressure. The solution to the semicircular surface crack is seen to be a significant improvement over existing approximate solutions. Application of the alternating method to other crack problems of current interest is briefly discussed.

Hartranft, R. J.↗

NASA NTRS1973

Near infra-red magnitudes of 248 early-type emission-line stars and related objects.

Nearly 250 early-type emission-line stars have been observed in the near infrared; approximately two thirds of these are found to exhibit excess radiation at these wavelengths. Two distinct mechanisms may contribute to the infra-red excesses: thermal radiation from circumstellar dust, and electron bremsstrahlung originating in a shell of ionized gas. It is not currently possible to distinguish between these two alternatives using infra-red photometry alone.

Allen, D. A.↗

NASA NTRS1974

Planetary magnetism

The origin and maintenance of planetary magnetic fields are discussed. The discussion is not limited to dynamo theories, although these are almost universally favored. Thermoelectric currents are found to be a possible alternative for Jupiter. Two energy sources for dynamos are considered: convection and precessionally induced fluid flow. The earth is the most favorable planet for precessionally driven dynamo, although Neptune is a possibility. Jupiter is likely to have a convectionally driven dynamo, as may Saturn, but the relevant properties of Saturn are not yet well known. Conclusions for each planet are given.

Stevenson, D.↗

NASA NTRS1977

Ride quality research techniques: Section on general techniques

Information is gathered about the methods currently used for the study of ride quality in a variety of transportation modes by a variety of research organizations, including universities, Federal agencies, contracting firms, and private industries. Detailed descriptions of these techniques and their strengths and weaknesses, and identifying the organizations using such methods are presented. The specific efforts of the Group's participants, as well as a variety of feasible approaches not currently in use, are presented as methodological alternatives under the three basic factors which must be considered in ride quality studies: research techniques, research environments, and choice of subjects.

Source record↗

NASA NTRS1980

Cogeneration Technology Alternatives Study (CTAS). Volume 3: Energy conversion system characteristics

Six current and thirty-six advanced energy conversion systems were defined and combined with appropriate balance of plant equipment. Twenty-six industrial processes were selected from among the high energy consuming industries to serve as a frame work for the study. Each conversion system was analyzed as a cogenerator with each industrial plant. Fuel consumption, costs, and environmental intrusion were evaluated and compared to corresponding traditional values. The advanced energy conversion technologies indicated reduced fuel consumption, costs, and emissions. Fuel energy savings of 10 to 25 percent were predicted compared to traditional on site furnaces and utility electricity. With the variety of industrial requirements, each advanced technology had attractive applications. Fuel cells indicated the greatest fuel energy savings and emission reductions. Gas turbines and combined cycles indicated high overall annual savings. Steam turbines and gas turbines produced high estimated returns. In some applications, diesels were most efficient. The advanced technologies used coal derived fuels, or coal with advanced fluid bed combustion or on site gasifications. Data and information for both current and advanced energy conversion technology are presented. Schematic and physical descriptions, performance data, equipment cost estimates, and predicted emissions are included. Technical developments which are needed to achieve commercialization in the 1985-2000 period are identified.

Source record↗

NASA NTRS1981

Comment on 'Azimuthal magnetic field at Jupiter' by J. L. Parish, C. K. Goertz, and M. F. Thomsen

In the first paper, an alternative to one of the models of current flow giving rise to the azimuthal component of the Jupiter magnetic field considered by Parish et al. (1980) is proposed which takes into account the magnetic fields due to return currents and is consistent with Pioneer 10 observations. In the present model, currents enter the equatorial sheet at both poles and then flow radially outward, with a total current flowing into the polar regions of about 1.4 x 10 to the 8th A. In the reply, it is contended that, although the return currents must be present, their net effects almost exactly cancel and their contributions to the near-equatorial field may be neglected for regions sufficiently far from the field lines on which the return current flows. Furthermore, the difference in the total currents estimated by Parish et al. and in the first paper is attributed to the uncertainties and inadequacy of the fit of either model to the observations and to a difference in mathematic expressions used for the field rather than a significant difference between models.

Connerney, J. E. P.↗

NASA NTRS1982

A modern approach to pilot/vehicle analysis and the Neal-Smith criteria

The present investigation is concerned with the development of a better pilot modelling technique via optimal control theory, taking into account concepts concerning 'pilot rating' considered by Neal and Smith (1970). The investigation conducted by Neal and Smith had the objective to provide data on the effects of Flight Control System dynamics and to develop a design criterion capable of pinpointing pilot problem areas encountered in performing a given task. Neal and Smith devised a 'pilot-in-the-loop' analysis capable of showing problem areas in pitch attitude tracking. Unfortunately the employed method has some drawbacks. The current investigation attempts, therefore, to provide an alternate approach which makes use of an optimal-control pilot model. An optimal control model (OCM) had been discussed by Kleinman et al. (1970). It is shown that the alternate approach, based on the OCM, offers some distinct advantages.

Bacon, B. J.↗

NASA NTRS1984

The B2 aluminides as alternative materials

The potential of the B2 aluminides as structural material alternatives for the strategic element containing superalloys currently used in gas turbine engines is being explored with emphasis on the equiatomic Fe and Ni aluminides. Although Co is a strategic material, the equiatomic Co aluminide is also being studied to gain a more complete understanding of these fourth period intermetallics. Research focuses on initial processing techniques such as ingot melting, power metallurgy, and rapid solidification with and without additional thermomechanical processing; high temperature deformation - primarily compressive creep; compositional effects within the binary B2 aluminides; third-element alloying addition effects on high temperature strength and oxidation resistance, and near room temperature ductility as influenced by processing, alloying, and grain size. Various programs now underway are reviewed and some highlights of research results are presented.

Stephens, J. R.↗

NASA NTRS1986

Determination of cosmogenic Ca-41 in a meteorite with tandem accelerator mass spectrometry

The first use of tandem accelerator mass spectrometry (TAMS) to measure the content of Ca-41 in a natural sample, the iron Bogou meteorite, is reported. Ca in the samples was extracted by hydroxide precipitation and purified by means of a caution exchange resin (AG 50W-X8). After adding 4 percent ammonium oxide, the precipitate was ignited to CaO in a quartz vial at about 1100 C. The Ca-41/Ca ratios were determined following acceleration by alternate measurements of the Ca-40 beam current in an image Faraday cup. Ca-41 particles were also measured using a gas counter. The measured Ca-41/Ca ratio was 3.8 + or -0.6 x 10 to the 12th, which corresponds to a Ca-41 activity of 6.9 + or -1.1 d.p.m. per kg. Calculation of the half-life of Ca-41 in the Bogou meteorite yielded an age of 103,000 years.

Kubik, P. W.↗

NASA NTRS1985

The B2 aluminides as alternative materials

The potential of the B2 aluminides as structural material alternatives for the strategic element containing superalloys currently used in gas turbine engines is being explored with emphasis on the equiatomic Fe and Ni aluminides. Although Co is a strategic material, the equiatomic Co aluminide is also being studied to gain a more complete understanding of these fourth period intermetallics. Research focuses on initial processing techniques such as ingot melting, power metallurgy, and rapid solidification with and without additional thermomechanical processing; high temperature deformation primarily compressive creep; compositional effects within the binary B2 aluminides; third-element alloying addition effects on high temperature strength and oxidation resistance, and near room temperature ductility as influenced by processing, alloying, and grain size. Various programs now underway are reviewed and some highlights of research results are presented.

Stephens, J. R.↗