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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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Trapped-flux spin-down torques on a spherical superconducting gyroscope

Magnetic flux trapped in the rotor of a superconducting gyroscope can cause the rotor to lose energy through dissipation in a readout loop encompassing the rotor and by the generation of eddy currents in the support electrodes. These losses are calculated and shown to be negligible for the rotor in the gyroscope-relativity experiment, a proposed satellite experiment which is to test predictions of the theory of general relativity.

Holdeman, L. B.↗
NASA NTRS1979

Measuring insulation thickness

Calibrated eddy-current meter measures thickness of thermal insulation on metal substrates with specially designed adapters; for example, thickness of fiberglass parts for boats or automobiles. Technique is particlarly useful for sprayed-on insulation.

Munn, D. M.↗
NASA NTRS1979

Overview and outline of Mass-Driver Two

An overview of the Princeton-M.I.T. second mass-driver is presented. Mass-Driver Two is a 13.1 cm caliber system which uses a two coil superconducting bucket and a two-phase in quadrature drive system. Discrete drive coils are individually energized with timing supplied by position-sensing optical detectors. Intermediate energy storage is provided by sector capacitors which are recharged every half cycle by an external power source. A vacuum environment is provided for the superconducting bucket by a 4 inch ID glass pipe with the drive coils surrounding it. Magnetic flight is generated by eddy current repulsion from six copper guide strips lining the glass pipe. The length is 2.5 meters equally divided between acceleration and deceleration sections. Nominal acceleration is 5000 m/sec per sec giving a maximum bucket velocity of 112 m/sec. Regenerative braking is used to decelerate the bucket. Current densities of 25 sq cm are achieved in the superconducting bucket coils and are maintained by a cryogenic service station.

Oneill, G. K.↗
NASA NTRS1979

High-acceleration mass drivers

High-acceleration mass drivers are discussed including the MD2 model of axial geometry, with individually powered drive coils of 13.1 cm diameter. Timing is derived through the interruption of light beams by the moving armature (bucket). Electric power is provided by the resonant discharge of sector capacitor banks through silicon-controlled rectifiers in a two-phase, quadrature circuit. The bucket flies in vacuum, guided by passive dynamic eddy-current magnetic forces, those currents flowing in strip conductors lining the inside of a nonconducting vacuum pipe. Quantitative measurements are obtained with a solid bucket carrying two superconducting coils with a current density of 25 kA/sq cm. A cryogenic station for cooling the bucket to liquid helium temperature is connected to the vacuum pipe.

Oneill, G. K.↗
NASA NTRS1979

Possible radio emission mechanism for pulsars

A mathematical model is presented and discussed as a possible mechanism to describe radio emission from pulsars. The model determines that the magnetic field in the neutron proton electron (npe) layer of a neutron star results from a quasistationary eddy current of superconducting and normal protons relative to normal electrons, which generates radio emission by the Josephson effect. The radiation propagates in the magnetically active medium, from the optically thick npe layer to the magnetosphere through breaks in the crust. As a result, hot radio spots form on the surface of the star, and a radiation pattern forms near the magnetic poles, the cross section of which gives the observed pulse structure. Due to the specific properties of the mechanism, variations of the quasistationary current are converted to amplitude frequency variations of the radiation spectrum. Variations of the fine structure of the spectrum pulse amplitude and spectral index, as well as their correlation are discussed.

Kovalev, Y. A.↗
NASA NTRS1979

Construction and testing of the 2.5m mass driver

Presented are the designs used in the construction of the 2.5 m mass driver and the results of the initial testing program. The mass driver consists of equal length sections of acceleration and deceleration each containing 59 drive coils of 13.1 cm caliber. Intermediate energy storage is provided by sector capacitors which are recharged every half cycle by an external power source. The drive coils are individually energized through SCR's with timing supplied by position sensing optical detectors. The drive consists of two phases which operate in quadrature. The initial bucket to be propelled through the mass driver contains two coils of aluminum wire chilled to liquid nitrogen temperatures to momentarily sustain superconducting field intensities. Magnetic flight is generated by eddy current repulsion from six copper guide strips lining the mass driver. Nominal acceleration is 5000 m/sec per sec giving a maximum bucket velocity of 112 m/s.

Snow, W. R.↗
NASA NTRS1980

Determination of efficiencies, loss mechanisms, and performance degradation factors in chopper controlled dc vehical motors. Section 2: The time dependent finite element modeling of the electromagnetic field in electrical machines: Methods and applications

The time dependent solution of the magnetic field is introduced as a method for accounting for the variation, in time, of the machine parameters in predicting and analyzing the performance of the electrical machines. The method of time dependent finite element was used in combination with an also time dependent construction of a grid for the air gap region. The Maxwell stress tensor was used to calculate the airgap torque from the magnetic vector potential distribution. Incremental inductances were defined and calculated as functions of time, depending on eddy currents and saturation. The currents in all the machine circuits were calculated in the time domain based on these inductances, which were continuously updated. The method was applied to a chopper controlled DC series motor used for electric vehicle drive, and to a salient pole sychronous motor with damper bars. Simulation results were compared to experimentally obtained ones.

Hamilton, H. B.↗
NASA NTRS1980

NBS: Nondestructive evaluation of nonuniformities in 2219 aluminum alloy plate: Relationship to processing

The compositional homogeneity, microstructure, hardness, electrical conductivity and mechanical properties of 2219 aluminum alloy plates are influenced by the process variables during casting, rolling and thermomechanical treatment. The details of these relationships wre investigated for correctly processed 2219 plate as well as for deviations caused by improper quenching after solution heat treatment. Primary emphasis was been placed on the reliability of eddy current electrical conductivity and hardness as NDE tools to detect variations in mechanical properties.

Swartzendruber, L.↗
NASA NTRS1982

One-step dual purpose joining technique

This fastener used in induction heating is a wire screen basically of an eddy current carrying material such as carbon steel. Selected wires in the screen are copper, sheathed in an insulating material. The screen is placed between two sheets of thermoplastics. When inductively heated, the composite softens and flows around the apertures of the screen. After this heating and joining, the copper wires may be used to conduct electricity.

Buckley, J. D.↗
NASA NTRS1982

Cyclic-inelastic deformation and fatigue resistance of notched-thin aluminum plates

The results of experiments designed to develop data to assess the accuracy and utility of the critical location concept in applications of fatigue-crack nucleation analysis at notch roots are presented and discussed. Fully reversed and nonzero mean-stress data are presented over a range of lives which encompass both elastic and inelastic deformations for thin-notched specimens and smooth specimens made of 2024 T351 aluminum-alloy sheet. Notch-root strains were measured via an extensometer, whereas the formation of small cracks was detected via an eddy-current transducer. Data reported indicated the validity of the assumption that smooth and notched specimens form cracks at the same cycle number when identical deformation histories are imposed at their respective critical locations. They also serve to demonstrate the accuracy and utility of the critical-location approach in analysis to predict the formation of small cracks at notches in coupons and components.

Leis, B. N.↗
NASA NTRS1984

Paint-Thickness Checker

Eddy-current flaw detector with cathode-ray tube (CRT) used to compare layer thickness of conductive paint on metallic substrates.

Nelson, C.↗
NASA NTRS1983

Design and fabrication of conventional and unconventional superconductors

The design and fabrication of conventional and unconventionally processed Ti-Nb base and Al5-compound-base, respectively, composite superconductors is discussed in a nine section review. The first two sections introduce the general properties of alloy and compound superconductors, and the design and processing requirements for the production of long lengths of stable low loss conductor. All aspects of flux jump stability, and the general requirements of cryogenic stabilization are addressed. Conductor design from an a.c.-loss standpoint; some basic formulae describing hysteretic and eddy current losses and the influences on a.c. loss of filament diameter, strand (conductor) diameter, twist pitch, and matrix resistivity are discussed. The basic techniques used in the fabrication of conventional multifilamentary conductors are described.

Collings, E. W.↗
NASA NTRS1982

Theory and applications of electromagnetic levitation

A simple treatment of the electromagnetic levitation problem is presented, with emphasis placed on approximate formulas useful in planning and interpreting laboratory measurements. Consideration is also given to numerical solutions for fields, eddy currents, and Lorentz forces for rapidly varying applied fields, with particular reference made to traveling wave levitation experiments. Applications of levitation processing are briefly reviewed, including thermophysical property measurements, undercooling studies, containerless crystal growth, and continuous casting of cylinders.

Frost, R. T.↗
NASA NTRS1983

Magnetic Bearings for Inertial Energy Storage

The selection of a noncontacting bearing technique with no wear out phenomena and which is vacuum compatible which is the decisive factor in selecting magnetic bearings for kinetic energy storage was investigated. Unlimited cycle life without degradation is a primary goal. Storage efficiency is a key parameter which is defined as the ratio of the energy remaining to energy stored after a fixed time interval at no load conditions. Magnetic bearings, although noncontacting, are not perfectly frictionless in that magnetic losses due to eddy currents and hysteresis can occur. Practical magnetic bearings, however, deviate from perfect symmetry and have discontinuities and asymmetric flux paths either by design or when controlled in the presence of disturbances, which cause losses. These losses can be kept smaller in the bearings than in a high power motor/generator, however, are a significant factor in selecting the magnetic bearing type.

Studer, P. A.↗
NASA NTRS1983

A Feasibility Study of Electromagnetic De-Spin System for Earth Orbiting Satellites

This investigation is a feasibility study of electromagnetic satellite de-spin systems based on induced eddy-currents in the satellite by an external dc magnetic field. Two concepts have been investigated: (1) one based on a large diameter coil positioned around the satellite such that the axis of the satellite rotation is in the plane of the coil; and (2) a magnet, either permanent or electromagnet, positioned close to the satellite by the orbiter RMS. A comparison is made of the two concepts by varying the appropriate parameters with a view to reduce the de-spin time to a reasonable value. Design parameters for the magnets and the coil are indicated.

Prasad K Kadaba↗
NASA NTRS1984

Two-dimensional scanner apparatus

An X-Y scanner utilizes an eddy current or ultrasonic current test probe to detect surface defects in small flat plates and the like. The apparatus includes a scanner which travels on a pair of slide tubes in the X-direction. The scanner, carried on a carriage which slides in the Y-direction, is driven by a helix shaft with a closed-loop helix groove in which a follower pin carried by scanner rides. The carriage is moved incrementally in the Y-direction upon the completion of travel of the scanner back and forth in the X-direction by means of an indexing actuator and an indexing gear. The actuator is in the form of a ratchet which engages ratchet gear upon return of the scanner to the indexing position. The indexing gear is rotated a predetermined increment along a crack gear to move carriage incrementally in the Y-direction. Thus, simplified highly responsive mechanical motion may be had in a small lightweight portable unit for accurate scanning of small area.

Kurtz, G. W.↗
NASA NTRS1985

Detecting Cracks in Rough Metal Surfaces

Test based on eddy-current probe technique identifies cracks in swaged metals. Hinged collar with spring-loaded latch holds probe in place on part tested. For repeated measurements on same or similar parts, collar loosened and moved to various measuring positions. Method suitable for many kinds of metal parts, including swaged fittings, tubing, and pipes. Used for rapid crack/no-crack determinations in suspect parts already installed.

Zuver, N. T.↗
NASA NTRS1985

Electro-science Requirements for Shuttle-attached Antenna Flight Experiments

The activities of an in-house electro-science task group organized to conduct studies of shuttle-attached flight experiments using the 15-meter hoop-column antennas as a research tool for developing both improved sensor technology and LSA technology are described. Some experiments could provide significant amounts of scientific data such as radio star mapping and definition of ocean current eddies over limited geographic regions. The experiments originate from the microwave remote sensing community and other areas which require the inherently higher resolution and boresite gain of large space antennas. Technology experiments are also being studied which would use the 15-meter antenna experiments as a stepping stone to 50 to 100 meter class reflector technology in the future. An antenna technology experiment using the 15-meter antenna in a shuttle-attached mission is discussed. Electromagnetic modeling is correct for each major subsystem and also to verify the interrelations of the subsystems.

Grantham, W. L.↗