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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Electrodynamic coupling in magnetically confined stellar X-ray loops

The solar coronal complex X-ray structure is now known to involve radiation loops that coincide spatially with the magnetic loops confining the radiating plasma. An effort is presently made to identify primary submodels involved in the global coupling between a mechanical energy reservoir of beta value greater than 1 and a contiguous site of X-ray activity whose beta value is lower than 1. The 'dynamo' model invoked establishes a quantitative connection between mechanical driver properties and the dimensions, field strength, and number density distribution of elemental magnetic loops.

Ionson, J. A.↗
NASA NTRS1985

Preliminary investigation of the electrodynamics of a conducting tether

An introductory study of the properties of an electrically conducting tether flown from the shuttle is presented. Only a single configuration is considered: a vertical conductor moving normally across the Earth's field, connecting the shuttle to a large conducting balloon that passively extracts electrons from the ionosphere. The distortions in the plasma at maximum current collection are described, as are the local and distant wakes. Numerical values are given.

Thompson, W. B.↗
NASA NTRS1982

The gravito-electrodynamics of charged dust in planetary ring systems

The dynamics of micron and submicron sized dust grains moving under the combined influence of planetary gravitation and the electromagnetic forces within the corotating regions of planetary magnetospheres are discussed. Magnetogravitational capture of charged grains in planetary rings is outlined. The adiabatic motion of charged dust is reviewed.

Mendis, D. A.↗
NASA NTRS1985

Evaluation of parameters for particles acceleration by the zero-point field of quantum electrodynamics

That particles may be accelerated by vacuum effects in quantum field theory has been repeatedly proposed in the last few years. A natural upshot of this is a mechanism for cosmic rays (CR) primaries acceleration. A mechanism for acceleration by the zero-point field (ZPE) when the ZPE is taken in a realistic sense (in opposition to a virtual field) was considered. Originally the idea was developed within a semiclassical context. The classical Einstein-Hopf model (EHM) was used to show that free isolated electromagnrtically interacting particles performed a random walk in phase space and more importantly in momentum space when submitted to the perennial action of the so called classical electromagnrtic ZPE.

Rueda, A.↗
NASA NTRS1984

Electrodynamic tethers. I - Power generation in LEO. II - Thrust for propulsion & power storage

The power gain and thrust for plasma engines available by unreeling 10 km of insulated Al wire from a spacecraft are investigated. The wire, unreeling in the vertical, would cut the earth's magnetic field lines, thereby generating 20 kW of power in the wire. A drag loss of 20.4 kJ/sec would reduce the power gain to 18.7 kW, an efficiency of 92 percent. Thicker wires could push the power gain to 1 MW at 95 percent efficiency. Conductive 'balloons' at the ends of the tether would function as ionospheric 'brushes' to complete the circuit. Reversing the IXB force by employing on-board stored power would drive the tether current against the induced voltage, providing a 1 N thrust for 8 kW of energy consumed, which could be supplied by solar panels during the day portion of orbit. The equivalent thrust by conventional stationkeeping means would consume 8000 kg of propellant/yr. Techniques for stabilizing the tether in the presence of variable magnetic fields are discussed.

Mccoy, J. E.↗
NASA NTRS1985

Electrodynamic interaction of Ganymede with the Jovian magnetosphere and the radial spread of wake-associated disturbances

An investigation is conducted of the electrostatics of the interaction of Jupiter's satellite Ganymede with the Jovian plasma and the MHD stability of the resulting downstream cavity, taking into account an evaluation of the effect of distorted magnetic field models on the radial extent of the disturbances. The objective of the investigation is an understanding of the data which have been provided by Voyager 2 during its approach to Jupiter, giving attention to the Voyager 2 magnetometer experiment. It is concluded that the magnetic field distortion by itself is insufficient to explain the large radial extent of the observed wake encounters. Linear treatment of MHD equations showed that the Kelvin-Helmholtz instability is initiated at the plasma-cavity interface.

Tariq, G. F.↗
NASA NTRS1985

Electrodynamics of the westward traveling surge

It is shown that the global convection pattern, the ionospheric current, and the field-aligned current associated with the westward traveling surge in the asymptotic state can be modeled quantitatively as consequences of a blockage of the Hall current from closure in the magnetosphere via field-aligned currents. The conductivity is allowed to increase self-consistently with increasing upward field-aligned current in the model. This inclusion of the self-consistent enhanced ionospheric conductivity due to discrete auroral precipitations is found to generate a localized intense westward electrojet on the poleward side of the Harang discontinuity. The westward electrojet is also found to rotate counterclockwise, merging into the eastward electrojet around the leading edge of the surge. Thus the major features of the westward traveling surge can be reproduced reasonably well in the model.

Kan, J. R.↗
NASA NTRS1986

System engineering study of electrodynamic tether as a spaceborne generator and radiator of electromagnetic waves in the ULF/ELF frequency band

The transmission and generation by orbiting tethered satellite systems of information carrying electromagnetic waves in the ULF/ELF frequency band to the Earth at suitably high signal intensities was examined and the system maintaining these intensities in their orbits for long periods of time without excessive onboard power requirements was investigated. The injection quantity power into electromagnetic waves as a function of system parameters such as tether length and orbital height was estimated. The basic equations needed to evaluate alternataing current tethered systems for external energy requirements are presented. The energy equations to tethered systems with various lengths, tether resistances, and radiation resistances, operating at different current values are applied. Radiation resistance as a function of tether length and orbital height is discussed. It is found that ULF/ELF continuously radiating systems could be maintained in orbit with moderate power requirements. The effect of tether length on the power going into electromagnetic waves and whether a single or dual tether system is preferable for the self-driven mode is discussed. It is concluded that the single tether system is preferable over the dual system.

Estes, R. D.↗
NASA NTRS1986

Laboratory simulation of the electrodynamic interactions of a tethered satellite with an ionospheric plasma

An improved experimental set-up in the Orleans Plasma Chamber allowed investigations of the I-V characteristics of a conductive spherical body (10 cm diameter) in a plasma environment. Moreover, the influence of a transversal magnetic field at 0.6 and 1.2 G was investigated, for the first time, both on the sheath potential profile and current collection. Floating potential profiles were measured at 16 different radial distances from the test body up to 9 body radii in 8 different angular positions. The test body potential could be increased in the range from -200 V up to +100 V. Preliminary results are shown and discussed.

Bonifazi, C.↗
NASA NTRS1986

Theory of plasma contractors for electrodynamic tethered satellite systems

Recent data from ground and space experiments indicate that plasma releases from an object dramatically reduce the sheath impedance between the object and the ambient plasma surrounding it. Available data is in qualitative accord with the theory developed to quantify the flow of current in the sheath. Electron transport in the theory is based on a fluid model of a collisionless plasma with an effective collision frequency comparable to frequencies of plasma oscillations. The theory leads to low effective impedances varying inversely with the square root of the injected plasma density. To support such a low impedance mode of operation using an argon plasma source for example requires that only one argon ion be injected for each thirty electrons extracted from the ambient plasma. The required plasma flow rates are quite low; to extract one ampere of electron current requires a mass flow rate of about one gram of argon per day.

Parks, D. E.↗
NASA NTRS1987

New methods and results for quantification of lightning-aircraft electrodynamics

The NASA F-106 collected data on the rates of change of electromagnetic parameters on the aircraft surface during over 700 direct lightning strikes while penetrating thunderstorms at altitudes from 15,000 t0 40,000 ft (4,570 to 12,190 m). These in situ measurements provided the basis for the first statistical quantification of the lightning electromagnetic threat to aircraft appropriate for determining indirect lightning effects on aircraft. These data are used to update previous lightning criteria and standards developed over the years from ground-based measurements. The proposed standards will be the first which reflect actual aircraft responses measured at flight altitudes. Nonparametric maximum likelihood estimates of the distribution of the peak electromagnetic rates of change for consideration in the new standards are obtained based on peak recorder data for multiple-strike flights. The linear and nonlinear modeling techniques developed provide means to interpret and understand the direct-strike electromagnetic data acquired on the F-106. The reasonable results obtained with the models, compared with measured responses, provide increased confidence that the models may be credibly applied to other aircraft.

Pitts, Felix L.↗
NASA NTRS1986

Electrodynamic tethers for energy conversion

Conductive tethers have been proposed as a new method for converting orbital mechanical energy into electrical power for use on-board a satellite (generator mode) or conversely (motor mode) as a method of providing electric propulsion using electrical energy from the satellite. The operating characteristics of such systems are functionally dependent on orbit altitude and inclination. Effects of these relationships are examined to determine acceptable regions of application. To identify system design considerations, a specific set of system performance goals and requirements are selected. The case selected is for a 25 kW auxiliary power system for use on Space Station. Appropriate system design considerations are developed, and the resulting system is described.

Nobles, W.↗
NASA NTRS1987

Plasma contactors for electrodynamic tethers

Plasma contactors could be used to ground satellites to space plasma to acquire a flow of electrons to propel or power the satellites. A tether would cut across geomagnetic field lines, producing a potential difference between the ends of the tether. Closing the connection between the ends would form a circuit in which an electrical load could be inserted. Design constraints of the circuit are low impedance and a fully reversible high current. The contactor would generate a neutral plasma to connect to the ionospheric plasma. The surface area of the connection would have to be kept large enough for the current density to be equal to the random electron current density in the unperturbed space plasmas. The other contactor would feed electrons and draw ions from the space plasma. Experimental results from spaceborne and ground-based space plasma simulator tests of hollow cathodes that have shown that multiampere currents can be collected are described.

Patterson, Michael J.↗
NASA NTRS1987

Electrodynamic plasma motor/generator experiment

The Plasma Motor/Generator Proof of Function (PMG/POF) experiment, a low-cost payload for flight aboard the Shuttle Orbiter using the Hitchhiker G carrier, is discussed. The primary objective of this experiment is to verify that hollow cathode plasma sources can couple electric currents from either end of a long wire moving through the space plasma in LEO into and through that plasma to produce a PMG circuit. The support structure and the electrical components of the experiment are described. The experimental operation is discussed, including the calibration, experimental measurements, and follow-on missions.

Mccoy, James E.↗
NASA NTRS1987

Theory of plasma contactors for electrodynamic tethered satellite systems

Recent data from ground and space experiments indicate that plasma releases from an object dramatically reduce the sheath impedance between the object and the ambient plasma surrounding it. Available data is in qualitative accord with the theory developed to quantify the flow of current in the sheath. Electron transport in the theory is based on a fluid model of a collisionless plasma with an effective collision frequency comparable to frequencies of plasma oscillations. The theory leads to low effective impedances varying inversely with the square root of the injected plasma density. To support such a low impedance mode of operation using an argon plasma source, for example, requires that only one argon ion be injected for each thirty electrons extracted from the ambient plasma. The required plasma flow rates are quite low; to extract one ampere of electron current requires a mass flow rate of about one gram of argon per day.

Parks, D. E.↗
NASA NTRS1987

On the glitches in the force transmitted by an electrodynamic exciter to a structure

Around resonance, the force transmitted by an exciter into a structure will be smaller or greater than a reference force generated by its coils due to electromechanical interaction. A simple analysis is presented which reveals how this phenomenon of force drop-off is controlled by three factors. The first factor, called Armature Mass Factor, describes a purely mechanical interaction between the structure and the exciter. The electromechanical energy conversion and its interaction with the structure yields two additional factors, called Electrical Resistance and Electrical Inductance Factors. They describe the effects of coil resistance, inductance and magnetic field strength relative to structural damping and stiffness. Present analysis indicates that, under proper circumstances, more than 90 percent of the force drop-off can be eliminated if armature-to-structure mass ratio is smaller or equal to half of modal loss factor.

Rao, Dantam K.↗
NASA NTRS1987

Power and charge dissipation from an electrodynamic tether

The Plasma Motor-Generator project utilizes the influence of the geomagnetic field on a conductive tether attached to a LEO spacecraft to provide a reversible conversion of orbital energy into electrical energy. The behavior of the current into the ionospheric plasma under the influence of the geomagnetic field is of significant experimental and theoretical interest. Theoretical calculations are reviewed which start from Maxwell's equations and treat the ionospheric plasma as a linear dielectric medium. These calculations show a charge emitting tether moving in a magnetic field will generate electromagnetic waves in the plasma which carry the charge in the direction of the magnetic field. The ratio of the tether's speed to the ion cyclotron frequency which is about 25 m for a LEO is a characteristic length for the phenomena. Whereas for the dimensions of the contact plasma much larger than this value the waves are the conventional Alfven waves, when the dimensions are comparable or smaller, diffraction effects occur similar to those associated with Fresnel diffraction in optics. The power required to excite these waves for a given tether current is used to estimate the impedance associated with this mode of charge dissipation.

Hite, Gerald E.↗