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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 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Influence of a new generation of operations support systems on current spacecraft operations philosophy: The users feedback

Current trends in the spacecraft mission operations area (spacecraft & mission complexity, project duration, required flexibility are requiring a breakthrough for what concerns philosophy, organization, and support tools. A major evolution is related to space operations 'informationalization', i.e adding to existing operations support & data processing systems a new generation of tools based on advanced information technologies (object-oriented programming, artificial intelligence, data bases, hypertext) that automate, at least partially, operations tasks that used be performed manually (mission & project planning/scheduling, operations procedures elaboration & execution, data analysis & failure diagnosis). All the major facets of this 'informationalization' are addressed at MATRA MARCONI SPACE, operational applications were fielded and generic products are becoming available. These various applications have generated a significant feedback from the users (at ESA, CNES, ARIANESPACE, MATRA MARCONI SPACE), which is now allowing us to precisely measure how the deployment of this new generation of tools, that we called OPSWARE, can 'reengineer' current spacecraft mission operations philosophy, how it can make space operations faster, better, and cheaper. This paper can be considered as an update of the keynote address 'Knowledge-Based Systems for Spacecraft Control' presented during the first 'Ground Data Systems for Spacecraft Control' conference in Darmstadt, June 1990, with a special emphasis on these last two years users feedback.

Darroy, Jean Michel↗
DOE OSTI2023

Projecting Future Energy Production from Operating Wind Farms in North America. Part III: Variability

Abstract Daily expected wind power production from operating wind farms across North America are used to evaluate capacity factors (CF) computed using simulation output from the Weather Research and Forecasting (WRF) Model and to condition statistical models linking atmospheric conditions to electricity production. In Parts I and II of this work, we focus on making projections of annual energy production and the occurrence of electrical production drought. Here, we extend evaluation of the CF projections for sites in the Northeast, Midwest, southern Great Plains (SGP), and southwest U.S. coast (SWC) using statewide wind-generated electricity supply to the grid. We then quantify changes in the time scales of CF variability and the seasonality. Currently, wind-generated electricity is lowest in summer in each region except SWC, which causes a substantial mismatch with electricity demand. While electricity of residential heating may shift demand, research presented here suggests that summertime CF are likely to decline, potentially exacerbating the offset between seasonal peak power production and current load. The reduction in summertime CF is manifest for all regions except the SGP and appears to be linked to a reduction in synoptic-scale variability. Using fulfillment of 50% and 90% of annual energy production to quantify interannual variability, it is shown that wind power production exhibits higher (earlier fulfillment) or lower (later fulfillment) production for periods of over 10–30 years as a result of the action of internal climate modes. Significance Statement Electrical power system reassessment and redesign may be needed to aid efficient increased use of variable renewables in the generation of electricity. Currently wind-generated electricity in many regions of North America exhibits a minimum in summertime and hence is not well synchronized with electricity demand, which tends to be maximized in summer. Future projections indicate evidence of reductions in wind power during summer that would amplify this offset. However, electrification of heating may lead to increased wintertime demand, which would lead to greater synchronization.

Coburn, Jacob↗
NASA NTRS1974

Anisotropic proton instability magnetospheric /APIM/ hiss - An introduction

Plasmaspheric hiss is broadband ELF noise between 100 and 2000 Hz generally occurring inside the plasmasphere. It is proposed that some plasmaspheric ELF hiss is generated by ring current protons. The mechanism by which waves are generated is the anisotropic proton instability magnetospheric (APIM) hiss mechanism. APIM hiss (with a frequency close to the lower hybrid resonance frequency) is a loss-cone, flute instability arising from proton velocity space anisotropies. The energy driving the waves comes from the free energy of the 'inverted population' of the proton loss-cone distribution. The APIM hiss mechanism predicts the bandwidth, center frequency, source location, and wave normal angle of some types of plasmaspheric hiss. APIM hiss is suggested as a possible additional loss mechanism for ring current protons.

Parady, B. K.↗
DOE OSTI2022

Current State of 44 Ti/ 44 Sc Radionuclide Generator Systems and Separation Chemistry

We report in recent years, there has been an increased interest in 44Ti/44Sc generators as an onsite source of 44Sc for medical applications without needing a proximal cyclotron. The relatively short half-life (3.97 hours) and high positron branching ratio (94.3%) of 44Sc make it a viable candidate for positron emission tomography (PET) imaging. This review discusses current 44Ti/44Sc generator designs, focusing on their chemistry, drawbacks, post-elution processing, and relevant preclinical studies of the 44Sc for potential PET radiopharmaceuticals.

43 PARTICLE ACCELERATORS↗
NASA NTRS1991

Evaluation of the damages caused by lightning current flowing through bearings

A laboratory for lightning current tests was set up allowing the generation of the lightning currents foreseen by the Standards. Lightning tests are carried out on different objects, aircraft materials and components, evaluating the direct and indirect effects of lightning. Recently a research was carried out to evaluate the effects of the lightning current flow through bearings with special reference to wind power generator applications. For this purpose, lightning currents of different amplitude were applied to bearings in different test conditions and the damages caused by the lightning current flow were analyzed. The influence of the load acting on the bearing, the presence of lubricant and the bearing rotation were studied.

Celi, O.↗
NASA NTRS1974

Self-energized plasma compressor

The self-energized plasma compressor is described which compresses plasma discharged from a coaxial plasma generator. The device includes a helically shaped coil which is coaxially aligned with the center axis of the coaxial plasma generator. The plasma generator creates a current through the helical coil which, in turn, generates a time varying magnetic field that creates a force which acts radially upon the plasma. The coaxial plasma generator and helical coil move the plasma under high pressure and temperature to the narrow end of the coil. Positioned adjacent to the narrow end of the coil are beads which are engaged by the plasma to be accelerated to hypervelocities for simulating meteoroids.

Shriver, E. L.↗
NASA NTRS1984

An analysis of a satellite multibeam altimeter

Since the GEOS-3 and SEASAT-1 radar altimeters measured altitude over a narrow swath along the satellite subtrack, ocean current and mesoscale feature maps could only be generated after a large number of satellite revolutions. The present paper analyzes a new multibeam altimeter technique that has the potential to cover wide swaths. The multibeam altimeter uses two antenna elements, simple parabolic dishes with offset feeds, deployed cross-track on singly hinged booms into a fixed measurement geometry to generate an interferometer pattern over the desired swath extent. Range gating allows the isolation of a single interferometeric lobe, and the desired altitude measurements are extracted by using a modified altitude tracker design. Implementing this sensor on future altimetry missions would allow the timely generation of ocean current and mesoscale feature maps for the first time.

Bush, G. B.↗
NASA NTRS1991

'Self-consistent' production of ion conics on return current region auroral field lines - A time-dependent, semi-kinetic model

We describe initial results from a time-dependent, semi-kinetic model of plasma outflow incorporating wave-particle interactions along current-carrying auroral field lines. Electrostatic waves are generated by the current driven ion cyclotron instability (CDICI), causing perpendicular velocity diffusion of ions plus electron heating via anomalous resistivity when and where the relative drift between electrons and ions exceeds certain critical velocities. Using the local bulk parameters we calculate these critical velocities, and so are able to self-consistently switch on and off the heating of the various particle species. Due to the dependence of these critical velocities on the bulk parameters of the species the heating effects exhibit quite complex spatial and temporal variations. A wide range of ion distribution functions are observed in these simulations, including conics with energies of a few electron volts and 'ring' distributions. The rings are seen to be a natural result of transverse heating and velocity filter effects and do not require coherent acceleration processes. We also observe the formation of a density depletion in hydrogen and enhanced oxygen densities at high altitudes.

Brown, David G.↗
NASA NTRS1976

Gas Filled Coaxial Accelerator with Compression Coil

A self-energized plasma compressor which compresses plasma discharged from a coaxial plasma generator. The device includes a helical shaped coil which is coaxially aligned with the center axis of the coaxial plasma generator. The plasma generator creates a current through the helical coil which, in turn, generates a time varying magnetic field that generates a force which acts radially upon the plasma. A seal is carried on the end of the coaxial plasma generator for containing gas therein. As the plasma is accelerated out the outer end of the generator, it forces the gas outwardly also compressing such. Beads are carried adjacent the small end of the helical shaped coil for being accelerated to hypervelocities by the plasma and gas. As a result of utilizing gas in the coaxial plasma generator, such minimizes ablation of the beads as well as accelerates such to higher velocities.

Espy, Patrick N.↗
NASA NTRS2010

Fabrication and Modification of Nanoporous Silicon Particles

Silicon-based nanoporous particles as biodegradable drug carriers are advantageous in permeation, controlled release, and targeting. The use of biodegradable nanoporous silicon and silicon dioxide, with proper surface treatments, allows sustained drug release within the target site over a period of days, or even weeks, due to selective surface coating. A variety of surface treatment protocols are available for silicon-based particles to be stabilized, functionalized, or modified as required. Coated polyethylene glycol (PEG) chains showed the effective depression of both plasma protein adsorption and cell attachment to the modified surfaces, as well as the advantage of long circulating. Porous silicon particles are micromachined by lithography. Compared to the synthesis route of the nanomaterials, the advantages include: (1) the capability to make different shapes, not only spherical particles but also square, rectangular, or ellipse cross sections, etc.; (2) the capability for very precise dimension control; (3) the capacity for porosity and pore profile control; and (4) allowance of complex surface modification. The particle patterns as small as 60 nm can be fabricated using the state-of-the-art photolithography. The pores in silicon can be fabricated by exposing the silicon in an HF/ethanol solution and then subjecting the pores to an electrical current. The size and shape of the pores inside silicon can be adjusted by the doping of the silicon, electrical current application, the composition of the electrolyte solution, and etching time. The surface of the silicon particles can be modified by many means to provide targeted delivery and on-site permanence for extended release. Multiple active agents can be co-loaded into the particles. Because the surface modification of particles can be done on wafers before the mechanical release, asymmetrical surface modification is feasible. Starting from silicon wafers, a treatment, such as KOH dipping or reactive ion etching (RIE), may be applied to make the surface rough. This helps remove the nucleation layer. A protective layer is then deposited on the wafer. The protective layer, such as silicon nitride film or photoresist film, protects the wafer from electrochemical etching in an HF-based solution. A lithography technique is applied to pattern the particles onto the protective film. The undesired area of the protective film is removed, and the protective film on the back side of the wafer is also removed. Then the pattern is exposed to HF/surfactant solution, and a larger DC electrical current is applied to the wafers for a selected time. This step removes the nucleation layer. Then a DC current is applied to generate the nanopores. Next, a large electrical current is applied to generate a release layer. The particles are mechanically suspended in the solvent and collected by filtration or centrifuge.

Ferrari, Mauro↗
NASA NTRS1983

High-voltage (270 V) dc power-generating system for fighter aircraft

The advantages of using high voltage, direct current advanced power generating systems in fighter aircraft are discussed. Weight reduction is achieved. Efficiency is increased 85 to 90 percent by eliminating the constant speed drive. Power interruptions are eliminated. There are no speed restrictions and no powerline constraints. Personal safety is increased by eliminating the hold on frequency, present in ac systems, which causes muscle contractions.

Mcginley, K. M.↗
NASA NTRS1990

A case study of the Thunderstorm Research International Project storm of July 11, 1978. II - Interrelations among the observable parameters controlling electrification

This paper discusses electrical system parameters that would be consistent with observations of the Thunderstorm Research International Project storm at the Kennedy Space Center on July 11, 1978, described by Nisbet et al. (1990). Three-dimensional electrodynamic modeling of the thundercloud electrification made it possible to estimate the current moments and electrical power generated continuously throughout the evolution of the two cells of the storm. The current moments generated were compared with the current moments transferred by intercloud and cloud-to-ground lightning. It is shown that, for the southern cell, which produced a charge moment of about 8.4 MC m, lightning utilized about 84 percent of the charge moment separated; for the northern cell, which produced about 1.1 MC m, lightning utilized about 60 percent of the charge moment separated.

Nisbet, John S.↗
NASA NTRS1993

Modeling of the coupled magnetospheric and neutral wind dynamos

The solar wind interaction with the earth's magnetosphere generates electric fields and currents that flow from the magnetosphere to the ionosphere at high latitudes. Consequently, the neutral atmosphere is subject to the dissipation and conversion of this electrical energy to thermal and mechanical energy through Joule heating and Lorentz forcing. As a result of the mechanical energy stored within the neutral wind (caused in part by Lorentz--and pressure gradient--forces set up by the magnetospheric flux of electrical energy), electric currents and fields can be generated in the ionosphere through the neutral wind dynamo mechanism. At high latitudes this source of electrical energy has been largely ignored in past studies, owing to the assumed dominance of the solar wind/magnetospheric dynamo as an electrical energy source to the ionosphere. However, other researchers have demonstrated that the available electrical energy provided by the neutral wind is significant at high latitudes, particularly in the midnight sector of the polar cap and in the region of the magnetospheric convection reversal. As a result, the conclusions of a number of broad ranging high-latitude investigations may be modified if the neutral-wind contribution to high-latitude electrodynamics is properly accounted for. These include the following: studies assessing solar wind-magnetospheric coupling by comparing the cross polar cap potential with solar wind parameters; research based on the alignment of particle precipitation with convection or field aligned current boundaries; and synoptic investigations attributing seasonal variations in the observed electric field and current patterns to external sources. These research topics have been initiated by satellite and ground-based observations and have been attributed to magnetospheric causes. However, the contribution of the neutral wind to the high-latitude electric field and current systems and their seasonal and local time dependence has yet to be quantitatively evaluated. In this program, we are evaluating the coupled magnetospheric and neutral wind dynamos at high latitudes under various conditions. In addition to examining the impact of seasonal variations, we are investigating the consequences of the separate dynamos having pure current-source or voltage-source behaviors.

Thayer, Jeff P.↗
DOE OSTI2020

Implementing Admittance Relaying for Microgrid Protection

An earlier study evaluated issues with microgrid protection. This highlighted the difficulties with microgrid protection, which include: 1. lack of fault current from inverter-interfaced generation, 2. varying fault current between grid-connected and islanded modes, 3. potential for normally-meshed operation and 4. unbalanced operation due to single-phase loads. It is worth noting that not all microgrid designs will include all these challenges. For example, microgrids could choose to omit meshed operation. Previous work identified differential protection based on the discrete S-transform for line protection and admittance protection for load protection as possible solutions . However, some severe limitations were identified. This included the potential for blinding of the discrete S-transform protection when fault contribution on either end of the line is similar, and loss of protection selectivity for admittance protection in the case of upstream line-ground faults. This report investigates admittance protection as a solution for line and load protection in greater detail by comparing analytical and simulated results. Section 2 describes the protection schemes analyzed and the behavior of inverter-interfaced microgrids under faults in more detail. Section 3 derives sequence networks for the fault cases considered. Section 4 presents a transient model constructed to validate the impedances calculated from the sequence networks. Section 5 compares the results from the sequence networks and transient model. Last, Section 6 presents the conclusions of this study in terms of the suitability of admittance relaying for protection of inverter-interfaced microgrids.

24 POWER TRANSMISSION AND DISTRIBUTION↗
NASA NTRS1972

Hall current effects in the Lewis magnetohydrodynamic generator

Data obtained in a magnetohydrodynamic generator are compared with theoretical values calculated by using the Dzung theory. The generator was operated with cesium-seeded argon as the working fluid. The gas temperature varied from 1800 to 2100 K, the gas pressure from 19 to 22 N/sq cm, the Mach number from 0.3 to 0.5, and the magnetic field strength from 0.2 to 1.6 T. The analysis indicates that there is incomplete seed vaporization and that Hall current shorting paths (through the working fluid to ground at both the entrance and exit of the channel) limit generator performance.

Nichols, L. D.↗
NASA NTRS1985

Thundercloud current determination from measurements at the earth's surface

For the analysis of the actual dominant mechanism or mechanisms of electrification in a given storm cell, it is of great importance to make observations which can be used to determine the configuration and the magnitudes of the currents and impedances of the generator systems in active thunderclouds. Krider and Musser (1982) have measured Maxwell currents below Florida thunderclouds and shown that their patterns are consistent with simple generator geometries. It is, therefore, of great interest to study the extent to which a set of Maxwell current measurements can be inverted to obtain the generator currents and locations. Nisbet (1983) has developed an electrical model for active thunderclouds which solves equations for current densities and electric fields. The present investigation is concerned with the extent to which such a model can be used to derive data about the cloud generator magnitudes and locations, taking into account also the conductivity profile from ground-based measurements or estimates of the Maxwell current density.

Nisbet, J. S.↗
NASA NTRS1972

Hall current effects in the Lewis magnetohydrodynamic generator.

Data obtained in the Lewis MHD generator are compared with theoretical values calculated using the Dzung (1966) theory. The generator is operated with cesium seeded argon as the working fluid. The gas temperature varies from 1800 to 2100 K, the gas pressure from 19 to 22 N/sq cm, the Mach number from .3 to .5, and the magnetic field strength from .2 to 1.6 tesla. The analysis indicates that there is incomplete seed vaporization and that Hall current shorting paths (through the working fluid to ground at both the entrance and exit of the channel) are limiting generator performance.

Nichols, L. D.↗
DOE OSTI2021

Electric field control of magnon spin currents in an antiferromagnetic insulator

Pure spin currents can be generated via thermal excitations of magnons. These magnon spin currents serve as carriers of information in insulating materials, and controlling them using electrical means may enable energy efficient information processing. Here, we demonstrate electric field control of magnon spin currents in the antiferromagnetic insulator Cr 2 O 3 . We show that the thermally driven magnon spin currents reveal a spin-flop transition in thin-film Cr 2 O 3 . Crucially, this spin-flop can be turned on or off by applying an electric field across the thickness of the film. Using this tunability, we demonstrate electric field–induced switching of the polarization of magnon spin currents by varying only a gate voltage while at a fixed magnetic field. We propose a model considering an electric field–dependent spin-flop transition, arising from a change in sublattice magnetizations via a magnetoelectric coupling. These results provide a different approach toward controlling magnon spin current in antiferromagnets.

36 MATERIALS SCIENCE↗