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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 901 records · Page 50
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Plasma dust crystallization

In a ground-based definition study, a concept for a new type of microgravity experiment is developed. We formed a new state of matter: a crystalline lattice structure of charged micron-size spheres, suspended in a charge-neutral plasma. The plasma is formed by a low-pressure radio-frequency argon discharge. Solid microspheres are introduced, and they gain a negative electric charge. They are cooled by molecular drag on the ambient neutral gas. They are detected by laser light scattering and video photography. Laboratory experiments have demonstrated that a two-dimensional nonquantum lattice forms through the Coulomb interaction of these spheres. Microgravity is thought to be required to observe a three-dimensional structure.

Goree, John↗
NASA NTRS1999

A View of Lightning from the Space Shuttle Red Sprites and Blue Jets

An examination and analysis of video images of lightning captured by the Low Light Level Monochrome TV cameras of the space shuttle, have provided a variety of examples of new forms of lightning-like discharges that appear to move out of the top of very active thunderstorms. These images were obtained during a number of shuttle missions while conducting the Mesoscale Lightning Observational Experiment (MLE). The video images illustrate a variety of filamentary and broad-like discharges to the stratosphere and maybe related to the intense electrical fields that are generated by the thunderstorm, which may somehow play a part in the Earth's global electrical circuit. A typical event is seen as a single or multiple-like filament that can appear to occur at altitudes between 60 to 95 km above the storm top. In addition, another phenomenon not explained at the present time, appears to move out the top of the storm and then proceeds toward the stratosphere at speeds of about lOOkm/sec. These events, much like a jet, reach an altitude of at least 33 km before they begin to spread out into a cone like shape. More observations obtained from ground and aircraft using low light level color TV cameras have confirmed that the sprites are red while the jets are blue in color, hence the name Red Sprites and Blue Jets. Still images and video data will be presented, illustrating these new atmospheric phenomena.

Vaughan, Otha H., Jr.↗
NASA NTRSDate not supplied

Extended Wear Testing of the 12-kW Advanced Electric Propulsion System Engineering Test Unit Hall Thruster

This work presents a summary of the first wear test of the 12 kW Advanced Electric Propulsion System (AEPS) intended to isolate the impact of discharge current on component wear rates. Testing was led by Aerojet Rocketdyne and performed with the AEPS Engineering Test Unit 2 (ETU-2) thruster. In total, approximately 860 hours of operation were accumulated split between operating conditions of 600 V/9 kW, 600 V/11 kW, and 600 V/12 kW. Thruster performance and stability were invariant throughout the wear test for all thruster throttle conditions and shown to be equal to the values previously measured with ETU-2. Inner front pole cover erosion rates were found to be invariant to discharge current as the measurements at all three operating conditions were equal to within the empirical uncertainty. Outer front pole cover erosion rates were found to be equal for the 600 V/9 kW and 600 V/12 kW conditions with operation at 600 V/11 kW yielding elevated erosion rates. Overall, the data shows that the AEPS thruster design has a high probability of meeting lifetime and performance requirements as the design proceeds to flight production and qualification.

Jason D Frieman↗
NASA NTRSDate not supplied

Extended Wear Testing of the 12-kW Advanced Electric Propulsion System Engineering Test Unit Hall Thruster

This work presents a summary of the first wear test of the 12 kW Advanced Electric Propulsion System (AEPS) intended to isolate the impact of discharge current on component wear rates. Testing was led by Aerojet Rocketdyne and performed with the AEPS Engineering Test Unit 2 (ETU-2) thruster. In total, approximately 860 hours of operation were accumulated split between operating conditions of 600 V/9 kW, 600 V/11 kW, and 600 V/12 kW. Thruster performance and stability were invariant throughout the wear test for all thruster throttle conditions and shown to be equal to the values previously measured with ETU-2. Inner front pole cover erosion rates were found to be invariant to discharge current as the measurements at all three operating conditions were equal to within the empirical uncertainty. Outer front pole cover erosion rates were found to be equal for the 600 V/9 kW and 600 V/12 kW conditions with operation at 600 V/11 kW yielding rates that were comparable to those on the inner front pole cover. Overall, the data shows that the AEPS thruster design has a high probability of meeting lifetime and performance requirements as the design proceeds to flight production and qualification.

HERMeS↗
NASA NTRSDate not supplied

Engineered Interfaces in Extruded Polyphenylsulfone-Boron Nitride Composite Insulation

Improving matrix-filler interactions is critical for optimizing dielectric performance in composite insulation; however, the technique used to introduce inorganic fillers into an organic matrix varies in its ability to satisfactorily reduce the size of cavities and interfaces. This study reports effects from changing the filler incorporation strategy on the rheology, dielectric performance and thermal conductivity of extruded polyphenylsulfone (PPSU) – hexagonal boron nitride (hBN) composite insulation. Depending on the technique used to introduce BN into the host matrix, the viscosity, torque, and melt viscosity temperature of the polymer were reduced, enabling better mixing, heat transfer, and smaller voids. This corresponded to an increase in dielectric strength compared to other formulations at either a similar or lower filler loading. On the other hand, the thermal conductivity in these specimens shifted further away from the thermal conductivity target of 1 W/m·K, which was an indication of a larger separation distance between the particles in samples with smaller interfaces. A trade-off between dielectric strength and thermal conductivity may exist when maximizing thermal conduction without sacrificing dielectric strength.

Polyphenylsulfone↗
DOE OSTI2021

Surface Charge Distribution Mapping Using an Electrostatic Probe

Undesired accumulation of charge on dielectric materials causing electrostatic discharges can be an issue in pulsed power systems and electrical systems in general. As such, an understanding of surface charge distribution, charge accumulation, and decay is required. An in-house no-contact electrostatic probe designed with a 2 mm resolution was fabricated to measure and map surface charge distribution. Designed as a contactless instrument, the probe consisting of a metal rod and low leakage amplifier circuit probes the electric potential near the surface. A scan of the surface then provides the raw data, a potential distribution. The actual probe response - i.e., the surface charge to voltage transfer function, is accounted for in post-processing. This is accomplished via an Inverse Wien Filter - a technique often applied in image processing - to deconvolve the probe response from the measured data. A commercially available electrostatic probe, the Trek 341B meter with a 3455ET probe, capable of measuring +/- 20 kV was compared to the in- house probe that is designed to cover a wider range from +/- 35 kV. A resolution better than the simple probe resolution is achieved through the distribution’s scanning voltage method and deconvolution. Applying repeated scans, surface charge decay was tracked on various polymer materials to determine the material and environment dependence; materials included were PA6, PTFE, and others. As an example of material dependence, samples charged to 20 kV at 65% humidity experience full charge decay in approximately 45 seconds for PA5 (152 mm dia.), while it took about 100 times longer for PTFE (51 mm dia.) to observe the same decay/redistribution of charge.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Towards fully predictive gyrokinetic full- f simulations: validation and triangularity studies in TCV

Designing economical magnetic confinement fusion power plants motivates computational tools that can estimate plasma behavior from engineering parameters without direct reliance on experimental measurement of the plasma profiles. In this work, we present full-f global long-wavelength gyrokinetic simulations of edge and scrape-off layer turbulence in tokamaks that use only magnetic geometry, heating power, and particle inventory as inputs. Unlike many modeling approaches that employ free parameters fitted to experimental data, raising uncertainties when extrapolating to reactor scales. This approach directly simulates turbulence and resulting profiles through gyrokinetics without such empirical adjustments. This is achieved via an adaptive sourcing algorithm in Gkeyll that strictly controls energy injection and emulates particle sourcing due to neutral recycling. We show that the simulated kinetic profiles compare reasonably well with Thomson scattering and Langmuir probe data for Tokamak á Configuration Variable (TCV) discharge #65125, and that the simulations reproduce characteristic features such as blob transport and self-organized electric fields. Applying the same framework to study triangularity effects suggests mechanisms contributing to the improved confinement reported for negative triangularity (NT). Simulations of TCV discharges #65125 and #65130 indicate that NT increases the E x B flow shear (by about 20% in these cases), which correlates with reduced turbulent losses and a modest change in the distribution of power exhaust to the vessel wall. While the physical models contain approximations that can be refined in future work, the predictive capability demonstrated here, evolving multiple profile relaxation times with kinetic electron and ion models in hundreds of GPU hours, indicates the feasibility of using Gkeyll to support design studies of fusion devices.

Hoffmann, Antoine Cyril David [Princeton Plasma Ph↗
NASA NTRS2008

New Techniques to Evaluate the Incendiary Behavior of Insulators

New techniques for evaluating the incendiary behavior of insulators is presented. The onset of incendive brush discharges in air is evaluated using standard spark probe techniques for the case simulating approaches of an electrically grounded sphere to a charged insulator in the presence of a flammable atmosphere. However, this standard technique is unsuitable for the case of brush discharges that may occur during the charging-separation process for two insulator materials. We present experimental techniques to evaluate this hazard in the presence of a flammable atmosphere which is ideally suited to measure the incendiary nature of micro-discharges upon separation, a measurement never before performed. Other measurement techniques unique to this study include; surface potential measurements of insulators before, during and after contact and separation, as well as methods to verify fieldmeter calibrations using a charge insulator surface opposed to standard high voltage plates. Key words: Kapton polyimide film, incendiary discharges, brush discharges, contact and frictional electrification, ignition hazards, insulators, contact angle, surface potential measurements.

Buhler, Charles↗
NASA NTRS1979

RF radiation produced by intracloud lightning discharges

The RF radiation produced during intracloud lightning flashes is presented, together with associated fast and slow electric field changes. These data were collected during the Thunderstorm Research International Project in Florida during the summer of 1977. The RF radiation is essentially simultaneous with the fast-field change but has a tendency to peak during the initial half-cycle of the bipolar field changes associated cloud processes. This is in marked contrast to previous observations of RF radiation during return strokes in cloud-to-ground discharges and provides a clue to the physics of the intracloud discharge.

Levine, D. M.↗
DOE OSTI2023

Waves of Electric Charge Generated by Pulse Corona of Alternating Polarity

The project contributes to DoE Office of Science program “Opportunities in Frontier Plasma Science” by providing plasma science experiments at the Princeton Collaborative Research Facility (PCRF) – the Princeton Plasma Physics Laboratory. The research consisted of - extensive experimental/simulation studies of a pulse corona discharge pattern and dynamics performed at the University of Notre Dame; - non-intrusive measurements of electric field distribution and dynamics performed at PCRF by the method employing Electric Field-Induced Second Harmonic Generation (EFISH); and - analysis of the data acquired.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1990

Dissociation phenomena in electron-beam sustained carbon dioxide lasers

A number of applications are emerging requiring efficient, long pulse, long-life sealed CO2 lasers. Examples include the proposed NASA and ESA wind lidars. Electron-beam sustained discharge devices are strong contenders. Unlike self-sustained discharges, e-beam sustenance readily provides efficient performance from large volume discharges and offers pulse lengths well in excess of the microsecond or so generally associated with self-sustained devices. In the case of the e-beam sustained laser, since the plasma is externally maintained and operated at electric field strengths less than that associated with the glow to arc transition, the discharges can be run even in the presence of strongly attacking species such as O2. Build up of large levels of attacking contaminants is nevertheless undesirable as their presence reduces the current drawn by the plasma and thus the pumping rate to the upper laser level. The impedance rise leads to a mismatch of the pulse forming network with a consequent loss of control over energy deposition, operating E/N, and gain. Clearly CO2 dissociation rates, the influence of dissociation products on the discharge and gain, and tolerance of the discharge to these products need to be determined. This information can then be used to assess co-oxidation catalyst requirements for sealed operation.

Harris, Michael R.↗
NASA NTRS1988

Lightning parameterization in a storm electrification model

The parameterization of an intracloud lightning discharge has been implemented in our Storm Electrification Model. The initiation, propagation direction, termination and charge redistribution of the discharge are approximated assuming overall charge neutrality. Various simulations involving differing amounts of charge transferred have been done. The effects of the lightning-produced ions on the hydrometeor charges, electric field components and electrical energy depend strongly on the charge transferred. A comparison between the measured electric field change of an actual intracloud flash and the field change due to the simulated discharge show favorable agreement.

Helsdon, John H., Jr.↗
NASA NTRS2014

Development and Implementation of a Hardware In-the-Loop Test Bed for Unmanned Aerial Vehicle Control Algorithms

Successful prediction and management of battery life using prognostic algorithms through ground and flight tests is important for performance evaluation of electrical systems. This paper details the design of test beds suitable for replicating loading profiles that would be encountered in deployed electrical systems. The test bed data will be used to develop and validate prognostic algorithms for predicting battery discharge time and battery failure time. Online battery prognostic algorithms will enable health management strategies. The platform used for algorithm demonstration is the EDGE 540T electric unmanned aerial vehicle (UAV). The fully designed test beds developed and detailed in this paper can be used to conduct battery life tests by controlling current and recording voltage and temperature to develop a model that makes a prediction of end-of-charge and end-of-life of the system based on rapid state of health (SOH) assessment.

Battery Testbed↗
DOE OSTI2025

Return on Investment and Sustainability of HVDC Links: Role of Diagnostics, Condition Monitoring, and Material Innovations

HVDC cable systems are becoming an upscaled technical option, compared to AC, because of various factors, including easier interconnections, lower losses, and longer transmission distances. In addition, renewables providing direct DC energy, electrified transportation, and aerospace where DC can be favored because of higher carried specific power all point in the direction of broad future usage of HV and MV DC links. However, contrary to AC, there is little return from on-field installation as regards long-term cable reliability and aging processes. This gap must be covered by intensive research, and contributing to this research is the purpose of this paper. The focus is on key points for HVDC (and MVDC) cable reliability and sustainability, from design modeling able to account for voltage transients and extrinsic aging (such as that caused by partial discharges) to the impact of aging on insulation conductivity (which rules the electric field distribution, thus aging rate). Also, recyclable and nanostructured materials, as well as health conditions, are considered. It is shown how cable design can account for accelerated aging due to voltage transients, as well as for aging-time dependence of conductivity, and how design can be free of extrinsic aging caused by PDs. Algorithms for health condition evaluations, which have additional value in a relatively new technology such as HVDC polymeric cables, are applied to insulation system aging under partial discharges, showing how they can provide an indication of insulation degradation globally or locally (weak spots) and of possible maintenance times. All of this can effectively contribute to reducing the risk of major cable breakdown and damage under operation, which would significantly affect the return on investment (ROI).

Montanari, Gian Carlo (ORCID:0000000320258693)↗
NASA NTRS1972

Pulsed electromagnetic gas acceleration

Photographs of the exhaust plume of a pulsed MPD discharge through selected narrow band spectral filters reveal a species structure related to the location of the argon mass injection ports. This species structure provides the key to interpretation of time-resolved interferometric velocity measurements in the exhaust. The resulting exhaust velocity increases monotonically from 8500 m/sec at a position 5 cm downstream of the anode face to 16,500 m/sec 40 cm downstream. The latter value is approximately twice the Alfven critical speed for argon. The growth of the axial electric field near the downstream face of the anode indicates that the discharge operates in a starved mode. Data from biased double probes imply an electron temperature of 0.8 eV in the exhaust plume.

Jahn, R. G.↗
DOE OSTI2022

Pumped Thermal Energy Storage With Liquid Storage

Pumped Thermal Energy Storage (PTES) uses electricity to power a heat pump; transferring heat from a cold space to a hot space forms a hot and a cold thermal reservoir, thereby storing energy. To discharge, the temperature difference between the two stores is used to drive a heat engine which generates electricity. In this chapter, PTES systems which store energy in liquids will be described. The chapter will concentrate on Joule-Brayton power cycles with molten salt storage. Part-load operation of Joule-Brayton PTES with liquid storage can be managed with "inventory control," and it is demonstrated that this control method leads to relatively good performance over a range of operating points.

Carnot batteries↗
DOE OSTI2022

Developing CdTe homojunctions applying high throughput deposition

In this project, we attempted to make CdTe homojunctions using single crystal p-type doped substrates and closed-space sublimation epitaxy (CSSE) n-type doped films. The project included modeling which determined the ideal thickness for the n-type layer as being <200 nm. Boules of high concentration indium-doped CdTe and CdSe 0.4 Te 0.6 (CST) were grown using modified vertical Bridgman (MVB) methods. Similarly, iodine-doped CdTe crystals were grown for the first time. Washington State University (WSU) stock phosphorus-doped CdTe was used as the p-type substrate layer. The crystals were characterized by Hall effect and time-resolved photoluminescence (TRPL, for electrical properties), photoluminescence microscopy (for uniformity), X-ray diffraction (for crystal structure), and glow discharge mass spectrometry (GDMS, for dopant and impurity concentration). CdTe:I crystals were also characterized by visible and infrared transmission measurements, and various Cd or Te heat treatments were performed to assess changes in optical and electrical properties. The grown n-type materials – CdTe:In, CdSe0.4Te0.6:In, and CdTe:I – were provided to the National Renewable Energy Laboratory (NREL) for growth of CSSE thick films for characterization by two photon TRPL (for carrier lifetime), electron back-scatter diffraction (EBSD, to assess epitaxy), and Hall effect. Several measurements of secondary ion mass spectroscopy (SIMS) were performed. Nearly 100% of the indium from the crystal was incorporated into the measured thick films, while only ~2-22% of the iodine from the crystal was incorporated. The net result of the diffusion issue is that homojunction devices created using CSSE have a buried homojunction, as indicated by the near infrared peak in the external quantum efficiency (EQE). Various parameterization of front and back contacts suggested that the poor device performance was primarily a result of this buried junction and not due to other effects. There may also be an issue with the CSSE film lifetime in addition to the dopant profile.

14 SOLAR ENERGY↗
NASA NTRS2016

Characterization of DBD Plasma Actuators Performance Without External Flow - Part I: Thrust-Voltage Quadratic Relationship in Logarithmic Space for Sinusoidal Excitation

Results of characterization of Dielectric Barrier Discharge (DBD) plasma actuators without external flow are presented. The results include aerodynamic and electric performance of the actuators without external flow for different geometrical parameters, dielectric materials and applied voltage level and wave form.

Dielectric Barrier Discharge↗