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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 1,315 records · Page 73
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Constraints on lunar structure

A brief review is given of the constraints placed on lunar structure and composition by seismic data and density models. Bounds on the crustal velocity structure in Mare Cognitum are derived using travel-time data from artificial impacts, and a velocity model is determined on the basis of synthetic seismograms. It is shown that the velocities of P- and S-waves in the mantle can be fixed by a least-squares analysis of arrival times from meteor impacts and moonquakes, and that lunar density can be determined from the seismic structure, mean density, and moment of inertia. Olivine-pyroxene mixtures and certain olivine-rich compositions are found to be consistent with the seismic-velocity and density limits. Maximum radii are calculated for pure Fe and pure FeS cores, and it is concluded that the possibility of an ancient lunar magnetic dynamo may have to be reevaluated in the light of these figures.

Dainty, A. M.↗
NASA NTRS1976

On the question of the energy of the precessional dynamo

The various estimates for the coupling mechanism by which precession transfers rotational, kinetic energy of earth into the energy of its magnetic field are generally considering hydromagnetic stresses that originate between mantle and core. Estimates of the energy of the geomagnetic field calculated from the data of spherical harmonic analysis derive precession energy values in reasonable agreement with the observed external energy of the geomagnetic field and with the rate of ohmic dissipation of energy in the core.

Dolginov, S. S.↗
NASA NTRS1976

Energy storage and deposition in a solar flare

X-ray pictures of a solar flare taken with the S-056 X-ray telescope aboard Skylab are interpreted in terms of flare energy deposition and storage. The close similarity between calculated magnetic-field lines and the overall structure of the X-ray core is shown to suggest that the flare occurred in an entire arcade of loops. It is found that different X-ray features brightened sequentially as the flare evolved, indicating that some triggering disturbance moved from one side to the other in the flare core. A propagation velocity of 180 to 280 km/s is computed, and it is proposed that the geometry of the loop arcade strongly influenced the propagation of the triggering disturbance as well as the storage and site of the subsequent energy deposition. Some possible physical causes for the sequential X-ray brightening are examined, and a magnetosonic wave is suggested as the triggering disturbance. 'Correct' conditions for energy release are considered

Vorpahl, J. A.↗
NASA NTRS1982

Solar wind helium ions - Observations of the Helios solar probes between 0.3 and 1 AU

A Helios solar probe survey of solar wind helium ion velocity distributions and derived parameters between 0.3 and 1 AU is presented. Distributions in high-speed wind are found to generally have small total anisotropies, with some indication that, in the core part, the temperatures are greater parallel rather than perpendicular to the magnetic field. The anisotropy tends to increase with heliocentric radial distance, and the average dependence of helium ion temperatures on radial distance from the sun is described by a power law. Differential ion speeds with values of more than 150 km/sec are observed near perihelion, or 0.3 AU. The role of Coulomb collisions in limiting differential ion speeds and the ion temperature ratio is investigated, and it is found that collisions play a distinct role in low-speed wind, by limiting both differential ion velocity and temperature.

Marsch, E.↗
NASA NTRS1983

Multifrequency observations of the flaring quasar 1156+295

A report is presented on the optically violent variable quasar 1156+295, known also as 4C 29.45 and Ton 599. A large outburst of this quasar was discovered in April 1981 in the course of a program to obtain simultaneous multifrequency spectra of variable quasars. Ultraviolet observations taken with the International Ultraviolet Explorer satellite were coordinated with ground-based observations at radio, infrared, and optical wavelengths. Measurements were made at four epochs starting immediately after the outburst was discovered, when the B-magnitude was 14.0, and at intervals of 4 days, 60 days and 1 year. The luminosity integrated only over observed wavelength bands was approximately 3 x 10 to the 48th ergs/sec on the first epoch of observation. Modeling of the source with a synchrotron self-Compton model suggests that the core of the source has a linear dimension of 0.01 pc, a magnetic field strength in the range 0.1-30 gauss, and a bulk relativistic motion in the quasar rest frame characterized by a Lorentz factor in the range 2-8.

Glassgold, A. E.↗
NASA NTRS2013

Orbital Manuvering System Design and Performance For the Magnetosperic Multiscale Constellation

The Magnetospheric Multiscale (MMS) mission, launched on March 13, 2015, is the fourth mission of NASA's Solar Terrestrial Probe program. The MMS mission consists of four identically instrumented observatories that function as a constellation to provide the first definitive study of magnetic reconnection in space. Since it is frequently desirable to isolate electric and magnetic field sensors from stray effects caused by the spacecraft's core-body, the suite of instruments on MMS includes six radial and two axial instrument-booms with deployed lengths ranging from 5-60 meters (see Figure 1). The observatory is spin-stabilized about its positive z-axis with a nominal rate slightly above 3 rev/min (RPM). The spin is also used to maintain tension in the four radial wire-booms. Each observatory's Attitude Control System (ACS) consists of digital sun sensors, star cameras, accelerometers, and mono-propellant hydrazine thrusters-responsible for orbital adjustments, attitude control, and spin adjustments. The sections that follow describe performance requirements, the hardware and algorithms used for 6-DOF estimation, and then similarly for 6-DOF control. The paper concludes with maneuver performance based on both simulated and on-orbit telem.

Determination and Control↗
NASA NTRS2020

Core Losses in Co-Rich Inductors with Tunable Permeability

High frequency, low loss power systems enable electrified aircraft propulsion. Filter inductors that reduce noise in high current systems can account for 50% of the motor drive mass. Efficient inductor cores with tunable permeability reduce system mass by producing less heat, that removes heat sink mass. Requirements for filter inductors vary based on the chosen topology, but all inductor cores must operate below saturation levels. As the saturation flux density is limited (less than ~2 T), high differential current applications require cores with low relative permeabilities. The large induced anisotropies possible in Co-rich metal amorphous nanocomposite materials enables gapless inductors with relative permeabilities down to ~20. These materials have fine grain size ~8nm with a faulted, close packed structure. The impact of different processing methods on core losses are presented along with comparison to other low permeability soft magnetic materials.

Leary, Alex↗
NASA NTRS2026

Recommended Practice for Use of ExB Probes in Electric Propulsion Testing

An ExB probe is an electric propulsion plume diagnostic that has at its core a Wien filter. Ions entering the instrument experience perpendicular electric and magnetic fields and are filtered based on their velocity. While the ExB probe can be used to estimate the ion velocity distribution function, in the electric propulsion community, it is commonly used to measure species fractions. There are numerous probe designs, implementation and operation procedures, and data analysis approaches described and in use across the community. This paper provides recommendations and descriptions of best practices for design, implementation, and data analysis for the ExB probe, with a particular emphasis on Hall and ion thrusters. This work contributes to the broader community goal to standardize the use of diagnostics in electric propulsion testing.

ExB probe↗
DOE OSTI2021

Distributed sensing of electromagnetic components using optical fiber based methods

An OFDR based fiber-optics sensor for distributed real-time temperature rise monitoring of a transformer in operation has been disclosed. The fiber-optic sensor provides an effective solution to monitoring the physical structures of the transformer core, as well as accurately detecting the non-uniform temperature distribution inside the transformer, and thus provides innovative feedback to the transformer design by minimizing the core losses. Additionally, the method may be responsive to the presence of magnetic and electric fields, as well as responsive to various chemical species. The method allows novel approaches to real-time asset monitoring of power transformers while operational.

Ohodnicki, Paul R.↗
DOE OSTI2018

Pair-density waves, charge-density waves, and vortices in high- T c cuprates

A recent scanning tunneling microscopy (STM) experiment reports the observation of a charge-density wave (CDW) with a period of approximately 8a in the halo region surrounding the vortex core, in striking contrast to the approximately 4a period CDWs that are commonly observed in the cuprates. Inspired by this work, we study a model where a bidirectional pair-density wave (PDW) with period 8 is at play. This further divides into two classes: (1) where the PDW is a competing state of the d-wave superconductor and can exist only near the vortex core where the d-wave order is suppressed and (2) where the PDW is the primary order, the so-called “mother state” that persists with strong phase fluctuations to high temperature and high magnetic field and lies behind the pseudogap phenomenology. We study the charge-density wave structures near the vortex core in these models. We emphasize the importance of the phase winding of the d-wave order parameter. The PDW can be pinned by the vortex core due to this winding and become static. Furthermore, the period-8 CDW inherits the properties of this winding, which gives rise to a special feature of the Fourier transform peak, namely, it is split in certain directions. There is also a line of zeros in the inverse Fourier transform of filtered data. We propose that these are key experimental signatures that can distinguish between the PDW-driven scenario from the more mundane option that the period-8 CDW is primary. We discuss the pro's and con's of the options considered above. Lastly, we attempt to place the STM experiment in the broader context of pseudogap physics of underdoped cuprates and relate this observation to the unusual properties of x-ray scattering data on CDW carried out to very high magnetic field.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS2017

Decadal Polar Motion of the Earth Excited by the Convective Outer Core From Geodynamo Simulations

Long time geodetic observation records show that the orientation of the Earth's rotation axis with respect to the terrestrial reference frame, or polar motion, changes on a broad range of timescales. Apart from external torques from the luni-solar tides, these changes are excited by interactions among different components of the Earth system. The convective fluid outer core has long been conjectured a likely contributor to the observed polar motion on timescales upward of decades, such as the 30 year Markowitz wobble. We investigated the electromagnetic coupling scenario across the core-mantle boundary via numerical geodynamo simulation for different geodynamo parameters (Rayleigh numbers and magnetic Rossby numbers). Our simulated polar motion varies strongly with the dynamo parameters, while its excitation on decadal timescales appear to converge asymptotically within the adopted range of numerical Rossby numbers. Three strongest asymptotic modes emerge from numerical results, with periods around 30, 40, and 60 years for the prograde excitation and around 24, 30, and 60 years for the retrograde excitation. Their amplitudes are all larger than 5 times 10 (sup minus 8), or approximately 10 milliseconds of arc.The results suggest that the electromagnetic core-mantle coupling could explain a substantial portion, if not all, of the observed decadal polar motion. In particular, the predicted 60 year polar motion deserves special attention for future observations and studies.

Kuang, W.↗
DOE OSTI2023

Empirical probability and machine learning analysis of m , n = 2, 1 tearing mode onset parameter dependence in DIII-D H-mode scenarios

m, n = 2, 1 tearing mode onset empirical probability and machine learning analyses of a multiscenario DIII-D database of over 14 000 H-mode discharges show that the normalized plasma beta, the rotation profile, and the magnetic equilibrium shape have the strongest impact on the 2,1 tearing mode stability, in qualitative agreement with neoclassical tearing modes (m and n are the poloidal and toroidal mode numbers, respectively). In addition, 2,1 tearing modes are most likely to destabilize when n > 1 tearing modes are already present in the core plasma. The covariance matrix of tearing sensitive plasma parameters takes a nearly block-diagonal form, with the blocks incorporating thermodynamic, current and safety factor profile, separatrix shape, and plasma flow parameters, respectively. This suggests a number of paths to improved stability at fixed pressure and edge safety factor primarily by preserving a minimum of 1 kHz differential rotation, increasing the minimum safety factor above unity, using upper single null magnetic configuration, and reducing the core impurity radiation. In addition, lower triangularity, lower elongation, and lower pedestal pressure may also help to improve stability. Furthermore, the electron and ion temperature, collisionality, resistivity, internal inductance, and the parallel current gradient appear to only weakly correlate with the 2,1 tearing mode onsets in this database.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

Hyper-Velocity Nanoparticle Plasma Jet as Fast Probe for Runaway Electrons in Tokamak Disruptions

The large energy focalized deposition of the runaway electron (RE) beam on the first wall can potentially yield to destructive effects on the reactor vessel during the explosive instability of a major disruption in a large tokamak (e.g. RE beam estimation is multi-MA of ~10 MeV energy in ITER.) Impurity injection is seen as an effective way to suppress REs after thermal quench (TQ). Injected material in solid state is advantageous, but it must be in small size grain form, with large surface-to-mass ratio to facilitate its rapid ablation within plasma. However, the results using shattered pellet injection (SPI), a technique aiming to satisfy these condition, indicated that the relatively unexplored RE evolution phases and RE beam-plasma interaction are far from being properly diagnosed and fully understood. We proposed the idea to probe REs with a pulsed power hyper-velocity large-mass nanoparticle plasma jet (NPPJ). NPPJ provides a high specific surface area and swift injection to core, hence fast increase of three basic parameters: 1) the electron density ne (bound and free through ionization, if the cold post-TQ plasma has a still high enough T e ), 2) the effective charge (Z eff ) which rises both the dynamical friction force and plasma resistivity, and, finally, 3) the value of the (Dreicer and critical) threshold E-field above which electrons are accelerated and become REs. But the fast transient phenomena of RE ”seed” creation, RE ”avalanche” multiplication, and RE beam formation and interaction with the background plasma all take place dominantly in the core plasma, where the induction E-field has its maximum. Thus, the RE probe success requires a rapid (1 - 2 ms) injection of sufficient mass able to penetrate through the strong toroidal magnetic field (2 - 5 T) over a long distance (~1 - 2 m) with a large assimilation fraction in the core plasma. As a RE probe, NPPJ is a unique combination of fast response with trigger-to-delivery time of few milliseconds, large mass-velocity (>75 mg at several km/s) and deep injection into post-TQ central plasma. The Objectives of this Category #1 project (concept development) were as follows: 1: We investigated the essential basic physics aspects of creating a plasma with ~10 15 to 10 16 cm -3 boron nitride (BN) NP density suited for a pulsed power plasma gun acceleration to several km/s. We concluded that, for RE NPPJ probe, BN (diameter Ø10 to 100 nm NPs) are in all respects usable. 2: We advanced solutions to get BN NPPJ by adapting FAR-TECH’s technology for C 60 NPPJ. 3: We developed self-consistent models for RE current density j RE (R; t) evolution in the TQ aftermath, with fast and simultaneous increase of n e (R; t) and Z eff (R; t) > 1 upon the specific injection of C 60 (i.e. C ions) and BN NP (i.e. B and N ions), respectively. We showed that prompt post-TQ injection and high velocity are of essence in RE probe diagnostics and suppression. 4: We used the in-house HEM-2D code to simulate the C$_{60}^{q+}$ NPPJ transverse penetration through tokamak-level B-field (BT ~2 to 5 T) and distance (~1 to 2m), with fragmentation of C$_{60}^{q+}$ and developed the algorithm for BN Q+ NPPJ ablative sublimation of BN Q+ NP by the collisions with post-TQ plasma electrons. HEM-2D results indicated that fragmenting C$_{60}^{1+}$ NPPJ penetrates up to ~60 cm in 100 us when injecting at 1.6 ms after TQ and gradually released C 2 fragments and C ions.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2022

The effects of field history on magnetic skyrmion formation in [Pt/Co/Ir] 3 multilayers

Here, we report on the formation of Néel-type magnetic bubble skyrmions at room temperature in [Pt/Co/Ir] 3 multilayered thin films after an in-plane magnetic field treatment. Polar magneto-optical Kerr Effect (p-MOKE) microscopy images show that the dendritic magnetic configurations observed after AC demagnetization evolve into magnetic bubble skyrmions after the application and subsequent removal of an in-plane magnetic field. Micromagnetic simulations were used to systematically investigate the role of the in-plane magnetic field magnitude, misalignment of the sample, and the Dzyaloshinskii-Moriya interactions (DMI) in generating bubble skyrmions during the field treatment. The simulations show that in-plane fields slightly below the saturation field are the most effective at producing skyrmions, and, furthermore, a small field angle away from the sample plane not only leads to improved skyrmion formation but also provides a means to select the skyrmion polarity where the direction of the out-of-plane component of the field is opposite to the direction of the skyrmion cores. This field treatment scheme leads to a simple and reliable way to create magnetic bubble skyrmions in multilayered thin films with DMI.

36 MATERIALS SCIENCE↗
NASA NTRS2003

Experimental High Temperature Characterization of a Magnetic Bearing for Turbomachinery

Open loop, experimental force and power measurements of a radial, redundant-axis, magnetic bearing at temperatures to 1000 F (538 C) and rotor speeds to 15,000 RPM along with theoretical temperature and force models are presented in this paper. The experimentally measured force produced by a single C-core using 22A was 600 lb. (2.67 kN) at room temperature and 380 lb. (1.69 kN) at 1000 F (538 C). These values were compared with force predictions based on a 1D magnetic circuit analysis and a thermal analysis of gap growth as a function of temperature. Tests under rotating conditions showed that rotor speed has a negligible effect on the bearing s load capacity. One C-core required approximately 340 W of power to generate 190 lb. (8.45 kN) of magnetic force at 1000 F (538 C); however the magnetic air gap was much larger than at room temperature. The data presented is after the bearing had already operated six thermal cycles and eleven total (not consecutive) hours at 1000 F (538 C).

Montague, Gerald↗
DOE OSTI2018

Direct measurement of the transition from edge to core power coupling in a light-ion helicon source

Here, we present time-resolved measurements of an edge-to-core power transition in a light-ion (deuterium) helicon discharge in the form of infra-red camera imaging of a thin stainless steel target plate on the Proto-Material Exposure eXperiment device. The time-resolved images measure the two-dimensional distribution of power deposition in the helicon discharge. The discharge displays a mode transition characterized by a significant increase in the on-axis electron density and core power coupling, suppression of edge power coupling, and the formation of a fast-wave radial eigenmode. Although the self-consistent mechanism that drives this transition is not yet understood, the edge-to-core power transition displays characteristics that are consistent with the discharge entering a slow-wave anti-resonant regime. RF magnetic field measurements made across the plasma column, together with the power deposition results, provide direct evidence to support the suppression of the slow-wave in favor of core plasma production by the fast-wave in a light-ion helicon source.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

Characteristics of temperature rise in variable inductor employing magnetorheological fluid driven by a high-frequency pulsed voltage source

A variable inductor with magnetorheological (MR) fluid has been successfully applied to power electronics applications; however, its thermal characteristics have not been investigated. To evaluate the performance of the variable inductor with respect to temperature, we measured the characteristics of temperature rise and developed a numerical analysis technique. The characteristics of temperature rise were determined experimentally and verified numerically by adopting a multiphysics analysis technique. In order to accurately estimate the temperature distribution in a variable inductor with an MR fluid-gap, the thermal solver should import the heat source from the electromagnetic solver to solve the eddy current problem. To improve accuracy, the B–H curves of the MR fluid under operating temperature were obtained using the magnetic property measurement system. In addition, the Steinmetz equation was applied to evaluate the core loss in a ferrite core. The predicted temperature rise for a variable inductor showed good agreement with the experimental data and the developed numerical technique can be employed to design a variable inductor with a high-frequency pulsed voltage source.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗