Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “spin current”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Design and implementation of a J -coupled spectrometer for multidimensional structure and relaxation detection at low magnetic fields

In recent years, it has been realized that low and ultra-low field (mT-nT magnetic field range) nuclear magnetic resonance (NMR) spectroscopy can be used for molecular structural analysis. However, spectra are often hindered by lengthy acquisition times or require large sample volumes and high concentrations. Here, we report a low field (50 µT) instrument that employs a linear actuator to shuttle samples between a 1 T prepolarization field and a solenoid detector in a laboratory setting. The current experimental setup is benchmarked using water and 13 C-methanol with a single scan detection limit of 2x10 20 spins (3 μL, 55 M H 2 O) and detection of 2.9x10 19 (200 μL, 617 mM 13 C-methanol) spins with signal averaging. The system has a dynamic range of >3 orders of magnitude. Investigations of room-temperature relaxation dynamics of 13Cmethanol show that sample dilution can be used in lieu of sample heating to acquire spectra with linewidths comparable to high-temperature spectra. These results indicate that the T 1 and T 2 mechanisms are governed by both the proton exchange rate and the dissolved oxygen in the sample. Finally, a 2D correlation spectroscopy (COSY) experiment is reported, performed in the strong coupling regime that resolves the multiple resonances associated with the heteronuclear Jcoupling. The spectrum was collected using 10 times less sample and in less than half the time from previous reports in the strong coupling limit.

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

Developing a New Polyolefin Precursor for Low-Cost, High-Strength Carbon Fiber

Current high-strength carbon fibers (CFs) are mostly derived from PAN polymer precursor, which are very expensive with limited usage in the high-end products. On the other hand, it has also stimulated research interest to develop new low-cost precursors and manufacturing process. Despite numerous studies, researchers have yet to develop a new polymeric precursor that is less expensive, melt-spinnable, and offers a high C-yield. In this three-year R&D project, we proposed three consecutive research phases, including (i) the development of new polyolefin-based precursors that can be thermally transformed to C material in one heating step under inert atmosphere and achieved a C-yield >80%, which is more than 60% higher than that of current PAN precursor, (ii) With the suitable new polyolefin-based precursor, we can focus on CF manufacturing process, including fiber spinning, stabilization, and carbonization, to form high quality carbon fibers with the desirable polymorphous morphology, and (iii) the investigation of thermal conversion process under tension for converting polyolefin-based precursor fibers to high tensile strength carbon fibers with specific graphite crystallite size, orientation of basal line, order-disorder ratio, fiber diameter, and reduced structural defect (voids). composites.

08 HYDROGEN↗
NASA NTRS1975

Design of multi-mission chemical propulsion modules for planetary orbiters. Volume 1: Summary report

Results are presented of a conceptual design and feasibility study of chemical propulsion stages that can serve as modular propulsion units, with little or no modification, on a variety of planetary orbit missions, including orbiters of Mercury, Saturn, and Uranus. Planetary spacecraft of existing design or currently under development, viz., spacecraft of the Pioneer and Mariner families, are assumed as payload vehicles. Thus, operating requirements of spin-stabilized and 3-axis stabilized spacecraft have to be met by the respective propulsion module designs. As launch vehicle for these missions the Shuttle orbiter and interplanetary injection stage, or Tug, plus solid-propellant kick motor was assumed. Accommodation constraints and interfaces involving the payloads and the launch vehicle are considered in the propulsion module design. The applicability and performance advantages were evaluated of the space-storable high-energy bipropellants. The incentive for using this advanced propulsion technology on planetary missions is the much greater performance potential when orbit insertion velocities in excess of 4 km/sec are required, as in the Mercury orbiter. Design analyses and performance tradeoffs regarding earth-storable versus space-storable propulsion systems are included. Cost and development schedules of multi-mission versus custom-designed propulsion modules are examined.

Source record↗
NASA NTRS2002

Development of a Two-Wheel Contingency Mode for the MAP Spacecraft

In the event of a failure of one of MAP's three reaction wheel assemblies (RWAs), it is not possible to achieve three-axis, full-state attitude control using the remaining two wheels. Hence, two of the attitude control algorithms implemented on the MAP spacecraft will no longer be usable in their current forms: Inertial Mode, used for slewing to and holding inertial attitudes, and Observing Mode, which implements the nominal dual-spin science mode. This paper describes the effort to create a complete strategy for using software algorithms to cope with a RWA failure. The discussion of the design process will be divided into three main subtopics: performing orbit maneuvers to reach and maintain an orbit about the second Earth-Sun libration point in the event of a RWA failure, completing the mission using a momentum-bias two-wheel science mode, and developing a new thruster-based mode for adjusting the inertially fixed momentum bias. In this summary, the philosophies used in designing these changes is shown; the full paper will supplement these with algorithm descriptions and testing results.

Starin, Scott R.↗
NASA NTRS2007

Burst Oscillations: A New Spin on Neutron Stars

Observations with NASA's Rossi X-ray Timing Explorer (RXTE) have shown that the X-ray flux during thermonuclear X-ray bursts fr-om accreting neutron stars is often strongly pulsed at frequencies as high as 620 Hz. We now know that these oscillations are produced by spin modulation of the thermonuclear flux from the neutron star surface. In addition to revealing the spin frequency, they provide new ways to probe the properties and physics of accreting neutron stars. I will briefly review our current observational and theoretical understanding of these oscillations and discuss what they are telling us about neutron stars.

Strohmayer, Tod↗
NASA NTRS2009

Pair-Starved Pulsar Magnetospheres

We propose a simple analytic model for the innermost (within the light cylinder of canonical radius, approx. c/Omega) structure of open-magnetic-field lines of a rotating neutron star (NS) with relativistic outflow of charged particles (electrons/positrons) and arbitrary angle between the NS spin and magnetic axes. We present the self-consistent solution of Maxwell's equations for the magnetic field and electric current in the pair-starved regime where the density of electron-positron plasma generated above the pulsar polar cap is not sufficient to completely screen the accelerating electric field and thus establish thee E . B = 0 condition above the pair-formation front up to the very high altitudes within the light cylinder. The proposed mode1 may provide a theoretical framework for developing the refined model of the global pair-starved pulsar magnetosphere.

Muslimov, Alex G.↗
NASA NTRS2010

Burst Oscillations: Watching Neutron Stars Spin

It is now almost 15 years since the first detection of rotationally modulated emission from X-ray bursting neutron stars, "burst oscillations," This phenomenon enables us to see neutron stars spin, as the X-ray burst flux asymmetrically lights up the surface. It has enabled a new way to probe the neutron star spin frequency distribution, as well as to elucidate the multidimensional nature of nuclear burning on neutron stars. I will review our current observational understanding of the phenomenon, with an eye toward highlighting some of the interesting remaining puzzles, of which there is no shortage.

Strohmayer, Tod↗
NASA NTRS2013

MRAM Technology Status

Magnetoresistive Random Access Memory (MRAM) is much different from conventional types of memory like SRAM, DRAM, and Flash, where electric charge is used to store information. Instead of exploiting the charge of an electron, MRAM uses its spin to store data. This new type of electronics is known as "spintronics." The primary focus of this report is the current generation of MRAM technology, and its reliability, vendors, and space-readiness.

Heidecker, Jason↗
NASA NTRS2013

MRAM Technology Status

Magnetoresistive Random Access Memory (MRAM) is much different from conventional types of memory like SRAM, DRAM, and Flash, where electric charge is used to store information. Instead of exploiting the charge of an electron, MRAM uses its spin to store data. This new type of electronics is known as “spintronics.” The primary focus of this report is the current generation of MRAM technology, and its reliability, vendors, and space-readiness.

Heidecker, Jason↗
DOE OSTI2020

Canted antiferromagnetic order in the monoaxial chiral magnets V 1/3 TaS 2 and V 1/3 NbS 2

The Dzyaloshinskii-Moriya (DM) interaction is present in the transition metal dichalcogenides (TMDC) magnets of form M 1 / 3 T S 2 ( M = 3 d transition metal, T ϵ { Nb , Ta } ), given that the intercalants M form 3 × 3 superlattices within the structure of the parent materials T S 2 and break the centrosymmetry. Competition between DM and ferromagnetic exchange interactions has been shown to stabilize a topological defect known as a chiral soliton in select intercalated TMDCs, initiating interest both in terms of fundamental physics and the potential for technological applications. In the current article we report on our study of the materials V 1 / 3 TaS 2 and V 1 / 3 NbS 2 , using a combination of x-ray powder diffraction, magnetization, and single crystal neutron diffraction. Historically identified as ferromagnets, our diffraction results instead reveal that vanadium spins in these compounds are arranged into an A-type antiferromagnetic configuration at low temperatures. Refined moments are 1.37(6) and 1.50(9) μ B for V 1 / 3 TaS 2 and V 1 / 3 NbS 2 , respectively. Transition temperatures T c = 32 K for V 1 / 3 TaS 2 and 50 K for V 1 / 3 NbS 2 are obtained from the magnetization and neutron diffraction results. We attribute the small net magnetization observed in the low-temperature phases to a subtle ( ~ 2 ° ) canting of XY spins in the out-of-plane direction. These new results are indicative of dominant antiferromagnetic exchange interactions between the vanadium moments in adjacent a b planes, likely eliminating the possibility of identifying stable chiral solitons in the current materials.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Control of magnon–photon coupling by spin torque

We demonstrate the influence of damping and field-like torques in the magnon–photon coupling process by classically integrating the generalized Landau–Lifshitz–Gilbert equation with RLC equation in which a phase correlation between dynamic magnetization and microwave current through combined Ampère and Faraday effects are considered. We show that the gap between two hybridized modes can be controlled in samples with damping parameter in the order of 10 –3 by changing the direction of the dc current density J if a certain threshold is reached. Furthermore, our results suggest that an experimental realization of the proposed magnon–photon coupling control mechanism is feasible in yttrium iron garnet/Pt hybrid structures.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Spinning metasurface stack for spectro-polarimetric thermal imaging

Spectro-polarimetric imaging in the long-wave infrared (LWIR) region plays a crucial role in applications from night vision and machine perception to trace gas sensing and thermography. However, the current generation of spectro-polarimetric LWIR imagers suffers from limitations in size, spectral resolution, and field of view (FOV). While meta-optics-based strategies for spectro-polarimetric imaging have been explored in the visible spectrum, their potential for thermal imaging remains largely unexplored. In this work, we introduce an approach for spectro-polarimetric decomposition by combining large-area stacked meta-optical devices with advanced computational imaging algorithms. The co-design of a stack of spinning dispersive metasurfaces along with compressive sensing and dictionary learning algorithms allows simultaneous spectral and polarimetric resolution without the need for bulky filter wheels or interferometers. Our spinning-metasurface-based spectro-polarimetric stack is compact (<10×10×10cm) and robust, and it offers a wide field of view (20.5°). We show that the spectral resolving power of our system substantially enhances performance in machine learning tasks such as material classification, a challenge for conventional panchromatic thermal cameras. Our approach represents a significant advance in the field of thermal imaging for a wide range of applications including heat-assisted detection and ranging (HADAR).

Optics↗
NASA NTRS2017

Data Collection and Analysis Software Development for Rotor Dynamics Testing in Spin Laboratory

Gas turbine engine components undergo high rotational loading another complex environmental conditions. Such operating environment leads these components to experience damages and cracks that can cause catastrophic failure during flights. There are traditional crack detections and health monitoring methodologies currently being used which rely on periodic routine maintenances, nondestructive inspections that often times involve engine and components dis-assemblies. These methods do not also offer adequate information about the faults, especially, if these faults at subsurface or not clearly evident. At NASA Glenn research center, the rotor dynamics laboratory is presently involved in developing newer techniques that are highly dependent on sensor technology to enable health monitoring and prediction of damage and cracks in rotor disks. These approaches are noninvasive and relatively economical. Spin tests are performed using a subscale test article mimicking turbine rotor disk undergoing rotational load. Non-contact instruments such as capacitive and microwave sensors are used to measure the blade tip gap displacement and blade vibrations characteristics in an attempt develop a physics based model to assess/predict the faults in the rotor disk. Data collection is a major component in this experimental-analytical procedure and as a result, an upgrade to an older version of the data acquisition software which is based on LabVIEW program has been implemented to support efficiently running tests and analyze the results. Outcomes obtained from the tests data and related experimental and analytical rotor dynamics modeling including key features of the updated software are presented and discussed.

Rotor Dynamics↗
NASA NTRS2016

Simulation of an Electromechanical Spin Motor System of a Control Moment Gyroscope

A two-phase brushless DC motor (BDCM) with pulse-width modulated (PWM) voltage drive is simulated to control the flywheel speed of a control moment gyroscope (CMG). An overview of a double-gimballed control moment gyroscope (DGCMG) assembly is presented along with the CMG torque effects on the spacecraft. The operating principles of a two-phase brushless DC motor are presented and the system's electro-mechanical equations of motion are developed for the root-mean-square (RMS) currents and wheel speed. It is shown that the system is an extremely "stiff" set of first-order equations for which an implicit Euler integrator is required for a stable solution. An adaptive proportional voltage controller is presented which adjusts the PWM voltages depending on several control modes for speed, current, and torque. The simulation results illustrate the interaction between the electrical system and the load dynamics and how these influence the overall performance of the system. As will be shown, the CMG spin motor model can directly provide electrical power use and thermal power output to spacecraft subsystems for effective (average) calculations of CMG power consumption.

Inampudi, Ravi↗
NASA NTRS2010

Simulated Service and Stress Corrosion Cracking Testing for Friction Stir Welded Spun Formed Domes

Simulated service testing (SST) development was required to help qualify a new 2195 aluminum lithium (Al-Li) alloy spin forming dome fabrication process for the National Aeronautics and Space Administration (NASA) Exploration Development Technology Program. The application for the technology is to produce high strength low weight tank components for NASA s next generation launch vehicles. Since plate material is not currently manufactured large enough to fabricate these domes, two plates are joined by means of friction stir welding. The plates are then pre-contour machined to near final thicknesses allowing for a thicker weld land and anticipating the level of stretch induced by the spin forming process. The welded plates are then placed in a spin forming tool and hot stretched using a trace method producing incremental contours. Finally the dome receives a room temperature contour stretch to final dimensions, heat treatment, quenching, and artificial aging to emulate a T-8 condition of temper. Stress corrosion cracking (SCC) tests were also performed by alternate immersion in a sodium chloride (NaCl) solution using the typical double beam assembly and with 4-point loaded specimens and use of bent-beam stress-corrosion test specimens under alternate immersion conditions. In addition, experiments were conducted to determine the threshold stress intensity factor for SCC (K(sub ISCC)) which to our knowledge has not been determined previously for Al-Li 2195 alloy. The successful simulated service and stress corrosion testing helped to provide confidence to continue to Ares 1 scale dome fabrication

Stewart, Thomas J.↗
DOE OSTI2023

Active Thermochemical Tables: Enthalpies of Formation of Bromo- and Iodo-Methanes, Ethenes and Ethynes

Here, the thermochemistry of halocarbon species containing iodine and bromine is examined through an extensive interplay between new Feller–Peterson–Dixon (FPD) style composite methods and a detailed analysis of all available experimental and theoretical determinations using the thermochemical network that underlies the Active Thermochemical Tables (ATcT). From the computational viewpoint, a slower convergence of the components of composite thermochemistry methods is observed relative to species that solely contain first row elements, leading to a higher computational expense for achieving comparable levels of accuracy. Potential systematic sources of computational uncertainty are investigated, and, not surprisingly, spin-orbit coupling is found to be a critical component, particularly for iodine containing molecular species. The ATcT analysis of available experimental and theoretical determinations indicates that prior theoretical determinations have significantly larger uncertainties than originally reported, particularly in cases where molecular spin-orbit effects were ignored. Accurate and reliable heats of formation are reported for 38 halogen containing systems, based on combining the current computations with previous experimental and theoretical work via the ATcT approach.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Atomic Resolution Cryogenic 4D-STEM Imaging via Robust Distortion Correction

Cryogenic four-dimensional scanning transmission electron microscopy (4D-STEM) imaging is a useful technique for studying quantum materials and their interfaces by simultaneously probing charge, lattice, spin, and chemistry on the atomic scale with the sample held at temperatures ranging from room to cryogenic. However, its applications are currently limited by the instabilities of cryo-stages and electronics. To overcome this challenge, we develop an algorithm to effectively correct the complex distortions present in atomic resolution cryogenic 4D-STEM data sets. This method uses nonrigid registration to identify localized distortions in a 4D-STEM and relate them to an undistorted experimental STEM image, followed by a series of affine transformations for distortion corrections. This method allows a minimum loss of information in both reciprocal and real spaces, enabling the reconstruction of sample information from 4D-STEM data sets. This method is computationally cheap, fast, and applicable for on-the-fly data analysis in future in situ cryogenic 4D-STEM experiments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Electronic and Spintronic Open-Shell Macromolecules, Quo Vadis ?

Open-shell macromolecules (i.e., polymers containing radical sites either along their backbones or at the pendant sites of repeat units) have attracted significant attention owing to their intriguing chemical and physical (e.g., redox, optoelectronic, and magnetic) properties, and they have been proposed and/or implemented in a wide range of potential applications (e.g., energy storage devices, electronic systems, and spintronic modules). These successes span multiple disciplines that range from advanced macromolecular chemistry through nanoscale structural characterization and on to next-generation solid-state physics and the associated devices. In turn, this has allowed different scientific communities to expand the palette of radical-containing polymers relatively quickly. However, critical gaps remain on many fronts, especially regarding the elucidation of key structure–property–function relationships that govern the underlying electrochemical, optoelectronic, and spin phenomena in these materials systems. Here, we highlight vital developments in the history of open-shell macromolecules to explain the current state of the art in the field. Moreover, we provide a critical review of the successes and bring forward open opportunities that, if solved, could propel this class of materials in a meaningful manner. Finally, we provide an outlook to address where it seems most likely that open-shell macromolecules will go in the coming years. Furthermore, our considered view is that the future of radical-containing polymers is extremely bright and the addition of talented researchers with diverse skills to the field will allow these materials and their end-use devices to have a positive impact on the global science and technology enterprise in a relatively rapid manner.

36 MATERIALS SCIENCE↗