Index to NASA Tech Briefs, 1975

This index contains abstracts and four indexes--subject, personal author, originating Center, and Tech Brief number--for 1975 Tech Briefs

Penning traps as a versatile tool for precise experiments in fundamental physics

This review article describes the trapping of charged particles. The main principles of electromagnetic confinement of various species from elementary particles to heavy atoms are briefly described. The preparation and manipulation with trapped single particles, as well as methods of frequency measurements, providing unprecedented precision, are discussed. Unique applications of Penning traps in fundamental physics are presented. Ultra-precise trap-measurements of masses and magnetic moments of elementary particles (electrons, positrons, protons and antiprotons) confirm CPT-conservation, and allow accurate determination of the fine-structure constant alpha and other fundamental constants. This together with the information on the unitarity of the quark-mixing matrix, derived from the trap-measurements of atomic masses, serves for assessment of the Standard Model of the physics world. Direct mass measurements of nuclides targeted to some advanced problems of astrophysics and nuclear physics are also presented

Thermal modeling of industrial-scale vanadium redox flow batteries in high-current operations

A cell-resolved model that simulates the dynamic thermal behavior of a Vanadium Redox Flow Battery during charge and discharge is presented. It takes into account, at a cell level, the reversible entropic heat of the electrochemical reactions, irreversible heat due to overpotentials, self-discharge reactions due to ion crossover, and shunt current losses. The model accounts for the heat transfer between cells and toward the environment, the pump hydraulic losses and the heat transfer of piping and tanks. It provides the electrolyte temperature in each cell, at the stack inlet and outlet, along the piping and in the tanks. Validation has been carried out against the charge/discharge measurements from a 9kW/27kWh VRFB test facility. The model has been applied to study a VRFB with the same stack but a much larger capacity, operating at \uf0b1400 A for 8 h, in order to identify critical thermal conditions which may occur in next-generation industrial VRFB stacks capable to operating at high current density. The most critical condition has been found at the end a long discharge, when temperatures above 50\ub0C appeared, possibly resulting in \u3016VO\u3017_2^+ precipitation and battery faults. These results call for heat exchangers tailored to assist high-power VRFB systems

The radiation environment near the lunar surface: CRaTER observations and Geant4 simulations

[1] At the start of the Lunar Reconnaissance Orbiter mission in 2009, its Cosmic Ray Telescope for the Effects of Radiation instrument measured the radiation environment near the Moon during the recent deep solar minimum, when galactic cosmic rays (GCRs) were at the highest level observed during the space age. We present observations that show the combined effects of GCR primaries, secondary particles (“albedo”) created by the interaction of GCRs with the lunar surface, and the interactions of these particles in the shielding material overlying the silicon solid-state detectors of the Cosmic Ray Telescope for the Effects of Radiation. We use Geant4 to model the energy and angular distribution of the albedo particles, and to model the response of the sensor to the various particle species reaching the 50 kilometer altitude of the Lunar Reconnaissance Orbiter. Using simulations to gain insight into the observations, we are able to present preliminary energy-deposit spectra for evaluation of the radiation environment\u27s effects on other sensitive materials, whether biological or electronic, that would be exposed to a similar near-lunar environment

Radiation effects on two‐dimensional materials

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135401/1/pssa201600395_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135401/2/pssa201600395.pd

The Plasma and Suprathermal Ion Composition (PLASTIC) investigation on the STEREO observatories

The Plasma and Suprathermal Ion Composition (PLASTIC) investigation provides the in situ solar wind and low energy heliospheric ion measurements for the NASA Solar Terrestrial Relations Observatory Mission, which consists of two spacecraft (STEREO-A, STEREO-B). PLASTIC-A and PLASTIC-B are identical. Each PLASTIC is a time-of-flight/energy mass spectrometer designed to determine the elemental composition, ionic charge states, and bulk flow parameters of major solar wind ions in the mass range from hydrogen to iron. PLASTIC has nearly complete angular coverage in the ecliptic plane and an energy range from ∼0.3 to 80 keV/e, from which the distribution functions of suprathermal ions, including those ions created in pick-up and local shock acceleration processes, are also provided

Fluid modeling and simulation of the electron population in Hall Effect Thrusters with complex magnetic topologies

Mención Internacional en el título de doctorLa propulsión eléctrica es una tecnología consolidada, utilizada por vehículos espaciales para llevar a cabo maniobras no atmosféricas. Este tipo de motores cohete ha estado presente en numerosas aplicaciones en las últimas décadas y sus usos van desde el mantenimiento de la posición orbital de satélites comerciales a transferencias interplanetarias en misiones de exploración. La mayor ventaja de los numerosos tipos de propulsores eléctricos es su capacidad de proporcionar un determinado impulso a un coste de propelente reducido, en comparación con otros tipos de propulsión. El desarrollo de los motores de plasma, la clase más común de propulsor eléctrico, se ha visto impedido en mayor medida que los cohetes químicos, por ejemplo, debido a la complejidad de la interacción de los fenómenos físicos y a dificultades asociadas con las campañas experimentales. En las últimas dos décadas se ha introducido el uso de simulaciones numéricas para ayudar a la caracterización de estos aparatos. A pesar de que el diseño asistido por ordenador juega aún un papel muy reducido, el incremento de recursos computacionales y la creciente exactitud de los modelos físicos han permitido a estas simulaciones describir numerosos mecanismos físicos, explorar el espacio de diseño de estos aparatos y complementar los ensayos experimentales. Esta tesis está centrada en el estudio numérico de la población de electrones en descargas de plasma poco colisionales, bajo la influencia de campos eléctricos y magnéticos. El trabajo realizado ha contribuido al desarrollo de una nueva herramienta de simulación híbrida, cuasi-neutra, bidimensional y axisimétrica, denominada HYPHEN; su naturaleza híbrida se debe al tratamiento por separado de las especies pesadas, descritas a través de un conocido método de partículas, y de la población de electrones, descrita como un fluido. Una de nuestras mayores contribuciones es la introducciÃsn de un modelo anisotrÃspico de dos temperaturas, que permite capturar los efectos de la falta de uniformidad del campo magnético sobre el transporte de electornes. Esta función abre el camino para la caracterización de nuevos propulsores electromagnéticos. Actualemente, el código está orientado hacia la simulación de las regiones del canal y de la pluma cercana en motores de efecto Hall, en los que se enfoca esta tesis. Parte del trabajo se ha dedicado a dotar al código de las capacidades necesarias para la simulación de topologías magnéticas complejas. El presente documento detalla la motivación detrás de HYPHEN, su metodología de diseño y la influencia de trabajos previos. Se ha prestado una especial atención al modelo fluido propuesto, detallando el uso de una malla alineada con el campo magnético para el tratamiento numérico de la población confinada de electrones, para la cual se han utilizado diversos métodos ad-hoc de discretización temporal y espacial. Varios modelos auxiliares también se han descrito, con el objetivo de caracterizar la respuesta de la capa límite del plasma y de los distintos procesos colisionales en el seno del mismo. Se presenta también el estudio de los aspectos numéricos del modelo fluido, incluyendo la sensibilidad a condiciones iniciales, a los valores del paso temporal, el refinamiento de la malla, etc. Finalmente, HYPHEN se ha testeado para la configuración de un conocido motor Hall. Los resultados demuestran que las propiedades físicas y las actuaciones obtenidas son comparables con resultados provenientes de estudios experimentales. Bajo este contexto, se ha llevado a cabo un estudio paramétrico para determinar la dependencia de la respuesta del motor con algunos de los parámetros más relevantes del modelo, tales como el transporte anómalo de electrones o la fracción de termalización de la capa límite, y con los diferentes modelos colisionales.Electric propulsion is an established technology used for non-atmospheric spacecraft maneuvering. This type of rockets have been present in numerous applications in the last decades, and their uses range from station keeping of commercial satellites to interplanetary transfers in deep space exploration missions. While electric propulsion thrusters are multi-faceted, presenting numerous and distinct types, their best selling point is the capability to deliver a given impulse at much lower propellant cost, in comparison to other types of propulsion. The maturation of plasma thrusters, the most common type of electric propulsion devices, has faced more limitations than chemical rockets, for example, due to the complexity of the physical interactions at play, and the difficulties associated with experimental campaigns. Over the past two decades, numerical simulations were introduced as a novel tool in the characterization of these devices. While true computer-aided-design is not yet a reality, the increment of computational resources and the heightened fidelity of the physical models have allowed to describe numerous physical mechanisms, explore the design space of these devices and complement experimental testing. This thesis focuses on the numerical study of the electron population in weakly collisional plasma discharges, under the influence of applied magnetic and electric fields. The work has been a primary contribution in the development of a new, quasi-neutral, two-dimensional, axisymmetric, hybrid simulation tool, called HYPHEN. Its hybrid nature responds to the different treatment of the heavy species populations, described through a well known discrete-particle approach, and the electron population, described as a fluid. One of our main contributions has been the introduction of a two-temperature anisotropic approach, which allows capturing of the magnetic non-uniformity effects over electron transport; this feature paves the way for the characterization of some novel electromagnetic propulsion technologies. Presently, the code is oriented to the simulation of the channel and near-plume regions in Hall effect thrusters, which have been the main focal point of the thesis. Dedicated efforts have been directed to providing the capabilities for the simulation of the plasma under complex magnetic field topologies. The manuscript details the motivation and design methodology behind HYPHEN, as well as the influence of previous work. Special attention has been given to the particularities of the proposed fluid model; this includes the use of a magnetic field aligned mesh for the numerical treatment of the electron population under magnetic confinement, for which ad-hoc spatial and temporal discretization methods have been proposed. Additional ancillary physical models have also been developed, characterizing the response of plasma boundary layers and the various collisional processes in the plasma. The numerical aspects of the model have been investigated, including the sensitivity to initial conditions, time-step values, mesh refinement, etc. Finally, HYPHEN has been tested in the context of a representative Hall-thruster configuration. The results were found to be in line with experimentally reported thruster performances and plasma discharge quantities. Additionally, a parametric investigation has been carried out in order to investigate the dependency of the thruster response with the most relevant model parameters, such as the anomalous electron transport or the boundary layer thermalization fraction, and the different collisional models.This work has been partially supported by the CHEOPS project, that received funding from the European Union’s Horizon 2020 research and innovation program, under grant agreement No. 730135. Additional support came from Project ESP2016-75887, funded by the National research and development program of Spain.Programa Oficial de Doctorado en Plasmas y Fusión NuclearPresidente: José Javier Honrubia Checa.- Secretario: Mario Merino Martínez.- Vocal: Paul-Quentin Elia

Long Duration Exposure Facility (LDEF). Mission 1 Experiments

Spaceborne experiments using the space shuttle payload known as the Long Duration Exposure Facility are described. Experiments in the fields of materials, coatings, thermal systems, power and propulsion, electronic, and optics are discussed