Results for “current generation” — Page 36

NASA NTRS2012

Simple Cell Balance Circuit

A method has been developed for continuous cell voltage balancing for rechargeable batteries (e.g. lithium ion batteries). A resistor divider chain is provided that generates a set of voltages representing the ideal cell voltage (the voltage of each cell should be as if the cells were perfectly balanced). An operational amplifier circuit with an added current buffer stage generates the ideal voltage with a very high degree of accuracy, using the concept of negative feedback. The ideal voltages are each connected to the corresponding cell through a current- limiting resistance. Over time, having the cell connected to the ideal voltage provides a balancing current that moves the cell voltage very close to that ideal level. In effect, it adjusts the current of each cell during charging, discharging, and standby periods to force the cell voltages to be equal to the ideal voltages generated by the resistor divider. The device also includes solid-state switches that disconnect the circuit from the battery so that it will not discharge the battery during storage. This solution requires relatively few parts and is, therefore, of lower cost and of increased reliability due to the fewer failure modes. Additionally, this design uses very little power. A preliminary model predicts a power usage of 0.18 W for an 8-cell battery. This approach is applicable to a wide range of battery capacities and voltages.

Johnson, Steven D.↗

NASA NTRS2022

Strong Reconnection Electric Fields in Shock-Driven Turbulence

Turbulent magnetic reconnection in a quasi-parallel shock under parameters relevant to the Earth's bow shock is investigated by means of a two-dimensional particle-in-cell simulation. The addressed aspects include the reconnection electric field, the reconnection rate, and the electron and the ion outflow speeds. In the shock transition region, many current sheets are generated in shock-driven turbulence, and electron-only reconnection and reconnection where both ions and electrons are involved can occur in those current sheets. The electron outflow speed in electron-only reconnection shows a positive correlation with the theoretical speed, which is close to the local electron Alfvén speed, and a strong convection electric field is generated by the large electron outflow. As a result, the reconnection electric field becomes much larger than those in the standard magnetopause or magnetotail reconnection. In shock-driven reconnection that involves ion dynamics, both electron outflows and ion outflows can reach of the order of 10 times the Alfvén speed in the X-line rest frame, leading to a reconnection electric field the same order as that in electron-only reconnection. An electron-only reconnection event observed by the magnetospheric multiscale mission downstream of a quasi-parallel shock is qualitatively similar to those in the simulation and shows that the outflow speed reaches approximately half the local electron Alfvén speed, supporting the simulation prediction.

magnetic reconnection↗

NASA NTRSDate not supplied

Multi-Functional Flash Lidar for Precision Safe Landing in Challenging Terrains

A Flash Lidar utilizing a novel Super-Resolution (SR) technique has been developed for providing Terrain Relative Navigation and Hazard Avoidance capabilities onboard landing vehicles. Processing algorithms for precision navigation and safe landing location identification take advantage of the uniform fixed pixels property of generated high resolution Digital Elevation Maps (DEMs) to achieve high reliability operation in near real-time. This paper describes the current and next generation breadboard units, report the results of recent dynamic tests, and explain the operational concept as envisioned for future landing missions.

3-D Imaging↗

NASA NTRSDate not supplied

Multi-Functional Flash Lidar for Precision Safe Landing in Challenging Terrains

A Flash Lidar utilizing a novel Super-Resolution (SR) technique has been developed for providing Terrain Relative Navigation and Hazard Avoidance capabilities onboard landing vehicles. Processing algorithms for precision navigation and safe landing location identification take advantage of the uniform fixed pixels property of generated high resolution Digital Elevation Maps (DEMs) to achieve high reliability operation in near real-time. This paper describes the current and next generation breadboard units, report the results of recent dynamic tests, and explain the operational concept as envisioned for future landing missions.

3-D Imaging↗

NASA NTRSDate not supplied

Development of Flash Lidar Sensor for Precision Safe Landing

A Flash Lidar utilizing a novel Super-Resolution (SR) technique has been developed for providing Terrain Relative Navigation and Hazard Avoidance capabilities onboard landing vehicles. Processing algorithms for precision navigation and safe landing location identification take advantage of the uniform fixed pixels property of generated high resolution Digital Elevation Maps (DEMs) to achieve high reliability operation in near real-time. This paper describes the current and next generation breadboard units, report the results of recent dynamic tests, and explain the operational concept as envisioned for future landing missions.

3-D Imaging↗

NASA NTRSDate not supplied

Development of a Compact Lidar Sensor for Terrain Relative Navigation and Terrain Hazard Avoidance

A Flash Lidar utilizing a novel Super-Resolution (SR) technique has been developed for providing Terrain Relative Navigation and Hazard Avoidance capabilities onboard landing vehicles. Processing algorithms for precision navigation and safe landing location identification take advantage of the uniform fixed pixels property of generated high resolution Digital Elevation Maps (DEMs) to achieve high reliability operation in near real-time. This paper describes the current and next generation breadboard units, report the results of recent dynamic tests, and explain the operational concept as envisioned for future landing missions.

3-D Imaging↗

NASA NTRSDate not supplied

High Resolution Terrain Sensing Lidar for Precision Navigation and Safe Landing of Space and Aerial Vehicles

A Flash Lidar utilizing a novel Super-Resolution (SR) technique has been developed for providing Terrain Relative Navigation and Hazard Avoidance capabilities onboard landing vehicles. Processing algorithms for precision navigation and safe landing location identification take advantage of the uniform fixed pixels property of generated high resolution Digital Elevation Maps (DEMs) to achieve high reliability operation in near real-time. This paper describes the current and next generation breadboard units, report the results of recent dynamic tests, and explain the operational concept as envisioned for future landing missions.

Precision Landing↗

NASA NTRS1981

A simple mechanism for blocking

Numerical experiments show that blocking in a barotropic atmosphere can occur as a resonant enhancement of Rossby lee waves forced by two stationary sources of potential vorticity. In particular, if an upstream source of stationary forcing enhances the northerly flow over orography, then blocking occurs downstream of the mountain. In an analytical study, we show that, in the presence of friction, Rossby lee waves generate a rectified current downstream of the mountain, which does not vanish in the limit of zero friction. The relevance of this study to observed generation of blocking in the Atlantic Ocean and immediately upstream of the Rockies is discussed.

Kalnay-Rivas, E.↗

NASA NTRS1994

Power-Conserving Stepping-Motor Drive Circuits

Two improved drive circuits for sinusoidally commutated stepping motor include feedback loops reducing unnecessary consumption of power by reducing drive-current amplitude, I, when motor operates under light load. Basic design strategy attempts to supply only little more current than minimum needed to overcome friction in lightly loaded condition. In this sinusoidally commutated two-phase stepping motor, magnetic field generated by drive currents in phase-A and phase-B stator windings urges rotor toward commanded angle x.

Nola, Frank J.↗

NASA NTRS2017

High Current Lanthanum Hexaboride Hollow Cathode for 20-200 kW Hall Thrusters

The demand for higher power Hall and ion thrusters continues for providing high thrust and long life for deep space mission. The X3 nested Hall thruster is capable of power levels in the 20 to 200-kW range, and is being developed by the University of Michigan and Aerojet for future cargo and manned-missions. The cathode for this thruster is required to produce discharge currents of 50 to 350 A with lifetimes in excess of 10 khrs. A high-current lanthanum hexaboride (LaB6) hollow cathode was previously developed at JPL for these applications, and was successfully operated at over 250 A of discharge current. An updated version of this cathode has been designed, built and tested at JPL, and then used to run the X3 nested Hall thruster at currents of up to 250 A. The new version is designed to reduced orifice plate overheating at high currents, and is capable of injecting auxiliary gas directly into the near-cathode plume from two locations to minimize energetic ion generation at high current. The cathode is predicted to be capable of producing over 350 A of discharge current, and has been tested to date at JPL at steady-state discharge currents from 25 A to 300 A.

Goebel, Dan M.↗

NASA NTRS2008

Medical Grade Water Generation for Intravenous Fluid Production on Exploration Missions

This document describes the intravenous (IV) fluids requirements for medical care during NASA s future Exploration class missions. It further discusses potential methods for generating such fluids and the challenges associated with different fluid generation technologies. The current Exploration baseline mission profiles are introduced, potential medical conditions described and evaluated for fluidic needs, and operational issues assessed. Conclusions on the fluid volume requirements are presented, and the feasibility of various fluid generation options are discussed. A separate report will document a more complete trade study on the options to provide the required fluids.At the time this document was developed, NASA had not yet determined requirements for medical care during Exploration missions. As a result, this study was based on the current requirements for care onboard the International Space Station (ISS). While we expect that medical requirements will be different for Exploration missions, this document will provide a useful baseline for not only developing hardware to generate medical water for injection (WFI), but as a foundation for meeting future requirements. As a final note, we expect WFI requirements for Exploration will be higher than for ISS care, and system capacity may well need to be higher than currently specified.

Niederhaus, Charles E.↗

NASA NTRS1994

The effect of parallel currents on auroral micropulsations

Field aligned currents play an important role in the global coupling between the magnetosphere and the ionosphere and in their relationship to the auroral phenomena. Moreover, there exists evidence that resonant oscillations are related to large-scale Birkeland currents. The spatial confinement of the field-aligned currents forms an inhomogeneous system susceptible to low-frequency oscillations, which can be excited due to periodic variations in the solar wind pressure or to the Kelvin-Helmholtz (KH) instability. In this paper we present a study of ultralow-frequency (ULF) oscillations in an inhomogeneous magnetic field formed by a large-scale current. We investigate the effects of the field-aligned currents on the generation of localized Alfven waves. The field oscillations are described by an eigenvalue wave equation which includes the effects of the field aligned currents and which produces a discrete spectrum of Alfven waves. These waves are observed mainly in three regions of the magnetosphere: in the magnetosheath, in the polar cusp, and in the plasmasphere. In the present study we limit our investigation to the auroral region.

Tavares, M.↗

NASA NTRS1978

Optimal guidance and control for investigating aircraft noise-impact reduction

A methodology for investigating the reduction of community noise impact is reported. This report is concerned with the development of two models to provide data: a guidance generator and an aircraft control generator suitable for various current and advanced types of aircraft. The guidance generator produces the commanded path information from inputs chosen by an operator from a graphic scope display of a land-use map of the terminal area. The guidance generator also produces smoothing at the junctions of straight-line paths.The aircraft control generator determines the optimal set of the available controls such that the aircraft will follow the commanded path. The solutions for the control functions are given and shown to be dependent on the class of aircraft to be considered, that is, whether the thrust vector is rotatable and whether the thrust vector affects the aerodynamic forces. For the class of aircraft possessing a rotatable thrust vector, the solution is redundant; this redundancy is removed by the additional condition that the noise inpact be minimized. Information from both the guidance generator and the aircraft control generator is used by the footprint program to construct the noise footprint.

Stewart, E. C.↗

NASA NTRS2000

Parametric Study of Radiator Concepts for a Stirling Radioisotope Power System Applicable to Deep Space Mission

The Department of Energy (DOE) and the NASA Glenn Research Center are developing a Stirling converter for an advanced radioisotope power system to provide spacecraft onboard electric power for NASA deep space missions. This high-efficiency converter is being evaluated as an alternative to replace the much lower efficiency radioisotope thermoelectric generator (RTG). The current power requirement (six years after beginning of mission (BOM) for a mission to Jupiter) is 210 W(sub e) (watts electric) to be generated by two separate power systems, one on each side of the spacecraft. Both two-converter and four-converter system designs are being considered, depending on the amount of required redundancy.

Juhasz, Albert J.↗

NASA NTRS2016

Electron Scale Structures and Magnetic Reconnection Signatures in the Turbulent Magnetosheath

Collisionless space plasma turbulence can generate reconnecting thin current sheets as suggested by recent results of numerical magnetohydrodynamic simulations. The Magnetospheric Multiscale (MMS) mission provides the first serious opportunity to verify whether small ion-electron-scale reconnection, generated by turbulence, resembles the reconnection events frequently observed in the magnetotail or at the magnetopause. Here we investigate field and particle observations obtained by the MMS fleet in the turbulent terrestrial magnetosheath behind quasi-parallel bow shock geometry. We observe multiple small-scale current sheets during the event and present a detailed look of one of the detected structures. The emergence of thin current sheets can lead to electron scale structures. Within these structures, we see signatures of ion demagnetization, electron jets, electron heating, and agyrotropy suggesting that MMS spacecraft observe reconnection at these scales.

Yordanova, E.↗

NASA NTRS1995

A quality monitor and monitoring technique employing optically stimulated electron emission

A light source directs ultraviolet light onto a test surface and a detector detects a current of photoelectrons generated by the light. The detector includes a collector which is positively biased with respect to the test surface. Quality is indicated based on the photoelectron current. The collector is then negatively biased to replace charges removed by the measurement of a nonconducting substrate to permit subsequent measurements. Also, the intensity of the ultraviolet light at a particular wavelength is monitored and the voltage of the light source varied to maintain the light a constant desired intensity. The light source is also cooled via a gas circulation system. If the test surface is an insulator, the surface is bombarded with ultraviolet light in the presence of an electron field to remove the majority of negative charges from the surface. The test surface is then exposed to an ion field until it possesses no net charge. The technique described above is then performed to assess quality.

Yost, William T.↗

NASA NTRS2001

Electron Dynamics in the Magnetotail

The goal of this research has been to study the effects of electrons on magnetotail dynamics and current sheet structure. The approach is to follow ion trajectories in a global model of the magnetotail, use a Boltzmann approximation to include electrons, and then to update the field model according to the currents that are generated by the cross-tail electric field and/or induced fields. Parallel (and perpendicular) electric fields that form are included through the Boltzmann relation. Transverse electron currents are to be included through adiabatic drift equations.

Schriver, David↗

NASA NTRS2001

Status of Pulsed Inductive Thruster Research

The TRW Pulsed Inductive Thruster (PIT) is an electromagnetic propulsion system that can provide high thrust efficiency over a wide range of specific impulse values. In its basic form, the PIT consists of a flat spiral coil covered by a thin dielectric plate. A pulsed gas injection nozzle distributes a thin layer of gas propellant across the plate surface at the same time that a pulsed high current discharge is sent through the coil. The rising current creates a time varying magnetic field, which in turn induces a strong azimuthal electric field above the coil. The electric field ionizes the gas propellant and generates an azimuthal current flow in the resulting plasma. The current in the plasma and the current in the coil flow in opposite directions, providing a mutual repulsion that rapidly blows the ionized propellant away from the plate to provide thrust. The thrust and specific impulse can be tailored by adjusting the discharge power, pulse repetition rate, and propellant mass flow, and there is minimal if any erosion due to the electrodeless nature of the discharge. Prior single-shot experiments performed with a 1-meter diameter version of the PIT at TRW demonstrated specific impulse values between 2,000 seconds and 8,000 seconds, with thruster efficiencies exceeding 55% for ammonia and hydrazine propellants. This paper outlines current and planned activities to transition the single shot device into a multiple repetition rate thruster capable of supporting future DOD and NASA strategic enterprise missions.

Hrbud, Ivana↗