Search NASA⌕ Search

SEARCH · Search NASA

Results for “Field Operators”

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 1,099 records · Page 61
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

An experimental and computational investigation of the steady and unsteady transonic flow fields about an airfoil in a solid-wall test channel

An experimental and computational investigation of the steady and unsteady transonic flow field about a thick airfoil is described. An operational computer code for solving the two-dimensional, compressible Navier-Stokes equations for flow over airfoils was modified to include solid-wall, slipflow boundary conditions to properly assess the code and help guide the development of improved turbulence models. Steady and unsteady flow fields about an 18% thick circular arc airfoil at Mach numbers of 0.720, 0.754, and 0.783 and a chord Reynolds number of 11 x 10 to the 6th are predicted and compared with experiment. For the first time, computed results for unsteady turbulent flows with separation caused by a shock wave were obtained which qualitatively reproduce the time-dependent aspects of experiments. Features such as the intensity and reduced frequency of airfoil surface-pressure fluctuations, oscillatory regions of trailing-edge and shock-induced separation, and the Mach number range for unsteady flows were all qualitatively reproduced.

Levy, L. L., Jr.↗
NASA NTRS1986

Overcash, D. R.

The objectives of this investigation were to determine the characteristics of semiconductor devices at low temperatures. The output characteristics of several currently available semiconductor devices and devices fabricated at Marshall Space Flight Center were measured over a range of gate voltages. Large variations in low-temperature performance, not only from type to type, but from field effect transistor (FET) to FET of the same type were obtained. By increasing the carrier concentrations at low temperatures through extra heavy doping, metal oxide semiconductor field effect transistor (MOSFET) device was fabricated that operated at 4.2K. To verify the low-temperature operation of a heavily doped device, this procedure was repeated. Their noise spectrum was analyzed at 4.2K. Suggestions were made as to possible fabrication methods, techniques, and other semiconductor materials that might improve the device charactersitics at low temperatures. A procedure for using an electric field to drift dopants through the insulating oxide to produce a very thin, heavily doped region under the gate of a MOSFET was initiated. Capacitance s a function of voltage plots was suggested as a method for determining the level of dopant drift.

Source record↗
NASA NTRS2009

NASA Tech Briefs, July 2009

Topics covered include: Dual Cryogenic Capacitive Density Sensor; Hail Monitor Sensor; Miniature Six-Axis Load Sensor for Robotic Fingertip; Improved Blackbody Temperature Sensors for a Vacuum Furnace; Wrap-Around Out-the-Window Sensor Fusion System; Wide-Range Temperature Sensors with High-Level Pulse Train Output; Terminal Descent Sensor Simulation; A Robust Mechanical Sensing System for Unmanned Sea Surface Vehicles; Additive for Low-Temperature Operation of Li-(CF)n Cells; Li/CFx Cells Optimized for Low-Temperature Operation; Number Codes Readable by Magnetic-Field-Response Recorders; Determining Locations by Use of Networks of Passive Beacons; Superconducting Hot-Electron Submillimeter-Wave Detector; Large-Aperture Membrane Active Phased-Array Antennas; Optical Injection Locking of a VCSEL in an OEO; Measuring Multiple Resistances Using Single-Point Excitation; Improved-Bandwidth Transimpedance Amplifier; Inter-Symbol Guard Time for Synchronizing Optical PPM; Novel Materials Containing Single-Wall Carbon Nanotubes Wrapped in Polymer Molecules; Light-Curing Adhesive Repair Tapes; Thin-Film Solid Oxide Fuel Cells; Zinc Alloys for the Fabrication of Semiconductor Devices; Small, Lightweight, Collapsible Glove Box; Radial Halbach Magnetic Bearings; Aerial Deployment and Inflation System for Mars Helium Balloons; Steel Primer Chamber Assemblies for Dual Initiated Pyrovalves; Voice Coil Percussive Mechanism Concept for Hammer Drill; Inherently Ducted Propfans and Bi-Props; Silicon Nanowire Growth at Chosen Positions and Orientations; Detecting Airborne Mercury by Use of Gold Nanowires; Detecting Airborne Mercury by Use of Palladium Chloride; Micro Electron MicroProbe and Sample Analyzer; Nanowire Electron Scattering Spectroscopy; Electron-Spin Filters Would Offer Spin Polarization Greater than 1; Subcritical-Water Extraction of Organics from Solid Matrices; A Model for Predicting Thermoelectric Properties of Bi2Te3; Integrated Miniature Arrays of Optical Biomolecule Detectors; A Software Rejuvenation Framework for Distributed Computing; Kurtosis Approach to Solution of a Nonlinear ICA Problem; Robust Software Architecture for Robots; R4SA for Controlling Robots; Bio-Inspired Neural Model for Learning Dynamic Models; Evolutionary Computing Methods for Spectral Retrieval; Monitoring Disasters by Use of Instrumented Robotic Aircraft; Complexity for Survival of Living Systems; Using Drained Spacecraft Propellant Tanks for Habitation; Connecting Node; and Electrolytes for Low-Temperature Operation of Li-CFx Cells.

Source record↗
NASA NTRS1979

SeaSat-A Satellite Scatterometer Mission Summary and Engineering Assessment Report

The SeaSat-A satellite was launched on June 26, 1978 and operated in orbit through October 9, 1978. The SeaSat-A satellite scatterometer ocean surface wind field sensor began taking data on July 10, 1978 with virtually continuous operation for 95-1/2 days. A review of mission events significant to the scatterometer and a report on the hardware and software engineering assessment are presented.

Johnson, J. W.↗
NASA NTRS1991

CFD analysis of a hydrogen fueled ramjet engine at Mach 3.44

The full Navier-Stokes solver, RPLUS, has been used to compute the flow field of a ramjet engine in the low supersonic operating regime. Computations have been made for the case where hydrogen is transversely injected and ignited using nine species and eighteen reactions to model the combustion process. The flow fields for two methods of hydrogen injection have been computed and compared to the available experimental data. The purpose of these computations was to assess the mixing effectiveness of the injected hydrogen with the primary supersonic stream. Results indicate significant ignition delay resulting from the poor mixing dynamics in the combustor section.

Duncan, Beverly↗
NASA NTRS2008

Devices and methods of operation thereof for providing stable flow for centrifugal compressors

Centrifugal compressor flow stabilizing devices and methods of operation thereof are disclosed that act upon the flow field discharging from the impeller of a centrifugal compressor and modify the flow field ahead of the diffuser vanes such that flow conditions contributing to rotating stall and surge are reduced or even eliminated. In some embodiments, shaped rods and methods of operation thereof are disclosed, whereas in other embodiments reverse-tangent air injection devices and methods are disclosed.

Skoch, Gary J.↗
NASA NTRS1992

Electromechanical systems with transient high power response operating from a resonant AC link

The combination of an inherently robust asynchronous (induction) electrical machine with the rapid control of energy provided by a high frequency resonant AC link enables the efficient management of higher power levels with greater versatility. This could have a variety of applications from launch vehicles to all-electric automobiles. These types of systems utilize a machine which is operated by independent control of both the voltage and frequency. This is made possible by using an indirect field-oriented control method which allows instantaneous torque control in all four operating quadrants. Incorporating the AC link allows the converter in these systems to switch at the zero crossing of every half cycle of the AC waveform. This zero loss switching of the link allows rapid energy variations to be achieved without the usual frequency proportional switching loss. Several field-oriented control systems were developed by LeRC and General Dynamics Space Systems Division under contract to NASA. A description of a single motor, electromechanical actuation system is presented. Then, focus is on a conceptual design for an AC electric vehicle. This design incorporates an induction motor/generator together with a flywheel for peak energy storage. System operation and implications along with the associated circuitry are addressed. Such a system would greatly improve all-electric vehicle ranges over the Federal Urban Driving Cycle (FUD).

Burrows, Linda M.↗
NASA NTRS1979

A laser accelerator

It is shown that a laser can efficiently accelerate charged particles if a magnetic field is introduced to improve the coupling between the particle and the wave. Solving the relativistic equations of motion for an electron in a uniform magnetic field and superposed, circularly polarized electromagnetic wave, it is found that in energy-position phase space an electron traces out a curtate cycloid: it alternately gains and loses energy. If, however, the parameters are chosen so that the electron's oscillations in the two fields are resonant, it will continually accelerate or decelerate depending on its initial position within a wavelength of light. A laboratory accelerator operating under these resonant conditions appears attractive: in a magnetic field of 10,000 gauss, and the fields of a 5 x 10 to the 12th W, 10 micron wavelength laser, an optimally positioned electron would accelerate to 700 MeV in only 10 m.

Colson, W. B.↗
NASA NTRS2023

Improved Space Weather Observations and Modeling for Aviation Radiation

In recent years there has been a growing interest from the aviation community for space weather radiation forecasts tailored to the needs of the aviation industry. In 2019 several space weather centers began issuing advisories for the International Civil Aviation Organization alerting users to enhancements in the radiation environment at aviation flight levels. Due to a lack of routine observations, radiation modeling is required to specify the dose rates experienced by flight crew and passengers. While mature models exist, support for key observational inputs and further modeling advancements are needed. Observational inputs required from the ground-based neutron monitor network must be financially supported for research studies and operations to ensure real-time data is available for forecast operations and actionable end user decision making. An improved understanding of the geomagnetic field is required to reduce dose rate uncertainties in regions close to the open/closed geomagnetic field boundary, important for flights such as those between the continental US and Europe which operate in this region. Airborne radiation measurements, which are crucial for model validation and improvement, are lacking, particularly during solar energetic particle events. New measurement campaigns must be carried out to ensure progress and in situ atmospheric radiation measurements made available for real-time situational awareness. Furthermore, solar energetic particle forecasting must be improved to move aviation radiation nowcasts to forecasts in order to meet customer requirements for longer lead times for planning and mitigation.

space weather↗
NASA NTRS2014

Investigation of Unsteady Flow Field in a Low-Speed One and a Half Stage Axial Compressor: Effects of Tip Gap Size On the Tip Clearance Flow Structure at Near Stall Operation - Part 2

The primary focus of this paper is to investigate the effect of rotor tip gap size on how the rotor unsteady tip clearance flow structure changes in a low speed one and half stage axial compressor at near stall operation (for example, where maximum pressure rise is obtained). A Large Eddy Simulation (LES) is applied to calculate the unsteady flow field at this flow condition with both a small and a large tip gaps. The numerically obtained flow fields at the small clearance matches fairly well with the available initial measurements obtained at the Johns Hopkins University with 3-D unsteady PIV in an index-matched test facility which renders the compressor blades and casing optically transparent. With this setup, the unsteady velocity field in the entire flow domain, including the flow inside the tip gap, can be measured. The numerical results are also compared with previously published measurements in a low speed single stage compressor (Maerz et al. [2002]). The current study shows that, with the smaller rotor tip gap, the tip clearance vortex moves to the leading edge plane at near stall operating condition, creating a nearly circumferentially aligned vortex that persists around the entire rotor. On the other hand, with a large tip gap, the clearance vortex stays inside the blade passage at near stall operation. With the large tip gap, flow instability and related large pressure fluctuation at the leading edge are observed in this one and a half stage compressor. Detailed examination of the unsteady flow structure in this compressor stage reveals that the flow instability is due to shed vortices near the leading edge, and not due to a three-dimensional separation vortex originating from the suction side of the blade, which is commonly referred to during a spike-type stall inception. The entire tip clearance flow is highly unsteady. Many vortex structures in the tip clearance flow, including the sheet vortex system near the casing, interact with each other. The core tip clearance vortex, which is formed with the rotor tip gap flows near the leading edge, is also highly unsteady or intermittent due to pressure oscillations near the leading edge and varies from passage to passage. For the current compressor stage, the evidence does not seem to support that a classical vortex breakup occurs in any organized way, even with the large tip gap. Although wakes from the IGV influence the tip clearance flow in the rotor, the major characteristics of rotor tip clearance flows in isolated or single stage rotors are observed in this one and a half stage axial compressor.

Unsteady↗
NASA NTRS1986

Computation of nozzle flow fields using the PARC2D Navier-Stokes code

Supersonic nozzles which operate at low Reynolds numbers and have large expansion ratios have very thick boundary layers at their exit. This leads to a very strong viscous/inviscid interaction upon the flow within the nozzle and the traditional nozzle design techniques which correct the inviscid core with a boundary layer displacement do not accurately predict the nozzle exit conditions. A full Navier-Stokes code (PARC2D) was used to compute the nozzle flow field. Grids were generated using the interactive grid generator code TBGG. All computations were made on the NASA MSFC CRAY X-MP computer. Comparison was made between the computations and in-house wall pressure measurements for CO2 flow through a conical nozzle having an area ratio of 40. Satisfactory agreement existed between the computations and measurements for a stagnation pressure of 29.4 psia and stagnation temperature of 1060 R. However, agreement did not exist at a stagnation pressure of 7.4 psia. Several reasons for the lack of agreement are possible. The computational code assumed a constant gas gamma whereas gamma for CO2 varied from 1.22 in the plenum chamber to 1.38 at the nozzle exit. Finally, it is possible that condensation occurred during the expansion at the lower stagnation pressure.

Collins, Frank G.↗
NASA NTRSDate not supplied

Atacama Rover Astrobiology Drilling Studies Project: Final Year

The Atacama Rover Astrobiology Drilling Studies (ARADS) project, a simulated Mars rover biomarker detection mission, was iteratively developed over four years from 2015 -2019, including three NASA centers, the Centro de Astrobiologia, Johns Hopkins University, Honeybee Robotics, Maxar and the University of Antofagasta. The final (4th) ARADS field season, in 2019, tested an integrated mobile life-prospecting platform loosely inspired by the 2000’s Astrobiology Field Laboratory concept, with a 1m rotary-percussive drill and sample transfer robot arm that fed three astrobiology instruments operating in-situ on the KREX2 medium rover prototype. A fourth instrument was field tested earlier in 2019 due to flight mission requirements. In the final ARADS field deployment in September 2019, the project conducted a remote mission operation simulation (Stoker 2022)demonstrating sample drilling, acquisition and transfer into the rover instruments (while minimizing cross-contamination), performing in-situ analysis of the samples, and returning the results to a remote science operations team(which commanded the daily science goals and uploaded operations sequences).

astrobiology↗
NASA NTRS1998

Numerical Differentiation for Adaptively Refined Finite Element Meshes

Postprocessing of point-wise data is a fundamental process in many fields of research. Numerical differentiation is a key operation in computational electromagnetics. In the case of data obtained from a finite element method with automatic mesh refinement much work needs still to be done. This paper addresses some issues in differentiating data obtained from a finite element electromagnetic code with adaptive mesh refinement, and it proposes a methodology for deriving the electric field given the magnetic field on a mesh of linear triangular elements. The procedure itself is nevertheless more general and might be extended for numerically differentiating any point-wise solution based on triangular meshes.

Borgioli, Andrea↗
NASA NTRS2011

A (201)Hg+ Comagnetometer for (199)Hg+ Trapped Ion Space Atomic Clocks

A method has been developed for unambiguously measuring the exact magnetic field experienced by trapped mercury ions contained within an atomic clock intended for space applications. In general, atomic clocks are insensitive to external perturbations that would change the frequency at which the clocks operate. On a space platform, these perturbative effects can be much larger than they would be on the ground, especially in dealing with the magnetic field environment. The solution is to use a different isotope of mercury held within the same trap as the clock isotope. The magnetic field can be very accurately measured with a magnetic-field-sensitive atomic transition in the added isotope. Further, this measurement can be made simultaneously with normal clock operation, thereby not degrading clock performance. Instead of using a conventional magnetometer to measure ambient fields, which would necessarily be placed some distance away from the clock atoms, first order field-sensitive atomic transition frequency changes in the atoms themselves determine the variations in the magnetic field. As a result, all ambiguity over the exact field value experienced by the atoms is removed. Atoms used in atomic clocks always have an atomic transition (often referred to as the clock transition) that is sensitive to magnetic fields only in second order, and usually have one or more transitions that are first-order field sensitive. For operating parameters used in the (199)Hg(+) clock, the latter can be five orders of magnitude or more sensitive to field fluctuations than the clock transition, thereby providing an unambiguous probe of the magnetic field strength.

Burt, Eric A.↗
NASA NTRS1992

Effects of Centrifuge Diameter and Operation on Rodent Adaptation to Chronic Centrifugation

This study examined the responses of rats to centrifugation in a constant acceleration field (1.5 G). Centrifuge diameter (1.8m, 2.5m or 6.0m) and schedule of operation (Daily or weekly stop) varied between groups. Body mass, food consumption, water consumption and neurovestibular function were measured weekly. Body temperature and activity were continuously monitored using telemetry. A subset of subjects were videotaped (50 minutes per day) to allow for movement analysis. Exposure to a hyperdynamic field of this magnitude did cause the expected depression in the physiological variables monitored. Recovery was accomplished within a relatively rapid time frame; all variables returned to precentrifugation levels. In general, the magnitudes of the changes and the rate of recovery were similar at different centrifuge diameters and stopping frequency. There were cases, however, in which the magnitude of the response and/or the rate of recovery to a new steady-state were altered as a result of centrifuge diameter. In summary, these results indicate that stopping frequency has little, if any, effect on adaptation to chronic centrifugation. However, the angular velocity (omega), and therefore centrifuge diameter is an important consideration in the adaptation of an organism to chronic centrifugation.

Fuller, Charles A.↗
NASA NTRS1997

Effects of Centrifuge Diameter and Operation on Rodent Adaptation to Chronic Centrifugation

This study examined the responses of rats to centrifugation in a constant acceleration field (1.5 G). Centrifuge diameter (1.8m, 2.5m or 6.0m) and schedule of operation (Daily or weekly stop) varied between groups. Body mass, food consumption, water consumption and neurovestibular function were measured weekly. Body temperature and activity were continuously monitored using telemetry. A subset of subjects were videotaped (50 minutes per day) to allow for movement analysis. Exposure to a hyperdynamic field of this magnitude did cause the expected depression in the physiological variables monitored. Recovery was accomplished within a relatively rapid time frame; all variables returned to precentrifugation levels. In general, the magnitudes of the changes and the rate of recovery were similar at different centrifuge diameters and stopping frequency. There were cases, however, in which the magnitude of the response and/or the rate of recovery to a new steady-state were altered as a result of centrifuge diameter. In summary, these results indicate that stopping frequency has little, if any, effect on adaptation to chronic centrifugation. However, the angular velocity (omega), and therefore centrifuge diameter is an important consideration in the adaptation of an organism to chronic centrifugation.

Fuller, Charles A.↗
NASA NTRS2010

Low field SQUID MRI devices, components and methods

Low field SQUID MRI devices, components and methods are disclosed. They include a portable low field (SQUID)-based MRI instrument and a portable low field SQUID-based MRI system to be operated under a bed where a subject is adapted to be located. Also disclosed is a method of distributing wires on an image encoding coil system adapted to be used with an NMR or MRI device for analyzing a sample or subject and a second order superconducting gradiometer adapted to be used with a low field SQUID-based MRI device as a sensing component for an MRI signal related to a subject or sample.

Penanen, Konstantin I.↗
NASA NTRS2011

Low field SQUID MRI devices, components and methods

Low field SQUID MRI devices, components and methods are disclosed. They include a portable low field (SQUID)-based MRI instrument and a portable low field SQUID-based MRI system to be operated under a bed where a subject is adapted to be located. Also disclosed is a method of distributing wires on an image encoding coil system adapted to be used with an NMR or MRI device for analyzing a sample or subject and a second order superconducting gradiometer adapted to be used with a low field SQUID-based MRI device as a sensing component for an MRI signal related to a subject or sample.

Penanen, Konstantin I.↗