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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS2015

Progress in Open Rotor Research: A U.S. Perspective

In response to the 1970s oil crisis, NASA created the Advanced Turboprop Project (ATP) to mature technologies for high-speed propellers to enable large reductions in fuel burn relative to turbofan engines of that era. Both single rotation and contra-rotation concepts were designed and tested in ground based facilities as well as flight. Some novel concepts configurations that were not well publicized at the time, were proposed as part of the effort. The high-speed propeller concepts did provide fuel burn savings, albeit with some acoustics and structural challenges to overcome. When fuel prices fell, the business case for radical new engine configurations collapsed and the research emphasis returned to high bypass ducted configurations. With rising oil prices and increased environmental concerns there is renewed interest in high-speed propeller based engine architectures. Contemporary analysis tools for aerodynamics and aeroacoustics have enabled a new era of blade designs that have both high efficiency and acceptable noise characteristics. A recent series of tests in the U.S. have characterized the aerodynamic performance and noise from these modern contra-rotating propeller designs. Additionally the installation and noise shielding aspects for conventional airframes and blended wing bodies have been studied. Historical estimates of propfan performance have relied on legacy propeller performance and acoustics data. Current system studies make use of the modern propeller data with higher fidelity installation effects data to estimate the performance of a contemporary aircraft system with favorable results. This paper presents the current state of high-speed propeller open rotor research within the U.S. from an overall viewpoint of the various efforts ongoing. The current projections for the technology are presented.

Aerodynamics↗
NASA NTRS1989

High-speed flows of H(+) and He(2+) ions at the magnetosphere

Observations of high-speed flows of H(+) and He(2+) ions obtained by the hot plasma composition experiment on AMPTE/CCE provide direct support for the single-particle approach to acceleration in current layers. These high-speed flows are attributed to single-fluid momentum balance across a magnetopause with a normal magnetic field and a tangential electric field. The flow speeds of the two ion species are found to be approximately equal.

Paschmann, G.↗
NASA NTRS1971

Integrated circuit electrometer and sweep circuitry for an atmospheric probe

The design of electrometer circuitry using an integrated circuit operational amplifier with a MOSFET input is described. Input protection against static voltages is provided by a dual ultra low leakage diode or a neon lamp. Factors affecting frequency response leakage resistance, and current stability are discussed, and methods are suggested for increasing response speed and for eliminating leakage resistance and current instabilities. Based on the above, two practical circuits, one having a linear response and the other a logarithmic response, were designed and evaluated experimentally. The design of a sweep circuit to implement mobility measurements using atmospheric probes is presented. A triangular voltage waveform is generated and shaped to contain a step in voltage from zero volts in both positive and negative directions.

Zimmerman, L. E.↗
NASA NTRS1984

On the response to ocean surface currents in synthetic aperture radar imagery

The balance of wave action spectral density for a fixed wave-number is expressed in terms of a new dimensionless function, the degree of saturation, b, and is applied to an analysis of the variations of this quantity (and local spectral level) at wave-numbers large compared to that of the spectral peak, that are produced by variations in the ocean surface currents in the presence of wind input and wave breaking. Particular care is taken to provide physically based representations of wind input and loss by wave breaking and a relatively convenient equation is derived that specifies the distribution of the degree of saturation in a current field, relative to its ambient (undisturbed) background in the absence of currents. The magnitude of the variations in b depends on two parameters, U(o)/c, where U/(o) is the velocity scale of the current and c the phase speed of the surface waves at the (fixed) wave-number considered or sampled by SAR, and S = (L/lambda) (u*/c)(2), where L is the length scale of the current distribution, lambda the wavelength of the surface waves the length scale of the current distribution, lambda the wavelength of the surface waves and u* the friction velocity of the wind.

Phillips, O. M.↗
DOE OSTI2024

Effect of Approach Speed and Electrode Geometry on Electrostatic Discharges Off Floating Dielectrics

With the damaging effects of electrostatic discharges (ESDs), it is important to study them within various parameter regimes relevant to real-world scenarios. One such scenario studied here is a floating dielectric with no nearby ground plane with a grounded object approaching at a high rate of speed. One may encounter this scenario when moving objects by hand. Discharge current and radiated fields are captured for discharges drawn from polytetrafluoroethylene (PTFE) and poly methyl methacrylate (PMMA) with approach speeds ranging from 20 to 100 mm/s. Previous studies have shown that at lower speeds in metal-to-metal or metal-to-ground backed dielectric geometries, the peak current and discharge distance decrease with increasing speed. However, in the speed range studied here, an increase in distance and current are observed for increasing speed. Namely, the highest speeds coincide with the highest peak currents and discharge distances of approximately 800 mA and up to 24 mm. Further, with no grounded backing, as opposed to setups in other ESD studies, the electric field between the dielectric and an approaching electrode has a more uniform distribution with highest fields at the electrode, which is elucidated to be the driving factor in the differences revealed in this study. Two spheres of differing diameters and a conical electrode are used to draw discharges off the dielectric surfaces. Captured radiated fields via B-dot sensor, plasma imagery via intesified charge-coupled device (ICCD), and mapping of surface potential reveal that a majority of the energy lost during a discharge goes to gas losses and radiated fields.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Design and Comparison of Surface Inset Permanent Magnet Machine and Surface Permanent Magnet Machine without Heavy Rare Earth Magnets for Traction Applications

This paper presents two machine designs: a surface inset permanent magnet (SIPM) machine and a surface permanent magnet (SPM) machine, both without heavy rare-earth magnets, that achieve 50 kW/L active power density and a constant-power speed ratio of 3 for EV traction applications. Compared to surface PM machines, SIPM machines do not require a special containment sleeve to hold the magnets in place at high speeds, provided that the rotor laminations are carefully designed together with the magnet mounting configuration to ensure the rotor’s structural integrity. Comparisons between the SPM and SIPM machines sharing the same stator, same current level, and same power speed envelope are presented. Both deliver very similar performance characteristics, but the SIPM machine’s simpler magnet containment configuration may give it an advantage in terms of reduced material and manufacturing costs.

42 ENGINEERING↗
NASA NTRS1991

An assessment of current methods for drag-due-to-lift minimization at supersonic speeds

The estimation and minimization of drag-due-to-lift at supersonic speeds has been examined in this study. Correlations of theory with experimental data are used to assess the applicability and limitations of the linearized theory. The role of leading-edge thrust and the use of twist and camber to develop distributed thrust are also discussed. A semiempirical design and estimation method which takes into account the shortcomings of the linear theory is presented. The use of this method will allow the design of more nearly optimum lifting surfaces and provide an accurate prediction of their level of performance. A preliminary examination is made of the use of an Euler code for estimation of the aerodynamic characteristics of a twisted and cambered wing.

Mann, Michael J.↗
NASA NTRS1985

Small-scale cyclones on the periphery of a Gulf Stream warm-core ring

Small-scale cyclones found around Gulf Stream warm-core ring 82B are investigated by using infrared satellite images and current information obtained with an acoustic-Doppler velocimeter. Currents in these cyclones reveal speeds ranging from 20 to 80 cm/s. One small cyclone or 'ringlet' found in June 1982 was studied extensively by removing the basic rotational velocities of 82B. The azimuthal velocity field for this ringlet was used with the gradient current equation to calculate the absolute dynamic topography at 100 dbar. It was found that the ringlet was 13 dyn-cm lower than its surroundings. In addition, neglect of the centrifugal term would have changed the dynamic topography of the ringlet by 30 percent. From a comparison with CTD data the absolute reference level was determined, and a vertical profile of horizontal currents was calculated for the ringlet. Other cyclones were found throughout the slope water region around warm-core ring 82B with observable lifetimes of 1 to 2 weeks. The northeast quadrant of 82B was a favored generation site for ringlets. Two cyclones were observed to form in this region and were advected anticyclonically around 82B. Typically, at any one time, six cyclones with diameters of approximately 40 to 50 km can be detected north of the Gulf Stream by using satellite images.

Kennelly, M. A.↗
NASA NTRS1991

Out-of-ecliptic tests of the inverse correlation between solar wind speed and coronal expansion factor

The paper addresses the question of whether out-of-ecliptic measurements satisfy the inverse correlation between wind speed at 1 AU and flux-tube divergence in the corona, already found from measurements in the ecliptic. Using the in-ecliptic calibration, out-of-ecliptic speeds are derived from coronal expansion factors determined from global observations of photospheric field and their current-free coronal extension. These derived speeds are compared with speeds inferred from interplanetary scintillation measurements during 1972-1988 and with in situ speeds measured by the Pioneer 11 spacecraft at 16 deg N latitude during 1984-1988. These three sets of wind speed show the same overall variation with latitude and time during the sunspot cycle, with higher latitudes having more years of fast wind than lower latitudes and all latitudes having slow wind at sunspot maximum. Although some detailed discrepancies are also present, the overall agreement is comparable to that achieved in the ecliptic plane.

Sheeley, N. R., Jr.↗
NASA NTRS1983

Design of a high-speed digital processing element for parallel simulation

A prototype of a custom designed computer to be used as a processing element in a multiprocessor based jet engine simulator is described. The purpose of the custom design was to give the computer the speed and versatility required to simulate a jet engine in real time. Real time simulations are needed for closed loop testing of digital electronic engine controls. The prototype computer has a microcycle time of 133 nanoseconds. This speed was achieved by: prefetching the next instruction while the current one is executing, transporting data using high speed data busses, and using state of the art components such as a very large scale integration (VLSI) multiplier. Included are discussions of processing element requirements, design philosophy, the architecture of the custom designed processing element, the comprehensive instruction set, the diagnostic support software, and the development status of the custom design.

Milner, E. J.↗
NASA NTRS1992

Two-equation turbulence modeling for 3-D hypersonic flows

An investigation to verify, incorporate and develop two-equation turbulence models for three-dimensional high speed flows is presented. The current design effort of hypersonic vehicles has led to an intensive study of turbulence models for compressible hypersonic flows. This research complements an extensive review of experimental data and the current development of 2D turbulence models. The review of experimental data on 2D and 3D flows includes complex hypersonic flows with pressure profiles, skin friction, wall heat transfer, and turbulence statistics data. In a parallel effort, turbulence models for high speed flows have been tested against flat plate boundary layers, and are being tested against the 2D database. In the present paper, we present the results of 3D Navier-Stokes numerical simulations with an improved k-omega two-equation turbulence model against experimental data and empirical correlations of an adiabatic flat plate boundary layer, a cold wall flat plate boundary layer, and a 3D database flow, the interaction of an oblique shock wave and a thick turbulent boundary layer with a free stream Mach number = 8.18 and Reynolds number = 5 x 10 to the 6th.

Bardina, J. E.↗
NASA NTRS1977

Discontinuous transitions in a current-carrying plasma

The properties of 'discontinuous' transitions in a current-carrying plasma are investigated by adopting an approach based on the two-fluid equations for a plasma. Braginskii's (1965) transport equations for a two-fluid plasma carrying a current are presented, and allowance is made for collisions with a background neutral gas as well as for effects of reflected particles. The speed of sound in a current-carrying plasma is derived so that the Mach number can be defined correctly as the ratio of the flow speed to the wave phase velocity in such a plasma. The various types of discontinuities permitted by the relevant jump relations in the absence of reflected particles are classified, the effect of reflected particles on such discontinuities is examined, and it is shown that the degree of indeterminacy of a discontinuity can be changed by the presence of reflected particles. Consideration of shocks containing a population of reflected particles and adiabatic transitions indicates that the pressure of reflected particles alone can give rise to both weak and strong transitions. The construction of discontinuous periodic flow solutions is also discussed.

Lee, H.-J.↗
DOE OSTI2020

Noise Erasure in Quantum-Limited Current Amplifiers

Superconducting quantum interference devices (SQUIDs) are extraordinarily sensitive to magnetic flux and thus make excellent current amplifiers for cryogenic applications. One such application of high interest to Sandia is the set-up and state read-out of quantum dot based qubits, where a qubit state is read out from a short current pulse (microseconds to milliseconds long) of approximately 100 pA, a signal that is easily corrupted by noise in the environment. A Parametric SQUID Amplifier can be high bandwidth (in the GHz range), low power dissipation (less than 1pW), and can be easily incorporated into multi-qubit systems. In this SAIL LDRD, we will characterize the noise performance of the parametric amplifier front end -- the SQUID -- in an architecture specific to current readout for spin qubits. Noise is a key metric in amplification, and identifying noise sources will allow us to optimize the system to reduce its effects, resulting in higher fidelity readout. This effort represents a critical step in creating the building blocks of a high speed, low power, parametric SQUID current amplifier that will be needed in the near term as quantum systems with many qubits begin to come on line in the next few years.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1993

A ground-based memory state tracker for satellite on-board computer memory

The TOPEX/POSEIDON satellite, currently in Earth orbit, will use radar altimetry to measure sea surface height over 90 percent of the world's ice-free oceans. In combination with a precise determination of the spacecraft orbit, the altimetry data will provide maps of ocean topography, which will be used to calculate the speed and direction of ocean currents worldwide. NASA's Jet Propulsion Laboratory (JPL) has primary responsibility for mission operations for TOPEX/POSEIDON. Software applications have been developed to automate mission operations tasks. This paper describes one of these applications, the Memory State Tracker, which allows the ground analyst to examine and track the contents of satellite on-board computer memory quickly and efficiently, in a human-readable format, without having to receive the data directly from the spacecraft. This process is accomplished by maintaining a groundbased mirror-image of spacecraft On-board Computer memory.

Quan, Alan↗
NASA NTRS2007

NASA/GE Highly-Loaded Turbine Research Program

An overview of the NASA/GE Highly-Loaded Turbine Research Program at the NASA Glenn Research Center is presented. The program is sponsored by the Subsonic Fixed Wing Project of the Fundamental Aeronautics Program. The goals of the turbine research program are presented along with their relationship to the higher-level program goals. Two turbine research programs are described; the highly-loaded, single-stage high pressure turbine (HPT) and the highly loaded low pressure turbine (LPT). The HPT program is centered on an extremely high pressure ratio single-stage turbine with an engine stage pressure ratio of 5.5. It was designed with a 33% increase in stage loading. It has shown performance levels 2 points better than current engines operating at the higher work level. Some advantages of the turbine include reduced weight and parts count. Optimization of the blade shape to reduce shock losses is described. The LPT program utilizes a four-stage low pressure turbine with an integral first stage vane/transition duct strut; counter-rotation; low-solidity blading; fully optimized flowpath including vanes, blades, and endwalls; and a fluidically controlled turbine vane frame/exit guide vane. The implementation of the LPT into GE s and NASA s test facilities is described. A description of NASA's Single Spool Turbine Facility that is currently under renovation is given. Facility limits on pressures, temperatures, flow rates, rotational speeds, and power absorption are described. The current renovation status is given.

Giel, Paul W.↗
NASA NTRS1990

Mechanical design problems associated with turbopump fluid film bearings

Most high speed cryogenic turbopumps for liquid propulsion rocket engines currently use ball or roller contact bearings for rotor support. The operating speeds, loads, clearances, and environments of these pumps combine to make bearing wear a limiting factor on turbopump life. An example is the high pressure oxygen turbopump (HPOTP) used in the Space Shuttle Main Engine (SSME). Although the HPOTP design life is 27,000 seconds at 30,000 rpms, or approximately 50 missions, bearings must currently be replaced after 2 missions. One solution to the bearing wear problem in the HPOTP, as well as in future turbopump designs, is the utilization of fluid film bearings in lieu of continuous contact bearings. Hydrostatic, hydrodynamic, and damping seal bearings are all replacement candidates for contact bearings in rocket engine high speed turbomachinery. These three types of fluid film bearings have different operating characteristics, but they share a common set of mechanical design opportunities and difficulties. Results of research to define some of the mechanical design issues are given. Problems considered include transient strat/stop rub, non-operational rotor support, bearing wear inspection and measurement, and bearing fluid supply route. Emphasis is given to the HPOTP preburner pump (PBP) bearing, but the results are pertinent to high-speed cryogenic turbomachinery in general.

Evces, Charles R.↗
NASA NTRS1975

On the reality of the Venus winds

The Venera measurements of wind speed along with the Mariner measurements of lower-region of strong turbulence are evidence for a wide band of variable high speed retrograde horizontal winds which girdle Venus at the equator. In one interpretation of the Mariner 10 UV photographs, the 20km region above the top of the visible cloud is characterized by variable high-speed retrograde horizontal winds which orbit Venus with an average period of 4 earth days, and by many features indicating vertical convection. This suggests that the Venera-Mariner band of winds at 45km extends to the top of the UV cloud and beyond, and that the upper-region of strong turbulence detected by the Mariners may result from vertical convection currents carried along by high speed horizontal winds. In another interpretation, the predominate motions are attributed to wavelike disturbances with a 4-day period. For this case the upper-region of strong turbulence may be due in large part to vertical wind-shear resulting from a rapid decrease in wind speed within a relatively short distance about the Venera-Mariner band of high speed winds.

Ainsworth, J. E.↗
DOE OSTI2020

Giant Domain Wall Conductivity in Self‐Assembled BiFeO 3 Nanocrystals

Abstract Ever‐increasing demand on electronic devices with ultrahigh‐density non‐volatile data storage has attracted great interest in novel ferroelectric memories based on conductive ferroelectric domain walls. Embedded in an insulating material, ferroelectric domain walls have the capability of being (re)created, displaced, erased, and altered in their spatial configurations and electronic characteristics. However, the domain wall conductivities are in most cases not yet sufficiently high to ensure the current density required to drive read‐out circuits operating at high speeds. In this work, a giant domain wall current (>10 µA) of a single charged domain wall is obtained through conductive atomic force microscopy with a bias field of 4 V. This is achieved in self‐assembled BiFeO 3 nanocrystals grown by sol‐gel method on Nb‐doped SrTiO 3 substrates. Local configurations of domains and domain wall types are studied using vector piezoresponse force microscopy and high‐resolution transmission electronic microscopy. The enhancement of the wall current is shown to be due to the formation of conducting pathways of charged defects accumulated along domain walls and traversing the nanocrystals. The diverse domain walls can be manipulated by electric field in a perpendicular architecture. The perpendicular array structure of BiFeO 3 nanocrystals should have great potentials for developing perpendicular nanoelectronic prototypes.

Liu, Lisha↗