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Results for “ELECTROMAGNETIC MEASUREMENT”

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 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Measurement of energy distribution in flowing hydrogen microwave plasmas

An electrothermal propulsion concept utilizing a microwave plasma system as the mechanism to convert electromagnetic energy into kinetic energy of a flowing gas is investigated. A calorimetry system enclosing a microwave plasma system has been developed to accurately measure the energy inputs and outputs of the microwave plasma system. The rate of energy transferred to the gas can be determined to within + or - 1.8 W from an energy balance around the microwave plasma system. The percentage of the power absorbed by the microwave plasma system transferred to the hydrogen gas as it flows through the system is found to increase with the increasing flow rate, to decrease with the increasing pressure, and to be independent of the absorbed power. An upper bound for the hydrogen gas temperature is estimated from the energy content, heat capacity, and flow rate of the gas stream. A lower bound for an overall heat-transfer coefficient is then calculated, characterizing the energy loss from the hydrogen gas stream to the air cooling of the plasma discharge tube wall. The heat-transfer coefficient is found to increase with the increasing flow rate and pressure and to be independent of the absorbed power. This result indicates that a convective-type mechanism is responsible for the energy transfer.

Chapman, R.↗
NASA NTRS2017

Wide-Field Imaging Using Nitrogen Vacancies

Nitrogen vacancies in bulk diamonds and nanodiamonds can be used to sense temperature, pressure, electromagnetic fields, and pH. Unfortunately, conventional sensing techniques use gated detection and confocal imaging, limiting the measurement sensitivity and precluding wide-field imaging. Conversely, the present sensing techniques do not require gated detection or confocal imaging and can therefore be used to image temperature, pressure, electromagnetic fields, and pH over wide fields of view. In some cases, wide-field imaging supports spatial localization of the NVs to precisions at or below the diffraction limit. Moreover, the measurement range can extend over extremely wide dynamic range at very high sensitivity.

Englund, Dirk Robert↗
NASA NTRS1997

The NASA High Intensity Radiated Fields Laboratory

High Intensity Radiated Fields (HIRF) are the result of a multitude of intentional and nonintentional electromagnetic sources that currently exists in the world. Many of today's digital systems are susceptible to electronic upset if subjected to certain electromagnetic environments (EME). Modern aerospace designers and manufacturers increasingly rely on sophisticated digital electronic systems to provide critical flight control in both military, commercial, and general aviation aircraft. In an effort to understand and emulate the undesired environment that high energy RF provides modern electronics, the Electromagnetics Research Branch (ERB) of the Flight Electronics and Technology Division (FETD) conducts research on RF and microwave measurement methods related to the understanding of HIRF. In the High Intensity Radiated Fields Laboratory, the effects of high energy radiating electromagnetic fields on avionics and electronic systems are tested and studied.

Williams, Reuben A.↗
NASA NTRS1981

Instabilities of low frequency, parallel propagating electromagnetic waves in the earth's foreshock region

An instability analysis is presented for parallel and antiparallel propagating electromagnetic waves generated by reflected and diffuse suprathermal ions upstream of the earth's bow shock. Calculations are performed on the basis of upstream particle observations made by the ISEE 1 Quadrispheric Lepedea instrument and low-energy electron measurements made by the ISEE 1 electron spectrometer for a single period. The electromagnetic dispersion relation is computed and the unstable modes and growth times of the fastest growing waves are determined. It is found that the reflected ions destabilize the plasma most strongly at a wave frequency 0.1 that of the ion gyrofrequency by a resonant ion beam instability for waves propagating upstream and by a nonresonant firehose-like instability for waves propagating downstream. The diffuse ions also destabilize the plasma most strongly at the same frequency by means of resonant instabilities of both right- and left-hand polarized waves propagating away from the bow shock.

Sentman, D. D.↗
NASA NTRS1975

The gravity and shape of the moon

This review discusses the current knowledge of the gravity and geometry of the moon, and their implications as to lunar structure. Measurements pertaining to the gravity field are, first and foremost, Doppler tracking of spacecraft that have orbited the moon, but also the laser ranging from the earth to the moon and the gravity meters and accelerometers landed with the Apollo spacecraft. Measurements pertaining to the geometry include (1) those related to the shape: the metric photography and laser altimeters on Apollo 15, 16, and 17; the electromagnetic sounder on Apollo 17; the landmark tracking from earlier Apollo orbiters; and occupations, plus (2) measurements related to the orientation: the laser ranging and interferometry from the earth. The review does not cover determinations of topography from photography taken for geologic or landing reconnaissance purposes. The discussion of tectonic implications is limited to inferences of a quantitative nature. The emphasis is on work since 1970; see Kaula [1969, 1971] for reviews of earlier work.

William M. Kaula↗
NASA NTRS2021

A Gravitational-wave Measurement of the Hubble Constant Following the Second Observing Run of Advanced LIGO and Virgo

This paper presents the gravitational-wave measurement of the Hubble constant (H(0)) using the detections from the first and second observing runs of the Advanced LIGO and Virgo detector network. The presence of the transient electromagnetic counterpart of the binary neutron star GW170817 led to the first standard-siren measurement of H(0). Here we additionally use binary black hole detections in conjunction with galaxy catalogs and report a joint measurement. Our updated measurement is H(0) = 69(+16,-8) km/s Mpc (68.3% of the highest density posterior interval with a flat-in-log prior) which is an improvement by a factor of 1.04 (about 4%) over the GW170817-only value of 6(+17,-8) km/s Mpc. A significant additional contribution currently comes from GW170814, a loud and well-localized detection from a part of the sky thoroughly covered by the Dark Energy Survey. With numerous detections anticipated over the upcoming years, an exhaustive understanding of other systematic effects are also going to become increasingly important. These results establish the path to cosmology using gravitational-wave observations with and without transient electromagnetic counterparts.

B. P. Abbott↗
NASA NTRS2003

Astrobiology Exploration Strategies for the Mars Polar Regions Using Balloon Platforms

Montgolfiere balloons can provide a unique near-surface platform for an extended traverse over the polar regions of Mars. During the polar summer, such solar powered balloons would remain in the constant sun of the polar summer and could remain airborne for many weeks or even months as the atmospheric circulation would drive the balloons around the polar region many times before the balloon would cross the terminator. Such a platform for scientific measurements could provide in situ sampling of the atmosphere for trace disequilibrium species that might be indicators of present geological or biological activity in this region. It could furthermore provide high resolution imaging, deep electromagnetic (EM) sounding for subsurface stratigraphy and liquid water, and high spatial resolution neutron measurements of subsurface ice. Technologies for robust balloon deployment on entry and controlled encounters with the surface and near subsurface for sample acquisition in otherwise inaccessible regions are presently being studied and developed with support from NASA.

Mahaffy, P. R.↗
NASA NTRS2003

Astrobiology Exploration Strategies for the Mars Polar Regions Using Balloon Platforms

Montgolfiere balloons can provide a unique near-surface platform for an extended traverse over the polar regions of Mars. During the polar summer, such solar powered balloons would remain in the constant sun of the polar summer and could remain airborne for many weeks or even months as the atmospheric circulation would drive the balloons around the polar region many times before the balloon would cross the terminator. Such a platform for scientific measurements could provide in situ sampling of the atmosphere for trace disequilibrium species that might be indicators of present geological or biological activity in this regon. It could furthermore provide high resolution imaging, deep electromagnetic (EM) sounding for subsurface stratigraphy and liquid water, and high spatial resolution neutron measurements of subsurface ice. Technologies for robust balloon deployment on entry and controlled encounters with the surface and near subsurface for sample acquisition in otherwise inaccessible regions are presently being studied and developed with support from NASA.

Mahaffy, P. R.↗
NASA NTRS2010

Recent Stirling Conversion Technology Developments and Operational Measurements at NASA Glenn Research Center

In support of the Advanced Stirling Radioisotope Generator (ASRG) project and other potential applications, NASA Glenn Research Center (GRC) has initiated convertor technology development efforts in the areas of acoustic emission, electromagnetic field mitigation, thermoacoustic Stirling conversion, and multiple-cylinder alpha arrangements of Stirling machines. The acoustic emission measurement effort was developed as a health monitoring metric for several Stirling convertors undergoing life testing. While accelerometers have been used in the past to monitor dynamic signature, the acoustic sensors were chosen to monitor cycle events, such gas bearing operation. Several electromagnetic interference (EMI) experiments were performed on a pair of Advanced Stirling Convertors (ASC). These tests demonstrated that a simple bucking coil was capable of reducing the alternating current (ac) magnetic field below the ASRG system specification. The thermoacoustic Stirling concept eliminates the displacer typically found in Stirling machines by making use of the pressure oscillations of a traveling acoustic wave. A 100 W-class thermoacoustic Stirling prototype manufactured by Northrop Grumman Space and Technology was received and tested. Another thermoacoustic prototype designed and fabricated by Sunpower, Inc., will be tested in the near future. A four cylinder free piston alpha prototype convertor was received from Sunpower, Inc. and has been tested at GRC. This hardware was used as a proof of concept to validate thermodynamic models and demonstrate stable operation of multiple-cylinder free-piston Stirling conversion. This paper will discuss each of these activities and the results they produced.

Oriti, Salvatore M.↗
NASA NTRS1970

Thermodielectric radiometer

Radiometer measures microsecond pulses of radiant flux in the presence of electromagnetic noise. It consists of a charged capacitor that delivers a voltage pulse proportional to the thermally induced depolarization of its polymeric dielectric.

Beam, B. H.↗
NASA NTRS1976

Upper limits to the interstellar radiation field between 775 and 1050 A

A 40-A resolution extreme-ultraviolet spectrometer, sensitive to radiation in the 775-1050 A band, was flown on a Black Brant VC rocket to measure the night sky brightness in this region of the electromagnetic spectrum. A weak signal above background was recorded in most channels as the spectrometer's field of view scanned the sky in the vicinity of the galactic plane from Monoceros to Andromeda. Because the earth's upper atmosphere may produce some radiation in this wavelength region, the possibility cannot be excluded that some or all of the observed signal is terrestrial in origin. However, observational upper limits can be established at the 95-per cent confidence level for the intensity of an extraterrestrial extreme ultraviolet background which ranges from 6 millionths erg/sq cm/s/sr/A at 1050 A to 4 ten-millionths erg/sq cm/s/sr/A at 775 A. These results are consistent with existing theoretical predictions.

Paresce, F.↗
NASA NTRS1977

Electromagnetic sounding of the moon using Apollo 16 and Lunokhod 2 surface magnetometer observations /preliminary results/

A technique of deep electromagnetic sounding of the moon using simultaneous magnetic-field measurements at two lunar surface sites is described. The method, used with the assumption that deep electrical conductivity is a function only of lunar radius, has the advantage of allowing calculation of the external driving field from two surface-site measurements only and therefore does not require data from a lunar orbiting satellite. A transient-response calculation is presented for the example of a magnetic-field discontinuity, measured simultaneously by Apollo 16 and Lunokhod 2 surface magnetometers.

Vanian, L. L.↗
NASA NTRS1992

New Techniques for Exciting Linearly Tapered Slot Antennas with Coplanar Waveguide

Two new techniques for exciting a linearly tapered slot antenna (LTSA) with coplanar waveguide (CPW) are introduced. In the first approach, an air bridge is used to couple power from a CPW to an LTSA. In the second approach, power is electromagnetically coupled from a finite CPW (FCPW) to an LTSA. Measured results at 18 GHz show excellent return loss and radiation patterns.

Simons, R. N.↗
NASA NTRS2000

Comparison of Commercial Electromagnetic Interface Test Techniques to NASA Electromagnetic Interference Test Techniques

This report documents the development of analytical techniques required for interpreting and comparing space systems electromagnetic interference test data with commercial electromagnetic interference test data using NASA Specification SSP 30237A "Space Systems Electromagnetic Emission and Susceptibility Requirements for Electromagnetic Compatibility." The PSpice computer simulation results and the laboratory measurements for the test setups under study compare well. The study results, however, indicate that the transfer function required to translate test results of one setup to another is highly dependent on cables and their actual layout in the test setup. Since cables are equipment specific and are not specified in the test standards, developing a transfer function that would cover all cable types (random, twisted, or coaxial), sizes (gauge number and length), and layouts (distance from the ground plane) is not practical.

Smith, V.↗
NASA NTRS2001

Laboratory for Extraterrestrial Physics

The NASA Goddard Space Flight Center (GSFC) Laboratory for Extraterrestrial Physics (LEP) performs experimental and theoretical research on the heliosphere, the interstellar medium, and the magnetospheres and upper atmospheres of the planets, including Earth. LEP space scientists investigate the structure and dynamics of the magnetospheres of the planets including Earth. Their research programs encompass the magnetic fields intrinsic to many planetary bodies as well as their charged-particle environments and plasma-wave emissions. The LEP also conducts research into the nature of planetary ionospheres and their coupling to both the upper atmospheres and their magnetospheres. Finally, the LEP carries out a broad-based research program in heliospheric physics covering the origins of the solar wind, its propagation outward through the solar system all the way to its termination where it encounters the local interstellar medium. Special emphasis is placed on the study of solar coronal mass ejections (CME's), shock waves, and the structure and properties of the fast and slow solar wind. LEP planetary scientists study the chemistry and physics of planetary stratospheres and tropospheres and of solar system bodies including meteorites, asteroids, comets, and planets. The LEP conducts a focused program in astronomy, particularly in the infrared and in short as well as very long radio wavelengths. We also perform an extensive program of laboratory research, including spectroscopy and physical chemistry related to astronomical objects. The Laboratory proposes, develops, fabricates, and integrates experiments on Earth-orbiting, planetary, and heliospheric spacecraft to measure the characteristics of planetary atmospheres and magnetic fields, and electromagnetic fields and plasmas in space. We design and develop spectrometric instrumentation for continuum and spectral line observations in the x-ray, gamma-ray, infrared, and radio regimes; these are flown on spacecraft to study the interplanetary medium, asteroids, comets, and planets. Suborbital sounding rockets and groundbased observing platforms form an integral part of these research activities. This report covers the period from approximately October 1999 through September 2000.

Vondrak, Richard R.↗