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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 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Jovian radiation and charging environment considerations in Galileo

The Galileo spacecraft which will orbit Jupiter in 1987 will encounter one of the most interesting natural environments. These include high energy radiation electrons and ions and magnetospheric plasmas. The evaluation of Galileo design commenced with a careful consideration of the plasma environment and the now standard spacecraft charging analysis. In addition the intense high energy radiation environment has necessitated the consideration of charges deposited internally to the spacecraft. This paper presents some of the analyses and the design changes which have occurred as a result of the above mentioned environmental interaction considerations.

Leung, P.↗
NASA NTRS1991

Effects Of Interference On Scattering By Parallel Fibers

Report discusses radiative transfer of heat through fibrous materials, focusing on interactions between electromagnetic waves scattered from individual fibers. Equations for coherent addition of scattered waves presented and used to derive equations for intensity of scattered radiation, with emphasis on cases of evenly spaced coplanar fibers and randomly positioned fibers. Theory predicts scattering efficiency of randomly positioned fibers less than that predicted by independent-scattering theory.

White, Susan M.↗
NASA NTRS1979

Ultrathin films as photomechanical transducers

In order to investigate the photomechanical effect in ultrathin films, several commercially available polymers of various structure and properties have been studied experimentally below the glass transition temperature. In the experiments using an Instron test machine equipped with a 200-g load cell and a microscope stage illuminator as the light source, the load at the fixed strain was recorded as a function of time. Plots of the steady-state change in stress as a function of the intensity of the incident radiation are presented for several of the materials studied. The response is found to be linear; the greater the intensity of the incident radiation, the greater is the change in stress.

Sarbolouki, M. N.↗
NASA NTRS1935

Infrared radiation from explosions in a spark-ignition engine

This report presents the results of an investigation to determine the variations in intensity and spectral distribution of the radiant energy emitted by the flames during normal and knocking explosions in an engine. Radiation extending into the infrared was transmitted by a window of fluorite, placed either near the spark plug or over the detonation zone at opposite ends of the combustion chamber. Concave, surface-silvered mirrors focused the beam, first at the slit of a stroboscope which opened for about 2 degrees of crank angle at any desired point in the engine cycle, and then upon the target of a sensitive thermocouple for measuring radiation intensity. Spectral distribution of the radiant energy was determined by placing over the window, one at a time, a series of five filters selected with a view to identifying, as far as possible without the use of a spectrograph, the characteristic emissions of water vapor, carbon dioxide, and incandescent carbon.

Marvin, Charles F , Jr↗
NASA NTRS1997

The Use of a Chlorophyll Meter (SPAD-502) for Field Determinations of Red Mangrove (Rhizophora Mangle L.) Leaf Chlorophyll Amount

The red mangrove Rhizophora mangle L., is a halophytic woody spermatophyte common to the land-sea interface of tropical and subtropical intertidal zones. It has been reported that 60 to 75% of the coastline of the earth's tropical regions are lined with mangroves. Mangroves help prevent shoreline erosion, provide breeding, nesting and feeding areas for many marine animals and birds. Mangroves are important contributors of primary production in the coastal environment, and this is largely proportional to the standing crop of leaf chlorophylls. Higher intensities of ultraviolet radiation, resulting from stratospheric ozone depletion, can lead to a reduction of chlorophyll in terrestrial plants. Since the most common method for determining chlorophyll concentration is by extraction and this is labor intensive and time consuming, few studies on photosynthetic pigments of mangroves have been reported. Chlorophyll meter readings have been related to leaf chlorophyll content in apples and maples. It has also been correlated to nitrogen status in corn and cotton. Peterson et al., (1993) used a chlorophyll meter to detect nitrogen deficiency in crops and in determining the need for additional nitrogen fertilizer. Efforts to correlate chlorophyll meter measurements to chlorophyll content of mangroves have not been reported. This paper describes the use of a hand-held chlorophyll meter (Minolta SPAD-502) to determine the amount of red mangrove foliar chlorophyll present in the field.

Connelly, Xana M.↗
NASA NTRS1992

Radiation model predictions and validation using LDEF data

Radiation dosimetry aboard LDEF, as well as post-flight measurements of the radioactivity induced in numerous LDEF spacecraft components, provide unique data for evaluating the accuracy of current models for predicting both the space radiation environments (trapped proton intensity, spectra, and directionality; cosmic ray fluence) and the radiation environments induced in spacecraft components (fluence, energy spectra, secondary particle, linear energy transfer, etc.). By determining the accuracy of such models using LDEF data, and with model updates where required, improved radiation environment predictions can be made for future missions, which in turn allows improved predictions for specific radiation effects for future spacecraft components (single event upsets of microelectronics, radiation damage to focal plane arrays, noise in sensitive instrumentation, etc.). Herein, the status and results from radiation model predictions and comparisons with LDEF data is given. The calculations are made using radiation transport codes coupled with a 3-D geometry/mass model of LDEF, together with current models of the space radiation environment.

Armstrong, T. W.↗
NASA NTRS1997

Portable light source unit for simulating fires having an adjustable aperture

A portable, hand held light source unit is employed to check operation of fire detectors, such as hydrogen fire detectors. The unit emits radiation in a narrow band of wavelengths which are generated by the type of fire to be tested, but not by other light sources such as the sun or incandescent lamps. The unit can test fire detectors at different distances, and of different sensitivities. The intensity of the radiation emitted by the unit is adjustable for this purpose by means of a rotatable disk having a plurality of different sized apertures for selective placement between the light source and an output lens. The disk can also be rotated to a calibration position which causes a microprocessor circuit in the unit to initiate a calibration procedure. During this procedure, the lamp intensity is measured by a photodetector contained within the unit, and the microprocessor adjusts the lamp current to insure that its intensity remains within a preset range of values. A green and a red LED are mounted on the unit which indicate to an operator whether the calibration is successful, as well as the condition of the unit's battery power supply.

Youngquist, Robert C.↗
NASA NTRS1987

Inverse Compton scattering of ambient radiation by a cold relativistic jet - A source of beamed, polarized continuum in blazars?

A general formalism is developed for computing the intensity and polarization of unpolarized radiation scattered by a group of electrons with a specified distribution of momenta. The case of isotropic incident radiation with a power-law spectrum is addressed, and the 'head-on' approximation is developed to describe the nearly unidirectional character of the incident radiation in the electron rest frame. The formalism is implemented numerically, verifying the validity of the 'head-on' approximation and illustrating the polarization and intensity properties of radiation scattered by jets with different electron momentum distribution. The results are placed in an astrophysical setting, determining the optical depths and kinetic energies required for the scattered radiation to dominate over the isotropic component in blazars. It is argued that Comptonization of unbeamed AGN radiation by a relativistic jet can account for the polarization and the overall spectral shape of the IR-optical continuum in blazars.

Begelman, Mitchell C.↗
NASA NTRS1991

Integrated far-infrared background from galaxies

The integrated radiation from galaxies is calculated at far-IR and submillimeter wavelengths. The peak of the far-IR background radiation is 100-130 microns, and its total energy content is 0.5-6 percent of the cosmic microwave background (CMB). At wavelengths longward of 400 microns, the CMB dominates over the far-IR radiation from galaxies in intensity. The autocorrelation of fluctuations from the average angle of the far-IR background of galaxies is calculated. The contribution of galaxies to the anisotropy of the background radiation at wavelengths longer than about 400 microns where the CMB is predominant is obtained. It is found that, in general, earlier galaxy formation predicts stronger far-IR background radiation. The prompt initial enrichment model for the chemical evolution of disk galaxies, in particular those with an exponential star formation rate, produces much larger intensity of the integrated radiation than the accretion model.

Wang, Boqi↗
NASA NTRS1987

Fluorescent excitation of interstellar H2

The infrared emission spectrum of H2 excited by ultraviolet absorption, followed by fluorescence, was investigated using comprehensive models of interstellar clouds for computing the spectrum and to assess the effects on the intensity to various cloud properties, such as density, size, temperature, and the intensity of the UV radiation field. It is shown that the absolute H2 IR line intensities depend primarily on the density of the cloud and the strength of the incident UV radiation, and to a much lesser exent on the temperature of the gas, the total thickness of the cloud, and the optical properties of the grains. A variety of recent observational results are discussed with reference to theoretical models. It is shown that the rich H2 emission spectrum of the reflection nebula NGC 2023 can be reproduced by a model with density of about 10,000/cu cm, temperature of about 80 K, and UV flux approximately 300 times that of the Galactic background starlight.

Black, John H.↗
NASA NTRS1994

Evidence that Jupiter is not the source of the 2-3 kHz heliospheric radiation

It has been suggested that continuum radiation from Jupiter could provide the source for the 2- to 3-kHz radio emissions detected by Voyagers 1 and 2 in the outer heliosphere. By a fortuitous set of circumstances the Ulysses flyby of Jupiter in early 1992 provided an opportunity to compare the intensity of a strong, new heliospheric radio emission event with the intensity of continuum radiation from Jupiter. These comparisons show no evidence that Jupiter is the source of the heliospheric radio emissions.

Gurnett, D. A.↗
NASA NTRS1972

Review of results in infrared space astronomy.

Some stars, in particular, T Tauri stars, have substantial IR excesses at 10 microns. It is now understood that the long wavelength radiation comes from a shell of dust which surrounds the star and absorbs the stellar radiation. Part of the mass which is lost from supergiants is condensed into solid particles which remain in the stellar environment and provide the excess IR radiation. The most intense far-infrared object outside the solar system is the galactic center. Diffuse galactic IR objects include extended regions of gas and dust surrounding very hot young stars and regions of gas and dust surrounding cooler stars. Other subjects considered include IR galaxies and cosmic radiation.

Hoffmann, W. F.↗
NASA NTRS1985

Microwave responses of the western North Atlantic

Features and objects in the Western North Atlantic Ocean - the Eastern Seaboard of the United States - are observed from Earth orbit by passive microwaves. The intensities of their radiated flux signatures are measured and displayed in color as a microwave flux image. The features of flux emitting objects such as the course of the Gulf Stream and the occurrence of cold eddies near the Gulf Stream are identified by contoured patterns of relative flux intensities. The flux signatures of ships and their wakes are displayed and discussed. Metal data buoys and aircraft are detected. Signal to clutter ratios and probabilities of detection are computed from their measured irradiances. Theoretical models and the range equations that explain passive microwave detection using the irradiances of natural sources are summarized.

Stacey, J. M.↗
NASA NTRS2006

Aerosol Indirect Effect Studies at Southern Great Plains During the May 2003 Intensive Operations Period

During May 2003 the Department of Energy's Atmospheric Radiation Measurement Program conducted an Intensive Operations Period (IOP) to measure the radiative effects of aerosol and clouds. A suite of both in situ and remote sensing measurements were available to measure aerosol and cloud parameters. This paper has three main goals: First, it focuses on comparison between in situ retrievals of the radiatively important drop effective radius r(sub e) and various satellite, airborne, and surface remote sensing retrievals of the same parameter. On 17 May 2003, there was a fortuitous, near-simultaneous sampling of a stratus cloud by five different methods. The retrievals of r(sub e) agree with one another to within approx.20%, which is approximately the error estimate for most methods. Second, a methodology for deriving a best estimate of r(sub e) from these different instruments, with their different physical properties and sampling volumes, is proposed and applied to the 17 May event. Third, the paper examines the response of r(sub e) to changes in aerosol on 3 days during the experiment and examines the consistency of remote sensing and in situ measurements of the effect of aerosol on r(sub e). It is shown that in spite of the generally good agreement in derived r(sub e), the magnitude of the response of r(sub e), to changes in aerosol is quite sensitive to the method of retrieving r(sub e) and to the aerosol proxy for cloud condensation nuclei. Nonphysical responses are sometimes noted, and it is suggested that further work needs to be done to refine these techniques.

Feingold, Graham↗
NASA NTRS1952

Radiant heat transfer from flames in a single tubular turbojet combustor / Leonard Topper

An experimental investigation of thermal radiation from the flame of a single tubular turbojet-engine combustor to the combustor liner is presented. The effects of combustor inlet-air pressure, air mass flow, and fuel-air ratio on the radiant intensity and the temperature and emissivity of the flame are reported. The total radiation of the "luminous" flames (containing incandescent soot particles) was much greater (4 to 21 times) than the "nonluminous" molecular radiation. The intensity of radiation from the flame increased rapidly with an increase in combustor inlet-air pressure; it was affected to a lesser degree by variations in fuel-air ratio and air mass flow.

COMBUSTION RESEARCH - GENERAL↗