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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 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

The large scale dust distribution in the inner galaxy

Initial results are presented from a new large-scale survey of the first quadrant of the galactic plane at wavelengths of 160, 260, and 300 microns. The submillimeter wavelength emission, interpreted as thermal radiation by dust grains, reveals an optically thin disk of angular width about 0.09 deg (FWHM) with a mean dust temperature of 23 K and significant variation of the dust mass column density. Comparison of the dust column density with the gas column density inferred from CO survey data shows a striking spatial correlation. The mean luminosity per hydrogen atom is found to be 2.5 x 10 to the -30th W/H, implying a radiant energy density in the vicinity of the dust an order of magnitude larger than in the solar neighborhood. The data favor dust in molecular clouds as the dominant submillimeter radiation source.

Hauser, M. G.↗
NASA NTRS1983

Microwave holographic surface measurement of the Tidbinbilla 64-m antenna

The use of a holographic technique for accurately measuring the surface figure of the Tidbinbilla (Canberra, Australia) 64-m antenna is described. Described by Bennet et al. (1976) and Scott and Ryle (1977), the technique consists of measuring the complex far-field response of the antenna at a single frequency using a terrestrial, satellite-borne or celestial radiation source of small angular diameter. This two-dimensional pattern is then Fourier transformed to yield the complex illumination function across the antenna aperture; antenna surface deviations are manifested as phase fluctuations in this function. The speed and low cost of using the technique are real advantages where observing schedules with the telescopes are heavily subscribed. For the 64-m antenna, the unweighted rms surface deviation is found to be about 1.8 mm; when weighted by the radial amplitude taper it is about 1.1 mm. Two earlier estimates by other methods had yielded tolerances of about 1.2 mm rms and 1.1 mm rms. It is planned to use the technique to survey the 22-m antennas of the Australian Telescope accurate to approximately 0.1 mm rms near 10 Ghz.

Rahmat-Samii, Y.↗
NASA NTRS1984

Technology for satellite power conversion

Techniques for satellite electromagnetic energy transfer and power conversion at millimeter and infrared wavelengths are discussed. The design requirements for rectenna receiving elements are reviewed for both coherent radiation sources and Earth thermal infrared emission. Potential power transmitters including gyrotrons, free electron lasers, and CO2 lasers are assessed along with the rectification properties of metal-oxide metal diode power converters.

Campbell, D. P.↗
NASA NTRS1984

Observed Spatial Properties of the Solar Eigenfunctions and the Implications for the Existence of Resolved Multiplets

Solar oscillations are manifested in the solar atmosphere as spatial and temporal perturbations in the local thermodynamical and mechanical properties. When measuring the solar radius/diameter, these perturbations enter the observation through changes in the radiative source function and opacity at the extreme limb. When compared to the disk center, the observable portion of these perturbations is changed in spatial character by projection effects and oblique optical depth geometry. The time varying solar radius signal at SCLERA (Santa Catalina Laboratory for Experimental Relativity) is produced by an edge definition sensitive to the resultant changes in the spatial shape of the limb intensity profile. An attempt is made to further determine the shape and properties of the limb signals which display global solar oscillations.

Caudell, T. P.↗
NASA NTRS1983

Heterodyne applications of tunable semiconductor diode lasers

Infrared tunable diode lasers were developed in the 1960s and have been a valuable radiation source for high resolution laboratory and in situ spectroscopy. Use of Pb-salt Tunable Diode Lasers (TDL) in heterodyne applications impose stringent requirements on the TDL not normally required for laboratory spectroscopy. A review will be made of progress associated with TDLs in such heterodyne applications. Areas addressed will include such items as lifetime, operating temperature, and factors affecting excess noise. The review will emphasize the experience at Langley Research Center, but will include material from other users. The Langley information will include a description and current status of the Laser Heterodyne Spectrometer experiment and atmospheric solar absorption data obtained from a groundbased heterodyne system.

Sidney, B. D.↗
NASA NTRS1985

Mechanisms of transmission and control of low-frequency sound in aircraft interiors

A simplified analytical model is used to study the principal mechanisms at work in propeller noise source radiation, fuselage response, and the behavior of the coupled inner acoustic field, in order to control low frequency sound in aircraft interiors. Both active and passive methods of noise control are comparatively evaluated in light of the transmission mechanisms. Fuselage vibrational response is noted to be dominated by only a few lower order circumferential modes.

Fuller, C. R.↗
NASA NTRS1983

Transient thermal modeling of the nonscanning ERBE detector

A numerical model to predict the transient thermal response of the ERBE nonscanning wide field of view total radiometer channel was developed. The model, which uses Monte Carlo techniques to characterize the radiative component of heat transfer, is described and a listing of the computer program is provided. Application of the model to simulate the actual blackbody calibration procedure is discussed. The use of the model to establish a real time flight data interpretation strategy is recommended. Modification of the model to include a simulated Earth radiation source field and a filter dome is indicated.

Mahan, J. R.↗
NASA NTRS1985

Effects of high energy radiation on the mechanical properties of epoxy-graphite fiber reinforced composites

In an effort to elucidate the changes in molecular structural and mechanical properties of epoxy/graphite fiber composites upon exposure to ionizing radiation in a simulated space environment, spectroscopic and surface properties of tetraglycidyl-4,4'-diamino diphenyl methane (TGDDM) red with diamino diphenyl sulfone (DDS) and T-300 graphite fiber were investigated following exposure to ionizing radiation. Cobalt-60 gamma radiation and 1/2 MeV electrons were used as radiation sources. The system was studied using electron spin resonance (ESR) spectroscopy, infrared absorption spectroscopy, contact angle measurements, and electron spectroscopy for chemical analysis.

Fornes, R. E.↗
NASA NTRS1986

Middle Atmosphere Program. Handbook for MAP, volume 19

This MAP handbook is concerned with rocket techniques and instrumentation as they are currently employed in the middle atmosphere. It is composed of nine chapters, written by experts on rocket experiments. The emphasis is on measurement techniques rather than results, although results are incorporated wherever they provide examples which illustrate the measurement features. The chapters first cover techniques relating to measurements of neutral dynamics and chemistry, then measurements of the various intermittent and excessive radiation sources which effect the middle atmospheric environment, and finally measurements of the plasma environment including electric fields. The weighting toward plasma related parameters is not accidental, but reflects both the historical headstart given by early development of radio wave and probe techniques to measure electron density, and by the relatively limited number of techniques available for neutral atmospheric measurements.

Goldberg, R. A.↗
NASA NTRS1985

Observation of atmospheric minor constituents by FTIR at Syowa Station, Antarctica

As a part of the Antarctic MAP activity, a ground-based spectroscopic observation of atmospheric infrared transmission was started at Syowa station (69 deg 00'S, 39 deg 35'E) in March 24, 1983. Observations of sunlight as a radiation source were made with a Fourier transform infrared spectrometer having a maximum path difference of 80 mm and an apodized FWHM resolution of approx. 0.12/cm. In routine operation through the year, the resolution of approx. 0.8/cm was applied for economy of data-processing time. The 408 spectra for 72 days were obtained in about 10 months until January 23, 1984. From the absorption features revealed in the spectra over the wave number range of 500 to 7500/cm, a preliminary estimate of N202 gamma sub 1 band absorption was attempted. An apparent transmittance was defined at the wave number 2576/cm, where the absorption by N20 molecules affected the observed intensity strongly. A ray-tracing technique and a line-by-line calculation with a model atmosphere and the AFGL atmospheric absorption line parameters compilation were applied to the calculation of the synthetic spectra.

Makino, Y.↗
NASA NTRS1986

Feasibility of a nuclear gauge for fuel quantity measurement aboard aircraft

Capacitance fuel gauges have served as the basis for fuel quantity indicating systems in aircraft for several decades. However, there have been persistent reports by the airlines that these gauges often give faulty indications due to microbial growth and other contaminants in the fuel tanks. This report describes the results of a feasibility study of using gamma ray attenuation as the basis for measuring fuel quantity in the tanks. Studies with a weak Am-241 59.5-keV radiation source indicate that it is possible to continuously monitor the fuel quantity in the tanks to an accuracy of better than 1 percent. These measurements also indicate that there are easily measurable differences in the physical properties and resultant attenuation characteristics of JP-4, JP-5, and Jet A fuels. The experimental results, along with a suggested source-detector geometrical configuration are described.

Signh, J. J.↗
NASA NTRS1985

1985 Annual Conference on Nuclear and Space Radiation Effects, 22nd, Monterey, CA, July 22-24, 1985, Proceedings

Basic mechanisms of radiation effects in structures and materials are discussed, taking into account the time dependence of interface state production, process dependent build-up of interface states in irradiated N-channel MOSFETs, bias annealing of radiation and bias induced positive charges in n- and p-type MOS capacitors, hole removal in thin-gate MOSFETs by tunneling, and activation energies of oxide charge recovery in SOS or SOI structures after an ionizing pulse. Other topics investigated are related to radiation effects in devices, radiation effects in integrated circuits, spacecraft charging and space radiation effects, single-event phenomena, hardness assurance and radiation sources, SGEMP/IEMP phenomena, EMP phenomena, and dosimetry and energy-dependent effects. Attention is given to a model of the plasma wake generated by a large object, gate charge collection and induced drain current in GaAs FETs, simulation of charge collection in a multilayer device, and time dependent dose enhancement effects on integrated circuit transient response mechanisms.

Jones, C. W.↗
NASA NTRS1987

High-Rydberg Xenon Submillimeter-Wave Detector

Proposed detector for infrared and submillimeter-wavelength radiation uses excited xenon atoms as Rydberg sensors instead of customary beams of sodium, potassium, or cesium. Chemically inert xenon easily stored in pressurized containers, whereas beams of dangerously reactive alkali metals must be generated in cumbersome, unreliable ovens. Xenon-based detector potential for infrared astronomy and for Earth-orbiter detection of terrestrial radiation sources. Xenon atoms excited to high energy states in two stages. Doubly excited atoms sensitive to photons in submillimeter wavelength range, further excited by these photons, then ionized and counted.

Chutjian, Ara↗
NASA NTRS1987

Gamma-Ray Fuel Gauges for Airplanes

Accurate system overcomes problems of capacitance gauges. Feasibility study conducted on use of attenuation of gamma rays to measure quantities of fuel in tanks. Studies with weak Am241 59.5-keV radiation source indicate it is possible to monitor continuously fuel quantity in tanks to accuracy of better than 1 percent. Measurements also indicate easily measurable differences in physical properties and resultant attenuation characteristics of JP-4, JP-5, and Jet A fuels. Am241-based densitometers currently in use aboard some aircraft . Estimated complete system, including microprocessor and associated display devices, assembled at cost of less than $10,000 per fuel tank.

Singh, Jag J.↗
NASA NTRS1986

Radiation environment and shielding for early manned Mars missions

The problem of shielding a crew during early manned Mars missions is discussed. Requirements for shielding are presented in the context of current astronaut exposure limits, natural ionizing radiation sources, and shielding inherent in a particular Mars vehicle configuration. An estimated range for shielding weight is presented based on the worst solar flare dose, mission duration, and inherent vehicle shielding.

Hall, Stephen B.↗
NASA NTRS1987

High resolution infrared spectroscopy from space: A preliminary report on the results of the Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment on Spacelab 3

The ATMOS (Atmospheric Trace Molecule Spectroscopy) experiment has the broad purpose of investigating the physical structure, chemistry, and dynamics of the upper atmosphere through the study of the distributions of the neutral minor and trace constituents and their seasonal and long-term variations. The technique used is high-resolution infrared absorption spectroscopy using the Sun as the radiation source, observing the changes in the transmission of the atmosphere as the line-of-sight from the Sun to the spacecraft penetrates the atmosphere close to the Earth's limb at sunrise and sunset. During these periods, interferograms are generated at the rate of one each second which yield, when transformed, high resolution spectra covering the 2.2 to 16 micron region of the infrared. Twenty such occultations were recorded during the Spacelab 3 flight, which have produced concentration profiles for a large number of minor and trace upper atmospheric species in both the Northern and Southern Hemispheres. Several of these species have not previously been observed in spectroscopic data. The data reduction and analysis procedures used following the flight are discussed; a number of examples of the spectra obtained are shown, and a bar graph of the species detected thus far in the analysis is given which shows the altitude ranges for which concentration profiles were retrieved.

Farmer, Crofton B.↗
NASA NTRS1986

The electron-cyclotron maser instability as a source of plasma radiation

The generation of continuum bursts from the sun at dm and m wavelengths (in particular, type IV bursts) via the electron-cyclotron-maser instability is examined. The maser instability can be driven by an electron distribution with either a loss-cone anisotropy or a peak at large pitch angles. For omega(p)/Omega(e) much greater than 1, the maser emission is produced by electrons interacting through a harmonic (cyclotron) resonance and is electrostatic, being in the upper hybrid mode at frequencies approximately equal to omega(p). Coalescence processes are required to convert the electrostatic waves into transverse radiation which can escape from the source region. Whether the resultant spectrum is nearly a smooth continuum or has a zebra-stripe pattern (both of which occur in type IV bursts) depends on the form of the electron distribution, inhomogeneities in the density and magnetic field, and whether the maser reaches saturation. For at least the case of some type IV dm bursts with fine structure, comparison with observations seems to indicate that the electrons producing the emission are more likely to have a loss-cone distribution, and that the maser instability is not at saturation.

Winglee, R. M.↗