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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Long term spectral irradiance measurements of a 1000-watt xenon arc lamp

Spectral irradiance measurements over the range of 200 to 1060 nm were made on a 1000-watt xenon arc lamp over a period of 1500 hours. Four sets of measurements were made after periods of 70, 525, 1000, and 1500 hours of operation. The lamp (Hanovia Compact Xenon Arc Lamp) was mounted in the NASA Solar Irradiation System. When used in the System, the lamp is used as the radiating source for six test stations. Measurements were made of both the longterm stability (or variation of spectral irradiance as a function of time) and the actual spectral irradiance incident on the test specimen.

Schneider, W. E.↗
NASA NTRS1974

On the irradiation history and origin of gas-rich meteorites

Transmission electron microscope study of the track density gradients and irradiation geometries of track-rich grains and chondrules in sections of Fayetteville and Kapoeta, and in sections of lunar breccias and grains from lunar soil. A substantial fraction (50 to 90%) of the meteoritic track-rich grains and chondrules show evidence of having been irradiated anisotropically in their different faces, as would be expected for irradiation on the surface of a parent body. The observations thus support the hypothesis that the irradiation of these grains and chondrules took place on the regoliths of asteroidal-sized bodies. Measurements of steepest track density gradients indicate that, while there are finite differences between spectra exhibited by individual gas-rich meteorites, the average solar flare spectral shapes have been similar over the last 4 b.y. or so.

Rajan, R. S.↗
NASA NTRS1975

Irradiation and measurements of fluorinated ethylene-propylene-A on silicon solar cells in vacuum

Silicon monoxide (SiO) coated silicon solar cells covered with fluorinated ethylene-propylene-A (FEP-A) were irradiated by 1-MeV electrons in vacuum. The effect of irradiation on the light transmittance of FEP-A was checked by measuring the short-circuit current of the cells while in vacuum after each dose increment, immediately after the irradiation, and again after a minimum elapsed time of 16 hr. The results indicated no apparent loss in transmission due to irradiation of FEP-A and no delamination from the SiO surface while the cells were in vacuum, but embrittlement of FEP-A occurred at the accumulated dose.

Marsik, S. J.↗
NASA NTRS1975

The total and spectral solar irradiance and its possible variations

The present status of knowledge of the total and spectral irradiance of the sun is briefly reviewed. Currently accepted values of the solar constant and the extraterrestrial solar spectral irradiance are presented along with a discussion of how they were derived. Data on the variability of the solar constant are shown to be conflicting and inconclusive. Some of the alleged sun-weather relationships are cited in support of the need of knowing more precisely the variations in total and spectral solar irradiance. An overview of a solar monitoring program is discussed, with special emphasis on the Solar Energy Monitor in Space experiment which was proposed for several spacecraft missions. It is a combination of a solar constant detector and a prism monochromator. The determination of absolute values and the possible variations of the total and spectral solar irradiance, from measurements outside of the atmosphere is discussed.

Thekaekara, M. P.↗
NASA NTRS1975

Effect of electron irradiation in vacuum on FEP-A silicon solar cell covers

The effect of irradiation on the light transmittance of ethylene-propylene-A (FEP-A) was investigated by measuring the short-circuit current of the cells after each of several electron dose increments, immediately after total irradiation, and 16 hours after total irradiation. Results indicated no apparent overall loss in transmission due to irradiation of FEP-A. However, filter wheel measurements revealed a 'darkening' of the FEP-A at the blue end of the spectrum. Some embrittlement of the FEP-A occurred at an accumulated dose of 67,500,000 rads.

Marsik, S. J.↗
NASA NTRS1975

Alteration of an annealed and irradiated lunar fines sample by adsorbed water

Apollo 12 lunar fines sample 12070,403 was annealed at 1000 C and subsequently irradiated with a beam of 130 MeV Fe(9+) ions. Adsorptions of nitrogen and water were measured before and after the irradiation. Prior to the irradiation, the fines were nonporous and water had no effect on the physical characteristics of the lunar fines. In contrast, after the irradiation, the interaction with water caused an increase in the specific surface area and created a pore system. These results are definitive evidence that the interaction of water with damage tracks is the prime factor involved in the alteration of lunar fines by adsorbed water.

Holmes, H. F.↗
NASA NTRS1976

Solar irradiance - Total and spectral and its possible variations

The present status of our knowledge of the total and spectral irradiance of the sun is briefly reviewed. The currently accepted NASA/ASTM standard values of the solar constant and the extraterrestrial solar spectral irradiance are presented. The uncertainties in these values are relatively high. Data on the variability of the solar constant are conflicting and inconclusive. The variability of solar spectral irradiance is almost totally unknown and unexplored. Some alleged sun-weather relationships are cited in support of the need to know more precisely the variations in total and spectral solar irradiance. An overview of the solar monitoring program of NASA is presented, with special emphasis on the Solar Energy Monitor in Space (SEMIS) experiment which has been proposed for several spacecraft missions. The monitor is a combination of a solar-constant detector and a prism monochromator.

Thekaekara, M. P.↗
NASA NTRS1976

Effects of neutron irradiation on the characteristics of a buried channel CCD at 80 degrees Kelvin and 295 degrees Kelvin

Buried channel CCD shift registers were irradiated with 15 MeV neutrons. The irradiations were performed at 80 K and 295 K on operating devices with normal clocks and bias voltages applied. Dark current increased from the pre-irradiation value of 7 nA/sq cm to 1,600 nA/sq cm at 1 x 10 to the 13th power n/sq cm. The input gate threshold shift observed at 80K was minus 0.9 volts per 10 to the 13th power n/sq cm, a factor of 4 less than that predicted from a first order calculation of the equivalent ionization dose of neutrons in the oxide. Transfer efficiency measurements yielded a bulk electron trap creation rate for neutron irradiation of 14.0 cm to the minus 1 power at 295 K with a trap emission time constant of 25 microseconds.

Saks, N. S.↗
NASA NTRS1978

A local proton irradiation model for isotopic anomalies in the solar system

An attempt is made to explain the O-16 and Al-26 anomalies observed in solar-system bodies in the framework of a local irradiation model wherein a small amount of solar system matter of normal isotopic composition was irradiated by energetic protons from the primeval sun. Several isotopic constraints are summarized with which the model should be consistent, and a proton energy distribution and fluence and a target elemental composition are chosen such that the extraordinary component produced by irradiation satisfies the constraints. Detailed attention is given to the relevant oxygen reactions, Al-26 production, and effects of proton irradiation on isotopes of Mg, Ca, and Ba. A scenario is outlined which satisfies all the constraints. Consequences of the model are discussed with respect to the isotopic anomalies observed in Allende inclusions.

Lee, T.↗
NASA NTRS1978

Effect of ultrasonic irradiation on mammalian cells and chromosomes in vitro

Human peripheral blood and HeLa cells were irradiated in vitro at the ultrasonic frequency of 65 kHz. The whole blood and HeLa cell suspensions were exposed to continuous and pulsed ultrasonic power levels of 0.12, 0.16, 0.72, 1.12 and 2.24 W for a period of one minute. The method of ultrasonic irradiation was carried out with the whole blood or HeLa cell suspensions coupled directly to a cylindrical transducer while heating of the cell suspensions in excess of 41 C was avoided. Irradiated and unirradiated peripheral blood lymphocyte chromosome cultures were prepared and scored for selected numerical and morphological aberrations. There was no significant difference in the frequency of chromosomal aberrations between irradiated and unirradiated cells.

Roseboro, J. A.↗
NASA NTRS1981

The nature of compensatory and restorative processes in the livers of animals irradiated during hypokinesia

The nature of postirradiation repair in the livers of rats irradiated during hypokinesia is investigated. Hepatocyte population counts, mitotic activity, binuclear cell content, and karyometric studies were done to ascertain the effects of combined hypokinesia and radiation. Hypokinesia is shown to change the nature and rate of post-irradiation changes in the liver, the effect varying with the timing of irradiation relative to the length of hypokinesia. It is concluded that the changes in the compensatory and restorative processes are caused by stress developed in response to isolation and restricted mobility. By changing neuroendocrine system activity, the stress stimulates cell and tissue repair mechanisms at a certain stage essential to the body's reaction of subsequent irradiation.

Chernov, I. P.↗
NASA NTRS1981

Electrostatic discharging behaviour of Kapton irradiated with electrons

The electrostatic charging and discharging of Kapton when irradiated with monoenergetic electrons of 5 to 30 keV energy were studied. The leakage currents and rates of discharging always increased with the incident electron energy and flux, whereas the surface voltage showed a more complex behavior depending on the thickness of the material: for the thinner films it exhibited a maximum and then fell at higher energies. The surface voltage, the rate of discharging, and the peak current and total charge flow during a discharge were enhanced as the temperature was decreased from 70 C to -180 C, and were accompanied by a decreasing leakage current. Visible light or the presence of an aluminum coating on the irradiated surface caused reductions in the surface voltage and changes in the discharging characteristics. The results are discussed in terms of the leakage currents and the secondary emission of electrons. Photomicrographs taken after irradiation, and photographs of samples during irradiation, show good correlations between the positions of light flashes and of pinholes produced by the discharge arcs.

Verdin, D.↗
NASA NTRS1982

Solar irradiance modulation by active regions from 1969 through 1980

The solar irradiance variations resulting from sunspot deficits and facular excesses in emission have been calculated from 1969 through 1980. Agreement appears to exist between the calculations and the major features seen with the Nimbus 7 cavity pyrheliometer and with both the major and minor features detected by the Solar Maximum Mission ACRIM experiment. The 12-year irradiance variations calculated suggest a larger variance with increased solar activity, and little change in the average irradiance with solar activity. The largest excursions over these 12 years show a 0.4% variation. Removal of the activity influences upon solar irradiance during the numerous rocket experiments observing the solar constant may allow a better value for this quantity to be determined.

Schatten, K. H.↗
NASA NTRS1982

A technique for determining solar irradiance deficits

An analytic technique which determines the variation of solar irradiance from long term averages is presented. The technique involves computer-assisted data reduction techniques, and was designed to improve system reliability by determining the amount of storage capability required to supplement a baseline system. Variations in time intervals of up to 60 days can be determined, and 10 years of data collection are reviewed. The technique involves first calculating average monthly irradiance values, then examining the average irradiance deviation over time intervals. The calculation procedure is clarified by determining solar energy level probabilities and the long term solar energy deviation (achieved by repeatedly integrating actual irradiance figures). It is found that a 15% increase in collector area and the addition of energy storage or backup are essential contributions to achieving cost-effectiveness. In addition, one to seven no-sun day storage capacities are required to accommodate weather caused deficits.

Gonzalez, C. C.↗
NASA NTRS1982

Defects and annealing studies in 1-Me electron irradiated (AlGa)As-GaAs solar cells

The deep-level defects and recombination mechanisms in the one-MeV electron irradiated (AlGa)As-GaAs solar cells under various irradiation and annealing conditions are discussed. Deep-level transient spectroscopy (DLTS) and capacitance-voltage (CV) techniques were used to determine the defect and recombination parameters such as energy levels and defect density, carrier capture cross sections and lifetimes for both electron and hole traps as well as hole diffusion lengths in these electron irradiated GaAs solar cells. GaAs solar cells used in this study were prepared by the infinite solution melt liquid phase epitaxial (LPE) technique at Hughes Research Lab., with (Al0.9Ga0.1)-As window layer, Be-diffused p-GaAs layer on Sn-doped n-GaAs or undoped n-GaAs active layer grown on n(+)-GaAs substrate. Mesa structure with area of 5.86x1000 sq cm was fabricated. Three different irradiation and annealing experiments were performed on these solar cells.

Li, S. S.↗
NASA NTRS1983

The measurement of solar spectral irradiances at wavelengths between 40 and 4000 A

Two 1/8-meter Ebert-Fastie spectrometers were refurbished and upgraded in order to measure the solar spectral irradiances between 1160 A and 3100 A. An evacuated 1/4-meter normal-incidence spectrometer was also fabricated for spectral irradiance measurements over the wavelength range from 1250 A to 250 A. Procedures were developed for the calibration of all three instruments utilizing standards at the National Bureau of Standards. The two 1/8-meter spectrometers were flown to measure the solar spectral irradiances near solar maximum on two different dates. Data from these flights were analyzed. The performance of the spectrometers, and the results of an analysis of the variabilities of the solar spectral irradiances over the solar cycles 20 and 21 are discussed.

Timothy, J. G.↗
NASA NTRS1983

Data on total and spectral solar irradiance

This paper presents a brief survey of the data available on solar constant and extraterrestrial solar spectral irradiance. The spectral distribution of solar radiation at ground surface, computed from extraterrestrial solar spectral irradiance for several air mass values and for four levels of atmospheric pollution, is also presented. The total irradiance at ground level is obtained by integration of the area under the spectral irradiance curves. It is significant that, as air mass increases or as turbidity increases, the amount of energy in the infrared relative to the total increases and that the energy in the UV and visible decreases.

Mecherikunnel, A. T.↗
NASA NTRS1984

Solar Total Irradiance Variability Measurements by the SMM/ACRIM I Experiment

Convincing evidence of solar total irradiance variability and its relationships with solar activity was provided by the Active Cavity Radiometer Irradiance Monitor I (ACRIM I) experiment on the NASA Solar Maximum Mission (SMM). SMM/ACRIM I, the first flight experiment dedicated to the task of solar irradiance monitoring, has produced a multiyear solar total irradiance data base with + or - 0.02% or better long term precision since its launch in February, 1980. While the climatological significance of the results will not be apparent until many more years of continuous data are acquired, the discovery of variability on solar active region time scales has provided new insight into the physics of solar activity in the early years of the mission.

Willson, R. C.↗