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Results for “RADIATION INTENSITY”

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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Is photon angular momentum important in molecular collision processes occurring in a laser field

The importance of the rigorous treatment of photon angular momentum in molecular-collision processes occurring in the presence of intense radiation is investigated. An alternate approximate treatment, which essentially neglects the angular momentum coupling between the photon and the molecular degrees of freedom by averaging over the angular dependence of the interaction matrix elements, is presented and applied to a model calculation. The degeneracy-averaged results of this calculation compare remarkably well with the results of a rigorous calculation, from which we conclude (with reservation) that the explicit consideration of photoangular momentum coupling in molecular-collision problems is unnecessary.

Devries, P. L.↗
NASA NTRS1978

Quantum-mechanical theory including angular momenta analysis of atom-atom collisions in a laser field

The problem of two atoms colliding in the presence of an intense radiation field, such as that of a laser, is investigated. The radiation field, which couples states of different electronic symmetry, is described by the number state representation while the electronic degrees of freedom (plus spin-orbit interaction) are discussed in terms of a diabatic representation. The total angular momentum of the field-free system and the angular momentum transferred by absorption (or emission) of a photon are explicitly considered in the derivation of the coupled scattering equations. A model calculation is discussed for the Xe + F collision system.

Devries, P. L.↗
NASA NTRS1978

Analysis of dynamic effects in solar thermal energy conversion systems

The paper examines a study the purpose of which is to assess the performance of solar thermal power systems insofar as it depends on the dynamic character of system components and the solar radiation which drives them. Using a dynamic model, the daily operation of two conceptual solar conversion systems was simulated under varying operating strategies and several different time-dependent radiation intensity functions. These curves ranged from smoothly varying input of several magnitudes to input of constant total energy whose intensity oscillated with periods from 1/4 hour to 6 hours.

Hamilton, C. L.↗
NASA NTRS1980

Radio emission evolution of nonstationary sources in the Hedgehog model

Correlations are obtained for numerical calculation of flux F sub v and polarized radiation intensity of a cloud of arbitrary geometry, consisting of ultrarelativistic electrons that dissipate in a radial magnetic field of the nucleus at a random angle to the observer. It is possible that some of the variable extragalactic objects that were previously described by the Shklovskiy model are young formations in the examined model. Radio astronomical observations would permit a determination of their distance, age, and lifetime.

Kovalev, Y. A.↗
NASA NTRS1980

Global zones of energetic particle precipitation

The paper identifies global zones of energetic particle precipitation in the nighttime atmosphere during disturbed magnetic conditions in rocket, satellite, and ground-based measurements. The known equatorial zone of precipitated energetic ions and neutrals is found at altitudes above 170 km, with its origin in the double-charge-exchange process of hydrogen and helium with the ring current. The flux of electrons increases linearly with altitude in the region 100-300 km and correlates with the 391.4 nm radiation intensity and magnetic activity. Finally, it is shown that the South Atlantic magnetic anomaly provides additional support for the identification of distinct low and mid-latitude zones; poleward from the plasmapause the precipitation flux is nearly isotropic and variable, and it consists of electrons and ions with the maximum intensity of the proton auroral zone occurring about 5 deg equatorward of the maximum of the electron auroral zone.

Voss, H. D.↗
NASA NTRS1979

A technique for evaluating the Jovian entry-probe heat-shield material with a gasdynamic laser

The paper presents a technique for evaluating the Jovian entry-probe heat-shield material with a gasdynamic laser. This entry probe of Project Galileo will incorporate a forebody heat shield of carbon phenolic ablative; at the expected peak radiant intensity of 42 kW/sq cm this material can be evaluated by a CO2 gasdynamic laser. The typically quasigaussian spatial distribution of the laser output beam is converted to a spatially uniform beam by a new optical integrator; the ablation results can be related to the imposed intensity and then to the flight situation with a uniform beam. The tests show that the carbon phenolic tends to spall under intense radiation, and this process is quantified by a particle capture technique.

Dickey, R. R.↗
NASA NTRS1982

Solar Simulator at Marshall Space Flight Center

Solar Simulator is subject of 73-page report. Simulator can establish a variety of conditions that can be set at constant levels over a broad range. Conditions include solar-radiation intensity, spectrum and collimation; solar attitude; and wind speed and direction. Report describes Sun simulator, solar-collector system simulator, overall simulation setup, and instrumentation.

Source record↗
NASA NTRS1981

Design data package and operating procedures for MSFC solar simulator test facility

Design and operational data for the solar simulator test facility are reviewed. The primary goal of the facility is to evaluate the performance capacibility and worst case failure modes of collectors, which utilize either air or liquid transport media. The facility simulates environmental parameters such as solar radiation intensity, solar spectrum, collimation, uniformity, and solar attitude. The facility also simulates wind conditions of velocity and direction, solar system conditions imposed on the collector, collector fluid inlet temperature, and geometric factors of collector tilt and azimuth angles. Testing the simulator provides collector efficiency data, collector time constant, incident angle modifier data, and stagnation temperature values.

Source record↗
NASA NTRS1982

X-ray observations of Abell 2218 and implications for the Sunyaev-Zel'dovich effect

The Einstein Observatory was used to obtain a high-resolution X-ray image and an X-ray flux measurement of the galaxy cluster Abell 2218. The combined system of intracluster medium and galaxies is modeled as a gas in hydrostatic equilibrium in a common gravitational potential with an isothermal galaxy component. This model is then fitted in the least-squares sense to the X-ray surface brightness distribution and to the optically determined galaxy surface density profile to determine model parameters. The gas is found to be nominally isothermal, moderately dense, and very hot (10-30 keV); these conditions are consistent with the Sunyaev-Zel'dovich effect, i.e., the diminution in the cosmic microwave background radiation intensity in the direction of this cluster. It is noted that the considerable imprecision inherent in the method of distance measurement based on the combination of microwave measurements with X-ray and optical data makes it impossible to make a definitive statement about the distance to Abell 2218.

Boynton, P. E.↗
NASA NTRS1982

Radio wave heating of the corona and electron precipitation during flares

Electron-cyclotron masers, excited while energy release is occurring in a flaring magnetic loop, are likely to generate extremely intense radiation at decimeter wavelengths. The energy in the radiation can be comparable with that in the electrons associated with hard X-ray bursts, i.e., a significant fraction of the total energy in the flare. Essentially all of the radio energy is likely to be reabsorbed by gyroresonance absorption, either near the emitting region or at some distance away in neighboring loops. Enhanced diffusion of fast electrons caused by the maser can lead to precipitation at the maximum possible rate, and hence account for hard X-ray emission from the footpoints of the magnetic loops.

Melrose, D. B.↗
NASA NTRS1983

Analytical fuel property effects, small combustors, phase 1

The effects of nonstandard aviation fuels on a typical small gas turbine combustor was analyzed. The T700/CT7 engine family was chosen as being representative of the class of aircraft power plants desired. Fuel properties, as specified by NASA, are characterized by low hydrogen content and high aromatics levels. Higher than normal smoke output and flame radiation intensity for the current T700 combustor which serves as a baseline were anticipated. It is, therefore, predicted that out of specification smoke visibility and higher than normal shell temperatures will exist when using NASA ERBS fuels with a consequence of severe reduction in cyclic life. Three new designs are proposed to compensate for the deficiencies expected with the existing design. They have emerged as the best of the eight originally proposed redesigns or combinations thereof. After the five choices that were originally made by NASA on the basis of competing performance factors, General Electric narrowed the field to the three proposed.

Cohen, J. D.↗
NASA NTRS1983

An electron cyclotron maser instability for astrophysical plasmas

The electron cyclotron maser instability is analyzed for a plasma which consists of a suprathermal electron component characterized by velocity-space anisotropies in directions both parallel and perpendicular to the ambient magnetic field, as well as a high-density thermal plasma in which omega sub e is approximately equal to Omega sub e (where omega sub e and Omega sub e are the electron plasma and cyclotron frequencies). The complete relativistic resonance condition is used and shown to result in a 'resonance ellipse' in momentum space. The instability is considered for both cold and warm suprathermal electron distributions, and for frequencies omega approximately equal to Omega sub e in the ordinary mode and omega approximately equal to 2(Omega sub e) in the fast extraordinary mode. It is shown that the growth rates are comparable for these harmonics over a wide range of parameters which, since they are escape modes of the plasma, can lead to comparable radiation intensities.

Freund, H. P.↗
NASA NTRS1983

Stimulated emission and the flat Balmer decrements of cataclysmic variable stars

Balmer emission lines from cataclysmic variables often have nearly equal intensities rather than the rapid decrement predicted by simple nebular theory. Traditionally, this has been interpreted in terms of local thermodynamic equilibrium emission from a dense gas with small volume located just above the accretion disk. It is shown that the intense radiation field within a close binary system can affect excited state populations and optical emission in ways which allow a relatively low density gas to closely mimic the high density situation. In at least one case, the old nova V603 Aql, the emitting gas has a low density and nearly fills the orbital plane of the system. If this is characteristic of other systems, then the determination of orbital parameters and masses of cataclysmic variables from emission line radial velocities, as well as the prediction of soft X-ray emission from accreting binaries, will be affected.

Elitzur, M.↗
NASA NTRS1984

Design of an orbital heating simulator using IR techniques

The design of an IR rig to supply and monitor radiation fluxes in order to verify a thermal math model is discussed. The design incorporates IR lamps, Calrods and baffles to best suit the requirements of the specific zones. The required fluxes are calculated from the IR lamp/Calrod configuration software which can account for the effect of specular baffles and surface absorptivities. Radiation intensities are measured using the absorbed flux technique. Sensors, with surface properties matched to the appropriate spacecraft zone, are calibrated under conditions identical to test. The rig itself is capable of reproducing all test conditions and is versatile enough to handle other spacecrafts.

Donato, M.↗
NASA NTRS1984

Variable ultraviolet emission in SY Muscae

The results of continued IUE monitoring of the symbiotic variable SY Muscae, following an earlier report of a radical enhancement in UV emission from the star, are reported. Over the course of one year, the prominent emission lines of N V, O V, C IV, and He II appear to be gradually decreasing in absolute intensity. This appears to coincide with a steady decline in electron density in the emission line forming region. The data are consistent with a sudden ejection event in which material expelled from the surface of a hot subdwarf has exposed the underlying UV continuum of the star. A number of strong emission lines that are photoexcited by the intense radiation field of the secondary also exhibit broad pedestal emission that suggests turbulent velocities of about 150-300 km/s in an expanding shell or possibly in an accretion disk.

Michalitsianos, A. G.↗
NASA NTRS1984

Problems of rate chemistry in the flight regimes of aeroassisted orbital transfer vehicles

The dissociating and ionizing nonequilibrium flows behind a normal shock wave are calculated for the density and vehicle regimes appropriate for aeroassisted orbital transfer vehicles; the departure of vibrational and electron temperatures from the gas temperature as well as viscous transport phenomena are accounted for. From the thermodynamic properties so determined, radiative power emission is calculated using an existing code. The resulting radiation characteristics are compared with the available experimental data. Chemical parameters are varied to investigate their effect on the radiation characteristics. It is concluded that the current knowledge of rate chemistry leads to a factor-of-4 uncertainty in nonequilibrium radiation intensities. The chemical parameters that must be studied to improve the accuracy are identified.

Park, C.↗
NASA NTRS1985

Analytical Fuel Property Effects - Small Combustors. Phase II

A test program was conducted to study the effects of non-standard aviation fuels on a typical small gas turbine combustor, and to evaluate the effectiveness of design changes intended to counter the effects of these fuels. This study was a follow on to an earlier analytical study to predict the fuel effects and generate the design modifications evaluated in this program. The T700/CT7 engine family was chosen for both studies as being representative of the class of aircraft power plants desired for this study. Fuel properties, as specified by NASA, are characterized by low hydrogen content and high aromatics levels. No. 2 diesel fuel was also evaluated in this program. The tests demonstrated the anticipated higher than normal smoke output and flame radiation intensity with resulting increased metal temperatures on the baseline T700 combustor. Three new designs were evaluated using the non standard fuels. The three designs incorporated enhanced cooling features and smoke reduction features. All three designs, when burning the broad specification fuels, exhibited metal temperatures at or below the baseline combustor temperatures on JP-5. Smoke levels were acceptable but higher than predicted. This was partly due to the increase in baseline combustor smoke levels with the broad spec fuels being higher than anticipated. One combustor of the three clearly demonstrated the best smoke and metal temperature characteristics. It was also easiest to manufacture and incorporate into a production design. GE with NASA's concurrence selected and subjected this combustor to a final component test program.

Monty, J.↗
NASA NTRS1984

Improvement of the basic knowledge of the climatology of the vertical ozone layer by enhanced balloon sounding

Balloon sounding of the ozone in the Earth atmosphere was performed in order to determine the natural behavior of ozone and its recognizable deviations. The importance of ozone in the Earth atmosphere and the orographic situation of observatories and ozone sounding statistics since 1966 are explained. The physical processes governing the total amount of ozone, and the behavior of stratospheric ozone are described. Measurements in the upper stratosphere show a decrease of the ozone partial pressure above 26 km altitude since 1977. The behavior of tropospheric ozone is discussed. Data since 1977 show increasing ozone values in the troposphere, up to 50% to 70%. This increase is independent of the solar radiation intensity and the reinforced transport of stratospheric ozone into the troposphere. The increase in the troposphere cannot compensate the stratospheric decrease.

Attmannspacher, W.↗