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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 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Apparatus for processing electromagnetic radiation and method

Measuring apparatus including a ruled member having alternate transparent and opaque zones. An optical coupler connecting the ruled member with electromagnetic radiation-conversion apparatus. The conversion apparatus may include a photomultiplier and a discriminator. Radiation impinging on the ruled member will, in part, be converted to electrical pulses which correspond to the intensity of the radiation. A method of processing electromagnetic radiation includes providing a member having alternating dark and light zones, establishing movement of the member through the beam of electromagnetic radiation with the dark zones interrupting passage of radiation through the rule, providing an optical coupler to connect a portion of the radiation with a conversion station where the radiation portion is converted into an electrical pulse which is related to the intensity of the radiation received at the conversion station. The electrical pulses may be counted and the digitized signals stored or permanently recorded to produce positional information.

Gatewood, George D.↗
NASA NTRS1981

The variability of the sun's ultraviolet radiation

Solar UV intensity variations determined by direct irradiance measurements and by measurements of the plage/quiet sun contrast are reviewed. Typical values for the solar UV variability over a solar cycle are: less than 1% at wavelengths longer than 2100 A, 8% at 2080 A (continuum), 20% at 1900 A (continuum), 70% at H Ly alpha, 200% in certain emission lines in the 1200-1800 A range, and more than a factor of 4 in coronal lines at less than 1000 A.

Brueckner, G. E.↗
NASA NTRS2007

System for Thermal Imaging of Hot Moving Objects

The High Altitude/Re-Entry Vehicle Infrared Imaging (HARVII) system is a portable instrumentation system for tracking and thermal imaging of a possibly distant and moving object. The HARVII is designed specifically for measuring the changing temperature distribution on a space shuttle as it reenters the atmosphere. The HARVII system or other systems based on the design of the HARVII system could also be used for such purposes as determining temperature distributions in fires, on volcanoes, and on surfaces of hot models in wind tunnels. In yet another potential application, the HARVII or a similar system would be used to infer atmospheric pollution levels from images of the Sun acquired at multiple wavelengths over regions of interest. The HARVII system includes the Ratio Intensity Thermography System (RITS) and a tracking subsystem that keeps the RITS aimed at the moving object of interest. The subsystem of primary interest here is the RITS (see figure), which acquires and digitizes images of the same scene at different wavelengths in rapid succession. Assuming that the time interval between successive measurements is short enough that temperatures do not change appreciably, the digitized image data at the different wavelengths are processed to extract temperatures according to the principle of ratio-intensity thermography: The temperature at a given location in a scene is inferred from the ratios between or among intensities of infrared radiation from that location at two or more wavelengths. This principle, based on the Stefan-Boltzmann equation for the intensity of electromagnetic radiation as a function of wavelength and temperature, is valid as long as the observed body is a gray or black body and there is minimal atmospheric absorption of radiation.

Weinstein, Leonard↗
NASA NTRS1993

Radiation/convection coupling in rocket motors and plumes

The three commonly used propellant systems - H2/O2, RP-1/O2, and solid propellants - primarily radiate as molecular emitters, non-scattering small particles, and scattering larger particles, respectively. Present technology has accepted the uncoupling of the radiation analysis from that of the flowfield. This approximation becomes increasingly inaccurate as one considers plumes, interior rocket chambers, and nuclear rocket propulsion devices. This study will develop a hierarchy of methods which will address radiation/convection coupling in all of the aforementioned propulsion systems. The nature of the radiation/convection coupled problem is that the divergence of the radiative heat flux must be included in the energy equation and that the local, volume-averaged intensity of the radiation must be determined by a solution of the radiative transfer equation (RTE). The intensity is approximated by solving the RTE along several lines of sight (LOS) for each point in the flowfield. Such a procedure is extremely costly; therefore, further approximations are needed. Modified differential approximations are being developed for this purpose. It is not obvious which order of approximations are required for a given rocket motor analysis. Therefore, LOS calculations have been made for typical rocket motor operating conditions in order to select the type approximations required. The results of these radiation calculations, and the interpretation of these intensity predictions are presented herein.

Farmer, R. C.↗
NASA NTRS1966

Light-intensity modulator withstands high heat fluxes

Mechanism modulates and controls the intensity of luminous radiation in light beams associated with high-intensity heat flux. This modulator incorporates two fluid-cooled, externally grooved, contracting metal cylinders which when rotated about their longitudinal axes present a circular aperture of varying size depending on the degree of rotation.

Maples, H. G.↗
NASA NTRS1990

Proposal for a conceptually new compact collecting optics for powerful light sources

Testing of a spacecraft under simulated outer space conditions is the best guarantee for a successful mission, and for almost all of the parameters a good match (to within a few percent) may be reached in relevant test facilities (e.g., IR background, earthshine and albedo radiation, residual atmosphere, intensity stability, distribution and spectrum of the solar radiation). The collimation angle of the sun (32 arc min) is, however, a drastic exception, here only + or - 1.5 to 2 deg are achieved which means a relative deviation by nearly one order of magnitude. The main reason for this is the presently used collecting optics having unnecessary large diameters. Here a lens-mirror combination is proposed which allows the reduction of the diameter by nearly a factor of two and to achieve with the present Xenon arc lamps a collimation angle of + or - 0.8 deg.

Saenger, G.↗
NASA NTRS2009

Measuring tissue oxygenation

Methods and systems for calculating tissue oxygenation, e.g., oxygen saturation, in a target tissue are disclosed. In some embodiments, the methods include: (a) directing incident radiation to a target tissue and determining reflectance spectra of the target tissue by measuring intensities of reflected radiation from the target tissue at a plurality of radiation wavelengths; (b) correcting the measured intensities of the reflectance spectra to reduce contributions thereto from skin and fat layers through which the incident radiation propagates; (c) determining oxygen saturation in the target tissue based on the corrected reflectance spectra; and (d) outputting the determined value of oxygen saturation.

Soyemi, Olusola O.↗
NASA NTRS1994

Apparent sizes and spectral line profiles for spherical ('three-dimensional') astrophysical masers

Calculations are performed for the frequency-dependent transport of radiation in a uniform spherical maser. Coupling between the intensities at different frequencies is treated. Spherical masers are commonly utilized as idealized geometries in which to assess possible deviations (sometimes, 'three-dimensional effects') from the approximation of a linear geometry. We find that the spectral line profile rebroadens in approximately the same manner as that for a linear maser so that the relationship between the line breadth and the luminosity, beaming angle, and degree of saturation is essentially unchanged. The variation of the apparent size of a spherical maser with frequency is not found to be significant at frequencies within the line profile at which the intensity is appreciable. The 'standard approximation' is adequate for obtaining most of the basic properties of spherical masers that have been examined including the relationship between the pumping (or molecular populations) and the intensity of maser radiation. The improved methods employed here are, however, necessary to obtain variation of the apparent size with frequency in the saturated regime. These conclusions differ from those of previous investigators. The calculations here are more reliable than those of previous investigators because these are self-consistent and avoid certain inaccurate simplifications.

Emmering, Robert T.↗
NASA NTRS1986

IR heating of the cometary atmosphere

The transfer of radiation, solar and IR dust, in the cometary atmosphere is analyzed using a six-band radiative transfer model. The first five bands correlate with the strongest IR band of H2O and the sixth corresponds to the bulk of solar energy. The radiation field for each band is calculated as a function of the cometocentric distance using the three-stream approximation. It is observed that the mean intensity of the IR radiation field generated by the dust and the cometary nucleus drops from a very large value of about 40,000 erg/sq cm sec at the surface to 400 erg/sq cm sec at 7 km, rises to a peak value of 500 erg/sq cm sec at 100 km and then falls off monotonically. The causes of these changes in radiation field intensity are discussed. The effect of variation of the IR radiation field on the gas temperature is studied.

Marconi, M. L.↗
NASA NTRS1977

Simple device measures solar radiation

Simple inexpensive thermometer, insolated from surroundings by transparent glass or plastic encasement, measures intensities of solar radiation, or radiation from other sources such as furnaces or ovens. Unit can be further modified to accomplish readings from remote locations.

Humphries, W. R.↗
NASA NTRS1977

Measurements of the frequency spectrum of transition radiation

We report a measurement of the frequency spectrum of X-ray transition radiation. X rays were generated by electrons of 5 and 9 GeV in radiators of multiple polypropylene foils, and detected in the range 4 to 30 keV with a calibrated single-crystal Bragg spectrometer. The experimental results closely reproduce the features of the theoretically predicted spectrum. In particular, the pronounced interference pattern of multifoil radiators and the expected hardening of the radiation with increasing foil thickness are clearly observed. The overall intensity of the radiation is somewhat lower than predicted by calculations.

Cherry, M. L.↗
NASA NTRS1974

Analysis of the nature of excessive cosmic radiation in the area of the Brazilian magnetic anomaly at altitudes 250-500km, from Kosmos-225 satellite data

Results are presented from a study of the region of anomalous cosmic radiation in the area of the Brazilian magnetic anomaly at the altitudes 250-500 km, using data measurements taken on the Kosmos-225 satellite (14-29 June 1968). The existence of a stable intensity anomaly discovered in the experiments on the second and third Soviet spacecraft-satellites is confirmed. The total vector of the geomagnetic field at different altitudes was compared with isoline maps. An altitude profile of the South Atlantic anomaly of radiation intensity was obtained, using data from the same instrument. The nature of the anomalies in cosmic radiation intensity over the regions of negative magnetic anomalies is discussed.

Raychenko, L. V.↗
NASA NTRS1980

Control of the Earth's electric field intensity through solar wind modulation of galactic cosmic radiation: Support for a proposed atmospheric electrical sun-weather mechanism

The ionospheric potential and galactic cosmic radiation, found to be inversely correlated with the solar wind velocity are examined as being germane to weather modification. Since the ionospheric potential is proportional to the fair weather electric field intensity and cosmic radiation is the dominant source of atmospheric ionization, it is concluded that the Earth's overall electric field varies in phase with atmospheric ionization and that the latter is modulated by the solar wind. A proposed mechanism, in which solar control of ionizing radiation influences atmospheric electrification and thus possibly cloud physical processes is discussed. An experimental approach to critically test the proposed mechanism through comparison of the temporal variation of the Earth's electric field with conditions in the interplanetary medium is outlined.

Markson, R.↗