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  • 1
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    Interactions of satellite-speed helium atoms with satellite surfaces. 2: Energy distributions of reflected helium atoms (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Energy transfer in collisions of satellite-speed (7,000 m/sec) helium atoms with a cleaned 6061-T6 satellite-type aluminum surface was investigated using the molecular-beam technique. The amount of energy transferred was determined from the measured energy of the molecular-beam and the measured spatial and energy distributions of the reflected atoms. Spatial distributions of helium atoms scattered from a 6061-T6 aluminum surface were measured. The scattering pattern exhibits a prominent backscattering, probably due to the gross surface roughness and/or the relative lattice softness of the aluminum surface. Energy distributions of reflected helium atoms from the same surface were measured for six different incidence angles. For each incidence angle, distributions were measured at approximately sixty scattering positions. At a given scattering position, the energy spectra of the reflected helium atoms and the background gas were obtained using the retarding-field energy analyzer.
    Keywords: ATOMIC AND MOLECULAR PHYSICS
    Type: NASA-CR-147227 , UCLA-ENG-7638
    Format: application/pdf
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  • 2
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    Interactions of satellite-speed helium atoms with satellite-surfaces. 1: Spatial distributions of reflected helium atoms (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Interactions of satellite-speed helium atoms with practical satellite surfaces were investigated experimentally, and spatial distributions of satellite-speed helium beams scattered from four different engineering surfaces were measured. The 7000 m/sec helium beams were produced using an arc-heated supersonic molecular beam source. The test surfaces included cleaned 6061-T6 aluminum plate, anodized aluminum foil, white paint, and quartz surfaces. Both in-plane (in the plane containing the incident beam and the surface normal) and out-of-plane spatial distributions of reflected helium atoms were measured for six different incidence angles (0, 15, 30, 45, 60, and 75 deg from the surface normal). It was found that a large fraction of the incident helium atoms were scattered back in the vicinity of the incoming beam, particularly in the case of glancing incidence angles. This unexpected scattering feature results perhaps from the gross roughness of these test surfaces. This prominent backscattering could yield drag coefficients which are higher than for surfaces with either forward-lobed or diffusive (cosine) scattering patterns.
    Keywords: ATOMIC AND MOLECULAR PHYSICS
    Type: NASA-CR-143111 , UCLA-ENG-7546
    Format: application/pdf
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  • 3
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    Possible variations in atmospheric methane (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A model coupling photochemistry and vertical transport in the troposphere has been used to investigate the magnitude of possible future perturbations to atmospheric CH4. The response of atmospheric CH4 to an increase in the concentration of CO or to a variation in stratospheric O3 is studied. Both of the above mechanisms, which could be caused by man's activities, arise because a change in the concentration of tropospheric OH will lead to a change in the CH4 abundance. The calculations imply that a perturbation of about 30-40% in atmospheric CH4 could occur if stratospheric O3 were perturbed by 10% or if man-made CO continued to increase. The possible consequences of a CH4 perturbation may entail a perturbation in stratospheric photochemistry or in the thermal balance of the atmosphere.
    Keywords: ENVIRONMENT POLLUTION
    Type: Journal of Geophysical Research; 82; Apr. 20
    Format: text
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  • 4
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    Effect of odd hydrogen on ozone depletion by chlorine reactions (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The present paper discusses how the shape of the ozone layer changes under the influence of injected ClX for several choices of two key HOx reaction rates. The two HOx reactions are: OH + HO2 yields H2O + O2 and O + HO2 yields OH + O2. Results of calculations are presented which show that the two reaction rates determine the stratospheric concentrations of OH and HO2, and that these concentrations regulate the amount by which the stratospheric ozone column can be reduced due to injections of odd chlorine. It is concluded that the amount of ozone reduction by a given mixing ratio of ClX will remain very uncertain until the significance of several possible feedback effects involving HOx in a chlorine-polluted atmosphere are determined and measurements of the reaction rates and HOx concentrations are made at the relevant temperatures.
    Keywords: ENVIRONMENT POLLUTION
    Type: Geophysical Research Letters; 3; Feb. 197
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  • 5
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    Sources and sinks of atmospheric N2O and the possible ozone reduction due to industrial fixed nitrogen fertilizers (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The terrestrial and marine nitrogen cycles are examined in an attempt to clarify how the atmospheric content of N2O is controlled. We review available data on the various reservoirs of fixed nitrogen, the transfer rates between the reservoirs, and estimate how the reservoir contents and transfer rates can change under man's influence. It is seen that sources, sinks and lifetime of atmospheric N2O are not understood well. Based on our limited knowledge of the stability of atmospheric N2O we conclude that future growth in the usage of industrial fixed nitrogen fertilizers could cause a 1% to 2% global ozone reduction in the next 50 years. However, centuries from now the ozone layer could be reduced by as much as 10% if soils are the major source of atmospheric N2O.
    Keywords: ENVIRONMENT POLLUTION
    Type: Tellus; 29; June 197
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  • 6
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    Researches on interactions of satellite-speed helium atoms with aluminum and quartz surfaces (1976)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Three major areas were experimentally studied: (1) energy transfer in collisions of satellite-speed (700 m/sec) helium atoms with a cleaned satellite-type aluminum surface was investigated using the molecular-beam technique. Spatial and energy distributions of reflected helium atoms were measured and analyzed, (2) The gross accommodation coefficient for a satellite-speed (7000 m/sec) helium beam entering a 2-inch-diameter aluminum spherical cavity was determined by measuring the exit velocity distribution of the leaving helium atoms using a metastable time-of-flight method. Results indicate that the 7000-m/sec satellite-speed helium atoms entering the cavity gain full accommodation with the room-temperature inner surface of the sphere through a large number of collisions before leaving the spherical cavity; and (3) the feasibility of producing a satellite-speed atomic hydrogen beam by arc-heating, for use in studies of interactions of satellite-surfaces with hydrogen atoms under laboratory conditions, was investigated. It was found that a stable arc-heated molecular hydrogen beam can be obtained using the arc-heater, and that a partially dissociated hydrogen beam can be produced. Photographs of laboratory equipment are shown.
    Keywords: ATOMIC AND MOLECULAR PHYSICS
    Type: NASA-CR-146657
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  • 7
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    Effect of chlorofluoromethane infrared radiation on zonal atmospheric temperatures (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Estimates are made of changes in the atmospheric climate due to the radiative effects of 10 ppb of chlorofluoromethanes (CFM's). The estimates are derived on the basis of a 12-layer stratospheric general circulation model with a specified change of ocean temperature. Two tropical maxima in zonal average temperature change were observed: one in the upper troposphere and one centered at the tropopause. The temperature change exceeds the surface temperature change by a factor of at least two. If the 1975 CFM emission rate were to continue indefinitely, stratospheric water-vapor concentrations would increase by up to 60% due to CFM radiative effects. This would reduce ozone concentrations by an additional 4% of the natural ozone column.
    Keywords: ENVIRONMENT POLLUTION
    Type: Journal of the Atmospheric Sciences; 35; Nov. 197
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  • 8
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    Effect of water vapor on the destruction of ozone in the stratosphere perturbed by ClX or NOx pollutants (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Results are presented for a self-consistent one-dimensional coupled flow calculation for Ox, NOx, HOx, ClX, H2O, H2, CH4, H2O2, and N2O densities between 10 and 120 km. The results agree well with observations for the normal midlatitude atmosphere over this altitude range. ClX, NOx, and H2O are varied independently in the model considered. It is shown that the effect of depletion of ozone by ClX is to remove ozone preferentially above 30 km and to lower the altitude of maximum ozone density. This leads to enhanced solar heating of the lower stratosphere and tropopause and suggests the possibility of an increased flux of water into the stratosphere. Increasing water vapor in the stratosphere greatly enhances the rate of destruction of O3 by ClX and also causes an increase in the rate of destruction of O3 in the NOx-perturbed atmosphere.
    Keywords: ENVIRONMENT POLLUTION
    Type: Journal of Geophysical Research; 81; June 20
    Format: text
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