Solar dynamic concentrator durability in atomic oxygen and micrometeoroid environments
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Gulino, Daniel A.↗
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Atomic-oxygen durability of impact-damaged solar reflectors
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Gulino, Daniel A.↗
The divergence characteristics of constrained-sheath optics systems for use with 5-eV atomic oxygen sources
The potential usefulness of the constrained sheath optics concept as a means of controlling the divergence of low energy, high current density ion beams is examined numerically and experimentally. Numerical results demonstrate that some control of the divergence of typical ion beamlets can be achieved at perveance levels of interest by contouring the surface of the constrained sheath properly. Experimental results demonstrate that a sheath can be constrained by a wire mesh attached to the screen plate of the ion optics system. The numerically predicted beamlet divergence characteristics are shown to depart from those measured experimentally, and additional numerical analysis is used to demonstrate that this departure is probably due to distortions of the sheath caused by the fact that it attempts to conform to the individual wires that make up the sheath constraining mesh. The concept is considered potentially useful in controlling the divergence of ion beamlets in applications where low divergence, low energy, high current density beamlets are being sought, but more work is required to demonstrate this for net beam ion energies as low as 5 eV.
Anderson, John R.↗
Reactions of atomic oxygen (O/3P/) with various polymer films
An attempt is made to obtain the etch rates for various polymer films exposed to O(3P) downstream from, and out of the glow of, the O2 plasma. These rates are compared with published values from the following sources: etching in the glow of an O2 plasma, the Space Shuttle STS-8 flight experiment, and beam experiments. The etch rate data for Kapton fit a logarithmic plot (with a positive slope) of the reaction probability versus O(3P) impact energy.
Golub, Morton A.↗
Oscillator strengths and electron collisional excitation cross sections for atomic oxygen
The electron-impact excitations of 12 states of O I are analyzed using a close-coupling approximation. The absorption oscillator strengths for dipole-allowed transitions among the states are calculated. Cross sections for excitation of the states by electron impact in the energy region 13.87 to 100 eV are compared with the data of Smith (1976) and Doering and Gulcicek. It is observed that there is a correlation between the data at energies 13.87, 20, and 30 eV for the (3)P-3p(5)P transition and at energies 13.87 and 16.5 eV for the (3)P-3s(5)S(0) transitions; however, for the dipole-allowed (3)P-3d(3)D(0) and (3)P-3s(prime)(3)D(0) transitions there are discrepancies in magnitude.
Tayal, S. S.↗
Etching of plasma-polymerized tetrafluoroethylene, polytetrafluoroethylene, and sputtered polytetrafluoroethylene induced by atomic oxygen /O(3P)/
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Wydeven, Theodore↗
Differential collision cross-sections for atomic oxygen
Differential collision cross-sections of O on N2 and other gases were measured to understand vehicle-environmental contamination effects in orbit. The following subject areas are also covered: groundbased scientific observations of rocket releases during NICARE-1; data compression study for the UVI; science priorities for UV imaging in the mid-1990's; and assessment of optimizations possible in UV imaging systems.
Torr, Douglas G.↗
On the inversion of O(+)(2D-2P) 7320 A twilight airglow observations - A method for recovering both the ionization frequency and the thermospheric oxygen atom densities
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Mcdade, I. C.↗
Differential collision cross-sections for atomic oxygen: Analysis of space flight instruments for solar terrestrial physics
A summary of the status of the Cross-section Facility at MSFC is presented. A facility was designed, fabricated, assembled, tested, and operated for measurement of differential scattering cross sections important to understand the induced environment for a vehicle (e.g., Space Station) in low earth orbit. A user's manual for the facility is also presented. The performance of the facility was evaluated and found to be satisfactory in all the essential areas. Differential scattering cross sections were measured and results for the scattering measurements are included. Input to the development of the Ultraviolet Imager Optical System is also discussed. Design, fabrication, and evaluation of UV filters using a four-layer aluminum base are reported.
Torr, Douglas G.↗
Interaction of atomic oxygen with thin film and bulk copper: An XPS, AES, XRD, and profilometer study
The University of Alabama in Huntsville (UAH) experiment A-0114 was designed primarily to study degradation of material surfaces due to low earth orbital (LEO) atmospheric oxygen. The experiment contained 128 one inch circular samples: metals, polymers, carbons, and semiconductors. Among metal samples, copper has shown some interesting new results. Two types of copper samples, a film sputter coated on fused silica and a bulk piece of OFHC copper, were characterized employing a variety of techniques such as X-ray and Auger electron spectroscopies, X-ray diffraction, and high resolution profilometry. Cu 2p core level spectra were used to characterize the presence of Cu2O and CuO in addition to Cu Auger LMM lines. These results are supported by our recent X-ray diffraction studies which clearly establish the presence of Cu oxides which we were unable to prove in our earlier work. Profilometry showed an increase in thickness of the film sample where exposed to 106.7 +/- 0.5 nm from an initial thickness of 74.2 +/- 1.1 nm. Further studies with SEM and ellipsometry are underway.
Raikar, Genesh N.↗
A preliminary analysis of atomic oxygen dayglow using solar EUV measurements from ASSI
The mechanisms governing the interactions between two of the fundamental components of the solar-terrestrial system - solar ionizing radiation and the earth's upper atmosphere - are investigated. The physical parameters of the EUV emissions resulting from these interactions are characterized so that EUV remote sensing can gainfully be employed as a quantitative diagnostic of the terrestrial atmosphere and plasma environment. This analysis uses the solar flux measurements of the Airglow and Solar Spectrometer Instrument (ASSI) on board the San Marco D/L satellite. Preliminary modeling results of the altitude and zenith angle distribution of these emissions are presented along with the data.
Chakrabarti, S.↗
The interaction of atomic oxygen with copper: An XPS, AES, XRD, optical transmission, and stylus profilometry study
The University of Alabama in Huntsville (UAH) experiment A-0114 was designed to study the reaction of material surfaces with low earth orbits (LEO) atmospheric oxygen. The experiment contained 128 one-inch circular samples; metals, polymers, carbons, and semiconductors. Half of these samples were exposed on the front of the Long Duration Exposure Facility (LDEF) and remaining on the rear. Among metal samples, copper has shown some interesting new results. There were two forms of copper samples: a thin film sputter-coated on fused silica and a solid piece of OFHC copper. They were characterized by x-ray and Auger electron spectroscopies, x-ray diffraction, and high resolution profilometry. Cu 2p core level spectra were used to demonstrate the presence of Cu2O and CuO and to determine the oxidation states.
Raikar, Ganesh N.↗
Comparison of theory with atomic oxygen 130.4 nm radiation data from the Bow Shock ultraviolet 2 rocket flight
Comparison is made between the results obtained from a state-of-the-art flow and radiative model and bow shock vacuum ultraviolet (VUV) data obtained the recent Bow Shock 2 Flight Experiment. An extensive data set was obtained from onboard rocket measurements at a reentry speed of 5 km/sec between the altitudes of approximately 65-85 km. A description of the NO photoionization cell used, the data, and the interpretation of the data will be presented. The primary purpose of the analyses is to assess the utility of the data and to propose a radiation model appropriate to the flight conditions of Bow Shock 2. Theoretical predictions based on flow modeling discussed in earlier work and a new radiation model are compared with data.
Levin, Deborah A.↗
Poly(arylene ether)s That Resist Atomic Oxygen
Novel poly(arylene ether)s containing phosphine oxide (PAEPO's) made via aromatic nucleophilic displacement reactions of activated aromatic dihalides (or, in some cases, activated aromatic dinitro compounds) with new bisphenol monomers containing phosphine oxide. Exhibited favorable combination of physical and mechanical properties and resistance to monatomic oxygen in oxygen plasma environment. Useful as adhesives, coatings, films, membranes, moldings, and composite matrices.
Connell, John W.↗
Coatings Would Protect Polymers Against Atomic Oxygen
Proposed interposition of layers of silver oxide tens to hundreds of angstroms thick between polymeric substrates and overlying films helps protect substrates against chemical attack by monatomic oxygen. In original application, polymer substrate would be, sheet of polyimide supporting array of solar photovoltaic cells on spacecraft in low orbit around Earth. Concept also applicable to protection of equipment in terrestrial laboratory and industrial vacuum and plasma chambers in which monatomic oxygen present.
Banks, Bruce A.↗
Atomic Oxygen Removes Varnish And Lacquer From Old Paintings
Dry and relatively nondestructive plasma process found effective in removing protective coats from old paintings. Process generates monatomic oxygen, which reacts with varnish, lacquer, polyurethane, acrylic, and other organic coating materials; reactions produce mostly carbon monoxide and water vapor, then simply pumped away by vacuum system in which plasma generated. Does not attack oxide-based pigments in underlying paint layers, and brush-stroke marks remain undisturbed.
Rutledge, Sharon K.↗
Measurement of Atomic Oxygen in Diffuse Aurora and Ion Density in the E-Region
An ion mass spectrometer (IMS) was refurbished, calibrated and supplied to the University of Colorado payload (Dr. Charles Barth, P.I.) which was launched from White Sands in September of 1993 as NASA 33.062. The nose cone failed to deploy and their were problems with the ACS so the mission was declared a failure. However, the door covering the IMS deployed and the instrument obtained data. The launch occurred shortly after a payload carrying solar x-ray detectors was launched. Thus a small portion of the Colorado payload science was salvaged; namely, the NO(+)/O2(+) ratio to compare with the measured x-ray flux. Figure I shows the NO(+) to O2(+) ratio vs. altitude. The behavior is typical of the E-region.
Sharp, William E.↗
Simulations of Ground and Space-Based Oxygen Atom Experiments
A low-earth orbit (LEO) materials erosion scenario and the ground-based experiment designed to simulate it are compared using the direct-simulation Monte Carlo (DSMC) method. The DSMC model provides a detailed description of the interactions between the hyperthermal gas flow and a normally oriented flat plate for each case. We find that while the general characteristics of the LEO exposure are represented in the ground-based experiment, multi-collision effects can potentially alter the impact energy and directionality of the impinging molecules in the ground-based experiment. Multi-collision phenomena also affect downstream flux measurements.
Finchum, A.↗