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  • 1
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    Rare-isotope and kinetic studies of Pt/SnO2 catalysts (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Closed-cycle pulsed CO2 laser operation requires the use of an efficient CO-O2 recombination catalyst for these dissociation products which otherwise would degrade the laser operation. The catalyst must not only operate at low temperatures but also must operate efficiently for long periods. In the case of the Laser Atmospheric Wind Sounder (LAWS) laser, an operational lifetime of 3 years is required. Additionally, in order to minimize atmospheric absorption and enhance aerosol scatter of laser radiation, the LAWS system will operate at 9.1 micrometers with an oxygen-18 isotope CO2 lasing medium. Consequently, the catalyst must not only operate at low temperatures but must also preserve the isotopic integrity of the rare-isotope composition in the recombination mode. Several years ago an investigation of commercially available and newly synthesized recombination catalysts for use in closed-cycle pulsed common and rare-isotope CO2 lasers was implemented at the NASA Langley Research Center. Since that time, mechanistic efforts utilizing both common and rare oxygen isotopes have been implemented and continue. Rare-isotope studies utilizing commercially available platinum-tin oxide catalyst have demonstrated that the catalyst contributes oxygen-16 to the product carbon dioxide thus rendering it unusable for rare-isotope applications. A technique has been developed for modification of the surface of the common-isotope catalyst to render it usable. Results of kinetic and isotope label studies using plug flow, recycle plug flow, and closed internal recycle plug flow reactor configuration modes are discussed.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: Low-Temperature CO-Oxidation Catalysts for Long-Life CO2 Lasers; p 193-199
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    NASA TECHNICAL REPORTS
  • 2
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    LaRC-developed catalysts for CO2 lasers (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Pulsed CO2 lasers have many remote sensing applications from space, airborne, and ground platforms. The NASA Laser Atmospheric Wind Sounder (LAWS) system will be designed to measure wind velocities from polar earth orbit for a period of up to three years. Accordingly, this and other applications require a closed-cycle pulsed CO2 laser which necessitates the use of an efficient CO-O2 recombination catalyst for these dissociation products which otherwise would degrade the laser operation. The required catalyst must not only operate at low temperatures but also must operate efficiently for long time periods. The research effort at NASA LaRC has centered around development and testing of CO oxidation catalysts for closed-cycle, pulsed, common and rare-isotope CO2 lasers. Researchers examined available commercial catalysts both in a laser and under simulated closed-cycle laser conditions with efforts aimed toward a thorough understanding of the fundamental catalytic reaction. These data were used to design and synthesize new catalyst compositions to better meet the catalyst requirements for closed-cycle pulsed CO2 lasers. Syntheses and test results for catalysts developed at Langley Research Center which have significantly better long-term decay characteristics than previously available catalysts and at the same time operate quite well under lower temperature conditions are discussed.
    Keywords: LASERS AND MASERS
    Type: Low-Temperature CO-Oxidation Catalysts for Long-Life CO2 Lasers; p 69-90
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    NASA TECHNICAL REPORTS
  • 3
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    Pt/SnO2-based CO-oxidation catalysts for long-life closed-cycle CO2 lasers (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Noble-metal/tin-oxide based catalysts such as Pt/SnO2 have been shown to be good catalysts for the efficient oxidation of CO at or near room temperature. These catalysts require a reductive pretreatment and traces of hydrogen or water to exhibit their full activity. Addition of Palladium enhances the activity of these catalysts with about 15 to 20 percent Pt, 4 percent Pd, and the balance SnO2 being an optimum composition. Unfortunately, these catalysts presently exhibit significant decay due in part to CO2 retention, probably as a bicarbonate. Research on minimizing the decay in activity of these catalysts is currently in progress. A proposed mechanism of CO oxidation on Pt/SnO2-based catalysts has been developed and is discussed.
    Keywords: LASERS AND MASERS
    Type: Low-Temperature CO-Oxidation Catalysts for Long-Life CO2 Lasers; p 41-53
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    NASA TECHNICAL REPORTS
  • 4
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    Studies of CO oxidation on Pt/SnO2 catalyst in a surrogate CO2 laser facility (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Samples of 1% Pt/SnO2 catalyst were exposed to a stoichiometric gas mixture of 1% CO and 1.2% O2 in helium over a range of flowrates from 5 to 15 sccm and temperatures from 338 to 394 Kelvin. Reaction rate constants for the catalytic oxidation of carbon monoxide and their temperature dependence were determined and compared with previous literature values.
    Keywords: LASERS AND MASERS
    Type: Closed-Cycle, Frequency-Stable CO2 Laser Technology; p 199-209
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    NASA TECHNICAL REPORTS
  • 5
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    Catalysts for long-life closed-cycle CO2 lasers (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Long-life, closed-cycle operation of pulsed CO2 lasers requires catalytic CO-O2 recombination both to remove O2, which is formed by discharge-induced CO2 decomposition, and to regenerate CO2. Platinum metal on a tin (IV) oxide substrate (Pt/SnO2) has been found to be an effective catalyst for such recombination in the desired temperature range of 25 to 100 C. This paper presents a description of ongoing research at NASA-LaRC on Pt/SnO2 catalyzed CO-O2 recombination. Included are studies with rare-isotope gases since rare-isotope CO2 is desirable as a laser gas for enhanced atmospheric transmission. Results presented include: (1) achievement of 98% to 100% conversion of a stoichiometric mixture of CO and O2 to CO2 for 318 hours (greater than 1 x 10 to the 6th power seconds), continuous, at a catalyst temperature of 60 C, and (2) development of a technique verified in a 30-hour test, to prevent isotopic scrambling when CO-18 and O-18(2) are reacted in the presence of a common-isotope Pt/Sn O-16(2) catalyst.
    Keywords: LASERS AND MASERS
    Type: Closed-Cycle, Frequency-Stable CO2 Laser Technology; p 113-119
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    NASA TECHNICAL REPORTS
  • 6
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    In-flight source noise of an advanced full-scale single-rotation propeller (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Flight tests to define the far-field tone source at cruise conditions have been completed on the full-scale SR-7L advanced turboprop, which was installed on the left wing of a Gulfstream II aircraft. These measurements defined source levels for input into long-distance propagation models to predict en route noise. Infight data were taken for seven test cases. The sideline directivities measured showed expected maximum levels near 105 deg from the propeller upstream axis. However, azimuthal directivities based on the maximum observed sideline tone levels showed highest levels below the aircraft. The tone level reduction associated with reductions in propeller tip speed is shown to be more significant in the horizontal plane than below the aircraft.
    Keywords: ACOUSTICS
    Type: AIAA PAPER 91-0594
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    Catalyst for carbon monoxide oxidation (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A catalyst for the combination of CO and O2 to form CO2 which includes a platinum group metal, e.g., platinum; a reducible metal oxide having mulitple valence states, e.g., SnO2; and a compound which can bind water to its structure, e.g., silica gel. This catalyst is ideally suited for application to high powered, pulsed, CO2 lasers operating in a sealed or closed cycle condition.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
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    NASA TECHNICAL REPORTS
  • 8
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    Closed-Cycle, Frequency-Stable CO2 Laser Technology (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: These proceedings contain a collection of papers and comments presented at a workshop on technology associated with long-duration closed-cycle operation of frequency-stable, pulsed carbon dioxide lasers. This workshop was held at the NASA Langley Research Center June 10 to 12, 1986. The workshop, jointly sponsored by the National Aeronautics and Space Administration (NASA) and the Royal Signals and Radar Establishment (RSRE), was attended by 63 engineers and scientists from the United States and the United Kingdom. During the 2 1/2 days of the workshop, a number of issues relating to obtaining frequency-stable operation and to the catalytic control of laser gas chemistry were discussed, and specific recommendations concerning future activities were drafted.
    Keywords: LASERS AND MASERS
    Type: NASA-CP-2456 , L-16271 , NAS 1.55:2456
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    NASA TECHNICAL REPORTS
  • 9
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    Structureborne noise control in advanced turboprop aircraft (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Structureborne noise is discussed as a contributor to propeller aircraft interior noise levels that are nonresponsive to the application of a generous amount of cabin sidewall acoustic treatment. High structureborne noise levels may jeopardize passenger acceptance of the fuel-efficient high-speed propeller transport aircraft designed for cruise at Mach 0.65 to 0.85. These single-rotation tractor and counter-rotation tractor and pusher propulsion systems will consume 15 to 30 percent less fuel than advanced turbofan systems. Structureborne noise detection methodologies and the importance of development of a structureborne noise sensor are discussed. A structureborne noise generation mechanism is described in which the periodic components or propeller swirl produce periodic torques and forces on downstream wings and airfoils that are propagated to the cabin interior as noise. Three concepts for controlling structureborne noise are presented: (1) a stator row swirl remover, (2) selection of a proper combination of blade numbers in the rotor/stator system of a single-rotation propeller, and the rotor/rotor system of a counter-rotation propeller, and (3) a tuned mechanical absorber.
    Keywords: ACOUSTICS
    Type: NASA-TM-88947 , E-3362 , NAS 1.15:88947 , AIAA PAPER 87-0530
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    NASA TECHNICAL REPORTS
  • 10
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    Catalyst for carbon monoxide oxidation (1990)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A catalyst is disclosed for the combination of CO and O2 to form CO2, which includes a platinum group metal (e.g., platinum); a reducable metal oxide having multiple valence states (e.g., SnO2); and a compound which can bind water to its structure (e.g., silica gel). This catalyst is ideally suited for application to high-powered pulsed, CO2 lasers operating in a sealed or closed-cycle condition.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Format: application/pdf
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