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  • 11
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    Performance effects resulting from plugged liquid oxygen posts of the Space Shuttle Main Engine Injector (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The paper discusses the performance effects resulting from plugged LOX posts of the Space Shuttle Main Engine Injector. The simulation was performed with the REFLEQS 2-D code. Analysis was performed axisymmetrically and injector surface was divided into several regions to account for the mixture ratio variation on the injector surface. The reduction of vaccum specific impulse was approximately 0.01 second per plugged LOX post. This reduction is an order of magnitude higher than the result of Space Shuttle flight reconstruction data. It is presumed that this overprediction is due to the axisymmetric simulation that smears local effects.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: AIAA PAPER 92-3376
    Format: text
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  • 12
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    Vehicle health management using adaptive techniques (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Automated engine diagnostics using cognitive computing methodologies are investigated. Space shuttle main engine vibrational data is used to test the algorithms.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-TM-108472 , NAS 1.15:108472
    Format: application/pdf
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  • 13
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    Experimental modeling of jet-ring turbine disk cooling (1991)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The experimental facility and some early results are described from a current research program modeling turbine disk cooling with multiple impinging jets, such as employed on the Space Shuttle Main Engine oxygen turbopump. The study is designed to obtain detailed local convection heat transfer rates on specially constructed turbine disk models that employ either multiple cooling jet impingement near the disk outer radius from a jet ring, or alternatively, single entrance coolant supply into the center of the disk cavity. Jet impingement is an effective scheme for cooling of turbine disks at or near the blade attachment region, but the heat transfer mechanisms and merits relative to other schemes are not well understood. The present study employs two specially constructed full scale plastic model disks, contoured and plane, together with the corresponding stators. Local heat transfer rates are determined by a computer vision system from the response of thin liquid crystal coatings applied to the disk test faces. The present results indicate that multiple jet impingement directed at the blade attachment region results in higher cooling rates in that region than does the same flow supplied to the disk center, but this conclusion must be regarded as tentative.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: AIAA PAPER 91-0343
    Format: text
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  • 14
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    Computational fluid dynamics studies of nuclear rocket performance (1991)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A CFD analysis of a low pressure nuclear rocket concept is presented with the use of an advanced chemical kinetics, Navier-Stokes code. The computations describe the flow field in detail,including gas dynamic, thermodynamic and chemical properties, as well as global performance quantities such as specific impulse. Computational studies of several rocket nozzle shapes are conducted in an attempt to maximize hydrogen recombination. These Navier-Stokes calculations, which include real gas and viscous effects, predict lower performance values than have been reported heretofore.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: AIAA PAPER 91-3577
    Format: text
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  • 15
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    Blast wave in a nozzle for propulsive applications (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The reported investigation has been conducted in connection with studies concerning the development of a propulsion system based on the use of a detonating fluid propellant. Measurements have been made of the pressure and shock wave velocity in a conical nozzle at various ambient pressures and at an ambient temperature of 25 C. In the experiments a small amount of explosive was placed at the end wall of a conical aluminum nozzle and detonated by a microdetonator inside the nozzle. Differences regarding the characteristics of conventional chemical propulsion and detonation propulsion are illustrated with the aid of a graph. One- and two-dimensional numerical flow calculations were performed and compared with the experimental data.
    Keywords: SPACECRAFT PROPULSION AND POWER
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  • 16
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    Environmental Durability Issues for Solar Power Systems in Low Earth Orbit (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Space solar power systems for use in the low Earth orbit (LEO) environment experience a variety of harsh environmental conditions. Materials used for solar power generation in LEO need to be durable to environmental threats such as atomic oxygen, ultraviolet (UV) radiation, thermal cycling, and micrometeoroid and debris impact. Another threat to LEO solar power performance is due to contamination from other spacecraft components. This paper gives an overview of these LEO environmental issues as they relate to space solar power system materials. Issues addressed include atomic oxygen erosion of organic materials, atomic oxygen undercutting of protective coatings, UV darkening of ceramics, UV embrittlement of Teflon, effects of thermal cycling on organic composites, and contamination due to silicone and organic materials. Specific examples of samples from the Long Duration Exposure Facility (LDEF) and materials returned from the first servicing mission of the Hubble Space Telescope (HST) are presented. Issues concerning ground laboratory facilities which simulate the LEO environment are discussed along with ground-to-space correlation issues.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-TM-106775 , E-9226 , NAS 1.15:106775 , 1995 International Solar Energy Conference; Mar 19, 1995 - Mar 24, 1995; Lahaina, HI; United States
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  • 17
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    Low Earth orbit durability evaluation of protected silicone for advanced refractive photovoltaic concentrator arrays (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The need for efficient, cost effective sources of electrical power in space has led to the development of photovoltaic power systems which make use of novel refractive solar concentrators. These concentrators have been conceived in both point-focus and linear-focus designs. Current concentrator lenses are fabricated from flexible silicones with Fresnel facets along their inside surface. To insure the efficient operation of these power systems, the concentrator lenses must be durable and the silicone material must remain specularly transmitting over a reasonable lifetime in low Earth orbit (LEO) and other space environments. Because of the vulnerability of silicones to atomic oxygen and ultraviolet radiation in LEO these lenses have been coated with a multi-layer metal oxide protective coating. The objective of this research was to evaluate the LEO durability of the multilayer coated silicone for advanced refractive photovoltaic concentrator arrays with respect to optical properties and microstructure. Flat metal oxide coated silicone samples were exposed to ground-laboratory and in-space atomic oxyqen for durability evaluation.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-TM-106543 , E-8687 , NAS 1.15:106543 , AIAA PAPER 94-0374 , AIAA Aerospace Sciences Meeting and Exhibit; Jan 10, 1994 - Jan 13, 1994; Reno, NV; United States
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  • 18
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    Performance and durability of high emittance heat receiver surfaces for solar dynamic power systems (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Haynes 188, a cobalt-based superalloy, will be used to make thermal energy storage (TES) containment canisters for a 2 kW solar dynamic ground test demonstrator (SD GTD). Haynes 188 containment canisters with a high thermal emittance (epsilon) are desired for radiating heat away from local hot spots, improving the heating distribution, which will in turn improve canister service life. In addition to needing a high emittance, the surface needs to be durable in an elevated temperature, high vacuum environment for an extended time period. Thirty-five Haynes 188 samples were exposed to 14 different types of surface modification techniques for emittance and vacuum heat treatment (VHT) durability enhancement evaluation. Optical properties were obtained for the modified surfaces. Emittance enhanced samples were exposed to VHT for up to 2692 hours at 827 C and less than or equal to 10(exp -6) torr with integral thermal cycling. Optical properties were taken intermittently during exposure, and after final VHT exposure. The various surface modification treatments increased the emittance of pristine Haynes 188 from 0.11 up to 0.86. Seven different surface modification techniques were found to provide surfaces which met the SD GTD receiver VHT durability requirement. Of the 7 surface treatments, 2 were found to display excellent VHT durability: an alumina based (AB) coating and a zirconia based coating. The alumina based coating was chosen for the epsilon enhancement surface modification technique for the SD GTD receiver. Details of the performance and vacuum heat treatment durability of this coating and other Haynes 188 emittance surface modification techniques are discussed. Technology from this program will lead to successful demonstration of solar dynamic power for space applications, and has potential for application in other systems requiring high emittance surfaces.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-TM-106549 , E-8700 , NAS 1.15:106549 , 1994 ASME International Solar Energy Conference; Mar 27, 1994 - Mar 30, 1994; San Francisco, CA; United States
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  • 19
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    Exit of a blast wave from a conical nozzle (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The Eulerian computer code DORF was used in the analysis of a two-dimensional, unsteady flow field resulting from semi-confined explosions for propulsive applications. Initially, the ambient gas inside the conical shaped nozzle is set into motion due to the expansion of the explosion product gas, forming a shock wave. When this shock front exits the nozzle, it takes almost a spherical form while a complex interaction between the nozzle and compression and rarefaction waves takes place behind the shock. The results show an excellent agreement with experimental data.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-401 , Fluid and Plasma Dynamics Conference; Jul 14, 1976 - Jul 16, 1976; San Diego, CA
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  • 20
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    Numerical study of nozzle wall cooling for nuclear thermal rockets (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The flowfields and performance of nuclear thermal rockets, which utilize radiation and film-cooling to cool the nozzle extension, are studied by solving the Navier-Stokes equations and species equations. The thrust level of the rocket for the present study is about 75,000 lb(f) for a chamber pressure of 68 atm(l,000 psi) and a chamber temperature of 2700 K. The throat radius of the nozzle is 0.0936 m and the area ratios of the nozzles are 300 and 500. It is assumed that the flow is chemically frozen and the turbulence is simulated by the modified Baldwin-Lomax turbulence model. The calculated results for various area ratios and film mass-flow rates are presented as Mach number contours, variations of nozzle wall temperature, exit profiles, and vacuum specific impulses. The present study shows that by selecting the flow rate of the film-cooling hydrogen and area ratio of the nozzle correctly, high area ratio nozzle extensions can be cooled effectively with radiation and film-cooling without significant penalty in performance.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: AIAA PAPER 93-2498 , ; 12 p.|AIAA, SAE, ASME, and ASEE, Joint Propulsion Conference and Exhibit; Jun 28, 1993 - Jun 30, 1993; Monterey, CA; United States
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