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  • Propellants and Fuels  (13)
  • SPACECRAFT PROPULSION AND POWER  (4)
  • Antarctica  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Ecological research 4 (1989), S. 297-307 
    ISSN: 1440-1703
    Keywords: Antarctica ; Lichen activity ; Microclimate ; Modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract At a boulder on a hill near Casey Station, Wilkes Land, sensors for light, temperature and humidity were installed facing the four cardinal directions. The measurements lasted for about two months of the summer season 1985/86. The data recording was carried out at intervals of 6 minutes for all probes by automatic recording instruments. Data analysis was carried out with special regard to the biological effects of the parameters analyzed. These data of the microclimatic features taken from its original place of growth were used to a regression model of potential photosynthetic activity ofUsnea sphacelata, which is a characteristic species of this area. Although the individual time courses of the above mentioned parameters show long periods of favourable conditions for possible growth and metabolic processes, the combined analysis of these variables considering threshold values for metabolism shortens these time spans drastically. Thus, cross relationships within the physical descriptors and their effects on the actual values of photosynthesis as well as respiration become evident. They are illustrated by the results of models on photosynthesis and respiration ofU. sphacelata regarding the different cardinal directions.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2013-08-31
    Description: The structural integrity of high pressure liquid propellant rocket engine thrust chambers is typically maintained through regenerative cooling. The coolant flows through passages formed either by constructing the chamber liner from tubes or by milling channels in a solid liner. Recently, Carlile and Quentmeyer showed life extending advantages (by lowering hot gas wall temperatures) of milling channels with larger height to width aspect ratios (AR is greater than 4) than the traditional, approximately square cross section, passages. Further, the total coolant pressure drop in the thrust chamber could also be reduced, resulting in lower turbomachinery power requirements. High aspect ratio cooling channels could offer many benefits to designers developing new high performance engines, such as the European Vulcain engine (which uses an aspect ratio up to 9). With platelet manufacturing technology, channel aspect ratios up to 15 could be formed offering potentially greater benefits. Some issues still exist with the high aspect ratio coolant channels. In a coolant passage of circular or square cross section, strong secondary vortices develop as the fluid passes through the curved throat region. These vortices mix the fluid and bring lower temperature coolant to the hot wall. Typically, the circulation enhances the heat transfer at the hot gas wall by about 40 percent over a straight channel. The effect that increasing channel aspect ratio has on the curvature heat transfer enhancement has not been sufficiently studied. If the increase in aspect ratio degrades the secondary flow, the fluid mixing will be reduced. Analysis has shown that reduced coolant mixing will result in significantly higher wall temperatures, due to thermal stratification in the coolant, thus decreasing the benefits of the high aspect ratio geometry. A better understanding of the fundamental flow phenomena in high aspect ratio channels with curvature is needed to fully evaluate the benefits of this geometry. The fluid dynamic and conjugate heat transfer problem of high aspect ratio rocket engine coolant channels are being investigated numerically, but these efforts have been hampered by a lack of validating data. Wall temperature data is available for the conjugate problem for channels without curvature and aspect ratio = 5.0, and unheated fluid dynamic data are available for square and circular cross section channels with curvature at Reynold's numbers up to 40,000. But the effects of aspect ratio on secondary flow development have not been experimentally studied. To provide some insight into the effects of channel aspect ratio on secondary flow and to qualitatively provide anchoring for the numerical codes, a flow visualization experiment was initiated at the NASA Lewis Research Center.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: Pennsylvania State Univ., NASA Propulsion Engineering Research Center, Volume 2; p 101-105
    Format: application/pdf
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  • 3
    Publication Date: 2019-06-28
    Description: Design issues for lunar ascent and lunar descent rocket engines fueled by aluminum/oxygen propellant produced in situ at the lunar surface were evaluated. Key issues are discussed which impact the design of these rockets: aluminum combustion, throat erosion, and thrust chamber cooling. Four engine concepts are presented, and the impact of combustion performance, throat erosion and thrust chamber cooling on overall engine design are discussed. The advantages and disadvantages of each engine concept are presented.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: AIAA PAPER 92-1185
    Format: text
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  • 4
    Publication Date: 2019-07-13
    Description: The results of an experimental investigation on the combined effects of cooling channel aspect ratio and curvature for rocket engines are presented. Symmetrically heated tubes with average heat fluxes up to 1.7 MW/m(exp 2) were used. The coolant was gaseous nitrogen at an inlet temperature of 280 K (500 R) and inlet pressures up to 1.0 x 10(exp 7) N/m(exp 2) (1500 psia). Two different tube geometries were tested: a straight, circular cross-section tube, and an aspect-ratio 10 cross-section tube with a 45 deg bend. The circular tube results are compared to classical models from the literature as validation of the system. The curvature effect data from the curved aspect-ratio 10 tube compare favorably to the empirical equations available in the literature for low aspect ratio tubes. This latter results suggest that thermal stratification of the coolant due to diminished curvature effect mixing may not be an issue for high aspect-ratio cooling channels.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-TM-106985 , E-9760 , NAS 1.15:106985 , AIAA PAPER 95-2500 , AIAA, ASME, SAE and ASEE; Jul 10, 1995 - Jul 12, 1995; US
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  • 5
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Propellants and Fuels
    Type: GRC-E-DAA-TN16903 , 2014 Proplusion & Energy Forum; Jul 28, 2014 - Jul 30, 2014; Cleveland, Ohio; United States
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  • 6
    Publication Date: 2019-07-13
    Description: This presentation provides an overview of the Cryogenic Propellant Storage and Transfer (CPST) Mission from formulation through Systems Requirements Review and into preparation for Preliminary Design Review. Accomplishments of the technology maturation phase of the project are included. The presentation then summarizes the transition, due to Agency budget constraints, of CPST from a flight project into a ground project titled evolvable Cryogenics (eCryo).
    Keywords: Propellants and Fuels
    Type: GRC-E-DAA-TN16864 , Propulsion and Energy Forum 2014; Jul 28, 2014 - Jul 30, 2014; Cleveland, OH; United States
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  • 7
    Publication Date: 2019-07-13
    Description: A relocated rocket engine test facility, the Altitude Combustion Stand (ACS), was activated in 2009 at the NASA Glenn Research Center. This facility has the capability to test with a variety of propellants and up to a thrust level of 2000 lbf (8.9 kN) with precise measurement of propellant conditions, propellant flow rates, thrust and altitude conditions. These measurements enable accurate determination of a thruster and/or nozzle s altitude performance for both technology development and flight qualification purposes. In addition the facility was designed to enable efficient test operations to control costs for technology and advanced development projects. A liquid oxygen-liquid methane technology development test program was conducted in the ACS from the fall of 2009 to the fall of 2010. Three test phases were conducted investigating different operational modes and in addition, the project required the complexity of controlling propellant inlet temperatures over an extremely wide range. Despite the challenges of a unique propellant (liquid methane) and wide operating conditions, the facility performed well and delivered up to 24 hot fire tests in a single test day. The resulting data validated the feasibility of utilizing this propellant combination for future deep space applications.
    Keywords: Propellants and Fuels
    Type: NASA/TM-2012-217643 , E-18201 , E-18201-1 , Space Propulsion 2012; May 07, 2012 - May 10, 2012; Bordeaux; France
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  • 8
    Publication Date: 2019-07-13
    Description: The high specific impulse of cryogenic propellants can provide a significant performance advantage for in-space transfer vehicles. The upper stages of the Saturn V and various commercial expendable launch vehicles have used liquid oxygen and liquid hydrogen propellants; however, the application of cryogenic propellants has been limited to relatively short duration missions due to the propensity of cryogens to absorb environmental heat resulting in fluid losses. Utilizing advanced cryogenic propellant technologies can enable the efficient use of high performance propellants for long duration missions. Crewed mission architectures for beyond low Earth orbit exploration can significantly benefit from this capability by developing realistic launch spacing for multiple launch missions, by prepositioning stages and by staging propellants at an in-space depot. The National Aeronautics and Space Administration through the Office of the Chief Technologist is formulating a Cryogenic Propellant Storage and Transfer Technology Demonstration Mission to mitigate the technical and programmatic risks of infusing these advanced technologies into the development of future cryogenic propellant stages or in-space propellant depots. NASA is seeking an innovative path for human space exploration, which strengthens the capability to extend human and robotic presence throughout the solar system. This mission will test and validate key cryogenic technological capabilities and has the objectives of demonstrating advanced thermal control technologies to minimize propellant loss during loiter, demonstrating robust operation in a microgravity environment, and demonstrating efficient propellant transfer on orbit. The status of the demonstration mission concept development, technology demonstration planning and technology maturation activities in preparation for flight system development are described.
    Keywords: Propellants and Fuels
    Type: NASA/TM-2012-217642 , E-18200 , E-18200 , Space Propulsion 2012; May 07, 2012 - May 10, 2012; Bordeaux; France
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  • 9
    Publication Date: 2019-07-13
    Description: Exploration Systems Architecture Study conducted by NASA in 2005 identified the liquid oxygen (LOx)/liquid methane (LCH4) propellant combination as a prime candidate for the Crew Exploration Vehicle Service Module propulsion and for later use for ascent stage propulsion of the lunar lander. Both the Crew Exploration Vehicle and Lunar Lander were part the Constellation architecture, which had the objective to provide global sustained lunar human exploration capability. From late 2005 through the end of 2010, NASA and industry matured advanced development designs for many components that could be employed in relatively high thrust, high delta velocity, pressure fed propulsion systems for these two applications. The major investments were in main engines, reaction control engines, and the devices needed for cryogenic fluid management such as screens, propellant management devices, thermodynamic vents, and mass gauges. Engine and thruster developments also included advanced high reliability low mass igniters. Extensive tests were successfully conducted for all of these elements. For the thrusters and engines, testing included sea level and altitude conditions. This advanced development provides a mature technology base for future liquid oxygen/liquid methane pressure fed space propulsion systems. This paper documents the design and test efforts along with resulting hardware and test results.
    Keywords: Propellants and Fuels
    Type: IAC-11-C4.1.5 , E-17931 , E-17931-1 , 62nd International Aeronautical Congress; Oct 03, 2011 - Oct 07, 2011; Cape Town; South Africa
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  • 10
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Propellants and Fuels
    Type: E-18444-1 , 63rd International Astronautical Congress; Oct 02, 2012 - Oct 05, 2012; Naples; Italy
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