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  • 1
    facet.materialart.
    Unbekannt
    In:  Other Sources
    Publikationsdatum: 2019-08-27
    Beschreibung: NASA's In-Space Propulsion (ISP) Program is designed to develop advanced propulsion technologies that can enable or greatly enhance near and mid-term NASA science missions by significantly reducing cost, mass, and/or travel times. These technologies include: Solar Electric Propulsion, Aerocapture, Solar Sails, Momentum Exchange Tethers, Plasma Sails and other technologies such as Advanced Chemical Propulsion. The ISP Program intends to develop cost-effective propulsion technologies that will provide a broad spectrum of mission possibilities, enabling NASA to send vehicles on longer, more useful voyages and in many cases to destinations that were previously unreachable using conventional means. The ISP approach to identifying and prioritizing these most promising technologies is to use mission and system analysis and subsequent peer review. The ISP program seeks to develop technologies under consideration to Technology Readiness Level (TRL) -6 for incorporation into mission planning within 3-5 years of initiation. The NASA TRL 6 represents a level where a technology is ready for system level demonstration in a relevant environment, usually a space environment. In addition, maximum use of open competition is encouraged to seek optimum solutions under ISP. Several NASA Research Announcements (NRA's) have been released asking industry, academia and other organizations to propose propulsion technologies designed to improve our ability to conduct scientific study of the outer planets and beyond. The ISP Program is managed by NASA Headquarters Office of Space Science and implemented by the Marshall Space Flight Center in Huntsville, Alabama.
    Schlagwort(e): Spacecraft Propulsion and Power
    Materialart: International Electric Propulsion Conference 2003; Mar 17, 2003 - Mar 21, 2003; Toulouse; France
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Publikationsdatum: 2019-08-17
    Beschreibung: A mixing chamber used in rocket engine testing at the NASA Stennis Space Center is modelled by a system of two nonlinear ordinary differential equations. The mixer is used to condition the thermodynamic properties of cryogenic liquid propellant by controlled injection of the same substance in the gaseous phase. The three inputs of the mixer are the positions of the valves regulating the liquid and gas flows at the inlets, and the position of the exit valve regulating the flow of conditioned propellant. Mixer operation during a test requires the regulation of its internal pressure, exit mass flow, and exit temperature. A mathematical model is developed to facilitate subsequent controller designs. The model must be simple enough to lend itself to subsequent feedback controller design, yet its accuracy must be tested against real data. For this reason, the model includes function calls to thermodynamic property data. Some structural properties of the resulting model that pertain to controller design, such as uniqueness of the equilibrium point, feedback linearizability and local stability are shown to hold under conditions having direct physical interpretation. The existence of fixed valve positions that attain a desired operating condition is also shown. Validation of the model against real data is likewise provided.
    Schlagwort(e): Spacecraft Propulsion and Power
    Materialart: SE-2002-12-00083-SSC
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Publikationsdatum: 2019-08-17
    Beschreibung: Performance expectations of closed-Brayton-cycle heat exchangers to be used in 100-kWe nuclear space power systems were forecast. Proposed cycle state points for a system supporting a mission to three of Jupiter s moons required effectiveness values for the heat-source exchanger, recuperator and rejection exchanger (gas cooler) of 0.98,0.95 and 0.97, respectively. Performance parameters such as number of thermal units (Nm), equivalent thermal conductance (UA), and entropy generation numbers (Ns) varied from 11 to 19,23 to 39 kWK, and 0.019 to 0.023 for some standard heat exchanger configurations. Pressure-loss contributions to entropy generation were significant; the largest frictional contribution was 114% of the heat-transfer irreversibility. Using conventional recuperator designs, the 0.95 effectiveness proved difficult to achieve without exceeding other performance targets; a metallic, plate-fin counterflow solution called for 15% more mass and 33% higher pressure-loss than the target values. Two types of gas-coolers showed promise. Single-pass counterflow and multipass cross-counterflow arrangements both met the 0.97 effectiveness requirement. Potential reliability-related advantages of the cross-countefflow design were noted. Cycle modifications, enhanced heat transfer techniques and incorporation of advanced materials were suggested options to reduce system development risk. Carbon-carbon sheeting or foam proved an attractive option to improve overall performance.
    Schlagwort(e): Spacecraft Propulsion and Power
    Materialart: NASA/TM-2003-212597 , AIAA Paper 2003-5956 , NAS 1.15:212597 , E-14139 , First International Energy Conversion Engineering Conference; Aug 17, 2003 - Aug 21, 2003; Portsmouth, VA; United States
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    facet.materialart.
    Unbekannt
    In:  CASI
    Publikationsdatum: 2019-08-16
    Beschreibung: The focus of this project was to study the physical processes that govern tachocline dynamics and structure. Specific features explored included stratification, shear, waves, and toroidal and poloidal background fields. In order to address recent theoretical work on anisotropic mixing and dynamics in the tachocline, we were particularly interested in such anisotropic mixing for the specific tachocline processes studied. Transition to turbulence often shapes the largest-scale features that appear spontaneously in a flow during the development of turbulence. The resulting large-scale straining field can control the subsequent dynamics; therefore, anticipation of the large-scale straining field that results for individual realizations of the transition to turbulence can be important for subsequent dynamics, flow morphology, and transport characteristics. As a result, we paid particular attention to the development of turbulence in the stratified and sheared environment of the tachocline. This is complicated by the fact that the linearly stability of sheared MHD flows is non-self-adjoint, implying that normal asymptotic linear stability theory may not be relevant.
    Schlagwort(e): Fluid Mechanics and Thermodynamics
    Materialart: NWRA-CoRA-03-P258 , NASA-9026-Final
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Publikationsdatum: 2019-08-16
    Beschreibung: Results from a series of experiments to investigate techniques for extending the stable flow range of a centrifugal compressor are reported. The research was conducted in a high-speed centrifugal compressor at the NASA Glenn Research Center. The stabilizing effect of steadily flowing air-streams injected into the vaneless region of a vane-island diffuser through the shroud surface is described. Parametric variations of injection angle, injection flow rate, number of injectors, injector spacing, and injection versus bleed were investigated for a range of impeller speeds and tip clearances. Both the compressor discharge and an external source were used for the injection air supply. The stabilizing effect of flow obstructions created by tubes that were inserted into the diffuser vaneless space through the shroud was also investigated. Tube immersion into the vaneless space was varied in the flow obstruction experiments. Results from testing done at impeller design speed and tip clearance are presented. Surge margin improved by 1.7 points using injection air that was supplied from within the compressor. Externally supplied injection air was used to return the compressor to stable operation after being throttled into surge. The tubes, which were capped to prevent mass flux, provided 9.3 points of additional surge margin over the baseline surge margin of 11.7 points.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/TM-2003-212599 , E-14156 , ARL-TR-2921 , GT-2003-38524 , Turbo Expo 2003; Jun 16, 2003 - Jun 19, 2003; Atlanta, GA; United States
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Publikationsdatum: 2019-08-15
    Beschreibung: An aircraft gas turbine engine assembly includes an inter-turbine frame axially located between high and low pressure turbines. Low pressure turbine has counter rotating low pressure inner and outer rotors with low pressure inner and outer shafts which are at least in part rotatably disposed co-axially within a high pressure rotor. Inter-turbine frame includes radially spaced apart radially outer first and inner second structural rings disposed co-axially about a centerline and connected by a plurality of circumferentially spaced apart struts. Forward and aft sump members having forward and aft central bores are fixedly joined to axially spaced apart forward and aft portions of the inter-turbine frame. Low pressure inner and outer rotors are rotatably supported by a second turbine frame bearing mounted in aft central bore of aft sump member. A mount for connecting the engine to an aircraft is located on first structural ring.
    Schlagwort(e): Aircraft Propulsion and Power
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Publikationsdatum: 2019-08-15
    Beschreibung: The objectives of this program are to 1) Assess viability of using lithium-ion technology for future NASA applications, with emphasis upon Mars landers and rovers which will operate on the planetary surface; 2) Support the JPL 2003 Mars Exploration Rover program to assist in the delivery and testing of a 8 AHr Lithium-Ion battery (Lithion/Yardney) which will power the rover; 3) Demonstrate applicability of using lithium-ion technologyfor future Mars applications: Mars 09 Science Laboratory (Smart Lander) and Future Mars Surface Operations (General). Mission simulation testing was carried out for cells and batteries on the Mars Surveyor 2001 Lander and the 2003 Mars Exploration Rover.
    Schlagwort(e): Spacecraft Propulsion and Power
    Materialart: The 2002 NASA Aerospace Battery Workshop; NASA/CP-2003-212344
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Publikationsdatum: 2019-08-15
    Beschreibung: The Department of Energy, Lockheed Martin (LM), Stirling Technology Company, and NASA Glenn Research Center (GRC) are developing a high-efficiency Stirling Radioisotope Generator (SRG) for potential NASA Space Science missions. The SRG is being developed for multimission use, including providing spacecraft onboard electric power for NASA deep space missions and power for unmanned Mars rovers. NASA GRC is conducting an in- house supporting technology project to assist in developing the Stirling convertor for space qualification and mission implementation. Preparations are underway for a thermalhacuum system demonstration and unattended operation during endurance testing of the 55-We Technology Demonstration Convertors. Heater head life assessment efforts continue, including verification of the heater head brazing and heat treatment schedules and evaluation of any potential regenerator oxidation. Long-term magnet aging tests are continuing to characterize any possible aging in the strength or demagnetization resistance of the permanent magnets used in the linear alternator. Testing of the magnet/lamination epoxy bond for performance and lifetime characteristics is now underway. These efforts are expected to provide key inputs as the system integrator, LM, begins system development of the SRG. GRC is also developing advanced technology for Stirling convertors. Cleveland State University (CSU) is progressing toward a multi-dimensional Stirling computational fluid dynamics code, capable of modeling complete convertors. Validation efforts at both CSU and the University of Minnesota are complementing the code development. New efforts have been started this year on a lightweight convertor, advanced controllers, high-temperature materials, and an end-to-end system dynamics model. Performance and mass improvement goals have been established for second- and third-generation Stirling radioisotope power systems.
    Schlagwort(e): Spacecraft Propulsion and Power
    Materialart: NASA/TM-2003-212454 , E-13976 , NAs 1.15:212454 , Space Technology and Applications International Forum (STAIF-2003); Feb 02, 2003 - Feb 05, 2003; Albuquerque, NM; United States
    Format: application/pdf
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  • 9
    facet.materialart.
    Unbekannt
    In:  CASI
    Publikationsdatum: 2019-08-15
    Beschreibung: The Jupiter Icy Moons Orbiter (JIMO) mission is currently under study by the Office of Space Science under the Project Prometheus Program. JIMO is examining the use of Nuclear Electric Propulsion (NEP) to carry scientific payloads to three Jovian moons. A potential power system concept includes dual 100 kWe Brayton converters, a deployable pumped loop heat rejection subsystem, and a 400 Vac Power Management and Distribution (PMAD) bus. Many trades were performed in aniving at this candidate power system concept. System-level studies examined design and off-design operating modes, determined startup requirements, evaluated subsystem redundancy options, and quantified the mass and radiator area of reactor power systems from 20 to 200 kWe. In the Brayton converter subsystem, studies were performed to investigate converter packaging options, and assess the induced torque effects on spacecraft dynamics due to rotating machinery. In the heat rejection subsystem, design trades were conducted on heat transport approaches, material and fluid options, and deployed radiator geometries. In the PMAD subsystem, the overall electrical architecture was defined and trade studies examined distribution approaches, voltage levels, and cabling options.
    Schlagwort(e): Spacecraft Propulsion and Power
    Materialart: NASA/TM-2003-212596 , E-14153 , NAS 1.15:212596 , AIAA Paper 2003-6007 , First International Energy Conversion Engineering Conference; Aug 17, 2003 - Aug 21, 2003; Portsmouth, VA; United States
    Format: application/pdf
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  • 10
    Publikationsdatum: 2019-08-15
    Beschreibung: Diffusion flame stabilization is of essential importance in both Earth-bound combustion systems and spacecraft fire safety. Local extinction, re-ignition, and propagation processes may occur as a result of interactions between the flame zone and vortices or fire-extinguishing agents. By using a computational fluid dynamics code with a detailed chemistry model for methane combustion, the authors have revealed the chemical kinetic structure of the stabilizing region of both jet and flat-plate diffusion flames, predicted the flame stability limit, and proposed diffusion flame attachment and detachment mechanisms in normal and microgravity. Because of the unique geometry of the edge of diffusion flames, radical back-diffusion against the oxygen-rich entrainment dramatically enhanced chain reactions, thus forming a peak reactivity spot, i.e., reaction kernel, responsible for flame holding. The new results have been obtained for the edge diffusion flame propagation and attached flame structure using various C1-C3 hydrocarbons.
    Schlagwort(e): Fluid Mechanics and Thermodynamics
    Materialart: Seventh International Workshop on Microgravity Combustion and Chemically Reacting Systems; 249-252; NASA/CP-2003-212376/REV1
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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