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  • Spacecraft Propulsion and Power  (8)
  • ENVIRONMENT POLLUTION
  • Guanylate Cyclase/antagonists & inhibitors/metabolism
  • 2005-2009  (8)
  • 2005  (8)
Collection
Keywords
  • Spacecraft Propulsion and Power  (8)
  • ENVIRONMENT POLLUTION
  • Guanylate Cyclase/antagonists & inhibitors/metabolism
Years
  • 2005-2009  (8)
Year
  • 1
    Publication Date: 2019-07-13
    Description: Interest in science objectives at the outer planets, specifically at the moons of Jupiter, has spurred the development of high-power electric propulsion systems under the Prometheus program.
    Keywords: Spacecraft Propulsion and Power
    Type: AIAA Paper 2005-4412 , 41st AIAA Joint Propulsion Conference; Jul 10, 2005 - Jul 13, 2005; Tuscon, AZ; United States
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  • 2
    Publication Date: 2019-07-13
    Description: Destructive physical analysis of the discharge and neutralizer hollow cathode assemblies from the Deep Space 1 Flight Spare 30,000 Hr life test was performed to characterize physical and chemical evidence of operationally induced effects after 30,372 hours of operation with beam extraction. Post-test inspection of the discharge-cathode assembly was subdivided into detailed analyses at the subcomponent level. Detailed materials analysis and optical inspection of the insert, orifice plate, cathode tube, heater, keeper assembly, insulator, and low-voltage propellant isolator were performed. Energy dispersive X-ray (EDX) and scanning electron microscopy (SEW analyses were used to determine the extent and composition of regions of net deposition and erosion of both the discharge and neutralizer inserts. A comparative approach with an un-operated 4:1:1 insert was used to determine the extent of impregnate material depletion as a function of depth from the ID surface and axial position from the orifice plate. Analysis results are compared and contrasted with those obtained from similar analyses on components from shorter term tests, and provide insight regarding the prospect for successful longer-term operation consistent with SOA ion engine program life objectives at NASA.
    Keywords: Spacecraft Propulsion and Power
    Type: 29th International Electric Propulsion Conference, Princeton University; Oct 31, 2005 - Nov 04, 2005; NJ; United States
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  • 3
    Publication Date: 2019-07-13
    Description: A series of experimental measurements on a modified laboratory NSTAR engine were used to validate a zero dimensional analytical discharge performance model of a ring cusp ion thruster. The model predicts the discharge performance of a ring cusp NSTAR thruster as a function the magnetic field configuration, thruster geometry, and throttle level. Analytical formalisms for electron and ion confinement are used to predict the ionization efficiency for a given thruster design. Explicit determination of discharge loss and volume averaged plasma parameters are also obtained. The model was used to predict the performance of the nominal and modified three and four ring cusp 30-cm ion thruster configurations operating at the full power (2.3 kW) NSTAR throttle level. Experimental measurements of the modified engine configuration discharge loss compare well with the predicted value for propellant utilizations from 80 to 95%. The theory, as validated by experiment, indicates that increasing the magnetic strength of the minimum closed reduces maxwellian electron diffusion and electrostatically confines the ion population and subsequent loss to the anode wall. The theory also indicates that increasing the cusp strength and minimizing the cusp area improves primary electron confinement increasing the probability of an ionization collision prior to loss at the cusp.
    Keywords: Spacecraft Propulsion and Power
    Type: 29th International Electric Propulsion Conference, Princeton University; Oct 31, 2005 - Nov 04, 2005; Princeton, NJ; United States
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  • 4
    Publication Date: 2019-07-13
    Description: The Nuclear Electric Xenon Ion System (NEXIS) ion thruster was developed for potential outer planet robotic missions under NASA's Prometheus program. This engine was designed to operate at power levels ranging from 16 to over 20 kWe at specific impulses of 6000 to 7500 s for burn times of up to 10 years, satisfying the requirements of nuclear electric propulsion systems such as that on the proposed Prometheus 1 mission to explore the icy moons of Jupiter. State-of-the-art performance and life assessment tools were used to design the thruster. Following the successful performance validation of a Laboratory Model thruster, Development Model hardware was fabricated and subjected to vibration and wear testing. The results of a 2000-hour wear test are reported herein. Thruster performance achieved the target requirements and was steady for the duration of the test. Ion optics performance was similarly stable. Discharge loss increases of 6 eV/ion were observed in the first 500 hours of the test and were attributed to primary electron energy decreases due to cathode insert conditioning. Relatively high recycle rates were observed and were identified to be high-voltage-to-ground arcs in the back of the thruster caused by wire insulation outgassing and electron penetration through the plasma screen. Field emission of electrons between the accelerator and screen grids was observed and attributed to evolution of field emitter sites at accelerator grid aperture edges caused by ion bombardment. Preliminary modeling and analysis indicates that the NEXIS engine can meet mission performance requirements over the required lifetime. Finally, successful validation of the NEXIS design methodology, design tools, and technologies with the results of the wear test and companion performance and vibration tests presents significant applicability of the NEXIS development effort to missions of near-term as well as long-term interest for NASA.
    Keywords: Spacecraft Propulsion and Power
    Type: 29th International Electric Propulsion Conference, Princeton University; Oct 31, 2005 - Nov 04, 2005; Princeton, NJ; United States
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  • 5
    Publication Date: 2019-07-13
    Description: In the Very High Isp Thruster with Anode Layer (VHITAL) Program the performance, plume and lifetime capability of the radiatively-cooled two stage, bismuth-fueled VHITAL-160 will be characterized in the US and Russia.
    Keywords: Spacecraft Propulsion and Power
    Type: AIAA Joint Propulsion Conference 2005; Jul 11, 2005 - Jul 14, 2005; Tucson, AZ; United States
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  • 6
    Publication Date: 2019-07-13
    Description: Magnetic confinement studies were performed on the state-of-the-art NSTAR ion thruster. The goal of the experimental studies was determine the dependence of plasma confinement and plasma uniformity on the strength and shape of the imposed ring-cusp magnetic field.
    Keywords: Spacecraft Propulsion and Power
    Type: Joint Propulsion Conference; Jul 10, 2005 - Jul 12, 2005; Tucson, AZ; United States
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  • 7
    Publication Date: 2019-07-13
    Description: The Very High Isp Thruster with Anode Layer (VHITAL) is a two stage Hall thruster program that is a part of NASA's Prometheus Program in NASA's New Exploration Systems Mission Directorate (ESMD). It is a potentially viable low-cost alternative to ion engines for near-term NEP applications with the growth potential to support mid-term and far-term NEP missions... This paper will present an overview of the thruster fabrication, pre-existing TAL 160 demonstration, feed system development, lifetime assessment, contamination assessment, and mission study activities performed to date.
    Keywords: Spacecraft Propulsion and Power
    Type: IEPC-2005-238 , 29th International Electric Propulsion conference; Oct 21, 2005 - Nov 04, 2005; Princeton, NJ; United States
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  • 8
    Publication Date: 2019-07-13
    Description: The Nuclear Electric Xenon Ion System (NEXIS) ion thruster was developed for potential outer planet robotic missions under NASA's Prometheus program. This engine was designed to operate at power levels ranging from 16 to over 20 kWe at specific impulses of 6000 to 7500 s for burn times of up to 10 years, satisfying the requirements of nuclear electric propulsion systems such as that on the proposed Prometheus 1 mission to explore the icy moons of Jupiter. State-of-the-art performance and life assessment tools were used to design the thruster. Following the successful performance validation of a Laboratory Model thruster, Development Model hardware was fabricated and subjected to vibration and wear testing. The results of a 2000-hour wear test are reported herein. Thruster performance achieved the target requirements and was steady for the duration of the test. Ion optics performance was similarly stable. Discharge loss increases of 6 eV/ion were observed in the first 500 hours of the test and were attributed to primary electron energy decreases due to cathode insert conditioning. Relatively high recycle rates were observed and were identified to be high-voltage-to-ground arcs in the back of the thruster caused by wire insulation outgassing and electron penetration through the plasma screen. Field emission of electrons between the accelerator and screen grids was observed and attributed to evolution of field emitter sites at accelerator grid aperture edges caused by ion bombardment. Preliminary modeling and analysis indicates that the NEXIS engine can meet mission performance requirements over the required lifetime. Finally, successful validation of the NEXIS design methodology, design tools, and technologies with the results of the wear test and companion performance and vibration tests presents significant applicability of the NEXIS development effort to missions of near-term as well as long-term interest for NASA.
    Keywords: Spacecraft Propulsion and Power
    Type: IEPC-2005-281 , 29th International Electric Propulsion Conference; Oct 31, 2005 - Nov 04, 2005; Princeton, NJ; United States
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