Process for testing a xenon gas feed system of a hollow cathode assembly

The design and manufacturing processes for Hollow Cathode Assemblies (HCA's) that operate over a broad range of emission currents up to 30 Amperes, at low potentials, with lifetimes in excess of 17,500 hours. The processes include contamination control procedures which cover hollow cathode component cleaning procedures, gas feed system designs and specifications, and hollow cathode activation and operating procedures to thereby produce cathode assemblies that have demonstrated stable and repeatable operating conditions, for both the discharge current and voltage. The HCA of this invention provides lifetimes of greater than 10,000 hours, and expected lifetimes of greater than 17,500 hours, whereas the present state-of-the-art is less than 500 hours at emission currents in excess of 1 Ampere. Stable operation is provided over a large range of operating emission currents, up to a 6:1 ratio, and this HCA can emit electron currents of up to 30 Amperes in magnitude to an external anode that simulates the current drawn to a space plasma, at voltages of less than 20 Volts

The use of standard calendar software by individuals with acquired brain injury and cognitive complaints: a mixed methods study

PURPOSE: To explore the actual use of standard calendar software by people with acquired brain injury (ABI) and healthy individuals. METHOD: Mixed methods design with qualitative and quantitative analyses of the respondents' use of calendar software. Fifteen individuals with ABI and 15 healthy participants were enrolled. Participants were asked to execute five consecutive tasks using standard calendar software, which resembled everyday use of an electronic calendar. RESULTS: The core processes "task execution" and "information processing" were influenced by internal factors (cognitive and emotional processes and fatigue) as well as environmental factors (software features and distractions). Results obtained by qualitative and quantitative methods showed similar reaction patterns in both groups. However, ABI patients had more cognitive problems and showed stronger emotions during task performance than healthy participants. Healthy participants were more successful and needed less time and mental effort to perform a task. CONCLUSIONS: Although ABI patients were able to use standard calendar software, they became upset more easily, needed more effort, became tired sooner and more suddenly. Strategies to support ABI patients in the use of calendar software are suggested from multi-disciplinary perspectives

Functional Testing of the Space Station Plasma Contactor

A plasma contactor system has been baselined for the International Space Station Alpha (ISSA) to control the electrical potentials of surfaces to eliminate/mitigate damaging interactions with the space environment. The system represents a dual-use technology which is a direct outgrowth of the NASA electric propulsion program and, in particular, the technology development effort on ion thruster systems. The plasma contactor subsystems include a hollow cathode assembly, a power electronics unit, and an expellant management unit. Under a pre-flight development program these subsystems are being developed to the level of maturity appropriate for transfer to U.S. industry for final development. Development efforts for the hollow cathode assembly include design selection and refinement, validating its required lifetime, and quantifying the cathode performance and interface specifications. To date, cathode components have demonstrated over 10,000 hours lifetime, and a hollow cathode assembly has demonstrated over 3,000 ignitions. Additionally, preliminary integration testing of a hollow cathode assembly with a breadboard power electronics unit has been completed. This paper discusses test results and the development status of the plasma contactor subsystems for ISSA, and in particular, the hollow cathode assembly

Update of the NEXT Ion Thruster Service Life Assessment with Post-Test Correlation to the Long Duration Test

The service life assessment for NASA's Evolutionary Xenon Thruster is updated to incorporate the results from the successful and voluntarily early completion of the 51,184 hour long duration test which demonstrated 918 kg of total xenon throughput. The results of the numerous post-test investigations including destructive interrogations have been assessed against all of the critical known and suspected failure mechanisms to update the life and throughput expectations for each major component. Analysis results of two of the most acute failure mechanisms, namely pit-and-groove erosion and aperture enlargement of the accelerator grid, are not updated in this work but will be published at a future time after analysis completion

Differences in neuropsychiatric symptoms between nursing home residents with young-onset dementia and late-onset dementia

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