NASA LogoNTRSNTRS - NASA Technical Reports ServerSearchmore_vertCollectionsAboutNewsHelpLogin Back to ResultsTitanium Optics for Ion ThrustersIon thruster total impulse capability is limited, in part, by accelerator grid sputter erosion. A development effort was initiated to identify a material with a lower accelerator grid volumetric sputter erosion rate than molybdenum, but that could utilize the present NSTAR thruster grid design and fabrication techniques to keep development costs low, and perform as well as molybdenum optics. After comparing the sputter erosion rates of several atomic materials to that of molybdenum at accelerator voltages, titanium was found to offer a 45% reduction in volumetric erosion rates. To ensure that screen grid sputter erosion rates are not higher at discharge chamber potentials, titanium and molybdenum sputter erosion rates were measured at these potentials. Preliminary results showed only a slightly higher volumetric erosion rate for titanium, so that screen grid erosion is insignificant. A number of material, thermal, and mechanical properties were also examined to identify any fabrication, launch environment, and thruster operation issues. Several titanium grid sets were successfully fabricated. A titanium grid set was mounted onto an NSTAR 30 cm engineering model ion thruster and tested to determine optics performance. The titanium optics operated successfully over the entire NSTAR power range of 0.5 to 2.3 kW. Differences in impingement-limited perveances and electron backstreaming limits were found to be due to a larger cold gap for the titanium optics. Discharge losses for titanium grids were lower than those for molybdenum, likely due to a slightly larger titanium screen grid open area fraction. Radial distributions of beam current density with titanium optics were very similar to those with molybdenum optics at all power levels. Temporal electron backstreaming limit measurements showed that titanium optics achieved thermal equilibrium faster than molybdenum optics.Document ID20000023191Acquisition SourceGlenn Research CenterDocument TypeTechnical Memorandum (TM)AuthorsSoulas, George C.*(DYNACS Engineering Co., Inc. Brook Park, OH United States)*Haag, Thomas W.*(NASA Glenn Research Center Cleveland, OH United States)*Patterson, Michael J.*(NASA Glenn Research Center Cleveland, OH United States)*Rawlin, Vincent K.*(NASA Glenn Research Center Cleveland, OH United States)*Date AcquiredSeptember 7, 2013Publication DateDecember 1, 1999Subject CategorySpacecraft Propulsion And PowerReport/Patent NumberNASA/TM-1999-209650IEPC-99-149NAS 1.15:209650E-12004Meeting InformationMeeting: 26th International Electric Propulsion ConferenceLocation: KitakyushuCountry: JapanStart Date: October 17, 1999End Date: October 21, 1999Sponsors:American Inst. of Aeronautics and AstronauticsFunding Number(s)PROJECT: RTOP 632-1B-1BDistribution LimitsPublicCopyrightWork of the US Gov. Public Use Permitted.Available DownloadsNameType20000023191.pdfSTIcloud_downloadcontent_copyvisibilityRelated RecordsThere are no records associated with this record.visibility_offNo Preview Available
 No Fear Act | Freedom of Information Act | Office of the Inspector General | Agency Financial ReportsNASA Web Privacy Policy and Important Notices | NASA Guidelines for Quality of InformationDisclaimers, Copyright, Terms of Use | Accessibility | NASA OCIO | USA.gov | NASA.govContact Us | Site MapSTI LogoNASA Official: JoAnne R. Calhoun Site Curator: STI Compliance and Distribution Services Last Modified: September 12, 2024