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Erosion Rate Measurements for DART Spacecraft Ion Propulsion System

Crofton, Mark W. and Schoeffler, Donner T. and Young, Jason A. and Patterson, Michael J. (2022) Erosion Rate Measurements for DART Spacecraft Ion Propulsion System. Applied Sciences, 12 (15). Art. No. 7831. ISSN 2076-3417. doi:10.3390/app12157831.

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The Double Asteroid Redirection Test (DART) spacecraft was developed to provide the first measurement for orbital deflection of an asteroid upon intentional impact. The NEXT ion engine is part of the mission, on its maiden voyage. As part of the pre-launch risk reduction, erosion characteristics of the extraction grid system were evaluated using laser measurements of sputtered molybdenum atoms over the envelope of potential throttle conditions for the mission. Erosion rate dependence on propellant flow rate as well as relative density and directionality of molybdenum sputter from grid center to edge were measured. Sputtered atoms were found to have average radial velocity directed toward the engine perimeter and increasing with radial distance. The relative contribution of source and facility background gas and other sources of accelerator grid current was examined as well as the influence of several engine operating parameters. Facility background gas was found to influence engine operation more than a wall-mounted pressure gauge and typical assumptions about ingestion would indicate. Far-field flux was estimated over the full angular range based on the near-field relative density and velocity results and relying on quartz crystal microbalance data at one location to fix absolute numbers everywhere. The results substantially deepen knowledge and understanding of the complex grid erosion process of the engine and its lifetime, as grid failure via erosion is the normal life limiter. Study results are also relevant to thruster–spacecraft integration issues such as molybdenum deposition rate on solar cells and other spacecraft surfaces.

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Additional Information:© 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ( Received: 7 June 2022 / Revised: 14 July 2022 / Accepted: 18 July 2022 / Published: 4 August 2022. (This article belongs to the Special Issue Ti:Sapphire Lasers and Their Applications). This paper is an extended version of paper published in AIAA SciTech Forum, held in San Diego, CA, USA, 7–11 January 2019. Technical support was provided by Kevin McCormick, Mike Worshum, and Byron Zeigler. Vince Bilardo provided project management support, with assistance from Rostislav Spektor and Tom Curtiss. The original study and 2019 reports were funded by NASA Glenn Research Center, contract number NNJ11HB94C. Author Contributions: M.W.C. collected the data, analyzed and interpreted results, and wrote most of the manuscript; D.T.S. analyzed data and wrote Section 3.3; J.A.Y. wrote data acquisition and control software; M.J.P. operated the thruster, kept a detailed operations log, provided background information, and participated in technical discussions. All authors have read and agreed to the published version of the manuscript. Data Availability Statement: Data available from MWC upon reasonable request. The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results. Technical personnel from the funding organization, especially MJP, did participate in determining the scope and work plan for the study, and helped with other aspects of the project.
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Subject Keywords:laser; plasma; ion engine; accelerator grid; DART; asteroid; erosion; molybdenum; ion propulsion
Issue or Number:15
Record Number:CaltechAUTHORS:20220805-758048000
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Official Citation:Crofton, Mark W., Donner T. Schoeffler, Jason A. Young, and Michael J. Patterson. 2022. "Erosion Rate Measurements for DART Spacecraft Ion Propulsion System" Applied Sciences 12, no. 15: 7831.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:116149
Deposited By: George Porter
Deposited On:09 Aug 2022 23:00
Last Modified:09 Aug 2022 23:00

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