Electrostatic and Electrochemical Optimization of Electrospray Thrusters

2012-2013: As the electrospray phenomenon transitions from a laboratory-proven propulsion source to a flight-ready prototype, significant work must be done to develop the full propulsion system. The goal of this work is to design, develop, test, and redesign a package and propellant supply system which service and support an arrayed ion electrospray propulsion system. 2013-2014: The established, operational iEPS device has reached a stage where long-term testing is needed to verify consistent operation and to investigate performance variation with life, if any exists. Such a characterization will be performed once propellant handling protocols have been developed for the propellant supply system and lifetime-lengthening modifications have been made to the extractor grid geometry. 2014-2015: The established, operational iEPS device has been prepared for flight. However, current manufacturing techniques bottleneck in the fabrication of the array of emitter tips. Emitter array fabrication via direct synthesis of structures or through batch, uniform material removal is desired. Materials and processes will be surveyed and developed with a goal of making the entire iEPS fabrication process a reliable, repeatable batch process. The theme of the fellowship work has been the manufacture of flight-worthy ion electrospray propulsion systems (iEPS). Toward that end, activities have included hands-on manufacturing work, the design and analysis of microscale components and manufacturing processes, development of thruster support systems, the assembly of electrospray thrusters, and the testing of all of the aforementioned. Over the past two and a half years, the technology has rapidly advanced from a laboratory setup with various flaws to a mature prototype which is being demonstrated in space and commercialized privately. Much of this advancement is due to small, iterative changes to the design of the iEPS technology realized throughout the research. In the first year, some of the first system integration tests were performed. Thrusters were preliminarily tested with both single and dual grid configurations. Additionally, a first attempt at flight-like testing was made. Regarding the propellant supply system, protoype tanks were fabricated and assembled and preliminary testing of propellant filling and supply began. All of this initial testing informed changes to the design of the iEPS package, emitter, and extractor design and confirmed the propellant supply concept proposed and used in later systems. The second year of the fellowship included major changes to the iEPS package and extractor design, research into the difficulties of propellant management, an on-site experience at NASA Glenn Research Center, and preparation for and completion of the PhD qualifying exam process. Research was stopped halfway through the third year during which time the goal was the research into and design of manufacturing processes for bulk fabrication of emitter tips for electrospraying.