Description: This project will further development of a thruster capable of both chemical monopropellant and electrospray propulsion using a single "green" ionic liquid propellant. the thruster concept consists of an integrated microtube/electrospray thruster that shares all propulsion system hardware between electric and chemical thruster modes, i.e. one propellant, one propellant tank, one feed system, and one thruster. Thus, the thruster is not significantly more massive than a standalone state-of-the-art chemical or electric thruster, but capable of either thrust mode and selectable as mission needs arise. This has several benefits, including the optimization of trajectories using both chemical and electric thrust manuevers as well as a significantly increased mission design space for a single propulsion unit. The propulsion system is capable of both high impulse per unit volume and high thrust per unit volume as the total impulse per unit volume is 1500 N-s/U in the chemical thrust mode and 2750 N-s/U in the electric thrust mode, where either type of manuever could be selected on-the-fly. The specific objectives for this study are to build a single microtube setup and feed system and test both the chemical monopropellant mode and electrospray mode with the same setup. This setup will allow verification of thruster models stemming from previous chemical mode tests, verify electrospray operation at lower flow rates than we have previously tested, and study the interactions in switching from the chemical mode to the electric mode and vice-versa with specific attention paid to potential life limiting mechanisms. As an additional part of this contract, we will work in parallel to investigate techniques required to manufacture multi-emitter arrays and conduct fluid flow and electrostatic simulations to further develop the preliminary thruster design.

Benefits: Multi-mode propulsion fulfills NASA technology needs as outlined in the In-Space Propulsion Technology Roadmap, monopropellant microthrusters and electrospray thrusters, as well as fulfilling needs highlighted by the National Research Council, specifically the need for both chemical and non-chemical propulsion that fulfills the needs for high mobility micro-satellites and extremely fine pointing and positioning for certain astrophysics missions. Research has shown the benefits of multi-mode micropropulsion for NASA missions, including, more efficient small satellite formation flight, optimized attitude control, enhanced transfer rate and useful mass for Jovian missions, more favorable conditions for lunar impact, launch mass savings, and payload mass advantage to GEO.

Multi-mode micropropulsion has potential to meet Air Force needs for fractionated, composable, survivable, autonomous systems, i.e., satellites that can be assembled, tested, and launched within days of operational requirement. Specifically, the large mission design space resulting from ability to select and complete chemical or electric maneuvers at will significantly enhances the capabilities of these 'plug-and-play' satellites. It has potential to impact the exploding small/CubeSat market, an estimated market value of $7.4B, with a predicted 360% increase in launches over the next 5 yrs, and future plans for competing space-based internet constellations. The large mission design space enabled by multi-mode propulsion could be beneficial to this market in that a single, off-the-shelf system is capable of many different types of missions. An entirely new propulsion system would not have to be developed for each mission individually, reducing costs associated with development, testing, and risk.