A top candidate green monopropellant proposed as a safe replacement for hydrazine in spacecraft systems is also shown in tests to be a high performance propellant for ion electrospray thrusters. The proposed effort is to take full advantage of these remarkable characteristics to develop an efficient bimodal ion-chemical thruster system using a common propellant supply tank. This proposal responds directly to the Dual Mode Propulsion focus area in the T2.03 STTR topic. The expected mass and volume savings, increased propellant use efficiency and the added flexibility in thrusting options (high thrust with moderate Isp and lower thrust with high Isp) will significantly augment the operational propulsion and attitude control ranges, especially in small spacecraft applications. Phase I demonstrated and tested an efficient propellant management system interfacing the high pressure monopropellant tank with the ion electrospray thruster arrays. This allows the development in Phase II of a complete protoflight system, including multiple thruster arrays and control electronics, that can be integrated into a space mission. The Phase II development will leverage the existing ion electrospray thruster technology, and integrate it with the new propellant management system to provide a multi-thruster ion propulsion system. The assembly will be designed to interface with an existing compact chemical thruster to achieve a complete proto-flight bi-modal propulsion system, ready for integration and flight testing on a space platform. Potential NASA Applications (Limit 1500 characters, approximately 150 words) NASA applications are many, as most space system designs attempt to minimize bus mass and volume budgets to maximize payload capacity, and are concerned about propulsion. The combined capability for agile maneuvering, precision attitude control and thrusting and extended mission lifetime applies to missions in earth orbits or lunar and interplanetary space, and also fractionated observatories requiring multiple platforms with good control performances. Geosciences, heliophysics, astrophysics and lunar or interplanetary exploration will benefit. Potential Non-NASA Applications (Limit 1500 characters, approximately 150 words) Non-NASA space systems, from commercial or government organizations will also benefit from the bimodal propulsion advantages in performance ranges, mass and volume budget savings and extended lifetime. The potential applications are numerous and include earth observation, monitoring and communication systems, satellite constellations, robotic systems to assemble in space or retrieve debris.
