Ion Emissive Membranes for Propulsion Applications

Experiments show electrostatic thrusters with components such as the discharge chamber or acceleration channel, solenoid or permanent magnets, hollow cathode, and keeper can be replaced by a simple, propellant‐selective, solid‐state, ion‐conducting membrane (Wilbur et al., 2007; Wilbur, Wilson, and Williams, 2005). In addition, analyzes show these membranes can be shaped, structured, and assembled into integrated thruster systems that will operate at much greater thrust densities and thruster efficiencies than those for state‐of‐the‐art, Hall and ion thrusters (Wilbur, Farnell, and Williams, 2005). The implications of these findings are revolutionary and promise an electrostatic propulsion system much less massive, more reliable, and less costly than ion and Hall thruster systems as they can be fabricated readily using traditional ceramic manufacturing techniques. The status of the Emissive Membrane Ion Thruster (EMIT) concept is described and recent measurements are used to estimate the performance of a propulsion system based on this concept. Estimates are also provided for the specific masses of various components required for it to perform typical satellite missions and comparisons are made to conventional electric propulsion systems currently in use. The emissive membrane thruster is shown to enable operation at 20% to 50% greater thrust‐to‐power ratios at specific impulses from 1000 s to 5000 s. Related performance advantages will also be discussed and analyses will be presented that show why an EMIT system is less expensive, more reliable, easily scalable, and simpler compared to existing electric thruster systems.