Progress Toward a Variable Specific Impulse Electrospray Propulsion System

The ion Electrospray Propulsion System (iEPS) is a microelectromechanical systems (MEMS)-based electrostatic thruster for space propulsion applications. This device leverages the purely ionic electrospray emission regime, as well as a porous emitter substrate, to eliminate the need for cumbersome ancillary components and achieve small mass, volume, and area footprints that are favorable to nano/pico-satellite integration. In this paper, we review the early maturation of the iEPS concept and a first generation device. We outline the fabrication process, including a unique electrochemical etching technique for the porous metal substrate, and highlight the salient problems and conclusions. Potentials solutions to these issues are posed and incorporated within the framework of a second generation design that expands capability to variable specific impulse, constant power (multi-modal) operation using a dual-grid scheme. The merits of multi-modal operation are explored, along with a preliminary study of the ion optics problem governing the achievable performance.