Development of Multi‐Modal, High‐Density Electrospray Porous Metal Thrusters

To high-level, the stated objectives of the research plan are • to study the properties of electrospray emission from porous surfaces, with an emphasis on ionic liquids operating in the purely ionic mode, and develop a theoretical framework that includes, but is not limited to, and understanding of conditions that might permit concurrent activation of several charge sources in close proximity; • to perform systematic optimizations for emitter geometry and determine the feasibility of approaching the theoretical thrust density limit. The following is a list of the salient research accomplishments and related conclusions gleaned over the course of this research program. • Using a multi-grid extraction system it is possible to decouple the current of an electrosprayed beam from its energy. Among other things, this enables the ability to modulate the effective Isp at constant power and provides access to disparate operation modes (e.g. a high thrust / low Isp mode and a low thrust / high Isp mode). • While metallic emitter electrodes have far greater heritage in electrospray, their dielectric counterparts are much easier to manufacture and appear to represent acceptable surrogates as far as performance is concerned. • Laser micromachining of porous dielectrics (most notably glass) is a high-fidelity and scalable approach for creating dense electrospray emitter arrays. • These arrays, integrated with MEMS-based packages, are capable of producing tangible thrust levels with reasonable efficiency.