Design and manufacture of the next generation of ion electrospray thrusters

Abstract

In this thesis, a full re-design of the iEPS 2.3 system developed by the Space Propulsion Lab has been undertaken, producing its 3.0 incarnation. Each sub-component and assembly has been investigated and improvements to them explored, recommended and implemented. The supporting frames and extractor electrodes have undergone modifications and a full process re-design, respectively, in order to improve the reliability and performance thereof. Much of the work described in the following pages has focused around solving a core problem of emitter flooding - that is, excessive wetting of the emitter substrate before it can be fired, leading to a short-circuit and a failed engine. To this end, a solid-state valve which employs the electro-wetting phenomenon, and the supporting architecture for the same has been developed and integrated into a full thruster package. This has been tested in flight-like conditions and shown to reliably prevent the described failure mode without interfering in the overall performance, even rendering it more resilient to intermittent spikes in emission. In addition, two new materials to replace the current borosilicate glass emitter chips have been investigated, one made in-house and the other purchased off-the-shelf. Both were tested in overall current vs. voltage performance, time-of-flight spectroscopy and retarding potential analysis. The former material, while not fully developed, has nonetheless displayed remarkably promising results, outputting very high current in the pure ionic regime.