Microfabrication and test of an integrated colloid thruster

This paper reports on the design, fabrication and test of an integrated colloid micropropulsion system for spacecraft attitude control using the ionic liquid EMI-BF4 as fuel. The principle of operation of the thruster is identical to electrospray ionization. The objective of the project was to demonstrate the feasibility and operability of arrays of microfabricated capillary emitters with individual extractor electrodes. This design approach results in an identical electric field distribution from one capillary to the other, avoids crosstalk and therefore allows for a more finely modulated thrust control. Spraying tests with different thruster configurations were conducted under vacuum conditions. Tests were performed with different thruster configurations and starting voltages around 700V were observed

Design and fabrication of an integrated MEMS-based colloid micropropulsion system

The design, microfabrication and initial performance results of a prototype electrospray thruster with integrated individual extractor electrodes are reported in this paper. The aim was to demonstrate increased thrust with an array of emitters spraying simultaneously. Micromachining technologies were employed to achieve large emitter density per surface area, simple integration and good structural repeatability. The novelty of this work lies in the combination of high aspect ratio capillary emitters (height of 70 microns, inner diameter of 20 microns) with individual extractor electrodes having diameters from 80 microns upwards and a spacing as low as 25 microns from the capillary tips. The individual integrated electrodes, as opposed to the standard approach of one common electrode, allow for greater uniformity in critical voltages between capillaries and more finely modulated thrust control. Tests with the newly developed thrusters using the ionic liquid EMI-BF4 show that starting voltages below 700V and currents around 300nA per emitter can be achieved