| This dissertation presents the development of a single-propellant ElectroSpray (ES) microthruster capable of covering a wide range of specific impulse (O(103) s) and thrust (O(10 2) muN). It relies on the versatility of the ES with respect to changing droplet size and emitted current, and, as a result, mass-over-charge m/q, by varying liquid flow rate and physical properties. It includes a proof-of concept demonstration of multiplexing, that is, operating many nozzles in parallel, to provide sufficient trust for space applications.;The focus of the project was the design, fabrication and testing of Multiplexed Electrosprays (MES) devices with up to 91 capillaries. The MES device consisted of a planar array of emitters, an extractor consisting of a perforated plate, and an accelerator electrode, with the dual function of containing the beam opening and improving the system propulsive performance.;Uniformity of operation of all emitters was achieved by ensuring that the viscous pressure drop dominated over the electrodynamic pull at the capillary, which necessitated the increase of the hydraulic impedance of the system, by packing each nozzle with silica microbeads.;Calibration of the system performance was made by testing a single-nozzle emitter (1-MES) with identical geometry using a Time-of-Flight instrument. Since scale up from 1-MES to n-MES was verified for n=7 and n=37, all emitters in the array were assumed to operate in unison with the same average propulsion efficiency of a single-nozzle system.;The system was tested with two propellants, methylammonium formate (MAF) in formamide (FA) and pure ethylammonium nitrate (EAN), with propulsive efficiency of 85% and 62%, respectively. Despite its lower propulsion efficiency due to the polydispersity of the beam, EAN enabled an operational range broader than FA/MAF and the fluid was less volatile, which reduced evaporative losses.;The design of the accelerator stage was successful, with a remarkably low beam impact on the electrode at less than 1%. The achieved specific impulse, Isp, and trust, T, for the better performing propellant, EAN, covered the 710-1870 s range and 7.3-31.1 muN range, respectively, by operating 37 emitters in parallel at fixed applied voltage of Delta V = 7.56 kV.;Further scale up to n=91 demonstrated that more than 20% of the nozzles were not spraying properly, as a result of inhomogeneities in the silica microbead filling of the nozzles. Additional microfabrication design should be focused on increasing the MES hydraulic impedance, circumventing the need for microbeads and the unreliability of their filling process. Once realized, such a development would usher in a MES device for versatile in-space maneuvering of low-mass and power satellites by an additional scale up to n≈600. |
