Ease-of-access to space is growing rapidly with the advent of small satellites, enabling small organizations in industry and academia to contribute to space science and technology. Inevitably, propulsive devices have proven challenging to scale down while maintaining high performance. Cold-gas thrusters are useful for small spacecraft due to their relative simplicity, but their inherently low specific impulse is lowered even further by increased viscous losses at the micro-scale. Electrostatic ion acceleration may be useful for small satellite acceleration or station-keeping. With advancements in microelectromechanical systems (MEMS), it is possible to achieve thrust levels on the order of 1 to 100s of μN and high exhaust velocity using a chip-sized thruster. Both of the aforementioned propulsion types are useful for different mission regimes. There may be interest in developing hybrid or multi-modal thrusters that allow operation of a high-thrust or high specific impulse device in a single package. In this preliminary research, an electrospray thruster is housed within a cold gas nozzle, allowing either device to produce thrust at a given time. The cold gas thruster, fabricated using conventional methods, has a throat size of 0.6 mm and nozzle length of 1 mm. The modification of electrospray performance within the concentric dielectric nozzle was explored using simulations and experiment, finding a decrease of almost 20% in the voltage required for electrospray cone-jet onset.
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