DEVELOPMENT OF ELECTROSPRAY MICRO THRUSTER FOR ISRO SMALL SPACECRAFT

There has been a recent increase in demand for miniaturization of space components. It is economically advantageous to launch spacecraft carrying small payloads. Since small satellites have limited power generation capabilities, they require low power, plus low thrust micro propulsion systems to maintain their orbits and perform attitude control maneuvers. Micro thrusters based on electrospray emitters could find important applications in electric propulsion of micro and nanosatellites. The electrospray thruster utilizes ionic fluid as propellant. The ions generate during electrospray process and accelerate by applying electric field at electrode. Thrust and specific impulse are two important parameters in micro thrusters that are estimated from electrospray current flow rate and applied voltage. This article describes the design and development of a capillary emitter-based electrospray thruster. A prototype model thruster was fabricated with single emitter and square array (2 × 2) configuration using a 32 GA needle. The thruster was tested in ambient conditions with ethanol and ionic fluid: 1-butyl-3-methyl imidazolium nitrate (BMIm-NO3) and 1-ethyl-3-methyl imidazolium tetrafluoroborate (EMIm-BF4) at different flow rates and applied voltage. The different modes of electrospray, namely the dripping, unstable and stable cone-jet spray, rim-jet and multi-jet are observed. The current-flow rate (I-Q) characteristics are observed as I~Q<sup>0.4</sup> and similarly current-voltage (I-V) characteristics are observed as I~V<sup>0.8</sup>, which agrees well with the results reported in literature.