Bimodal propulsion system for small spacecraft: Design, fabrication, and performance characterization

Abstract

The use of multimodal space propulsion has the benefit of increasing satellite mission flexibility with the ultimate goal of decreasing mission development costs. The present paper explores the development of a dual-mode thruster for small spacecraft. By combining an electrospray within the confines of a cold gas nozzle, the fabricated and tested propulsive device can operate either in a high thrust or high specific impulse mode. The thruster herein makes use of a laser microfabricated porous glass triangular prism electrospray emitter using passively fed ionic liquid (EMI-BF4 ) as propellant. The electrospray performance has been indirectly quantified with beam current measurements on the order of 200 nA at an extraction voltage of 2.5 kV, which correlates to a significantly lower thrust than expected. For the second thrust mode, cold gas thrust and specific impulse were measured directly to be 7.9 mN and 44 s, respectively, using nitrogen propellant. The operation of this device in both modes has exemplified its potential applicability to microspacecraft while demonstrating the tradeoffs of bimodal thruster design.