Staging of electric propulsion systems: Enabling an interplanetary Cubesat

Abstract Advances in miniaturization using micromachining processes have led to propulsion systems small enough to consider the feasibility of carrying a large number of thrusters even on small spacecrafts such as Cubesats. Electrospray thrusters developed at the Space Propulsion Laboratory of the Massachusetts Institute of Technology are composed of a highly miniaturized emitter array attached to a tank structure. In terms of volume and mass, the thrusters are small compared to the tank and overall system. This feature makes it possible to envision a staging concept, in which multiple propulsion units are powered in succession, with staging of those that have depleted their propellant. As the satellite mission advances, such a staging operation reduces the spacecraft structural mass, leading to an increased total Δ v capability compared to traditional mission designs. This work examines the impact of such an operational concept in the context of a Cubesat that is capable of raising its orbit from a geosynchronous orbit (GEO) to interplanetary space. While this concept can be applicable to missions of different interplanetary objects such as Near-earth-objects, a mission from GEO to lunar space is investigated in this work as an example. To fully assess the benefit of the staging concept, comparison to a more traditional mission approach is made. When comparing the staging method to a fixed structural spacecraft for a 3U Cubesat, the reduction of propellant mass and time of flight is 12.7 % for a transfer from GEO to the Moon's Sphere of Influence.