Round-Trip Heliocentric Trajectories for Continuous-Thrust CubeSats

The technological maturity achieved by CubeSats now enables mission designers to consider these small spacecraft as viable options for planning robotic missions in interplanetary space. Equipping a CubeSat with a miniaturized solar electric thruster allows for optimized use of its limited propellant mass by designing an appropriate (optimal) transfer trajectory. Assuming a two-dimensional heliocentric mission scenario, this paper investigates the performance of an interplanetary CubeSat equipped with a miniaturized solar electric propulsion system in executing trajectories that reach a specified solar distance and subsequently return to Earth. The paper presents a procedure for designing such round-trip trajectories within an optimization framework, where the total flight time is minimized under a propellant mass constraint. Mission performance is evaluated as a function of the target solar distance, and numerical simulations are carried out for an interplanetary CubeSat with inertial and propulsion characteristics similar to those of a recently proposed small spacecraft.