Analysis of lifetime extension capabilities for CubeSats equipped with a low-thrust propulsion system for Moon missions

Abstract

In this paper, we analyze the mission lifetime extension capability for a CubeSat smaller than 3U in a circular lunar orbit at a 100-km altitude, assuming the utilization of a state-of-the-art low-thrust electric propulsion system such as pulsed plasma thrusters with an impulse bit (Ibit) and velocity change (ΔV) below 60 μNs and 120 m/s, respectively. Because of the non-spherical gravity field of the Moon and its strong influence on low-altitude lunar orbits, a long orbital lifetime is achievable only within a set of stable orbits which mainly depends on initial inclination and right ascension of the ascending node (RAAN); moreover, as a piggyback on a main mission, the deployment of CubeSats in those stable orbits is not guaranteed. For this reason, we propose an orbit correction strategy whose performance is constrained to the initial orbital parameters of the CubeSat (i.e., inclination and RAAN), its solar power generation capacity, its attitude control strategy, and its propulsion subsystem features, such as the thruster Ibit and budgeted ΔV. By analyzing the required time to perform the orbit correction maneuvers to extend the orbital lifetime and the minimum altitude achieved throughout the mission lifetime of the spacecraft, we demonstrated that a one-year mission can be achieved within initial orbital inclination values greater than 65°. For unstable orbits bounded by initial orbital inclination values smaller than 65°, the orbit lifetime can also be extended from a few days to up to one year. Better performance with our proposed orbit correction strategy can be achieved by using an electric propulsion system featuring Ibit and ΔV values greater than 40 μNs and 80 m/s, respectively. Our results show the feasibility of performing any orbit correction maneuver for the enhancement of the mission lifetime of a CubeSat, expanding the performance capabilities of CubeSats to any mission in a lunar orbit by reducing the limitation of deploying them in unstable orbits.