Low-Cost Versatile On-Orbit Servicing CubeSat with Refuellable Multimodal Water-Propellant Propulsion System 低成本多功能在軌服務 CubeSat 與可補給多模態水推進系統

With the exponential growth of small satellite constellations and commercial space activities, on-orbit servicing (OOS) has become a critical technology for extending spacecraft operational life, mitigating space debris, and reducing space mission costs. However, state-of-the-art OOS systems rely on large, high-cost satellites that are incompatible with the risk tolerance and rapid-response requirements of large-scale small satellite operations, while existing CubeSat-based OOS solutions face inherent limitations in multimodal maneuverability, miniaturized multifunctional docking, and high-precision autonomous rendezvous and docking (RVD). This paper presents a novel 16U CubeSat platform for versatile, low-cost, and reusable on-orbit servicing, featuring a refuellable multimodal propulsion system using water as the sole propellant. The proposed design integrates two complementary propulsion modes: a high-thrust hydrogen-oxygen combustion mode (2 N thrust, 250–350 s specific impulse) for rapid orbital maneuvering, and a low-thrust electromagnetic plasma mode (8–12 mN thrust, 900–1100 s specific impulse) for precision attitude and orbit control. A miniaturized deployable androgynous docking interface (0.25 U stowed volume) is developed to enable mechanical latching, propellant transfer, power transmission, and data exchange between CubeSats, with a hybrid-rigid-flexible Sarrus linkage mechanism and antagonistic shape memory alloy (SMA) actuation for passive energy absorption and zero-power locking. Furthermore, a high-precision GNC system is designed, incorporating a cubature Kalman filter (CKF) for staged relative navigation, a time-fuel optimal phase plane guidance law, and an improved deep learning-based visual pose estimation algorithm for close-proximity operations. A dual-satellite technology demonstration mission is designed and validated through high-fidelity numerical simulation and semi-physical prototype testing, covering short-range release and docking, long-range 180° phase-difference rendezvous (both impulsive and low-thrust modes), and on-orbit refuelling functional verification. Simulation results show that the system achieves millimeter-level pose estimation accuracy in the docking phase, accommodates 15° angular misalignment and 0.1 m/s docking velocity, and completes all mission phases with a total propellant consumption of 1.357 kg. This work provides a low-cost, reusable, and versatile OOS solution for CubeSat constellations, enabling high-frequency, multi-target on-orbit missions including satellite life extension, debris removal, and in-orbit asset maintenance, with significant engineering application potential for future low Earth orbit space ecosystem development.