Designing Coordinated Multi-Vehicle Networks for LEO-to-GEO Transport Using Low-Thrust Propulsion

Elements of on-orbit servicing (OOS), such as propellant depots and refuellable servicing spacecraft (servicers), offer promising means to extend the operational lifespan of Earth-orbiting assets. While current concepts for reusable in-space transportation often rely on a single, versatile servicer to transfer payload satellites to high-energy orbits, an alternative approach to this monolithic architecture may employ a network of space-resident transport vehicles to move payloads from low-Earth orbit (LEO) to geostationary orbit (GEO). This paper investigates how servicers equipped with low-thrust propulsion can be used to design fuel-optimal, multi-vehicle transport architectures under temporal constraints. A set of analytical solutions is derived to estimate the time-of-flight and propellant consumption for low-thrust transfers between circular inclined orbits with differing right ascension of the ascending node, accounting for constant thrust and J2 perturbation. Leveraging these analytical methods, a genetic algorithm is employed to optimize the placement of depots and staging orbits, as well as the sequence of maneuvers for each servicer. This methodology enables rapid trade space exploration of servicer constellation designs, which is further used to assess the impact of varying network size and servicer mass on transport performance through numerical Monte Carlo simulations.