Lunar capture orbits using a non-planar tether cutting maneuver

This paper studies a powered swing-by maneuver using tether propulsion. Previous studies have combined swing-by maneuvers with the application of an impulse at the periapsis to enhance the velocity change during the close approach. Although the application of an impulse at the spacecraft periapsis passage can generate a larger effect than the unpowered swing-by maneuver produces, this maneuver requires an additional fuel consumption. Thus, tether propulsion has been proposed by several authors as an alternative that does not require additional propellant consumption. In this case, the angular momentum of the tethered satellite system is converted into kinetic energy. Different from previous studies where only the planar motion of a tethered system is analyzed in gravity assist maneuvers, the aim of this paper is to find the optimal pitch–roll configuration of the tethered satellite system, such that a highly inclined circular orbit around the moon is achieved after tether cutting. This type of orbits about planetary moons is very attractive for observational purposes. Three planet–moon systems have been considered in this work to study the gravitational capture using tether propulsion: Earth–Moon, Jupiter–Europa, and Saturn–Enceladus. Two-body problem (patched conics) is used in the inner moon space. Because the pitch and roll rotations of the tethered satellite system are considered, the spacecraft would be injected into non-planar orbits. As a result, a 100-km-long tether cut at moon’s periapsis would be able to inject the payload into a highly inclined circular orbit about Moon, Europa, and Enceladus. Additionally, when the planet’s gravitational force is also considered in the trajectory of the tethered satellite system, numerical simulations show that the circular and periodic behavior of the payload’s orbit around the moon could be significantly altered, particularly in the Saturn–Enceladus system. Finally, the velocity changes, experimented by the two satellites in the periapsis of Moon, Europa, and Enceladus, respectively, are computed to perform an analysis of the ratios of the required propellant and tether masses to payload mass. The mass requirements for chemical fuel and tether show the great advantage of tether propulsion to conduct a propellantless orbital transfer. © 2025 Elsevier B.V., All rights reserved.