An Efficient Search Scheme for Using Weak Stability Boundary in a Backup Scenario of NRHO Transfer

Abstract

JAXA is considering several proposals for a cargo supply mission to Gateway, the base planned for human exploration of the Moon and Mars. Among them, this paper focuses on a scenario that uses two launch vehicles: the first lifts off, carrying the HTV-XG supply vehicle and then the second vehicle is launched into orbit without a payload, but with a large amount of remaining fuel (called “Second Stage Vehicle” hereafter). The orbiting supply vehicle makes a rendezvous and docks with the Second Stage Vehicle (SSV). Next, the apogee of the docked vehicles is raised using the thrust of the SSV. At perigee, a maneuver inserts the supply vehicle into a lunar transfer orbit by indirect transfer using a powered lunar swing-by then into a Near-Rectilinear Halo Orbit (NRHO) to dock with Gateway. In this scenario, there are more critical events than in a single launch: the launch of each vehicle, rendezvous, and docking of the supply vehicle with the SSV in Earth orbit, and other maneuvers. Since the nominal orbit is designed for optimal AV, if the apogee-raising or the lunar transfer orbit insertion maneuver fails, extra AV will be required, and the orbit using the powered lunar swing-by may not be able to reach NRHO. In addition, since propellant of the SSV is constantly evaporating, if the maneuver cannot be executed at the scheduled time, the available AV may decrease significantly. Consequently, an NRHO could not be reached by a powered lunar swing-by orbit. In this case, a fallback scenario is proposed to reach a usable orbit via the Weak Stability Boundary (WSB) using the tidal force of the Sun. This paper clarifies the conditions for connecting to an orbit via WSB and describes the method for efficiently transferring from conditions suitable for a lunar flyby to an orbit via WSB.