Energy-informed pathways: A fundamental approach to designing ballistic lunar transfers

Abstract

Ballistic Lunar Transfers (BLTs) offer propellant-efficient paths to the Moon. The nature of such transfers relies on the combined gravitational influence of the Earth, Moon, and Sun to reach the lunar vicinity. These transfers are often constructed as point designs to deliver results for a specific application. This investigation focuses on a broader, more foundational approach to BLTs seeking general design characteristics. This investigation introduces dynamics-based approaches for characterizing low-energy cislunar transfers. Principles from dynamical systems theory are applied in the Earth-Moon-Sun Bicircular Restricted Four-body Problem to enable the construction of such paths. Structures such as the instantaneous equilibrium solutions and the evolution of the Hamiltonian offer a dynamical foundation for the mechanisms that govern low-energy transfers. A targeting framework enables the methodical construction of BLT families by applying dynamically informed initial conditions from perigee maps and equilibrium solutions. With solutions generated in the four-body model, several strategies are incorporated to transition the solutions into a higher-fidelity force model governed by the ephemerides of the celestial bodies. Incorporating transfer geometries from the Earth-Moon and Sun-B1 rotating frame offers an effective transition strategy for ballistic lunar transfers to such a higher-fidelity force model. Connections between the underlying dynamics that govern ballistic lunar transfers and the practical results in the mission design process are highlighted.