A comparative assessment of heliocentric and controlled lunar impact end-of-life disposal strategies for Near Rectilinear Halo Orbits

In the coming decades, space traffic within the cislunar region is expected to grow exponentially, driven by an increasing number of planned missions to the Moon and related studies. Since severe issues with the management of man-made space debris have already been observed in near-Earth orbits, it is crucial to address this problem proactively to prevent a similar situation from developing in the cislunar region. This is particularly relevant given that managing debris in the cislunar environment would be considerably more challenging than in near-Earth orbits, due to the greater distance from Earth and the inherently nonlinear and chaotic dynamics that characterise cislunar space. The most effective approach to address these issues would be to incorporate mitigation measures directly into the mission design phase, for instance, carefully planning a priori low-cost, robust End-of-Life (EoL) disposal phases, particularly for spacecraft orbiting in regions expected to host a significant proportion of future space traffic. In this scenario, a key role is played by Near Rectilinear Halo Orbits (NRHOs), which are considered highly attractive candidates for future missions. Of the four main EoL disposal strategies available in the Earth–Moon (EM) system, two are particularly well-suited to spacecraft operating in NRHOs: heliocentric disposal and controlled lunar impact. The first relies on injecting the spacecraft onto the unstable manifold of the reference periodic orbit, allowing the trajectory to leave the EM vicinity passing through EM-L2[jls-end-space/], for then, with appropriate phasing between the EM and Sun–Earth (SE) systems, transit through either SE-L1 or L2[jls-end-space/]. To prevent re-entry into the Earth’s neighbourhood, the SE Zero-Velocity Curves (ZVCs) should then be closed to ensure a no-return escape. On the other hand, controlled lunar impact can be defined as an optimisation problem. After inserting the spacecraft on the unstable manifold, small manoeuvres are introduced to target Moon impact while ensuring that historical sites and protected regions are avoided. The results obtained are then refined using an ephemeris-based dynamical model. These two disposal strategies are applied to six cislunar Lagrangian Point Orbits (LPOs): 4 NRHOs, two in EM-L1 and two in EM-L2[jls-end-space/], and 2 Halo orbits, one in EM-L1 and one in EM-L2[jls-end-space/]. The results obtained are then compared in terms of (Formula presented), Time of Flight (ToF), and robustness. This work aims to provide a preliminary overview of disposal design for EM–NRHOs, including an assessment of the dynamical mechanisms that govern such disposal strategies.