A Comparative Analysis of Low-thrust and Neptune Gravity-assist Strategies for Redirecting Trans-Neptunian Objects to Mars

We investigate the feasibility of redirecting trans-Neptunian objects (TNOs) from the Kuiper Belt to Mars using sustained low-thrust propulsion combined with a single Neptune gravity assist. Numerical trajectory optimisation with global derivative-free solvers shows that carefully phased low-thrust control can reduce the required \(\Delta V\) to approximately 2.5–3.2 km s\(^{-1}\) for transfer times of several centuries. For the higher-eccentricity test case, a well-timed Neptune flyby further lowers the propulsive cost, whereas for the lower-eccentricity case, it yields only marginal savings at the expense of a longer transfer time. We illustrate the sensitivity to the initial semi-major axis, eccentricity, and inclination, describe the trade-off between pre- and post-assist control effort, and discuss structural and operational limitations. The results suggest dynamical accessibility for inward volatile delivery from the outer Solar System within an idealized model. Abstract Published by the Jagiellonian University 2026 authors