Physarum KISS: An innovative algorithm for the preliminary analysis of multi-gravity assist interplanetary trajectories

Multi-gravity assist (MGA) trajectories are used in space engineering for reducing the cost (propellant and time of flight) of interplanetary missions by using the gravitational field of celestial bodies. The probes Mariner 10 (mission to Mercury, launched by NASA on 1973), Voyager 1 (furthest human-made object, NASA, 1977), MESSENGER (mission to Mercury, NASA, 2004) and Cassini (mission to Saturn, NASA-ESA, 1997) are examples. Making use of gravity assist manoeuvres around planets, the velocity vector of the spacecraft relative to the Sun changes during a passage in proximity of the planet, while the velocity vector relative to the planet is rotated (no change in module). The problem of finding the sequence of planets (including resonances, i.e. multiple passages in proximity of the same planet) that guarantees the best transfer to a target space object is a fascinating problem in combinatorics and discrete optimisation. The computational complexity is NP-hard [1]. In this work,
a simple and innovative bio-inspired multidirectional algorithm for preliminary analysis of multiple gravity assist planets' sequences is introduced and compared to a branch & cut algorithm.