Optimisation Strategies for Galilean Moon Tours: Low-Thrust Multiple Gravity-Assist Trajectory Design for GTOC6

Around 1610 Galileo Galilei made his discovery of the four large moons orbiting Jupiter which are referred to now as the Galilean moons. The moons Europa and Ganymede attract a significant amount of scientific interest due to potential present subsurface oceans. As consequence, the design of missions to go there and explore the moon system are increasing. This culminated in the sixth edition of the Global Trajectory Optimisation Competition (GTOC6) which is focussed on solving low-thrust multiple gravity-assist trajectories to map the Galilean moons. The aim of the thesis is to understand the complexity of the GTOC6 problem and to explore and evaluate the quality of various optimisation strategies to solve flyby sequences with low-thrust arcs. First, insight to the complexity of the problem was gained by analysing the best solution to GTOC6 so far by the Chinese Centre for Space Utilisation (CSU). From the results a clear picture was drawn from what the trajectory model should be capable of. The low-thrust trajectory model is based on the spherical shaping method that is part of the Tudat astrodynamics toolbox. A full analysis of the shaping method was performed to identify the capabilities and shortcomings of the algorithm. One of the main shortcomings is the limited accuracy for trajectories where the departure and arrival conditions differ with several degrees and more for the right ascension of the ascending node (RAAN). For optimisation use was made of differential evolution (DE). An extensive test was performed to determine the optimal settings. The result was that defining the control parameters randomly during the evolution was the best option with respect to quality and convergence. What followed was defining the optimisation model for a variable number of flybys. Furthermore, a framework was developed with six different optimisation strategies. A sequence of maximum five flybys was set to test the strategies. The strategies define the amount of freedom aro
Space Exploration
Astrodynamics and Space Missions
Aerospace Engineering