A Heuristic method based on a shape based technique is used to compute near-optimal solutions for the preliminary design of low-thrust trajectories. The trajectory is assumed to be a Controlled Generalized Logarithmic Spiral and the required acceleration profile to follow it is determined therefrom. Given that Controlled Generalized Logarithmic Spirals can be defined by a small number of parameters, an heuristic algorithm is suitable to select the optimal set that satisfies the boundary conditions and minimize a certain costs. This paper addresses the quasi-optimal design of low-thrust interplanetary trajectories with gravity assist maneuvers, considering time of flight and propellant consumption as the objective functions. Within this scenario, the heuristic algorithm determines the sequence of Gravity Assists as well as the Generalized Logarithmic Spirals parameters connecting them. Additionally, the suitability of the solution as initial guess is assessed to solve the complete Optimal Control Problem employing direct methods.
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