ANALYSIS ABOUT CONSTRAINTS FOR LOW-THRUST GRAVITY-ASSIST SEQUENCING

Abstract

Exploring the solar system by sending spacecraft to different bodies and planets has significant scientific value. Two different means of enabling demanding missions to targets throughout the solar system are the application of gravity-assist manoeuvres and the usage of electrical low-thrust propulsion systems. Determining optimal trajectories for these kind of missions is a challenging task. A new method of determining low-thrust gravity-assist sequences, while incorporating the gravity-assist partner into the optimisation process, was proposed by Maiwald [1]. The developed search method is simple to use and shows promising results. The quality of the solution can be improved however. To accomplish this, two constraints are proposed, which are designed to reduce the size of the search space. The first constraint is meant to maximise the energy which is transferred to the spacecraft by conducting a gravity assist. The second constraint limits the possible next gravity-assist partner in an user specified range. Within the present thesis, the implementation and evaluation of these constraints is realised. At first, the constraints are deployed into the method and a series of simulations, using an example mission from Earth to Jupiter, is conducted. The results are evaluated and discussed afterwards. The evaluation of the tests revealed that the constraints have beneficial influences on the convergence properties of the solutions. The quality of the resulting low-thrust gravityassist trajectories could be improved by utilisation of the implemented constraints.