Mixed Low Thrust – Coast Arc Model for Gravity-Assist Interplanetary Trajectory Optimization

Paper number

IAC-07-C1.3.06

Author

Mr. Joris Olympio, Ecole des Mines de Paris, France

Coauthor

Dr. Regis Bertrand, Centre National d'Etudes Spatiales (CNES), France

Coauthor

Mr. Thierry Dargent, Thales Alenia Space, France

Coauthor

Prof. Jean-Paul Marmorat, France

Year

2007

Abstract

Trajectory optimization has always been of great interest in space exploration, from orbital transfer to interplanetary trajectory. Optimization methods, direct or indirect, are often of major use, although for low thrust interplanetary transfer, the initialization of these methods usually lack of efficiency. Recent advances manage to solve this problem by proposing low thrust models. These allow to compute a pseudo-optimal trajectory that can later be uses as an initial guess for a direct approach solver. Consequently, the more the model will be close to the optimal solution, the best chance we have to get a good optimum. Some work on the reliability of the model toward the real low thrust trajectory should be done.
So far, exponential sinusoid are used because they proved their efficiency and their ease of use, however one can emphasize that the initial guess proposed by exponential sinusoid methods has sometimes a cost very far from the one of the optimized trajectory. The differences essentially come from a control that is continuously thrusting, with no bang-bang sequences, and from model that cannot correctly describe the rendezvous phase. The latter is of great importance and a major issue in most low thrust models. Only shaping methods through parameterized pseudo equinoctial elements manage to solve the problem, but presents a violation of the dynamic and noticeable errors when propagated. So far, to our concern, no shape based methods which include coast arcs exist.
We then introduce a model implementing coast arcs, based on the inverse dynamic method, which can improve our low thrust trajectory modelling and with few parameters. The focus will be on the properties of the new model. These properties directly provide the thrusters capability, and the trajectory feasibility. Some conditions on the choice of the model parameters will be given. Then, we will introduce optimization problem that get the optimal value for the parameters under specific constraints. It is expected, that through this optimizer we can get a good initial guess that can be close to the optimal low thrust trajectory, i.e. we can reduce the cost given by other low thrust model. Furthermore, we will show that under some conditions, we can reduce the rendezvous manoeuvre cost. We will lastly give some practical example of our approach.

Abstract document

IAC-07-C1.3.06.pdf

Manuscript document

IAC-07-C1.3.06.pdf (🔒 authorized access only).

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