Reduction of Saturn orbit insertion impulse using deep-space low thrust

Orbit insertion at Saturn requires a large impulsive manoeuver due to the velocity difference between the spacecraft and the planet. This paper presents a strategy to reduce dramatically the hyperbolic excess speed at Saturn by means of deep-space electric propulsion. The interplanetary trajectory includes a gravity assist at Jupiter, combined with low-thrust maneuvers. The thrust arc from Earth to Jupiter lowers the launch energy requirement, while an ad hoc steering law applied after the Jupiter flyby reduces the hyperbolic excess speed upon arrival at Saturn. This lowers the orbit insertion impulse to the point where capture is possible even with a gravity assist with Titan. The control-law algorithm, the benefits to the mass budget and the main technological aspects are presented and discussed. The simple steering law is compared with a trajectory optimizer to evaluate the quality of the results and possibilities for improvement.The work of E. Fantino and J. Peláez has been supported by Khalifa University of Science and Technology’s internal grants FSU-2018-07 and CIRA-2018-85. Authors of the Space Dynamics Group acknowledge also the support provided by the project entitled “Dynamical Analysis of Complex Interplanetary Missions,”with reference ESP2017-87271-P, sponsored by Spanish Agencia Estatal de Investigación (AEI) of Ministerio de Economía, Industria y Competitividad (MINECO) and by European Fund of Regional Development (FEDER). The authors wish to thank the editorial board and the peer reviewers for their work and their valuable suggestions.Peer ReviewedPostprint (author's final draft