Electric sail option for cometary rendezvous

The recent successes of the European Rosetta mission have shown the possibility of a close observation with one of the most evasive celestial bodies in the Solar System, the comets, and the practical feasibility of a comet rendezvous to obtain detailed information and in situ measurements. This paper discusses a preliminary study of the transfer trajectory toward the comet 67P/Churyumov-Gerasimenko (the same target used by Rosetta) for a spacecraft whose primary propulsion system is an electric solar wind sail. The use of a propellantless propulsion system with a continuous thrust is theoretically able to simplify the transfer trajectory by avoiding the need of intermediate flyby maneuvers. The problem is addressed in a parametric way, by looking for the possible optimal launch windows as a function of the propulsion system performance. The study is completed by a mass breakdown analysis of the spacecraft, for some mission scenarios of practical interest, based on the actual payload mass of the spacecraft Rosetta.