Rapid Solar Sail Rendezvous Missions to Asteroid 99942 Apophis

摘要

Different concepts for eliminating the threat of collision with a near-Earth object have been suggested in recent years. Most of them require that a probe is inserted in orbit around the object to obtain accurate physical and orbital data. Asteroid 99942 Apophis is a member of the Aten group of asteroids, having orbital periods shorter than 1 year. Such an asteroid is used here as a practical example to investigate the characteristics of new mission concepts and as a candidate for a potential space agency project aimed to tag an asteroid either for scientific purposes or for a deflection mission decision. The purpose of this paper is to investigate the potentialities offered by a solar-sail-based rendezvous mission toward Apophis. In particular, rapid transfer trajectories are studied, that is, missions whose transfer times are less than one terrestrial year. We show that a realistic near-term mission option, with a transfer time of about 300 days, requires a solar sail with a characteristic acceleration of 0.5 mm/s~2. A square solar sail with a side of about 90 m is needed for a payload of 50 kg, whereas a greater sail with a side of 160 m is called for with a payload of 150 kg. The solar sail performance is compared to that achievable with conventional propulsion systems.