Reachable and Retrievable Asteroids considering Lunar and Solar Gravity Assists

This paper proposes the exploitation of lunar and solar gravity assists in reaching and retrieving asteroids. Asteroid retrieval will not only mitigate the threat but also allow easy and constant exploration and exploitation of the asteroid. The asteroids of high threat to the Earth, except for the PHA, are usually easily reachable asteroids as well, for their small orbit energy difference relative to the Earth. As a small energy change can allow for delivering spacecraft and capturing asteroids, such an energy change can be provided by the gravitational perturbation of the Sun and Moon. The idea of using lunar and solar gravity for spacecraft's escape and retrieving asteroids was proposed by the author a few years ago. This talk will clarify the key issues: 1) the mechanism and trajectory design method of employing lunisolar gravity, for delivering spacecraft to deep space, and retrieving and stabilizing asteroids to the vicinity of the Earth; 2) the capacity of lunisolar gravity for delivering and retrieving in terms of specific energy; 3) a list of easily reachable and retrievable asteroids and the possible asteroid flyby, rendezvous, sample-return, and retrieval missions with the proposed technique.