Design of 3-D trajectory sequences for multiple asteroid flyby missions

Prospecting is a necessary pre-requisite of future asteroid mining ventures. It is generally assumed that inspection for the purpose of identifying the asteroid composition can be effectively accomplished from a distance through remote sensing. To be carried out in a timely and economically viable way, prospecting is best performed by devising trajectories such that a single spacecraft manages to fly by as many asteroid as possible, yet seeking to minimize a cost function that we assume to be coincident with propellant consumption. In this paper, we present a method to identify trajectory sequences to multiple asteroids. We restrict our analysis to Near-Earth Asteroids (NEAs), i.e.,, those with perihelion at less than 1.3 AU from the Sun, focusing on Apollo class NEAs only. The volume of space where encounter seeking takes place is a torus-shaped 3-D region in the proximity of the ecliptic. Under the assumption of using impulsive maneuvers to connect ballistic coast arcs, we show that a deterministic building blocks approach is successful in finding a significant number of multi-flyby mission profiles with the desired characteristics. Using this scheme, it is possible to envisage realistic asteroid prospecting missions using a single launch to deploy a number of small spacecraft, with tens—or possibly hundreds—of asteroids visited in a few years.