Optimization of low-thrust trajectory for a mission to the asteroid 433 Eros with Earth gravity assist

Subject of this paper is the design of a space robotic mission to the asteroid 433 Eros [1]. The mission aims to grab a boulder from its surface and transport it inside the Earth's Hill sphere. This kind of mission was chosen to develop a method of analysis of all the opportune trajectories for a sample-return mission, using a generic Near-Earth asteroid as 433 Eros. The propulsion system used for the theorized mission consists of three autonomous ion thrusters fully adjustable in magnitude and direction of thrust. Furthermore, during the return flight an Earth gravity assist is used to increase the mass of boulder that the spacecraft can transport towards Earth. Selecting the same time window of the ARM, different trajectories, separately for the outbound and inbound flights, are calculated using indirect methods. Subsequently, a plausible interpretation of the different performances of the calculated trajectories is given, considering both the solar electric power available to the spacecraft and the geometric configuration of the bodies involved. At the end of this process, all the calculated trajectories for the outbound and inbound flights are compared, and possible final solutions for the mission are discussed.