Design of low-thrust missions to asteroids with analysis of the missed-thrust problem

Small bodies in the Solar System, such as asteroids and dwarf planets, are ideal targets for electric propulsion missions because of the high delta-V required to rendezvous with these targets. We study trajectories to the asteroid belt, including a human mission to Ceres and a sample return mission to (216) Kleopatra, along with trajectories to the Jupiter Trojan asteroids. For the human mission to Ceres, payload masses of 75 Mg are achievable with a 11.7 MW nuclear electric propulsion system and an initial mass in LEO of 289 Mg. For low-thrust sample return missions to the main belt asteroid Kleopatra, Mars and Earth are useful gravity assist bodies, with payload masses of 950-1150 kg possible using a 20 kW solar electric propulsion system. A mission to the Jupiter Trojan asteroids would be well-served by visiting two objects. The pair 1986 TS6 and Hektor stand out as ideal targets to visit for launch dates between 2020 and 2040, with missions possible using the off-the-shelf BPT-4000 Hall thruster and power levels in the 30-40 kW range. During a low-thrust mission, there is a significant possibility of an event which causes the spacecraft to miss some portion of a thrust arc. These missed thrust events can be overcome for reasonable propellant margins of 5--15\%, with higher margins required for higher power levels. Gravity-assist trajectories should feature a coast arc leading up to the flyby. If not, the mission may be lost if a missed-thrust event occurs during a thrust arc prior to the gravity assist