Designing Trajectories Resilient to Missed Thrust Events Using Expected Thrust Fraction

With the adoption of efficient low-thrust propulsion methods, the probabil- ity of a missed thrust event occurring has become a significant concern for short and long-duration missions. If the missed thrust event occurs during a critical portion of the trajectory, the mission can be compromised. Therefore, it is essential to develop trajectories that are resilient to missed thrust events. This paper investigates the use of expected thrust fraction, which embeds the stochastic nature of missed thrust events into a deterministic optimal control problem. The technique is applied to a sample Mars-to-Earth trajectory. The performance of trajectories designed using expected thrust fraction is compared with traditionally designed trajectories and trajectories with a forced terminal coast. Thus, the changes in resiliency to missed thrust events are quantified. In this investigation, trajectories designed using ex- pected thrust fraction arrive with a median lateness which is approximately half that of traditionally designed trajectories for a negligible change in de- livered mass. Expected thrust fraction can help astrodynamicists mitigate risks posed by the use of low-thrust propulsion.