Note: This post is adapted from my journal paper, which was accepted to Aerospace Science and Technology in Spring 2021. You can read the full paper here
Abstract – Designing Trajectories Resilient to Missed Thrust Events Using Expected Thrust Fraction
With the adoption of efficient low-thrust propulsion methods, the probability 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 expected thrust fraction arrive with a median lateness which is approximately half that of traditionally designed trajectories for a negligible change in delivered mass. Expected thrust fraction can help astrodynamicists mitigate risks posed by the use of low-thrust propulsion.
How the Control Angle Changes as Expected Thrust Fraction Becomes More Conservative
Key Takeaways
The full paper is online here, but here are, in my opinion, the most interesting aspects
- ETF-designed trajectories have a median 47.6% decrease in lateness and a 0.4% decrease in delivered mass.
- There’s an integral defining ETF, that can be solved independently from the trajectory design process.
- Additionally, a rather good closed-form approximation for this integral is solved
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