Note: This post is adapted from my conference paper, which was presented at the Space Flight Mechanics Conference in Winter 2021. You can read the full paper here.
Abstract – Expected Thrust Fraction: Resilient Trajectory Design Applied to the Earth Return Orbiter
Electric propulsion is an enabling technology for NASA’s Mars Sample Return mission that affords an order of magnitude reduction in fuel. Unfortunately, electric propulsion’s low-thrust capabilities require long thrusting arcs that make spacecraft susceptible to disturbances resulting in missed thrust events. One method for designing trajectories resilient to such missed thrust events is expected thrust fraction, which embeds their stochastic nature into a time-varying duty cycle. This paper investigates the application of expected thrust fraction to the Earth Return Orbiter’s outbound Earth-to-Mars trajectory and compares it with trajectories designed using traditional methods to mitigate missed thrust events. Through the use of expected thrust fraction, a trajectory with a baseline 65.4% success rate is improved to an 86.6% success rate at the cost of only a 12 kg reduction in delivered mass. Additionally, when expected thrust fraction is used in conjunction with a terminal coast, a 96.0% success rate is achieved, which is higher than any single mitigation technique.
Key Takeaways
The full paper is online here, but here are, in my opinion, the most interesting aspects
- Missed Thrust Event (MTE) resiliency can be increased from 65% -> 96% at the cost of only 12 kg of delivered mass.
- The recovery duration is the most important portion of the inoperability period.
- Expected Thrust Fraction with a terminal coast outperforms all other MTE mitigation methods.
Presentation
Due to COVID-19, this conference was held virtually, and I have uploaded a video of my presentation below.
Want More Gereshes?
If you want to receive new Gereshes blog post directly to your email when they come out, you can sign up for that here!
Don’t want another email? That’s ok, Gereshes also has a twitter account and subreddit!