Co-optimization of spacecraft and low-thrust trajectory with direct methods

TL;DR

This paper presents a co-optimization approach for spacecraft solar array size, thruster modes, and trajectory using direct methods, demonstrating improved mass delivery and smaller solar arrays for electric propulsion missions.

Contribution

It introduces a novel method for smoothly selecting optimal discrete thruster modes within a co-optimization framework, applied to a benchmark Earth to Comet 67P rendezvous problem.

Findings

Multiple thruster modes increase net useful mass.

Co-optimization reduces required solar array size.

Method successfully solves a complex benchmark problem.

Abstract

Solar-powered electric propulsion systems can operate in multiple modes and their operation is coupled to the power generated by solar arrays. However, the power produced by the solar arrays is a function of the solar array size and heliocentric distance to the Sun, which also depends on the to-be-optimized trajectory. The optimization of spacecraft solar array size, thruster modes, and trajectory can be performed simultaneously, capitalizing on the inherent couplings. In this work, we co-optimize the spacecraft's solar array size, thruster modes, and trajectory using a direct optimization, which allows for maximizing the net delivered mass. A particular challenge arises due to the existence of discrete operating modes. We proposed a method for smoothly selecting optimal operation modes among a set of finite possible modes. The utility of the proposed method is demonstrated successfully by solving a benchmark problem, i.e., the Earth to Comet 67P fixed-time rendezvous problem. The results indicate that utilizing multiple modes increases the net useful mass compared to a single mode and leads to a smaller solar array size for the spacecraft.