Note: This post is adapted from a journal paper I was a co-author on (my other Co-Authors, particularly Jared Sikes and James Pezent, deserve far more credit than I for both the GTOC solution and the paper), which was accepted to Acta Astronautica in Summer 2022. You can read the full paper here, or see my full publication list here.
Abstract – GTOC-11: Results from the University of Alabama
“In this work, Team ASRL’s solution approach for the 11th Global Trajectory Optimization Competition (GTOC-11) is described. This problem tasked the competing teams with constructing a futuristic Dyson Ring utilizing materials acquired from the asteroid belt. In total, 10 motherships would depart from Earth in the year 2121 and visit as many asteroids as possible. After visiting each asteroid, a low-thrust propulsion module would transfer the material down to the desired final Dyson stations. The final approach utilized a deterministic tree search that involved alternating between fixed time of flight Lambert searches and solutions to the full-fidelity optimal control problem. Once a single tour had been constructed, transfer trajectories were computed for each asteroid to as many of the building stations as possible. After computing a pool of thousands of these completed legs, a bin packing algorithm was used to determine the highest scoring combination of 10 solutions. This search process was implemented in Python using the soon-to-be-released trajectory optimization tool, ASSET. Ultimately, the team finished 5th with a score of 5525.38.”
Here’s our submission as a video, set to Copland’s Appalachian Spring. The green dots are the mother ships, the red dots are the controlled asteroids, and the orange dots are the Dyson stations.
What is GTOC?
The Global Trajectory Optimization Challenge (GTOC) is, as the name implies, an international competition for trajectory designers that occurs once every few years. A very hard trajectory design challenge (as well as a scoring function) is released and then all teams have one month from release to obtain the highest score. It was first organized in 2005 by Dario Izzo at the ESA advanced concepts teams and has become so popular that for the month that GTOC runs, there is a noticeable decrease in the productivity of trajectory design groups. The 11’th GTOC took place in December 2021, and GTOC-12 has a tentative schedule of registration beginning approximately March 2023, with the competition beginning in approximately June 2023.
Key Takeaways
The full paper is online here, but here are, in my opinion, the most interesting aspects,
- We placed 5th despite not using a supercomputer (all groups above us in ranking used supercomputers)
- This was my first GTOC, and I had a lot of fun participating!
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