Project Ideas
The GTOP database (Global trajectory optimization Problem database) was established by the Advanced Concepts Team (ACT) with the goal in mind to provide ongoing challenges for trajectory optimization. Given an easy interface to selected mission concepts, participants could search and submit solutions which were ranked according to their accumulative Delta-V. The GTOP database inspired researchers from Europe and above to improve their algorithms for getting a place in the leaderboard, but has been discontinued as the necessary software has no longer be maintained.
The long term goal of the ACT is to re-establish the GTOP as a modern online portal, which will enable users to publish trajectory problems and solutions online, further increasing collaboration, competition and open exchange.
Pykep (and the related pagmo open source project) are the key enablers for this portal. The goal of this project is to make pykep ready to handle the new GTOP trajectory problems, i.e. functionality that allows a reliable verification and ranking of submitted solution. This includes new methods in multi-objective optimization, to allow ranking trajectories not only by their Delta-V, but also by other performance criteria (i.e. time of flight, maximum thrust impulse) along multiple dimensions. Constructing the set of optimal trade-offs ("Pareto-front") is of mayor importance in mission design, as it allows to select fly-by sequences or deep space maneuvers, i.e.:
Märtens, Marcus, and Dario Izzo. "The asynchronous island model and NSGA-II: study of a new migration operator and its performance. " Proceedings of the 15th annual conference on Genetic and evolutionary computation. ACM, 2013.
Consequently, performance evaluation metrics from the field of multi-objective optimization need to be accessible. These may include
Furthermore, several evolutionary multi-objective optimization algorithms suitable for trajectory optimization need to be available via the pagmo interface, i.e.:
- SPEA-2
- IBEA
- Multi-objective PSO (MOPSO)
While the implementation of this functionality is a precondition for the establishment of the GTOP portal, pykep will benefit from a stronger interface to pagmo to provide a multi-dimensional and more detailed view on trajectories.
The performance of the multi-objective enhancements will be tested on a mission concept that will be documented and added as one or more examples to the list of advanced research topics to the pykep documentation.