Spanning tree trajectory optimization in the galaxy space

The 10th edition of the Global Trajectory Optimization Competition considered the problem of the galaxy settlement wherein competitors from all over the world were expected to design the trajectories of different settler vessels to maximize the given multi-faceted merit function.The synthesis methods used by the winning team,led jointly by the National University of Defense Technology(NUDT)and Xi’an Satellite Control Center(XSCC),are described along with a greedy search method and the improved solution obtained by University of Jena.Specifically,we presented a layout-first topology-second approach that allows an efficient settlement tree search guided by the pre-specified ideal spatial distribution.We also explained how the problem of constructing settlement trees can be modeled as the widely studied minimum spanning tree problem.Furthermore,University of Jena explored the possibility that a greedy search can generate even better settlement trees,based on the same initial conditions,when compared to that of the winning solution.

Solution set calculation of the Sun-perturbed optimal two-impulse trans-lunar orbits using continuation theory

The solution set of the Sun-perturbed optimal two-impulse trans-lunar orbit is helpful for overall optimization of the lunar exploration mission.A model for computing the two-impulse trans-lunar orbit,which strictly satisfies the boundary constraints,is established.The solution set is computed first with a circular restricted three-body model using a generalized local gradient optimization algorithm and the strategy of design variable initial continuation.By taking the solution set of a circular restricted three-body model as the initial values of the design variables,the Sun-perturbed solution set is calculated based on the dynamic model continuation theory and traversal search methodology.A comparative analysis shows that the fuel cost may be reduced to some extent by considering the Sun’s perturbation and choosing an appropriate transfer window.Moreover,there are several optimal two-impulse trans-lunar methods for supporting a lunar mission to select a scenario with a certain ground measurement and to control the time cost.A fitted linear dependence relationship between the Sun’s befitting phase and the trans-lunar duration could thus provide a reference to select a low-fuel-cost trans-lunar injection window in an engineering project.