Cargo Layout Optimization in Spacecraft: Exploring Heuristics for Branch-and Bound Method

This paper focuses on cargo layout optimization in a spacecraft such an H-IIA Transfer Vehicle (HTV), an Automated Transfer Vehicle (ATV), and a MultiPurpose Logistics Module (MPLM), and proposes its optimization method by exploring the branch-andbound method. Concretely, a heuristic relaxation for the branch-and-bound method is proposed to minimize the gap between the CG of a spacecraft and its actual center. To investigate the effectiveness of the proposed relaxation, intensive simulations were conducted and the following implications were found: (1) the proposed heuristic relaxation, based on both objective function relaxation and cargo placement relaxation, finds an optimal solution with the shortest calculation time, and it creates the mostly smallest number of nodes in comparison with the full-search method and two other branch-and-bound methods based on linear and quadratic programming problems; and (2) the proposed objective function relaxation contributes to not only heuristic relaxation but also to LP relaxation in terms of improving both calculation time and the number of nodes.