Robust Preliminary Space Mission Design under Uncertainty

Abstract

This chapter presents the design of a space mission at a preliminary stage, when uncertainties are high. At this particular stage, an insufficient consideration for uncertainty could lead to a wrong decision on the feasibility of the mission. Contrary to the traditional margin approach, the methodology presented here explicitly introduces uncertainties in the design process. The overall system design is then optimised, minimising the impact of uncertainties on the optimal value of the design criteria. Evidence Theory, used as the framework to model uncertainties, is presented in details. Although its use in the design process would greatly improve the quality of the design, it increases significantly the computational cost of any multidisciplinary optimisation. Therefore, two approaches to tackle an Optimisation Problem Under Uncertainties are proposed: (a) a direct solution through a multi-objective optimisation algorithm and (b) an indirect solution through a clustering algorithm. Both methods are presented, highlighting the techniques used to reduce the computational time. It will be shown in particular that the indirect method is an attractive alternative when the complexity of the problem increases.