Reliability Based Design Optimization of a CubeSat De-Orbiting Mechanism

Abstract

We optimize de-orbiting mechanism of a 3-Unit satellite structure to enable a reliable and efficient orbit decay process through enhancement of aerodynamic drag with a probabilistic design approach. The system consists of spiral springs as energy producing mechanisms needed for deployment and thin membranes needed as aero-brake structures. A multi-objective optimization problem is formulated to maximize both aerodynamic drag force and also moment produced by spiral springs for a carefree and fast orbit decay. Mass of membranes and stresses acting on spiral springs are subjected to constraints for lightweight and durability. An in-house code is developed to evaluate the deterministic optimization criteria in terms of the optimization variables which are attributes of thin membranes and spiral springs. In space environment, atmospheric density is highly affected by solar radiation and also the system components are strictly related to manufacturing quality, so uncertainties in design parameters are incoorperated into optimization and a reliability based design optimization of the de-orbiting mechanism is performed. Dimensions of membrane structures, outside diameter of spiral springs and atmospheric density are considered to be uncertain parameters. These uncertainties are propagated by Monte Carlo Simulation method which is integrated into reliability evaluation loop in the optimization framework. Finally, de-orbiting duration values of pareto optimal designs are computed using Satellite Tool Kit where it is shown that the selected optimum design is expected to satisfy the specified maximum life-time criterion.