Abstract: Manned spacecrafts usually use active thermal control system to dissipate waste heat through pumped single phase fluid loops. The design tasks of active thermal control system including loop schemes, selection of working fluid, components of loops, system parameters and control algorithms are analyzed. Principles of the system design including adaptability requirements, safety requirements, reliability requirements as well as economic requirements are presented. It is pointed out that design of thermal control system is equivalent to a constrained optimization problem with objective to minimize the total weight. The design method is also introduced and discussed. Finally, the design process and a case are given.

Key words: Manned spacecraft, Thermal control system, Fluid loops, Optimization, System design