Active thermal control system of a crew module for future manned space missions such as Deep Space Gateway and post ISS program will be presented. The total heat generation of 6 kW or more is transported by single-phase mechanical pump loops to the radiators mounted on the outer surface of the module. Not only the double loop system that consists of internal loop and external loop with different coolants but also single loop system is studied because the single loop system is more efficient for minimizing the radiator area under the same amount of heat dissipation condition and the pumps can be installed in the module. Several coolant candidates are investigated for the single loop system. The heat generated in the module is dissipated from the body mount radiators to the deep space. The side of the cylindrical module is covered with the radiators panels. The radiator panels consist of aluminum honeycomb panels which the flow paths are embedded in the aluminum core. The air conditioners or desiccant coolers are used for control of the air temperature and humidity. They make it possible to eliminate the inner loop containing low-temperature coolant, i.e. the coolant with a temperature below the dew point temperature, thereby the radiator area can be minimized. High-performance pumps have been developing for both the single loop system and double loop system. The pump performance test results will be presented.