Abstract: Space nuclear reactor power sources with a capacity of 100 kWe or more offer advantages such as high energy density, strong autonomy, and long operational lifespan. They are ideal power sources for future missions such as manned interstellar exploration, planetary resource exploitation, and high-resolution Earth observation at high-orbit. A direct cycle system coupling a gas-cooled reactor with a helium-xenon closed Brayton system is one of the preferred technologies for high-power space nuclear reactor power sources. This paper described the system components and working principles of this technology. Combining the R&D process and achievements of China's high-temperature gas-cooled reactor technology, it introduced the technological foundations that might be applied to space gas-cooled nuclear reactor power systems, including Tri-layered isotropic coated particle fuel, inert gas processes, and gas turbine cycle power generation. Considering the special scenarios of space applications, the paper summarized the main challenges and issues faced by high-power space gas-cooled nuclear reactor power sources, followed by the analyses of the key technologies and the related ideas or views involved in the R&D process. Based on this, some preliminary thoughts and suggestions were proposed to provide a support for the development of high-power space gas-cooled nuclear reactor power sources. 

Key words: space nuclear reactor power, high-temperature gas-cooler reactor, TRISO coated particle fuel, closed Brayton cycle, key technology, high-power