Sustainable energy is crucial for long-term space missions. Fission surface power is a leading option due to its ability to provide consistent electricity and heat irrespective of the sun’s position or distance. A heat pipe is the primary cooling solution for space fission power systems. It operates without the need for additional electricity or gravity. It offers the advantage of streamlining the reactor design by eliminating components such as pumps and piping. This paper presents the advancements in the Korean space heat pipe reactor development program over the past 4 years. The primary objectives of this program include the development of codes for space heat pipe reactors, the innovative design of a hybrid wick structure, and the evaluation of the thermal performance of liquid-metal heat pipes.