Analytical Modeling and Basic Design of a Small-Scale Stirling Engine for Radioisotope Power Systems

As a next-generation power source for spacecraft and lunar bases, Stirling converter technology utilizing radioisotopes has gained attention due to its ability to provide long-term power without recharging. This study presents the development of an analytical model for a small-scale free-piston Stirling engine for isotope power generation and performs optimization of its basic design. The performance evaluation was conducted using the Stirling cycle software SAGE, focusing mainly on the heat exchangers and dynamic components. In the heat exchanger analysis, the structural design of the hot- and cold-side heat exchangers and the regenerator was analyzed to determine an optimal configuration. The dynamics analysis focused on optimizing spring stiffness, operating frequency matching, and charging pressure. Additionally, performance improvements were verified by increasing the hot-side heat exchanger temperature, reducing the thickness of the engine head and cylinder liner, and minimizing piston clearance. Through this study, an optimized basic design for a small-scale Stirling converter was achieved, providing a fundamental basis for the development of small-scale radioisotope power generation systems (i.e., systems under 100W).