Miniature Resilient Power Converter for Low-Power Radioisotope Heat Sources

NASA seeks novel low power thermal-to-electric miniature energy conversion technology to potentially define the next-generation of future power systems. These converters are required to transform thermal energy from Radioisotope Heater Units into on-demand electricity essential to space exploration probes, unmanned surface rovers, small landers, small satellites, and similar small-scale systems operating in darkness. In response, Creare proposes to develop an extremely compact, robust, free-piston Otto‑cycle based energy conversion system. Our innovation fuses advances in miniature two-stroke engines, and high-reliability free-piston technology. We have achieved a remarkably simple system design with a single moving part, requiring no recuperators or valves. Keys to our high efficiency include reduced parasitic heat losses, the use of a high molecular mass/low thermal conductivity working fluid, tight clearances and high pressure ratios. Our converter leverages decades of advances at Creare in the design and fabrication of miniaturized spaceflight piston-compressors, high-reliability vacuum pumps, and low‑power thermodynamic systems such as turbo-Brayton generators and cryocoolers. In Phase I we will validate our performance models through the development of a laboratory-scale prototype, demonstrating power generation at prototypical heat source and heat sink temperatures. During Phase II we will demonstrate a complete prototype system and prime it for spaceflight testing.