The Advanced Stirling Radioisotope Generator (ASRG) is an advanced, high-efficiency, radioisotope power system being developed to provide spacecraft onboard electric power for future space missions. As a possible future improvement to the Stirling convertor used in the ASRG, a microfabricated regenerator is designed for reduced pressure drop and enhanced durability relative to the present woven screen and random fiber regenerator designs. Prototype units have been fabricated. Because some space and time resolved details of the flow and heat transfer cannot be measured in an engine-size regenerator having feature sizes as small as 14 μm, dynamic similitude is applied to develop a Large Scale MockUp (LSMU) of 30x scale. Experimental results from the LSMU show: 1) the value of using dynamic similarity in design, 2) the performance of the microfabricated regenerator relative to woven screen or random fiber performance, 3) the effect of doubling the channel length of each element of the microfabricated regenerator, 4) the effect of roughness that may arise during the microfabrication processing, and 5) the performance of computational methods developed for regenerator design. The microfabricated regenerator developed under this program represents a significant overall improvement in performance and durability over present regenerator designs.