NASA Glenn Research Center and the Department of Energy (DOE) are developing a Stirling converter for an advanced radioisotope power system to provide spacecraft on-board electric power for NASA deep space missions. NASA Glenn is addressing key technology issues through the use of two NASA Phase II SBIRs with Stirling Technology Company (STC) of Kennewick, WA. Under the first SBIR, STC demonstrated a parallel connection of two thermodynamically independent free-piston Stirling converters and a 40 to 50 fold reduction in vibrations compared to an unbalanced converter. The second SBIR is for the development of an Adaptive Vibration Reduction System (AVRS) that will practically eliminate vibrations over an entire mission lifetime, even with one failed converter. This paper discusses the status and results for these two SBIR projects and also presents results for characterizing the friction factor of high-porosity random fiber regenerators that were evaluated for this application.