Sunpower will introduce thermoacoustic Stirling heat engine (TASHE) technology into its existing Stirling convertor technology to eliminate the moving mechanical displacer. The displacer function will be performed by a thermal buffer tube and supporting thermoacoustic components containing no moving mechanical parts. Sunpower's linear alternator will be retained, except re-sized to accommodate the power of the TASHE. TASHE technology has evolved independently, spearheaded by efforts at Los Alamos National Laboratory and typically packages components (heat exchangers, thermal buffer tube) in a physically different layout than typical Stirling convertor technology. The innovation here is to recognize the similarity between components and repackage the thermoacoustic components as closely as possible to the proven layout used for Sunpower's engines. In this way it will be possible to make direct comparisons of size, weight and efficiency between thermoacoustic and displacer-type Stirling convertors. The research will help NASA assess the relative benefits of thermoacoustic and displacer-type Stirling convertors for space power applications and may lead to technology uniquely suited to some missions where displacer-type technology is unacceptable for whatever reason. In Phase 1 we will optimize the concentric TASHE design to provide as much electrical output as possible from a single GPHS (nominally 220 W of heat delivered to the convertor). This design will use the same temperature levels currently used for the ASC convertor of 850 C hot end and 90 C reject. This will provide a direct comparison of size, mass, and efficiency differences between TASHE and displacer type convertors designed for the same application and using the same temperature levels. During Phase 1 we will also scale up this basic TASHE to a higher output power (~400W), and higher temperature levels, to provide a conceptual design of a high efficiency TASHE suited for Venus exploration.