NASA Glenn Research Center (GRC) is developing fission power system technology for future space transportation and surface power applications. The early systems are envisioned in the 10 to 100kWe range and have an anticipated design life of 8 to 15 years with no maintenance. A non-nuclear system ground test in thermal-vacuum is planned by NASA GRC to validate technologies required to transfer reactor heat, convert the heat into electricity, reject waste heat, process the electrical output, and demonstrate overall system performance. This SBIR project by ACT will develop a single-facesheet Variable Conductance Heat Pipe (VCHP) radiator, operating near 450K, to support the Technology Demonstration Unit (TDU) for surface power and 100kW-class electric vehicles. ACT will utilize the experience gained during previous Phase I and Phase II VCHP radiator programs for NASA GRC to increase the specific power of the radiator and reduce the overall cost. A trade study will be conducted to compare single-facesheet and dual-facesheet VCHP radiator designs and the ability to directly bond a GFRC facesheet to a titanium heat pipe will be demonstrated. A complete preliminary design for a single-facesheet VCHP radiator for the non-nuclear system will be developed at the end of the Phase I program.