Manned lunar exploration will require extravehicular activity (EVA) suits that surpass existing technology. We propose an innovative thermal control system for EVA suits that uses an absorption heat pump with a flexible radiator that offers reduced size, lighter weight, conformability, rugged construction, and freeze tolerance. The heat pump absorbs a crew member's metabolic heat and rejects it via radiation to the environment. Innovative materials and construction enable a very lightweight and flexible system that is rugged and easily repairable. In Phase I we will prove feasibility by assessing material suitability for lunar operations, demonstrating the critical fabrication steps for key components, then testing these components to demonstrate thermal performance. In Phase II we will build, demonstrate, and deliver a complete prototype heat pump system.