Future manned space exploration missions will require space suits with capabilities beyond the current state of the art. Portable Life Support Systems for these future space suits face daunting challenges, since they must maintain healthy and comfortable conditions inside the suit for long-duration missions while minimizing weight and venting no consumables. We propose to develop an innovative system for thermal and humidity control in a space suit that is simple, rugged, lightweight, and nonventing. In Phase I we proved the feasibility of our approach by identifying the optimal materials, developing fabrication methods, building and testing a proof-of-concept system, and demonstrating by test that its performance is suitable for use in space suit life support systems. Results from these tests agree well with our design models, which we used to produce a conceptual design for a full-size system. In Phase II we will optimize the overall design for integration with space suit systems, produce a full-size prototype, and demonstrate operation in a prototypical environment.