This project addresses NASA’s need for low mass, safe, and highly robust single loop active thermal control systems (ATCS). The spacecraft ATCS must transport heat loads from inside a space habitat to subsystems that reject heat to the surroundings. Deep space habitats will require ATCS that maintain cabin temperature despite wide fluctuations in heat loads (during crewed and un-crewed periods) and sink temperatures. Historically, dual loop architectures have been utilized, because there are no known fluids that are both non-toxic (safe to use inside the habitat) and non-freezable (reliable for use outside of the habitat). Thus, a low-freeze point fluid is used in an external loop and a non-toxic fluid (water) in an internal loop, increasing overall mass and complexity. These dual loop architectures are safer with a nontoxic internal fluid but hazards still remain. Non-freezable, nontoxic coolants and freezable radiators will enable single loop ATCS architectures that have reduced complexity and mass over dual loop systems. Space Lab Technologies proposes FRESR, a Freezable Radiator for Efficient, Safe, and Robust single loop thermal control of crewed vehicles and habitats. FRESR builds upon and integrates ground tested heat exchanger/radiator technology, into a realizable single loop architecture with low mass materials and more reliable components. A FRESR ATCS includes human-safe coolant, eliminating the toxic hazard of ammonia or HFE7200; freeze tolerant components that allow thermal expansion during freeze; and self-regulating temperature control, making it robust to fluctuating heat loads and heat sinks. Space Lab, supported by the University of Colorado, will establish feasibility of integrating FRESR into a space habitat ATCS for exploration missions (such as Lunar Gateway or a lunar surface habitat). In Phase I, lightweight freeze-tolerant coolant tubes and radiator loops will be designed and tested as an integrated system in thermal vacuum.
FRESR™ would be useful in several NASA human exploration programs including ISS operations, Deep Space Gateway missions, and future surface missions (to the moon or Mars). The safe, mass efficient, and reliable design will make it an attractive addition to any space habitat. A FRESR single loop architecture for habitat thermal control will provide a significant advancement in the robustness of environmental control and life support systems.