Reliable air revitalization systems are in the critical path of the human exploration of space. The current state of the art regenerable solid sorbent CO2 removal systems have provided decades of service in low-earth orbit. However, certain novel technologies are rapidly developing that purport attractive and essential features for deep space missions: i.e., quiet, reliable, and continuous operation with lower-power, lower-volume, and lower-maintenance expectations. The recently successful ISS flight demonstration of the Capisorb Visible System (CVS) has increased awareness and confidence in the potential application of massively parallelized open-channel capillary fluidic devices and surfaces to perform the largely passive wet CO2 scrubbing air revitalization function. Such approaches have been exploited aboard submarines employing 'falling films' for decades with high-affinity amine liquid sorbents (MEA, DGA, etc.), a feat that could be replicated in re-formatted fashion in the microgravity environment of orbiting or coast spacecraft. The Liquid Amines Carbon dioxide Removal (LACR) system is a simple closed loop cycle with a flow-through 'thin capillary film' contactor that reacts with and absorbs CO2 directly from the cabin air. The sorbent is then drawn into a second capillary fluidic device where vacuum pressures and elevated temperatures reverse the reaction and degas the liquid, venting, re-routing, or storing the CO2 for subsequent processing. A single pump returns the regenerated sorbent to the contactor for continuous cabin air conditioning. The key components of the LACR system include a Porous-sheet Contactor (absorber), Capillary Conduit Degasser and Separator (desorber), and Capillary Condensing Heat eXchanger (CCHX). The design and function of these devices are reported along with quantitative performance characteristics of loop operation collected during ground tests. Scale-up of the system for a crew of four suggests significant (>2x) reductions in system size, mass, power, and consumables over the current state of the art.
Torres et al. (2024) studied this question.