Modeling Performance of the Full Scale CO2 Deposition System

To enable long-duration manned travel to the Moon and/or Mars, a highly reliable spacecraft cabin atmosphere revitalization system is required. One new carbon dioxide capture system currently in development is the CO2 Deposition System (CDep), which generates a cold surface to selectively deposit CO2 from cabin air. The cold surface may be generated via multiple methods and does not require use of sorbents. Therefore, CDep is a tunable assembly to minimize launch mass and power for any future spacecraft requirements. A full-scale (4-crew) ground test system is currently in development at Ames Research Center. The system utilizes multiple Stirling coolers and air-to-air heat exchangers to generate the cold surface and minimize power requirements. The system modeling is concurrently being developed in both STAR-CCM+ and Modelica to predict performance of the system. Utilizing the first principles STAR-CCM+ multi-physics code, the temperature, humidity, and CO2 concentration gradients across each of the heat exchangers and deposition surfaces were predicted, as well as the sublimation rates for downstream processing. Process modeling using Modelica was utilized to analyze the overall operation of the system to confirm the multi-physics results and examine the initial cool down and transitional phases alternating between deposition and sublimation. The results of the modeling work not only gave new insight into the CDep full-scale system, they informed design adjustments to improve the system prior to initial prototype completion.