A CO2 controller enabling cell culture research inside automated incubator onboard the ISS
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The majority of all Earth-based mammalian tissue and cell culture research is conducted in “CO2 incubators” where both the air temperature and concentration of carbon dioxide is precisely controlled to ensure optimal cell growth. In particular, the concentration of CO2 is important for controlling the pH level of the cell culture’s media and to reproduce in-vivo CO2 conditions. This paper describes the design and performance of a CO2-control system to enable cell culture work on board the ISS in combination with a temperature-controlled incubator. Precise on-orbit environmental control provides the means for reproducible inflight and mission-parallel ground control experiments so that spaceflight experiments can be directly compared with the terrestrial body of work. The on-orbit cell culture work is conducted using incubators developed at the University of Colorado. The incubator platform, the Space Automated Bioproduct Lab (SABL), is a mid-deck locker size payload that controls the incubator temperature to set-points ranging from -5°C to +43°C. The Atmosphere Control Module (ACM) is an insert specifically designed to fit on the back wall of SABL’s incubator chamber and to maintain the CO2 concentration to a set-point, typically 5%, with an incubator temperature of 37°C for most cells. The ACM holds 400g of CO2, enough to support 15 weeks of continuous experiments, based on the incubator’s CO2 leakage rate to ambient cabin. This paper will discuss ACM’s design challenges, including the storage and dispensing of supercritical CO2 and safe pressure-conditioning hardware required for a controlled release of CO2 gas. The ACM will launch on SpaceX’s CRS-9 mission in March 2016 along with its first cell culture experiments. This paper will discuss the safety and flight qualification and performance testing of ACM on ground in addition to, as available, on-orbit performance of the ACM during the first to be conducted experiments in spring 2016.