Water Removal Performance of the Humidity Control Subassembly with Variable Vacuum Orifice Sizing



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2020 International Conference on Environmental Systems


The Boeing Company (Boeing) CST-100 Starliner spacecraft utilizes the Humidity Control Subassembly (HCS) designed and manufactured by Paragon Space Development Corporation (Paragon) to control cabin atmospheric humidity during flight operations. The HCS utilizes Ionomer Membrane Water Processing (IWP) tubes that preferentially pass water to space vacuum to realize a passive, robust, and efficient approach to humidity control for short-duration crew transport missions. The Boeing CST-100 spacecraft and HCS are sized to accommodate the water removal of a maximum crew size of 7. The CST-100 is also to be used for crew sizes of 4 and 2. For these crew sizes, a set of reduced diameter orifices is added onto the HCS vacuum ports that will limit the water removal performance of the HCS. Furthermore, the CST-100 will be operating with a sublimator during descent, which will change the pressure at the HCS vacuum orifice location. Paragon executed a series of tests to determine the performance of the HCS when these orifices were added to the HCS vacuum ports at controlled vacuum pressures. Testing mimicked atmospheric operational parameters such as: air flow rate, temperature, and dew point that an IWP-based HCS would experience during flight operations. Results from the testing were analyzed by Boeing and compared to models to validate the orifice design. The results and modeling comparisons are reduced and summarized in this paper to quantify the effect of reduced orifice sizes on water vapor transport through the HCS


Joshua Hecht, Paragon Space Development Corporation, US
Barry Finger, Paragon Space Development Corporation, US
John Lumpkin, The Boeing Company, US
John Gray, The Boeing Company, US
Zexuan Zhang, The Boeing Company, US
Steve Giangrande, Collins Aerospace, US
Don Varanauski, The Boeing Company, US
ICES305: Environmental and Thermal Control of Commercial and Exploration Spacecraft
The proceedings for the 2020 International Conference on Environmental Systems were published from July 31, 2020. The technical papers were not presented in person due to the inability to hold the event as scheduled in Lisbon, Portugal because of the COVID-19 global pandemic.


Humidity, Humidity control subassembly (HCS), Boeing CST-100 spacecraft, Ionomer membrane water processing (IWP), Water removal, Vacuum orifice