Browsing by Author "Barnes, Bruce"
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Item Design and Analysis of a Fan Outlet Check Valve for the Exploration Portable Life Support System(49th International Conference on Environmental Systems, 2019-07-07) Waguespack, Glenn; Hanford, Anthony; Barnes, BruceCheck valves are required at the outlets of NASA’s Exploration Portable Life Support System (xPLSS) ventilation loop fans to permit forward flow through the ventilation loop while preventing backflow through the fans when they are not running. These check valves must maintain full specified functionality at all orientations in gravitational environments ranging from weightlessness to full terrestrial gravity. A check valve design has been developed to satisfy the above requirements via an iterative process combining mechanical design, computational fluid dynamics (CFD) analysis, Thermal Desktop® analysis, and static force analysis. The initial design concept was a flapper valve in which a mass-balanced flapper freely rotates from fully closed (0°) to a 45° angle, after which a torsional spring engages the flapper to prevent it from opening beyond the point at which reverse flow cannot close the valve. Analysis results, however, indicated that the magnitude of reverse flow induced during contingency purge operations would not always be sufficient to overcome gravitational and frictional moments to close the flapper in its unassisted, free-rotating range. The design was thus revised to provide spring engagement throughout the entire span of valve positions, removing the flapper’s dependency on reverse flow for valve closure. Since commercially-available torsion springs are too stiff for this application, the revised design uses a linear compression spring that engages the flapper at an offset from the flapper’s pivot point. CFD and static force analyses were used to determine acceptable design parameters, from which valve geometry and spring selection were determined.Item Exploration PLSS Thermal Desktop Modeling(49th International Conference on Environmental Systems, 2019-07-07) Barnes, Bruce; Abraham, Brittany; Miranda, Bruno; Speasmaker, Latham; Nguyen, QuocThe Exploration Portable Life Support System (xPLSS) maintains life support for a suited crew member during Extravehicular Activity (EVA). The thermal and pneumatic/hydraulic interactions within the xPLSS have been modeled using Thermal Desktop ®. In addition to these interactions, a human thermal model (METMAN) that includes metabolic, respiration, muscular work, and active body thermoregulation, was used to include the crew member as part of the loop. The model is a system level simulation and is being used to estimate thermal boundary conditions for detailed xPLSS component analyses. To date, this model has been used to evaluate the cooling system capabilities for keeping the crew member comfortable in a range of thermal environments and off nominal operating conditions, the thermal and pressure conditions during failed open relief valve scenarios, temperature effects on the removal efficiencies of the carbon dioxide and humidity control unit and detailed thermal analysis of batteries. In summary, this Thermal Desktop ® is supporting many of the design review products for the xPLSS as it comes to maturity and providing insight into the operations of the xPLSS in many operating conditions and scenarios.Item Oxygen Compatibility and Challenge Testing of the Portable Life Support System Variable Oxygen Regulator for the Advanced Extravehicular Mobility Unit(47th International Conference on Environmental Systems, 2017-07-16) Campbell, Colin; Cox, Marlon; Falconi, Eric; Meginnis, Carly; Barnes, Bruce; Conger, BruceThe Variable Oxygen Regulator (VOR), a stepper-actuated two-stage mechanical regulator, is being developed for the purpose of serving as the Primary Oxygen Regulator (POR) and Secondary Oxygen Regulator (SOR) within the Advanced Extravehicular Mobility Unit (EMU) Portable Life Support System (PLSS), now referred to as the xEMU and xPLSS. Three prototype designs have been fabricated and tested as part of this development. Building upon the lessons learned from the 35 years of Space Shuttle/International Space Station EMU Program operation, including the fleet-wide EMU Secondary Oxygen Pack (SOP) contamination failure that occurred in 2000, NASA is analyzing, designing, and testing the VOR for oxygen compatibility with controlled Non-Volatile Residue (NVR) and a representative worst-case hydro-carbon system contamination event (>100 mg/ft2 dodecane). This paper discusses the steps taken in testing of VOR 2.0 for oxygen compatibility, and discusses follow-on design changes implemented in the VOR 3.0 (3rd prototype) as a result.