Browsing by Author "Wickham, David T."
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Item Advanced Supported Liquid Membranes for Carbon Dioxide Control in Extravehicular Activity Applications(44th International Conference on Environmental Systems, 2014-07-13) Wickham, David T.; Gleason, Kevin J.; Engel, Jeffrey R.; Cowley, Scott W.; Chullen, CindaDeveloping a new, robust, portable life support system (PLSS) is currently a high priority for NASA in order to support longer and safer extravehicular activity (EVA) missions. One of the critical PLSS functions is maintaining the carbon dioxide (CO2) concentration in the suit at acceptable levels. Although the Metal Oxide (MetOx) canister has worked well, it has a finite CO2 adsorption capacity. Consequently, the unit would have to be larger and heavier to extend EVA times. Therefore, new CO2 control technologies must be developed to meet mission objectives without increasing the size of the PLSS. Although recent work has centered on sorbents that can be regenerated during the EVA, this strategy increases the system complexity and power consumption. A simpler approach is to use a membrane that selectively vents CO2 to space. A membrane has many advantages over current technology: it is a continuous system with no theoretical capacity limit, it requires no consumables, and it requires no hardware for switching beds between absorption and regeneration. Unfortunately, conventional gas separation membranes do not have adequate selectivity for use in the PLSS. However, the required performance could be obtained with a supported liquid membrane (SLM), which consists of a microporous material filled with a liquid that selectively reacts with CO2 over oxygen (O2). In a current Phase II Small Business Innovative Research project, Reaction Systems has developed a new reactive liquid that has effectively zero vapor pressure, making it an ideal candidate for use in an SLM. The SLM function has been demonstrated with representative pressures of CO2, O2, and water. The SLM vents moisture to space in addition to being effective for CO2 control. Therefore, this project has demonstrated the feasibility of using an SLM to control CO2 in an EVA application.Item Continued Advancement of Supported Liquid Membranes for Carbon Dioxide Control in Extravehicular Activity Applications(45th International Conference on Environmental Systems, 2015-07-12) Wickham, David T.; Gleason, Kevin J.; Engel, Jeffrey R.; Cowley, Scott W.; Chullen, CindaThe development of a new, robust, portable life support system (PLSS) is currently a high NASA priority to support longer and safer extravehicular activity (EVA) missions that will be necessary as space travel extends to near-Earth asteroids and eventually Mars. One of the critical PLSS functions is maintaining the carbon dioxide (CO2) concentration in the suit at acceptable levels. The Metal Oxide canister has a finite CO2 adsorption capacity. To extend mission times, the unit would have to be larger and heavier, which is undesirable; therefore, new CO2 control technologies must be developed. While recent work has centered on the use of alternating sorbent beds that can be regenerated during the EVA, this strategy increases the system complexity and power consumption. A simpler approach is to use a membrane that vents CO2 to space but retains oxygen (O2). A membrane has many advantages over current technology: it is a continuous system with no theoretical capacity limit, it requires no consumables, and it requires no hardware for switching beds between absorption and regeneration. Conventional gas separation membranes do not have adequate selectivity for use in the PLSS, but the required performance could be obtained with a supported liquid membrane (SLM), which consists of a microporous film filled with a liquid that selectively reacts with CO2 over O2. In a recently completed Phase II Small Business Innovative Research project, Reaction Systems developed a new reactive liquid that has effectively zero vapor pressure, making it an ideal candidate for use in an SLM. Results obtained with the SLM in a flat sheet configuration with representative pressures of CO2, O2, and water have shown that the CO2 permeation rate and CO2/O2 selectivity requirements have been met. In addition, the SLM vents moisture to space very effectively. The SLM has also been prepared and tested in a hollow fiber form, which will be necessary to meet size requirements in the PLSS. In initial tests, the required CO2 permeance values have been obtained, while the current CO2/O2 selectivity values are somewhat lower than needed. However, the performance of the SLM is a strong function of the method used to impregnate the sorbent in the hollow fiber walls, and rapid progress is being made in that area.