Air Revitalization for Vacuum Environments
The NASA life support system uses a regenerable vacuum swing adsorption process, known as Sorbent-Based Air Revitalization (SBAR), to separate water and carbon dioxide for disposal. The SBAR system is an adsorbent-based swing bed system that has been optimized to provide both humidity and carbon dioxide control for a spacecraft cabin atmosphere. The system comprises composite silica gel and zeolite-packed beds for adsorption and a bypass system for flow control. Under normal operating conditions, the disposal system would require a high-quality vacuum environment to operate. Improvements to the SBAR system include an enhanced inherent capacitance that extends the operation time within a non-vacuum environment for up to 4.5 hours. Flight time can be further expanded with multiple SBAR systems to allow for system regeneration. By scheduling periodic thermal regenerations&#151nominally during sleep periods&#151the SBAR technology may be suitable for missions of unlimited duration.
Solid State Carbon Dioxide (CO<sub>2</sub>) Sensor
The technology is a solid state, Carbon Dioxide (CO<sub>2</sub>) sensor configured for sensitive detection of CO<sub>2</sub> having a concentration within the range of about 100 Parts per Million (ppm) and 10,000 ppm in both dry conditions and high humidity conditions (e.g., > 80% relative humidity). The solid state CO<sub>2</sub> sensor achieves detection of high concentrations of CO<sub>2</sub> without saturation and in both dynamic flow mode and static diffusion mode conditions. The composite sensing material comprises Oxidized Multi-Walled Carbon Nanotubes (O-MWCNT) and a metal oxide, for example O-MWCNT and iron oxide (Fe2O3) nanoparticles. The composite sensing material has an inherent resistance and corresponding conductivity that is chemically modulated as the level of CO<sub>2</sub> increases. The CO<sub>2</sub> gas molecules absorbed into the carbon nanotube composites cause charge-transfer and changes in the conductive pathway such that the conductivity of the composite sensing material is changed. This change in conductivity provides a sensor response for the CO<sub>2</sub> detection. The solid state CO<sub>2</sub> sensor is well suited for automated manufacturing using robotics and software controlled operations. The solid state CO<sub>2</sub> sensor does not utilize consumable components or materials and does not require calibration as often as conventional CO<sub>2</sub> sensors. Since the technology can be easily integrated into existing programmable electronic systems or hardware systems, the calibration of the CO<sub>2</sub> sensor can be automated.
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