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—nominally during sleep periods—the 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.