mechanical and fluid systems
Spacecraft Atmosphere Carbon Dioxide (CO<sub>2</sub>) Capture via Deposition
Spacecraft Atmosphere Carbon Dioxide (CO<sub>2</sub>) Capture via Deposition is an air revitalization architecture that utilizes the different physical phase-change properties of International Space Station (ISS) cabin-like constituents (nitrogen, oxygen, carbon dioxide, water vapor, and various trace contaminants) to selectively separate constituents of interest, such as carbon dioxide and trace contaminants. As the main target constituent is CO<sub>2</sub>, which does not condense in atmospheric conditions, this architecture is referred to as CO<sub>2</sub> deposition, or CDep. The technology addresses future CO<sub>2</sub> removal and life support system needs using a completely different technical approach than currently employed on the ISS. Instead of using a sorbent, this technology utilizes cooling to directly freeze CO<sub>2</sub> out of the atmosphere. Specifically, it involves forcing a phase change of CO<sub>2</sub> from the cabin atmosphere by solidifying it onto a cold surface. The technology for spacecraft atmosphere CO<sub>2</sub> capture uses sequential heat exchangers to cool airflow from the spacecraft atmosphere, and uses deposition coolers that can operate in a deposition mode, in which CO<sub>2</sub> from the airflow is deposited to generate said CO<sub>2</sub> depleted air, and a sublimation mode in which deposited CO<sub>2</sub> is sublimated into CO<sub>2</sub> gas. The system can alternately cycle between the deposition mode and the sublimation mode. A deposition system can also remove humidity in addition to CO<sub>2</sub> via a multi-stage process, and can also significantly assist in controlling the trace contaminants.
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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