Non-thermal plasmas have been shown by research to be capable of decomposing various volatile organic carbons (VOCs) found in enclosed spacecraft environments into non-harmful CO_2 and H_2O. A Plasma Air Decontamination System (PADS) was developed by ORBITEC for trace contaminant control in cabin air. This technology is based on non-thermal, atmospheric pressure plasma discharges, which generate various highly reactive species that can react with and break down trace air contaminants. Three different PADS designs were evaluated before a final design was reached and a full system was built, supplemented with a downstream scrubber system to remove reaction byproducts. It uses a simple and modular design, and can be easily scaled up or down to meet the requirements of different applications. The prototype was tested with selected trace level contaminants including acetone, ammonia, dichloromethane, methane, and toluene. Data from performance tests showed that the system's single-pass removal efficiency varies among different contaminants and ranges from 10% to >99%. Reaction byproduct analysis by GC-MS indicated that the overwhelming majority of the test contaminants were broken down into CO_2, with a very small amount of byproducts resulting from recombination of molecular fragments. Compared to the high-temperature catalytic oxidizers used by the existing ISS trace contaminant control system (TCCS), this PADS technology operates at ambient temperature and atmospheric pressure, requires less energy, is capable of removing both ammonia and volatile organic carbons, has no moving parts, and requires almost no consumables. Although the capabilities of this technology are still limited in its current form, it provides many advantages not found in the TCCS and other similar air revitalization systems. It is believed that implementation of the PADS technology in a more mature form will have the potential to replace the existing high-temperature catalytic oxidizers, reduce the intensive resupply of activated carbons for adsorbent beds, and lead to significant savings in launch mass and cost for long-duration missions and a reduction in power requirements. In addition, it has the great potential as a dual-use technology for other life support applications.
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