Catalytic Oxidizer Development for the Trash Compaction & Processing System (TCPS)

At Sierra Space, we are developing an innovative Catalytic Oxidizer (CatOx) to process volatile organic compounds (VOCs) and other gaseous byproducts to maintain a safe and sterile environment in space habitats. Catalytic oxidation is a more energy-efficient and safer alternative to traditional VOC removal methods like thermal incineration, as it operates at lower temperatures and reduces the risk of producing toxic byproducts.

Our CatOx technology is incorporated onboard the Trash Compaction & Processing System (TCPS), planned for launch to the ISS in 2026, as a source contaminant control system. This system manages waste during extended space missions, such as those beyond low-Earth Orbit (LEO). The TCPS technology compacts astronaut trash into solid tiles that are easy to store, safe to handle, and capable of providing additional radiation protection. The system is designed to recover nearly all water from the trash for recycling. The CatOx removes any noxious or harmful contaminants for the ultimate in crew safety.

This technology is particularly promising for space missions due to the lower energy consumption and ability to handle low reactant concentrations without requiring high operational temperatures. A CatOx can be employed anywhere contaminant cleanup is desired; for crew safety, chemical processing, or even planetary protection systems. Our system utilizes novel breakthroughs in our proprietary catalyst to optimize first-pass efficiency, contaminant destruction efficiency, and thermal efficiency. Testing has demonstrated over 99.8% methane removal efficiency. We are conducting ongoing systematic tests and evaluations on our proprietary catalyst to optimize the performance of gaseous trace contaminant removal systems which will contribute to sustainable space exploration practices and minimize the environmental impact of space missions.

Designing the Catalytic Oxidizer

Sierra Space's CatOx combines heating, temperature monitoring, particulate filtering, and protection of the physical catalyst into one unit, all housed within an insulated case. Additionally, it incorporates a counter-flow heat exchanger, which preheats the incoming effluent gas using the heat from the outgoing purified gas. This design allows for reduced energy consumption and shields components downstream from excessive heat, at a size and mass lower than anything currently available.

The CatOx designed is a compact and efficient system, focused on maintaining controlled pressure and temperature for optimal catalyst performance. It consists of four key components: the catalyst bed, a high-efficiency thermal recuperator, insulation, and an outer enclosure. The system utilizes redundant heaters and temperature sensors for reliability and safety. Catalyst pellets are held in place with an internal compression system to maintain stability and a sintered metal filter to prevent particulate escape. The CatOx's design minimizes diameter to reduce temperature discrepancies.

The synthesis and formulation of catalysts are vital for creating efficient and effective catalytic systems used in applications like VOC and pollutant removal. Various synthesis methods, including impregnation and hydrothermal synthesis, produce catalysts with specific properties. Our company has advanced the impregnation method, allowing precise control over catalyst production to match the application. Vertical integration in our production process ensures quality and enables customization to meet specific needs.

Catalyst formulation often involves adding substances to enhance performance for different applications, such as promoters or supports that increase surface area. The goal is to optimize catalytic activity, selectivity, stability, and resistance to deactivation. Although many synthesis methods exist, few are scalable and economically viable.

We've developed a proprietary catalyst formulation with an optimized particle size for greater surface-to-volume ratio, increasing active sites and promoting efficient VOC degradation at lower temperatures. Our engineered catalyst supports various oxidation models and offers improved safety, efficiency, and resistance to contaminants.

Testing and Monitoring the Catalytic Oxidizer

Our team focused on assessing the TCPS CatOx performance for air purification with an experiment that involved loading catalysts into a reactor, performing leak tests at room and elevated temperatures, and setting specific gas flow rates and pressures for catalytic reaction consistency. A gas mixer precisely mixed methane with air, simulating a uniform hydrocarbon pollutant environment. For accurate measurements, a gas analyzer was calibrated with a baseline methane concentration.

Methane was used as a benchmark for oxidizer performance, with the understanding that its oxidation would demonstrate capability for handling more complex hydrocarbons due to their weaker bond interactions and thus easier activation and oxidation. The experiment utilized a single pass approach with continuous data acquisition, capturing data every second and reporting every 20 seconds.

Our methods provided detailed chemical composition data, crucial for process characterization and system performance optimization.

Different pressures were tested, with the CatOx maintaining over 99.8% methane removal efficiency across all ranges without Carbon Monoxide (CO) generation, demonstrating robustness and safety. Overall, the CatOx demonstrated high effectiveness and reliability in methane oxidation, suitable for TCPS or Environmental Control and Life Support Systems (ECLSS) applications.

Building for Future Sustainable Mission Architecture

Our CatOx is also being implemented in the Gaseous Trace Contaminant Removal (GTCR) Assembly for larger-scale applications including our commercial space station, where it removes contaminants from off-gassing equipment and crew metabolism, focusing on formaldehyde and methane. While its materials and design mirror those of the TCPS application, flow rates for the GTCR are scaled for larger habitats accommodating up to eight crew members, integrating an additively manufactured recuperator for energy recovery at higher flow rates.

The CatOx is versatile and can be used in other closed environments like submarines for hazardous gas cleaning, which share similarities to spacecraft ECLSS in requiring reduced chemical buildup without frequent resupply.

It boasts the high performance, low power, and compact design needed for space mission architecture while processing solid waste and food byproducts, eliminating harmful gases and converting them to CO2 and H2O, decreasing the need for additional consumables like charcoal filters. The TCPS CatOx's efficacy in destroying chemicals will reduce the mass of consumables needed for long missions, and its demonstration aboard the ISS as part of the TCPS will validate its capabilities for future extended space travel.

To learn more about our environmental control product line, visit our hardware catalog.

Public link

Please use the above public link if you want to share this noodl on another website.