Combined Experimental and Modeling Study of the Interactions of Acid Gas with Common Spacecraft Surfaces for Fire Safety Applications

All dates for this event occur in the past.

Scott Lab E439
201 W. 19th Avenue Columbus, OH 43210
Columbus, OH 43210
United States

Speaker: Justin Niehaus, aerospace engineering

Abstract:
A fire in a spacecraft poses detrimental consequences and risks mission success in addition to crew safety. This is compounded during long-duration missions when the crew has limited options to recover from a fire. A common spacecraft fire concern is the smoldering of wire insulation, typically made from Polyvinyl chloride (PVC) or Polytetrafluoroethylene (PTFE). This creates acid gases such as Hydrogen chloride (HCl), Hydrogen Fluoride (HF) and Hydrogen Cyanide (HCN). These poisonous gases are hazardous to the crew and tend to stick to surfaces making them difficult to track for potential fire detection techniques, or for post-fire clean-up. It is imperative to be able to understand and predict the fate of these poisonous species in a microgravity environment in order to design a safe vehicle. HCl interacts with a number of materials inside a spacecraft, primarily aluminum due to its abundance on a spacecraft. Aluminum has a natural oxide layer that protects it from corrosion but is typically treated to enhance this oxide layer. Among these treatments is a chromate conversion coating (CCC), and a traditional anodized material that has a thicker oxide layer. Physic-based models were developed to predict the uptake of HCl by these materials. To support these modeling efforts, experiments were performed in a cast acrylic test cell that measured the difference between the inlet and outlet concentration of HCl after inserting a sample rod of the test material. Different uptake capacities were realized for each type of sample tested. The amount of water vapor, or relative humidity in the flow during a reactor experiment was determined to influence HCl uptake. Experiments were performed to understand the interaction of gaseous HCl with aluminum surfaces in the presence of water vapor. The results show that increasing levels of relative humidity increased the capacity of aluminum to adsorb HCl. The results from the large-scale microgravity experiment, Saffire, are discussed as they pertain to HCl transport throughout a spacecraft. A ground-based large-scale facility was constructed to flow acid gas at the scale and configuration realized in the Saffire experiments. A CFD model of this duct was constructed to test kinetic parameters developed in this work at a larger scale and different geometric configuration and to predict the results of the large-scale facility. The models developed in this work were used to interpret the results of the microgravity tests and lead the discussion on what further experiments and models are needed in order to predict the fate of acid gas in a spacecraft environment. Conclusions from this research will be used in the design of spacecraft vehicles and large-scale microgravity fire safety experiments. The models built by this work will aid designers in sensor placement and could be used to predict acid gas transport from fires in partial gravity, as would be seen in Lunar and Martian habitats.

Zoom Link (or alternative) - if available

Committee Members
Professor Sandip Mazumder
Professor Jeffrey Bons
Assistant Professor Seung Hyun Kim
Professor Barbara Wyslouzil

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