Vented detector housing for use in the Mars atmosphere

This paper reports on the experimentally-measured mass transfer rates of water diffusing through small orifices and sintered porous metal high-efficiency particulate air (liEPA) filters in a simulated Martian atmosphere. This work was aimed at assessing the feasibility of replacing hermetically sealed enclosures with thinner-walled enclosures that implement HEPA filters to equalize pressure while minimizing contamination. The mass collection rate of water on a surface held at 150 K was measured as a function of total pressure and parts per million by volume of water (ppmv) ranging from 2.7 to 8.2 torr and 100 to 700 ppmv, respectively. The diffusion path was varied by changing the porosity, thickness, and area of the liEPA filters. For a given experimental configuration, the mass diffusion rate was nearly independent of total pressure and increased with increasing ppmv. Finally, an analysis was performed to estimate the pressure difference across a HEPA filter during launch conditions.