Development of an Electrostatic Precipitator to Remove Martian Atmospheric Dust From ISRU Gas Intakes During Planetary Exploration Missions

Manned exploration missions to Mars will need dependable in situ resource utilization (ISRU) for oxygen production. The Martian atmosphere is composed of 95.3% CO2, other gases, and 0.13% O-2 at similar to 9 mbar (1% of the Earth's pressure). However, it also contains 2-10-mu m dust uploaded by dust devils and high winds. Oxygen extraction requires removal of the dust with little pressure drop (Delta p). An electrostatic precipitator (ESP) has lower Delta p than a filter, but the low pressure causes an electrical breakdown at electric fields (similar to 1 kV/cm) similar to 30x lower than on Earth, making implementation challenging. Molecular mean free paths (lambda = 4 mu m) and ion mobility values (b = 0.008m(2)/V . s) are similar to 100x larger than at Earth's pressure (lambda = 44 nm) and (b = 8.4 x 10(-5)). The large lambda lowers Stokes drag, particularly for smaller particles. Pauthenier field charging dominates for particles with d > 5 mu m and diffusion charging for d < 2 mu m. The low E proportionally decreases both Pauthenier particle charging and the F = qE collection force. This greatly reduces the particle migration velocities (w), e. g., for d = 10 mu m, w = 0.01 m/s compared with 0.4 m/s on Earth. However, for small particles (d = 1 mu m), this is compensated by diffusion charging and reduced drag (w = 0.04 m/s on Mars, 0.05 m/s on Earth). The Martian atmosphere was simulated with 95% CO2/5% humid air at 9 mbar. Paschen curves were measured, and I-V curves (I similar to 5-300 mu A for V similar to 1.3-2.3 kV) were obtained for 5-10-cm-diameter wire/rod-cylinder ESPs. Only positive polarity yielded stable uniform corona. Charging of 0.5-1.3-cm-diameter spheres agreed with the Pauthenier theory. A Martian dust simulant collection efficiency test is in progress.