Technical Papers and Presentations

NASA’s future human exploration missions will require chemical processing plants to convert local resources into consumables to support astronaut activities [1]. The thin and mostly carbon dioxide atmosphere of Mars is estimated to have 5 – 10 particles/cm³ with diameter of 3.2 – 5 μm [2]. The dust in the Martian atmosphere can foul chemical reactors and pose a risk to life support systems. Electrostatic precipitation (ESP) can remove dust particles from the Martian atmosphere. The Electrostatics and Surface Physics Laboratory at NASA’s Kennedy Space Center has developed a COMSOL Multiphysics^® model of an ESP for dust filtration on Mars. The fundamental principles of an ESP can be simulated by four physics modules: Plasma, AC/DC, CFD, and Particle Tracing. In the ESP model presented here, the Plasma Module is solved together for a steady solution, and then the AC/DC, CFD, and Particle Tracing modules resolve a time-dependent solution.

The electron density distribution as well as the negative and positive ions distributions were obtained from the model. The analysis of those distributions showed that the density of CO₂⁺ ions is at least two orders of magnitude greater than either that of the electrons or of the other positive and negative ions, as shown in Figure 1 and Figure 2. This result is as expected; dust particles acquire a net charge of the same polarity as that of the high voltage potential. Experimental- and model-derived I-V curves for a range of ESP geometries were obtained, as shown in Figure 3. In all cases, the simulated corona onset voltage is less than experimental values. The computed curves match the experiment at the high end of the potential just before electrical breakdown occurs. This is the region of interest since it provides the maximum possible potential that generates the strongest electric field on the dust particle. Results of the COMSOL Multiphysics^®

model depend on the neutral and ionic species used. The species selection shown in Table 1 is thought to be the species that interact most significantly with the plasma in the CO₂ environment with the positive DC potential. Future refinements to the model with contributions from additional species can enhance the fidelity of the model. Finally, the relationship between precipitator diameter and length for the collection efficiency of dust particles in a range of flows is shown in Figure 4. The model will be used in future trade studies to optimize an ESP assembly that will provide sufficient dust filtration to support future astronaut activities on Mars.