Particle Loading Tests on HEPA Flat Sheet Media at Sub-Ambient Pressures Using a Lunar Dust Simulant

When humans return to the moon under NASA�s Artemis program, their activities on the lunar surface will inevitably lead to the intrusion of some level of lunar dust into the lander cabin and subsequently its potential transfer into orbiting segments after docking. The spacecraft�s cabin filtration system will need to be effective at removing the airborne lunar dust to properly purify the breathable cabin air and minimize subsequent dust transfer for the duration of the mission. The fine nature of the lunar dust will require high efficiency filtration, such as HEPA filtration. A series of tests were performed in a specially designed recirculating sealed flow loop, for testing filter media and filter elements at the NASA GRC. The flow loop was used to assess the performance and capacity of flat sheet filter media at representative cabin pressures using JSC-1AF lunar simulant and at high rates of particle loading. The pressure drop across the filter media was measured as a function of accumulated particle mass load at ambient pressure and at two sub-ambient pressures, 70.3 kPa and 56.4 kPa, and at a media velocity that was scaled relative to its pleated configuration. The challenge particle flows were generated by a custom designed particle generator that introduces dispersed particles of the lunar simulant at high concentrations. In addition, an optical particle counting instrument provided filter efficiency measurements within the sealed environment. The pressure drop was found to increase linearly with the amount of dust load on the media in all cases for this test range, but the rate of pressure drop increase was lower in the sub-ambient pressure cases. High filter efficiency was maintained even with high particle loads on the media.