1. V 20 m3Assumed from NASA documentation of Iunar lander (Lee, 2007; Wu et al. 2007) η 0.25, 0.5, 0.75 0.25, 0.5, 0.75 0.25, 0.5, 0.75 Assumed filter efficiencies for three scenarios. QI 0.0007 m3s-1Assumed to be 5% of Qr
2. For corresponding particle sizes per Riley et al. (2002). These values for deposition loss rate coefficients are based on best-fit curves to experimental data from the literature for particles of approximately 0.1 µm and larger, and smooth curve theory for particles smaller than 0.01 µm. β, 0.1 µm 0.00001 s-1
3. Filter efficiencies are chosen on the basis that filter performance is PM size-dependent (Abraham, 1999). Actual filters may be more or less efficient with respect to various particle sizes. Therefore, the parametric filter efficiencies matrixed against particle size-correlated deposition loss rate coefficients do not necessarily represent single, real filters' performance across the range of particle sizes. One particular filter, for example, may be more efficient with respect to coarse PM, but less so with respect to ultrafine particles. The three values for η, therefore, represent three efficiencies, as distinct from three filters of uniform efficiency across the range of PM sizes. There is no available data for regolith PM deposition loss rates in any Iunar habitat, as only sizing analyses have been performed on Iunar regolith. As a working assumption, therefore, the values used in Figure 8 for β are from Riley et al., for PM corresponding to the four particle sizes chosen. The data from Riley et al. are based on curves best-fit to experimental data compiled from nine studies in the literature for particles of approximately 0.1 µm and larger, and smooth curve theory for particles smaller than 0.01 µm. The application of this terrestrial data to a Iunar model is a working assumption given the paucity of data on Iunar PM size distributions. Sizes reported by Greenberg et al. (2007) are within ranges reported by Riley et al. (2002), although the former data was from re-aerosolized samples, and therefore numbers are not comparable to the latter.
4. Like Riley et al., Equation 1 assumes concentrations averaged over time, a constant PM mass within the habitat, that Caand Ccare not time-correlated with airflow rates and surface deposition orientation, and well-mixed isothermal conditions. Given the relatively small volume of the crew compartment and the constant recycling of spacecraft air, a well-mixed environment may be reasonable. Equation 1 also assumes a constant air density, constant airlock PM concentration, no resuspension or agglomeration of particles, no phase changes, and first-order losses and reactions. Activities associated with significant terrestrial indoor particle sources, such as combustion and cooking, are non-existent or minimal in spacecraft. Wallace (2006) lists several activities contributing to indoor PM; none occur in space. Other activities may represent measurable PM sources, but they are assumed to be less significant than Iunar regolith PM.