Venting and Outgassing Simulations of Pressurized Lunar Modules: Contamination of the Lunar Environment

Abstract

One objective of Artemis science is to determine the impact human activities have on the lunar environment, which might compromise science objectives and measurements. We perform a preliminary analysis of the contamination associated with airlock venting and outgassing from a prototype lunar-module geometry intended to host astronauts on the lunar surface. The air flow generated by the depressurization of the airlock, expanding in the lunar exosphere, is studied using the Direct Simulation Monte Carlo (DSMC) method for two different venting configurations and the particle flux on the surface is computed as a function of the distance from the the module. Outgassing from the main body of the module -- assumed to be covered with a Multi-Layer Insulation (MLI) blanketing -- and from the solar panels is then analyzed using a view-factor method, employing outgassing rates from the literature.Our results give preliminary indications of the distance at which contamination levels fall below the values characteristic of native species in the lunar atmosphere. Scientific measurements targeting 40Ar should be carried farther than 30--100 meters from the module, while the detection of lower-abundance species such as polar-crater water might require to travel up to and beyond 3 km from the module.

Figures (12)

• Figure 1: Artist's rendering of the Multi-Purpose Habitation lunar module (MPH, Left) and of the Lunar Cruiser pressurized rover (Right). Credit: Thales Alenia Space / Agenzia Spaziale Italiana (ASI) MPHthales, and JAXA LunarCruiserJAXA.
• Figure 2: Simplified geometry employed in our simulations.
• Figure 3: Position of the airlock depressurization vents for the simulations of Case 1 (Left) and Case 2 (Right).
• Figure 4: Airlock depressurization curves during venting from two valves each with an equivalent radius $R_v$. Only the case $R_v = 10~mm$ is selected in this work while the other curves (dashed lines) are not considered further.
• Figure 5: Evolution of the flow through a single vent of radius $R_v = 10~mm$. Solid blue line: mass flow rate through an individual vent. Dashed green line: Knudsen number at the vent location.