Generation of a lunar regolith agglutinate simulant using friction welding apparatus

An important ingredient of the lunar regolith is agglutinate, which is generated by micrometeorite bombardment and resulting fusion of the soil. The agglutinate component has proven difficult to replicate, yet it typically constitutes 25–30%, and up to 60%, by volume of the lunar soil. In this work, the results of deploying friction welding apparatus to generate the agglutinate component of lunar highland regolith are reported. Using Shawmere anorthosite from the Canadian Shield as source material, the agglutinate has been produced via the friction melting of machined rock cylinders rotated under load at 2000 rpm. The products are 0.5–5.0 mm globular aggregates comprising mineral fragments (1–30 μm) bonded by silicate glass. The glass is vesiculated and close in composition to the bulk rock. The size and morphology of the synthesized agglutinates are similar to natural agglutinates (e.g., as found in Apollo 16 regolith sample 64500). The source anorthosite has previously been used to produce a root simulant (UNB-AN-1) and an olivine-composition glass-bearing derivative (OB-1), currently deployed as a highland simulant (Battler and Spray, 2009). Generation of an agglutinate component from the same source rock provides for the production of a more advanced, high-fidelity regolith simulant for lunar geotechnical and engineering applications.