Microwave Processing Apollo Soil: Products for a Lunar Base

The chemical and physical characteristics of lunar soil, the fine fraction (<1 cm) of the lunar regolith, are at the root of the unique properties of this abundant resource on the Moon. These characteristics of the lunar soil make the soil an effective feedstock for microwave processing. Approximately 50% of typical lunar soil is <50 μm and consists mainly of impact-produced glass. This glass contains a myriad of tiny metallic Fe grains (3–40 nm). Most soil grains in a mature soil are also coated with thin patinas of silica-rich glass, containing additional and abundant nanophase Fe⁰. These minute metallic Fe grains impart properties to the soil that make it an excellent feedstock for numerous ISRU products. The lunar dust (<20 μm) has a high magnetic susceptibility such that it is almost completely reactive to a simple magnet. The unique abundance of nanophase Fe in the lunar soil also makes for the extreme coupling of the soil to microwave radiation. Effectively, "If a pile of lunar soil is placed in your kitchen microwave oven next to your cup of tea, the soil will melt at 1200 °C before your tea water will boil at 100 °C." Truly a remarkable and startling discovery, but true. This process involves the microwave heating of the fine fraction of the lunar soil, containing the majority of the impact glass with its minute metallic Fe grains which readily couple with 2.45 GHz microwaves. The microwave-treated ISRU products that can be used at a human lunar outpost are only limited by ones imagination.