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Several approaches are possible to extract aluminum and oxygen from aluminum oxides. The usual one is the cryolite electrolysis where synthetic cryolite is added to the refined aluminum oxide to lower its melting point and increase conductivity. This errodes carbon electrodes and requires maintenance on a scale that renders it impractical on Luna. Although the carbon is theoretically recoverable, this adds weight and complexity to the plant.
An alternative is to pressurise and electrolyse molten aluminum chloride. This has been tried in a pilot plant on Earth but the approach was abandoned due to extreme corrosion problems posed by the molten chloride.
The author suggests the reduction of refined aluminum oxide by the thermite process using magnesium as was historically used before the electrolysis process became possible.
The magnesium oxide produced by the thermite can be recovered, converted to the chloride with hydrochloric acid, dried and electrolysed at a relatively low temperature with no significant electrode errosion.
The main problem with this approach is that there will be losses of magnesium in the aluminum as an alloy, though it might be possible to recover this.
The author has obtained moonrock simulant samples from JSC and will attempt to process them when a workshop is built.
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