The field of astrometallurgy is a growing area of study. Metal production on the Moon is likely to
begin in less than a decade as major space agencies such as NASA (National Aeronautics and
Space Administration) and CNSA (China National Space Administration) are preparing to construct
permanent lunar bases. The utilisation of regolith to generate oxygen and metals is expected to be
important in the development of a sustainable lunar habitat. This paper provides an overview of
potential metallurgical processing methods for lunar conditions, emphasising the impact of lunar
factors on slag chemistry. The interaction between regolith and the extracted metals, as well as their
impact on slag composition and refractory performance, are critical considerations in metal
production on the lunar surface. The initial research on lunar metallurgical technologies is focused
on oxygen extraction and Fe-Si alloys are reported as the by-products of these processes. This
paper delves into the fundamental thermodynamics associated with the carbothermic reduction of
lunar regolith. Thermodynamic analysis using the FactSage™ ver 8.2 software package indicates
that the Fe-Si alloy can be produced as a metallic product from the lunar regolith at temperatures
ranging from 1400°C to 1600°C under terrestrial conditions. However, under ultra-high vacuum
conditions (3 × 10-15 bar) on the Moon, the required operating temperature for producing ferrosilicon
would be significantly reduced. Thermodynamic modelling results indicate that under lunar vacuum
conditions, Fe-Si alloys only exist as solid phases at lower temperatures below 650°C. At higher
temperatures, both Fe and Si are expected to be present in the gas phase. In this work, the
carbothermic reduction of the Lunar Mare Simulant (LMS-1) is conducted under terrestrial conditions.
The findings indicate that the process can readily yield Fe-Si alloys with 7–10 wt per cent Si at
1600°C. Additionally, energy dispersive spectroscopy (EDS) analysis of the resulting Fe-Si alloy
indicates the presence of phosphorus up to 1 wt per cent.