Research progress in the in-situ utilization of lunar soil

The in-situ utilization of lunar mineral resources is fundamental process for the establishment of a lunar base and subsequent exploration of deep space. However, the special environment of the moon and the cost of earth–moon transportation limit the direct application of existing mining and metallurgy technologies to achieve the in-situ utilization of lunar regolith. Since the 1980s, when NASA first proposed the “In-situ Resource Utilization” program (ISRU) and began to put it into practice, scientific researchers from all over the world have carried out fruitful research on the orientation of the in-situ utilization of lunar mineral resources and developed several technologies with great application potential. These methods can be divided into materialized molding and extractive metallurgy. Materialized molding processes, such as the sintering method and 3D additive manufacturing method, are mainly used to directly materialize the lunar soil to prepare building materials for the lunar base. Meanwhile, metallurgical extraction processes include carbon/hydrogenation medium reduction, electrolytic reduction, and vacuum pyrolysis, which can produce the corresponding metal or its suboxides and oxygen. At present, the main raw materials used in related engineering applications and ISRU research are lunar soil simulants. This paper briefly summarized the special space environment of the moon and its influence. Moreover, the characteristics and applications of lunar soil simulants synthesized in different countries were compared. The main steps, technological characteristics, research status, and application prospects of lunar soil and lunar soil simulant’s materialized molding process were then introduced. This work also summarized the general principles, basic processes, thermodynamics, and kinetics of the lunar soil’s in-situ extraction metallurgical technology, as well as the latest research progress. Finally, the advantages and disadvantages of these methods were discussed, and their applications in the in-situ utilization of lunar minerals were proposed. In addition, the possible impact of the special lunar environment on the implementation of related technologies and products in the future was discussed and prospected.