The Molten Soil Reactor

View of components - concentrator mirrors, reactor silo, heat transfer circuit, radiator, steam collection tank

This is a fluidized bed reactor that extracts metals and oxygen from molten regolith. The configuration shown is of the kind that was first constructed at scale, which processes  ilmenite (FeTiO3) into iron and water by bubbling hydrogen through the molten mix. The water produced is split into hydrogen and oxygen. The hydrogen is recycled in the next batch, the oxygen is mostly used as rocket fuel. The iron goes to a wide range of manufacturing and construction uses. Lunar dirt high in ilmenite is available near the site of Moon Town. The ilmenite in that soil can be concentrated until it composes more than 90% of the dirt placed in the reactor using electrostatic separation, as discussed here by William Agosto.

Variants of this system that work with carbon monoxide or carbon dioxide instead of hydrogen are a possibility.

First Iteration

These units are very large. The inner dimensions of the reactor silo are 27 m high, by 9 m in diameter, with a capacity of 1350 cubic meters. The mirrors focus 1400 m2 of sunlight on the heat pipe travelling through their focal point and then coiling through the interior of the silo. There is also a tank where water is condensed, and a radiator that cools the steam coming into that tank. The reactor silo is filled before dawn and emptied at sunset by autonomous rovers.

As the town is sited at Lalande Crater, 4.5 degrees S, the mirrors don’t need to track on 2 axes and can simply track around a north-south axis, with appropriate spacing to account for where the reflected light ends up.

Reference schematic from Space Resources Vol 3 – Materials

from pg 205 of Space Resources Vol 3 - Materials, NASA 1993 - article titled 'Processing Lunar Soils for Oxygen and Other Materials', by Knudsen and Gibson

Current 3d models:

A version of this model to serve as a basis for development is available in 3 formats. OBJ is the format that should import properly into any 3d software. FBX and GLB are formats best suited for games. 


There is a channel on our Discord server for discussion of the design of this equipment. Come join if there is anything you’d like to comment on or ask –

Also see the Projects page for general guidance on designing for Moonwards – materials, infrastructure, transport, practices, and main reference works.