Oxygen-Iron Extraction - Lunar Homestead

Version 1.2 June 9, 2021

Oxygen isn’t just for breathing (although that’s pretty important!). Homesteaders will need large quantities of oxygen for reaction mass (aka rocket fuel), industrial processes, and for SPORE (of course!).

There’s a lot of buzz about mining Lunar ice, splitting it into hydrogen and oxygen, and using it for rocket reaction mass. There are a whole lot of problems with this idea, which I will layout in my upcoming post “Lunar ice is a trap”.

The other option for obtaining large amounts of oxygen on Luna is to get it from Lunar rocks. Oxygen is the most common element on Luna, with more than 60% of it’s atoms being oxygen (1, pg 363). Unfortunately, this oxygen is chemically bonded to other elements and is rather difficult to extract. Fortunately, we’re smarter that rocks (well, most of us anyway).

Additionally, Homesteads are going to require large amounts of material to make habitats, equipment, and all kinds of other stuff. It’s a good thing that most oxygen extraction processes also extract iron at the same time (if basalt is the parent material).

That’s where the Oxygen-Iron Extraction project comes to the rescue. We are going to figure out how to extract the oxygen and build the prototype equipment to do it. And you can help us do it. But first, we need to decided which process to pursue first.

Lunar Oxygen Extraction project outline

This is a rough outline on how Lunar Oxygen Extraction Research Project can be conducted. Everything is subject to change. Let me know if you have ideas or comments.

Phase One – Define the Project

Project Assumptions
1. Basic assumptions
  1. We’re only going to focus on what Homesteaders can build using local resources and minimal tools. Other people are working on high-tech solutions that would require constant input from Earth.
  2. The only regular Earth input we’ll allow is 1-2 elements/chemicals that are not found on Luna and are required for a particular chemical process.
    1. These chemicals must be completely reusable. For example, hydrogen is combined with oxygen to produce water, which is then broken down into hydrogen and oxygen. The hydrogen is then run through the system again.
  3. Environmental
    1. Surface conditions are difficult and dangerous. So everything should be built within a pressurized hull. Doing so avoids a lot of problems.
      1. 1 SLH Atmosphere
      2. See SPORE for why surface operations should be limited.
      3. These chemicals must not be terribly toxic, explosive, hazardous, or difficult to contain/handle.
  4. Processes should not be raw material sensitive.
    1. Homesteaders are going to be shoveling everything they excavate into this machine.
    2. Having to pre-sort all the raw material into its component chemical parts will take time, effort, and require additional equipment.
    3. Processes that can handle anything, even at a lower efficiency, are preferred.
  5. Parameter priorities
    1. Able to be constructed/maintained locally
      1. Relying on Earth to build and ship this equipment will created a dangerous bottleneck.
    2. Minimal reliance on Earth for reagents
      1. Reuse of reagents
    3. Operable in 1 SLHA
      1. Environmental safety
    4. Ease of maintenance
      1. Homesteaders should be able to easily strip all equipment down to it’s basic components, swap out those components, and put it all back together again. EVERYTHING should be user serviceable.
    5. Simple
      1. Homesteaders will not be professional chemical engineers. Or probably engineers at all. So let’s keep it simple.
    6. Durable
      1. This is critical technology that will be in constant use. Well, maybe. It depends on their power consumption. But nobody wants to be constantly fixing finicky equipment.
    7. Energy input
      1. All Homesteads will be constrained by the available energy (electric, thermal, etc.). Solar energy is only available for 14 out of every 28 days.
      2. Processes either need the ability to be shut down for 14 days or operate on minimal (stored) electricity for 14 days.
    8. Heat output
      1. Waste heat is an issue since all the processes are within a pressurized hull. We’ll need a way to collect it, remove it from the habitable area, and use it for other processes.
    9. No hazardous materials are produced.
      1. Some processes produce hazardous by-products. These need to be avoided.
    10. Efficiency
      1. Efficiency matters very little. Homesteaders can build more units to compensate. As long as rare materials are reused.
    11. Processes that extract more than just oxygen are preferred.
      1. Obviously, we’ll try to extract any volatile elements.
      2. Some processes will extract iron and oxygen at the same time. This is the kind of process we need to explore. I would say that iron is almost as important as oxygen.
      3. Glass, aluminum, and titanium are also target resources.
      4. Processes that melt basalt will have …wait for it… molten basalt as a resource. Homesteaders can cast molten basalt into lots of useful things. We can also figure out how to recover some of the energy used to melt the basalt.
    12. Weight/mass/volume
      1. This is a primary concern with anything coming from Earth. Not so much for our Homesteaders. Weight and mass can be ignored. Volume is a minor concern because everything possible must be contained within the pressurized habitat.
    13. Other uses for the reagents
      1. Some reagents have other industrial or scientific uses. It might be useful to have a supply readily available to take advantage of other opportunities.
Lunar Homesteader resources (what will Homesteaders have easy/abundant access to?)
1. Solar Thermal Energy
  1. 14 days out of 28 days.
  2. Available at the surface/near-surface only
  3. This project isn’t concerned with how. Just how much solar thermal energy is required for the process or processes.
2. Solar Electric Energy
  1. Photovoltaic or Solar thermal conversion.
  2. 14 days out of 28 days.
  3. Available at the surface/near-surface only
  4. This project isn’t concerned with how. Just how much electricity is required for the process or processes.
3. Regolith (I know it’s empty right now)
  1. Homesteaders should avoid dealing with the Lunar regolith as much as possible.
  2. Problems with the Lunar regolith”
    1. Dust – deadly to machines and humans
    2. Abrasiveness – lots of small, very sharp edged particles
    3. Heterogeneous – the regolith is a complex mix of all kinds of rocks, glass, dust, agglutinates, etc. It’s a mess.
4. Mega-regolith
  1. The mega-regolith still contains a lot of regolith but it also has large chunks of bedrock.
  2. These large chucks are important because they should help us create a more uniform extraction process.
5. Basalt
  1. This is why we’re using a mare site as the reference site.
6. Oxygen
  1. I know we’re trying to extract oxygen here. However, Homesteaders will have access to lots of oxygen once the extraction process is underway. So if oxygen is needed in the extraction process, Homesteaders will have it.
  2. All the other major elements found in Lunar mare basalt are chemically bound to oxygen.
7. Iron
  1. Homesteaders should have an abundance of pure iron once the extraction process is underway.
  2. Iron is found in 19-22% concentrations in mare basalt.
8. Silicon
  1. Silicon Oxide (SiO2) is the major component of mare basalt, from 38-48% concentration in most samples.
9. Titanium
  1. Titanium Oxide (TiO2) is available at 2-11% concentrations in most samples.
  2. Titanium will probably require a lot more energy to extract than iron so it may not be available to early Homesteaders.
10. Aluminum
  1. Aluminum Oxide (Al2O3) is found in most Lunar basalt samples at 6-11% concentrations.
  2. Again, aluminum will probably take more energy to extract than iron so it may not be available to early Homesteaders.
11. Calcium
  1. Calcium Oxide (CaO) is found at 8-12% concentrations.
12. Magnesium
  1. Magnesium Oxide (MgO) is found in most Apollo 12 samples (and mare in general) at about 6-14% concentrations.
13. Other elements are found in much lower concentrations so we’re not going to worry about them for now.
Sources of oxygen
1. We don’t need to spend much time here. It’s already pretty established.
2. Basalt is the primary resource we’ll be dealing with. If our site is in a mare (and our reference site is), then the regolith and mega-regolith will primarily consist of basalt. Lunar basalts are composed of four major minerals:
  1. Pyroxene
  2. Plagioclase
  3. Olivine
  4. Metal oxides (abundance varies directly with TiO2 content)
3. Glass
  1. Lunar glass found in mare regions can contain significant amounts of FeO.
  2. Glass may become less common as Homesteaders dig deeper into the mega-regolith.
  3. We should make sure our processes can deal with it but not count on it to provide a substantial amount of oxygen.
Known processes
1. Ilmenite Reduction with H2 (Solid/Gas Interaction)
2. Molten Salt Electrolysis (CaCl2/Oxide Solid)
3. Molten Regolith Electrolysis (
4. Glass Reduction with H2 (Solid/Gas Interaction)
5. Molten Silicate Electrolysis (Silicate/Oxide Melt)
6. Fluxed Silicate Electrolysis (Silicate/Oxide Melt)
7. Vapor Phase Reduction (Pyrolysis)
8. Ilmenite Reduction with C/CO (Silicate/Oxide Melt)
9. Ilmenite Reduction with CH4 (Silicate/Oxide Melt)
10. Plasma Reduction with Cl2 (Silicate/Oxide Melt)
11. Reduction H2S (Silicate/Oxide Melt)
12. Caustic Dissolution & Electrolysis (Silicate/Oxide Melt)
13. Carbothermal Reduction (Silicate/Oxide Melt)
14. Ion Plasma Separation (Pyrolysis)
15. Carbochlorination (Silicate/Oxide Melt)
16. Extraction with F2 (Silicate/Oxide Melt)
17. Magma Partial Oxidation (Silicate/Oxide Melt)
18. Li or Na Reduction of Ilmenite (Silicate/Oxide Melt)
19. Plasma Reduction of Ilmenite (Pyrolysis)
20. Hydrofluoric Acid (HF) (Aqueous Solutions)
21. Sulfuric Acid (H2SO4) (Aqueous Solutions)

Phase Two – Identify the most promising processes

Phase Three – Experiments

Phase Four – Working (non-flight ready) scale prototype of a SPORE structure

The goal is to have a prototype “on the shelf”. We won’t know all the steps necessary until I am further along.

Phase Five – Public outreach and education

Scale non-functioning mock-up
Publish data and findings
Book – written for non-scientists

Resources

Lunar Sourcebook (www.lpi.usra.edu/publications/books/lunar_sourcebook)