Building a Lunar Iron Mine

Building a Lunar iron mine
Photo – http://www.miningartifacts.org/Minnesota-MInes.html

The book “Space Resources: Vol 3 – Materials” starts with a very interesting chapter titled “To Build a Mine: Prospect to Product” written by Richard E. Gertsuch. His paper details how to take a mining operation from conception to selling a marketable product. The paper’s focus is on Lunar-derived liquid oxygen. Ours is on metallic iron. While our Homesteaders may not plan on selling their iron, I figured it could be an interesting thought experiment.

The Earth definition of an ore is “a naturally occurring rock or sediment deposit that contains sufficiently concentrated elements that can be economically extracted”. Luna might have rich deposits of metallic iron but we haven’t found them yet.  That’s OK though because what Luna does have is perfectly workable.

Market Identification

  • Metallic iron
    • Products
      • Pressure hull construction
      • Shield construction
      • Structural components fabrication
      • Tool, equipment, and parts fabrication
    • By products
      • Oxygen
        • Life support
        • Propellant
        • Industrial processes
      • Titanium dioxide
        • Titanium feedstock
        • Protective coating
      • Glass
        • Homestead construction
        • Tools and equipment fabrication
      • Sulfur
      • Volatiles
        • Hydrogen
        • Helium
        • Carbon
        • Nitrogen
      • Spent regolith – All the recoverable iron (and volatiles) are gone.
        • Homestead shielding
        • Sintered into bricks for Homestead construction
      • Rejected oversized rocks
        • Crushed and fed into refining
        • Used in construction (walls, roads, etc.)
      • Heat
        • Used in other processes
    • Users and purchasers
      • Lunar Homesteaders
      • Cislunar orbital Homesteaders
      • Orbital Solar Power Stations
      • Cislunar cycling habitats
      • Government and commercial bases (not Homesteads)
      • Outbound (Mars, asteroids, etc.) Homesteaders – Initial Homestead “kit”
  • The “profit” in using Lunar iron is the cost savings of not have to launch all this stuff from Earth. As launch costs go down, so does the “profit”

Exploration

  • Where will we most likely find the highest concentrations of iron-rich minerals?
    • Maria – All the samples returned from Luna indicate that mare basalt has the highest concentrations of iron-rich minerals.
      • Ilmenite – Preferred
      • Spinel
      • Pigeonite (pyroxene)
      • Olivine
      • Agglutinates containing native iron metal
      • Armalcolite
      • Troilite
    • Highlands – The highlands also have iron minerals and Homesteaders will eventually extract the iron from them. But mare Homesteads will come first because they will have it a little easier (less material to process per unit of iron extracted).

Site Evaluation: Sampling Program

  • The purpose of the sampling program is to delineate enough ore reserves to make the mine profitable over its projected life and to help build an accurate ore body model.
  • Remote sensing is great but it rarely finds mining prospects, even on Earth. It’s good for getting you into the general area but nothing beats getting physical samples.
  • Since the Lunar regolith is such a mix of materials it may not be reasonable to conduct extensive sampling before starting the mining operation. Each scoopful of regolith can contain a different mix of material than the previous one and the next one.
  • My vision of Lunar Homesteading is that you can set one down anywhere on the surface and it will start turning out metallic iron. It would be nice to have a nearby concentration of iron-rich material but it’s absolutely not necessary. Flexibility will be paramount.
  • Besides, most Homesteaders won’t be defined by their mining operations. Sure, mining will always be a component because it’s necessary if they want to be self-sufficient in oxygen and construction materials. But I think (and hope) that most Homesteads and settlements will become known for their other activities and products.
  • Things we don’t know, even at our best sampled site (Apollo 17)
    • Grade variability
    • Minable depth variability
    • Overall distribution of grain size
    • Chemical and physical makeup of the regolith at all depths
    • Chemical and physical makeup of the underlying bedrock

Site Evaluation: The Ore Body Model

  • An ore body model (of which there are many) is a mathematical tool used to evaluate, design, and plan how to build a profitable mine. Accurate information is key to making an accurate model.
    • Factors considered in ore body models:
      • Ore grades – We’ll need to plan for a range of materials each with a range of concentrations.
      • Amount, and types, of waste
      • Geologic formations affecting mining
        • Craters
        • Boulders
        • Rilles
      • Mining methods
        • It’s not like we’re actually mining an ore body. We’re just scooping up regolith (rocks, fine powder, and dust) and processing it.
        • We will need to figure out the best ways to get regolith from the surface into the initial processing equipment. Efficiency and dust mitigation should be primary factors.
        • Rejection of oversized material
      • Refining methods
        • Mill feed speeds
        • Particle size sorting
        • Particle size reduction
        • Magnetic separation
          • Iron fines (as agglutinates)
          • Iron-rich minerals
        • Electrostatic separation
          • Iron fines (as agglutinates)
          • Iron-rich minerals
        • Hydrogen reduction
          • Ilmenite

Design and Construction

  • Lunar Homestead mining design rules:
    • Simple – Low tech is often the best tech.
      • Simple design
      • Least physical manipulation and processing of resources
      • Simple chemical reactions using the least amount and types of chemicals
    • Flexible – The equipment will have to deal with a variety of resources.
    • Rugged – The Lunar environment is harsh.
    • Small scale – It’s a Homestead, not an industrial complex. They can add additional units when they need to increase output. Think more, not bigger.
    • 100% user serviceable – Our Homesteaders should be able to fix or replace any component.
    • Maximum Lunar materials used in construction and maintenance – Make it out of iron!
    • Automated – The Lunar surface is no place for humans. Let the robots take the risk. Humans can solve problems and fix machines from the safety of their Homesteads and settlements.

Resources

  1. To Build a Mine: Prospect to Product. Gertsuch, Richard E. Space Resources (NASA SP-509) Vol 3 Resources, pages 4-14.

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