ACHIEVING SELF-RELIANCE
- how an off-Earth base could quickly become self-sufficient -

Machining Rion Motley discusses a number of processes that would take lunar metals and cast, roll, machine, and 3D print them into usable parts.

METAL BEFORE CREW ARRIVAL
As mentioned in the Resources section, about 1% of the lunar highlands is nickel-iron bits. This is unoxidized metal which could be obtained without needing to expend a large amount energy separating the metal atoms from their oxygen. However, the nickel-iron bits are often fused with other material (e.g. glass or rock particles). NASA researchers who work in the field of resource utilization have a few ideas as to how the nickel-iron can be separated from the other material.

Previously, NASA conducted the Excavation Regolith Challenge in which teams competed to have their robots excavate lunar dirt simulant and drop it into a hopper as fast as they could. The Challenge constrained the teams to have excavators limited to no more than 40 kg and 30 Watts. The winner excavated at a rate of 878 kg per hour. If one were to proportionately scale this up to a metric ton of telerobots and bearing in mind that only 1% of the lunar dirt is nickel-iron, operating at 24/7, it would seem that the telerobots could extract up to 22 metric tons of metal per day. Even if one is conservative, this means that hundreds of tons of metal could be available prior to crew arrival such that it wouldn't make sense to launch from Earth any of the metal parts that could be produced on the Moon.

METALLURGY
The melting of the lunar metal could be done via a combination of concentrated sunlight (e.g. parabolic mirrors) and induction heating using electricity from solar drapes. In this way the concentrated nickel-iron ore would be melted, any dross removed, and then the molten metal could be poured, extruded, rolled, or sprayed as metal powder. It should be noted that nickel-iron would require the least energy to extract but there are other, equally interesting metals that could be extracted on the Moon including aluminum and titanium.

AUTOMATED PRODUCTION OF PARTS
Rather than waiting for the Initial Crew to arrive before producing metal parts, it seems feasible that automated equipment could transform the molten metal into useful forms. It could be poured to make ingots or poured into molds such as to make telerobot chassis, airlock handles or whatnot. Using pressure, the metal could also be extruded to make solid bars. With a combination of extrusion, rolling, and bending, hollow round or square tubes could be produced which would find all sorts of applications within habitats. Of particular use, molten metal blocks could be successively rolled to produce increasingly thin sheets of metal. Machines could take the sheet metal and cut out patterns for chairs, counters, tables, equipment housing, toilets, and even the sheet metal used to make the inner and outer walls of habitats. Finally, with enough pressure, the molten metal could be sprayed to produce metal powder to use for 3D printing. When the Initial Crew arrives, the Machinist-Metallurgist would take the lead in working with the parts to assemble hardware for future habitats.

INITIAL EQUIPMENT
What would be the key, initial pieces of equipment needed to produce the metal parts? Machining equipment tends to be very massive and therefore very expensive to ship from Earth. We believe that the Generation 1 equipment could be made of rigid composite parts anchored deep into the lunar dirt for stability. That Generation 1 machining equipment would be used to produce much more massive Generation 2 equipment. Analogies to machining and metallurgy on Earth may not exactly apply here. Whereas on Earth economic efficiencies means that these processes are done in huge buildings at very large scale. In this situation where shipping costs are so high and one is not supplying large populations, then the scale on the Moon will be much smaller than such processes on Earth.

Our current thinking is that the metallurgy & processing equipment would be as follows:

• Metal-excavation telerobots
  
• Solar concentrators and arc furnace
  
• Ceramic crucible and powder sprayers
  
• Molds
  
• Continuous caster for bars and extruders for wires
  
• Multiple die sets
  
• Rolling mill to make sheet metal
  

And the machining equipment would be as follows:

• Power hammer
  
• Hydraulic press
  
• Sheet metal bake/shear
  
• Friction stir welder
  
• Planer
  
• Lathe
  
• Multi-axis CNC machining centers
  
• CNC routers
  
• Metal 3D printer
  

EXPONENTIAL BOOTSTRAPPING
Certain metal parts would have an exponential nature in that the resulting equipment would be used to produce more equipment. This would include the production of more automated, metal-extracting robots, and the metallurgy and machining equipment. As International Astronauts arrived, some of them would be machinists and metallurgists working in habitats dedicated to these processes. The result would be an exponentially growing settlement in which the large majority of the mass was being produced on the Moon and not shipped from Earth.