This may seem like a “no-brainer” but I feel it needs to be emphasized. If there is a way to use readily available Lunar resources then that’s what Homesteads need to do. Efficiency is a secondary concern. Comfort and aesthetics are a tertiary concern. Safety is still a primary concern however.
Why is In-Situ Resource Utilization (ISRU) so critical to Lunar Homesteads (and all other space settlements)? As we’ve seen, it’s really expensive to land anything on the Lunar surface. We won’t need to bring as much stuff if we can use the resources that are already there. ISRU also makes our Homesteads less dependent on Earth if something should happen to their supply chain. Plus, it’s really cool to take a raw resource and turn it into something useful and valuable.
Resources aren’t only the rocks, water, and other stuff naturally found on Luna. Anything we bring with us is also a local resource. The one-way lander that delivered a supply module is now a resource that needs to be put to use. Strip it for parts or recycle the materials into new products.
Everything that comes from Earth, and is staying on Luna, has to be designed with 100% repair, reuse, and recyclability in mind. Nothing can be considered trash and permanently discarded. We don’t want to junk up Luna even if resource scarcity wasn’t a problem (which it is).
If we’re really clever we’ll make things coming from Earth out of materials that are rare on Luna. Copper is a great example. A very useful metal that we’ve only found in very low concentrations in the Apollo samples. The mare basalt samples we’ve brought back and studied shows a concentration of around 10 μg/g (10 ppm) . Compare that to the 170 ppm in terrestrial basalts . We haven’t found any copper ores yet on Luna but we haven’t really looked either.
So, copper is hard to find in Lunar rocks. What if we build the disposable landers out of copper instead of aluminum? Aluminum is common in Lunar rocks so why pay to bring it there (the whole coal to Newcastle thing)? It’s worth considering even if copper isn’t optimal or has more mass (decreasing the overall payload). Or we can construct items with copper components designed to be replaced with Lunar iron or aluminum parts.
ISRU covers a broad range of activities. Mining and processing of rocks are the obvious ones. Solar power generation (solar energy is a resource) could be another but I actually file it in the Energy category. Storing the processed resources, like oxygen, fits under ISRU as well. Finally, the actual use of the processed resources, such as manufacturing of parts, is also often included in ISRU (LH includes it). My concept of ISRU starts at raw undisturbed potential resources and ends with finished parts and products.
Unfortunately, Lunar ISRU is mostly theoretical and unproven. Some experiments have been carried out but little actual equipment has been built. Which is a shame because we could have been working on this for the last 50+ years. There’s a whole section of research here if you want more information on Lunar ISRU.
88) Lunar Sourcebook (pg. 417)
89) Isotopic and Elemental Abundances of Copper and Zinc in: Lunar Basalts, Glasses, and Soils, a Terrestrial Basalt (https://www.lpi.usra.edu/meetings/lpsc2007/pdf/1222.pdf)