We know that human will very likely live partially if not entirely underground on Mars, in habitats constructed in massive lava tubes or structured buried beneath a few meters of Martian regolith—all in the name of radiation mitigation.
Therefore a lava tube was integrated into the SAM Mars yard from the opening discussion. When the Mars yard was to occupy the entire indoor space, the lava tube as to be roughly 25 feet deep and 12 feet tall. But with the SAM workshop taking form and the Mars yard redesigned to fit 2,600 sq-ft (roughly half of the total, usable indoor space), the lava tube was reduced to 15 feet deep by ten feet wide and a sloping 7 foot to 4 foot height. Even this relatively small space is completely engrossing once inside, and ample to pitch a pressurized tent, which is exactly what we intend to do.
While we investigated several construction techniques and various materials, we decided rebar and steel mesh (“chicken wire”) covered in high density spray foam was the way to go (see Sculpting SAM: Days 4-6).
