A small home.
A serious pressure vessel.

The pressure shell carries cabin pressure loads. An external protective canopy or retaining structure carries any regolith shielding load. Dumping soil onto a lightweight pressure vessel is not a design solution. Support reactions, differential settlement, seismic loads, thermal movement and inspection access must be resolved before selecting a shielding geometry.

For a simple cylindrical envelope with a 4 m diameter and 8 m straight section, the cylindrical volume alone is about 100.5 cubic metres. Endcaps, structure, equipment, internal partitions and circulation change usable volume substantially. This is a geometry study, not a selected flight module. Launch fairing fit, landed mass, centre of gravity, deployment clearances and available transport may force a different size.

Four people need sleep privacy, acoustic control, exercise, food preparation, hygiene, sanitation, medical access and a place to work. Scientific racks should be removable without blocking exits. Stowage must be restrained and traceable. Full-scale mockups should test reach, emergency egress, crew congestion and maintenance tasks before internal layout freezes.

Cabin pressure and oxygen fraction must be selected with physiology, fire safety, structural mass and suit operations considered together. ARLO has not selected an atmosphere. The qualification plan needs leak checks, proof and burst rationale, materials compatibility, combustion controls, detection, isolation and repair procedures. A beautiful cutaway cannot establish human safety.