Scale: 150+ People | Timeframe: Years 5+
Phase 5 is where a settlement stops surviving and starts re-industrializing: restoring the technology base of a town of 150-plus people, five or more years after collapse, rather than the family- or village-scale workarounds of earlier phases. The seven domains here split into two groups. Electricity, Electronics, Computing, and Networking build on each other directly — power, then the solid-state devices that run on it, then the logic those devices are wired into, then the links between the machines that logic becomes — and Radio & Telephone shares that same electrical foundation while branching off into wave propagation instead of digital logic. Advanced Chemistry and Photography & Optics stand apart from that chain entirely: one is industrial-scale materials science, the other a light-and-chemistry track that predates electricity by a century.
Electricity is the base layer: generators, motors, batteries, plating, and wiring, built up from atomic theory to a working distribution panel. Electronics picks up from there with semiconductor physics and the fabrication of transistors and diodes, then the logic gates and digital circuits built from them. Computing continues directly from those same logic gates, working up through binary arithmetic, assembly language, file systems, and magnetic storage to a working computer and its software, built from scratch. Networking is the domain after that — it starts from why computers need to talk to each other at all, then covers topologies, addressing, protocols, and the cables underneath, a layer that only makes sense once there is a computer on each end.
Radio & Telephone draws on the same underlying electrical theory but follows its own line: crystal detectors and tube theory through oscillators, transmitters, antennas, and real-world wave propagation, producing working radios and telephones rather than digital logic. Advanced Chemistry used to be the broadest domain here because it had become a holding pen: materials science, engines, aerodynamics, refrigeration, nuclear safety, plastics and telecommunications all sat inside it, none of which is chemistry. Those are now six domains of their own — Materials Science, Polymers, Engines, Refrigeration, Aeronautics and Radiation Safety — and Advanced Chemistry has been left with what it should always have been: organic and industrial chemical process, the reactions and the plant that runs them at a scale beyond a village workshop. It remains more a foundation other work draws on than a dependent step in this list. Photography & Optics is the one domain that doesn’t need any of the above: it runs from camera principles and light-sensitive chemistry through developing, printing, and the processes that came before film, a track that worked for a century before electricity ever entered a darkroom.
Electrical and Digital Systems
Power, then the solid-state devices, logic, and links built on top of it, plus radio’s own branch down the same electrical trunk.
Materials and Chemistry
What materials are and how they are made, from crystal structure and phase behaviour through to industrial-scale chemical process — none of it dependent on the electrical track above.
Heat Engines and Flight
An engine and a refrigerator are the same cycle run in opposite directions, which is why they sit together: one spends fuel to make work, the other spends work to move heat. Flight is what you get when an engine is light enough.
Light and Radiation
A century-old photographic process built on light and chemicals, and the one domain here you would rather never need.