Five root techs are known from the crash — always unlocked, never researched. Everything else is unlocked at the Research Lab, per base: what one settlement researches, every survivor there shares, and the base next valley over starts from scratch.
Starting a research draws its materials from the common stockpile, all at once, up front. Then someone stands at the Lab and does the work — the times below are for unskilled hands; Engineering experience shortens them. Chains walk downward: a tech’s prerequisite must be unlocked first.
And note what isn’t here: the everyday survival stack — Oxygen, Water and Fuel Tanks, the Kitchen, Grow Rooms, “Wheezy Bessie”, the MoonBeam Still, the Aquaforge, the Inferno Scrapburner — needs no lab time at all. Just materials, and somewhere dry to put it.
“Research is the art of paying iron today to stop paying blood tomorrow.” — Lab plaque, hand-engraved