In short, ordered from simples to not simples: Snacks - Food/Waste; optional Air/Bad Air and a Stress mechanic that impacts Kerbal skills (no "Touristification") Kerbal Health - Habitation mechanic + Radiation that impacts Kerbal overall health TAC LS -  Food, Oxygen, CO2, Waste; configurable difficulty (starved Kerbals die by default but this can be changed to Touristification). USI LS - Food + Waste + Habitation + Homesickness; highly configurable. Kerbalism - 'total c
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