[1.12.x] USI Life Support
So I have been considering over the past month or two the creation of a life support system tailored to fit in with the USI mods, and also bring together some the bits I like about other mods already on the market, and add a few of my own tweaks, etc.
This is pretty much my interpretation of how, if I were to go buy Kerbal in a store, I would expect a stock-ish life support system to work. I've been playing with it and minus a few refinements am very happy with the result.
With that, I
Your math looks right to me. Basically, I take ( Supplies + ( Fertilizer * 8.5 ) ) / ( daily Supplies consumption rate ) = how many days my mission can go. This simplified formula works because 1 Fertilizer (plus Mulch which you get for free) gets turned back into 8.5 supplies.
Just make sure your total ( daily Greenhouse Mulch in capacity ) >= ( daily Supplies consumption rate ) you're good to go. Well, don't forget enough power for all that
Edit: I noticed your question about recy