Sorium and/or Gallicite. Gallicite keeps the military running, sorium runs everything else.
Sorium is probably more consistent with Dune canon, being an essential component of Aurora starship fuel.
You forget duranium which everything is made of basically.
Duranium seems to show up in greater abundance than the other minerals in my games, though this could just be a RNG side effect.
Gallicite really slows down my military expansion, usually much more so than sorium. However, without sorium my civilian economy would cease to function, so that is arguably more important as my military relies on my civilian mega-carriers to move between systems.
My problem is gallicite too but its mostly self-inflicted in that I like all my military ships to have the best thermal insulation on their engines which as you might imagine makes my gallicite miners burst into tears.
Hah, I have the same addiction to reduced thermal engines... maybe I should try to break that habit and specialize that capability into my scout craft.
For small engines its not bad, but at max tech level 1% doubles the cost of engines which for the larger engines of your capitals starts to get massive.
I'm already at the point where I'm struggling to keep my maintenance clock in check for ships with large military engines. I've definitely out-paced myself in terms of engine size vs shipyard capacity there. I can build up to 400HS engines, but I can't practically operate anything larger than about 50HS.
I am thinking that for my next campaign I am going to pick a target engine tech and stop researching new engine tech once I reach that level in order to reduce my tendency to continually rebuild my fleets with larger ships with better engine tech. Having gained some more practical experience now I think I might be able to field some useful fleets from ion-tech onwards, so that might be my initial goal next campaign.
