Meson_Ray

Found through a ton of trial-and-error that it needed up to exotic fuel storage to unlock all the fuels. Since this node only unlocks antimatter parts, it wasn't really clear beforehand that it would open up Hydrazine as a fuel.

Tried researching all three levels of the engine. Are there other techs that might affect it?

It's definitely the closed cycle. I've narrowed the issue down to something about my save file - a fresh install of KSPI-E and fuel switcher from curse and the closed cycle can use any fuel in a sandbox game. But if I try to use it in my career save, it ends up only being able to use Nitrogen, LqdArgon, Argon, Hydrogen, Liquid Fuel and Lithium as propellants. I'd like to not have to restart my career - is there anywhere in the persistent.sfs that might be affecting the propellant types?

Asked in what I see now is the development thread, so I'll put it here in the support thread instead: In 1.2.2 with KSPI-E 1.12.9/1.12.10 with fuel switch 2.4.3/2.4.4 the closed cycle gas core engine only has some of the propellants available (hydrazine not being one). That combination was available in 1.2.1 with KSPI-E 1.11.4 and fuel switch 2.2.9. Is this switch working as intended or is hydrazine supposed to be available as a propellant for this engine?

In 1.2.2 with KSPI-E 1.12.9 with fuel switch 2.4.3 the closed cycle gas core engine only has some of the propellants available (hydrazine not being one). That combination worked in 1.2.1 with an older version of KSPI-E. Are there only some propellants available for the closed cycle engine? I have done a clean reinstall of both KSP and all installed mods, any suggestions?