It seems to me that the plasma consumption of the recipes is rather high. The ore melting consumes 100 plasma, which equates to 2.5GJ worth of energy - and while that still means 16 operations per Fusion power cell, with a rocket capacity of 50, a rocket of plasma cells can only support 800 smelting operations, so not much more than the 500 supported by a rocket of calcite (and rockets are much cheaper on Vulcanus than on Aquilo, even ignoring the Holmium (and Lithium Deuteride, made on Gleba, when playing with Particle Physics) requirement of fuel cells). The foundry itself consumes just 21MJ per craft (whether or not plasma is used), so a factor of >100 in total energy use seems strange (even gas phase "melting" would require less energy, and the recipe is just called "high temperature melting", and not eg. "mass spectrometric separation").
Similarly, I'd expect carbon fibre production to require only minimal amounts of plasma, instead of half a reactor per unmoduled biochamber.

Maybe reducing the consumption to 10% (10 for melting, and 1 for carbon fiber/circuits) would be a better balance?

The recipe for the ionized fuel seems totally fine, though I wonder about the reduced stack size and especially rocket capacity...

Hello there, I'm very much still looking for feedback on balance so this is super valuable!

You are correct that ore melting is simply too expensive, when I initially made the recipe I considered it a "convenience tax" for not having to import calcite but seeing as the tech comes very late in the game and also how slowly plasma trickles out of a reactor, I agree it needs to be cheaper. The idea was that you superheat it into a gaseous form before letting it cool down, burning off all impurities and eliminating the need for calcite. That said I realise the name is somewhat uninspired, so that, too, will be subject to change.

The carbon fibre recipe is a fair bit more productive than its vanilla counterpart, which makes it fairly strong when trying to produce quality carbon fibre. Seeing however as the meta is upcycling toolbelts, which require no spoilable components, I think I could also make this recipe cheaper.

The bulk circuit recipe isn't any more productive than its vanilla counterpart (largely to prevent net positive recycler loops) but has the advantage of a) The convenience of skipping sulfuric acid and b) the bulk recipes enable you to slap down fewer, higher quality machines with fewer, higher quality prod modules, so I'll wait for further feedback here.

Ionised fuel has its stack size and rocket capacity set as to not invalidate nuclear fuel completely. The idea is that you should have access to a nuclear fuel equivalent for trains/vehicles on all planets but need to set up some local infrastructure as a trade-off.

Since you've clearly put quite some thought into it, could I also ask you: What do you think of the tech tree, do the recipe unlocks make sense for you, progression and cost wise?

Thank you for your feedback!

The quality loop usage of the carbon fiber recipe is an interesting point, but I still think that with 1 plasma it would be a better fit - as you said, the "default" option uses a recipe without spoiling ingredients, and since there isn't any infinite research for carbon fiber, the advantage is limited.
I actually don't mind "high temperature melting", though if you prefer the idea of gas phase separation (whether by distillation or centrifugal separation), you could make the name/description a bit more interesting.
I agree that ignoring the sulfuric acid requirement and higher machine throughput is a significant bonus - though on the lore side, the idea of that intricate EM plant getting hit with half the output of a fusion reactor still feels strange (though I guess less so than for the biochamber).

In terms of the tech tree, I guess the ionized fuel could require Kovarex enrichment process (nuclear fuel) as a prerequisite; the other techs make sense, since fusion reactors require most vanilla techs as prerequisite anyway, and none of those seem like they should require Promethium science. As for the costs, I'm playing with the Particle Physics mod, which adds a new science pack for everything form quantum processors onward - this new science pack (which requires biter eggs, U235, Lithium Deuteride (Lithium + spoiling Gleba product), Tungsten Carbide and processing of those resources in a particle accelerator) is the main slowdown, since the other sciences are already automated by this point (I've also installed Paracelsin after I already got some quantum processors, which cut me off from making any more until I complete that planet, so my progression is all over the place). I guess there's a pretty wide range of plausible tech costs - anything from a quarter up to 5 times the current tech cost seems plausible to me, so I think the current values are fine.

Thank you for the feedback, for now I've reduced the cost of the ore melting recipes to 10%, set Kovarex as a requirement for ionized rocket fuel (only if your playthrough is using kovarex) and changed the locale for the ore melting recipes.
I'll wait for more feedback before I touch the circuit and biochamber recipes.

Paracelsin is a very fun resource balancing puzzle, if you added it later in your playthrough it has an option to disable the telescopic zinc recipes on Aquilo btw.

After some more feedback on discord I've now reduced the plasma cost of the carbon fiber recipe as well as the two military recipes!