Fusion is the power, and material production of late game NH. It serves as your gate to ZPM, as well as your gate to condensed 1M+ eu/t generation. It might be hard to make the first one, but soon you'll find yourself surrounded by multiple fusion reactors fueling your base. Besides new material creation, and power generation, fusion recipes exist to make earlier difficult to obtain items easier. Such as recipes for sunnarium and indium. Much of fusion recipes for plasmas and fluids are a WIP, and many are subject to change, while others are waiting to be added.
Entry to Fusion
Once you reach LuV, fusion opens up as a power option, as well as your gateway to progression. The initial build cost is going to seem high at first, as it required a LOT of materials, as well as a significant power investment. It will take you roughly 20h to process everything you need, assuming you can provide 2A zpm for that duration. However if you can make that much power, and have a T4 rocket, you'll have an easier time. The mega ebf and vacuum freezer are also super useful in this stage.
Once you have the reactor built, you can start using it for whatever you want. The mk1 using helium as a fuel source can output around 1M Eu/t in plasma, if you use the large turbine and a rotor around 150% efficiency. Setting up the fuel will be the challenge, as helium alone will require several multis to run constantly.
For processing materials, your first goal should be to make europium. It's your gate to zpm, as well as some other options, like LuV naq gens, and Crystal processor circuits.
The functionality of the reactor is fairly simple. Put the inputs in the fluid inputs, and supply the right eu/t. The starting Eu and the eu/t of the recipe are shown in nei, and can tell you what tier reactor you need. Each energy hatch added to the reactor will add to the amount of eu the reactor can store, as well as the eu/t it can do. A reactor can hold 16 energy hatches at most, with each adding 10M EU to the capacity, and 2048eu/t to the input voltage. This means the max starting EU recipe the mk1 can do is 16 x 10,000,000, and 2048 x 16 eu/t. For each tier after the mk1 reactor, the hatches will do 2x that. So the mk2 can store 20,000,000 per hatch, and input 4096eu/t.
Fusion overclocking doesn't work like normal GT machines. Essentially it works on the idea 2x eu/t 2x speed. However, this is also limited by reactor tier. A mk2 reactor can do a mk1 recipe in 1/2 the time for 2x the eu/t. However, if a recipe only needs 2 hatches, but you use and supply 4 with power, it won't overclock any additional times. This means every recipe will run at 2x eu/t 2x speed in the reactor 1 tier above the recipe tier, 4x eu/t 4x speed 2 tiers up, and 8x eu/t 8x 3 tiers up.
Fusion power is an incredibly sustainable/profitable option once unlocked. Mk1 setups can do 1M eu/t, and each tier after will essentially 2x the eu/t output. This is using helium plasma, which is one of the more simple/more profitable options. Simply supplying your reactor with either a pumped He-3 input from the moon, and some H2 you centrifuge to deuterium, will result in insane power. You can also centrifuge deuterium into tritium which can replace the He-3, but also quintuple your deuterium centrifuge and h2 costs. There are other options that you can find that might give more eu/t per reactor, they might even be more fun to setup than He plasma.