Fusion Reactor (Multiblock)
Since 0.1.0-beta.1 the Fusion Reactor is a scalable multiblock: a hollow cube shell of Fusion Casing and Fusion Containment Glass with the reactor controller set into one wall. The controller block alone is inert — it does nothing until a valid shell is formed around it, and a reactor placed before the beta stays dormant until you build it a shell.
Building a shell
Three sizes are valid — 3×3×3, 5×5×5 and 7×7×7 (outer dimensions):
- Build a hollow cube of Fusion Casing (crafted from Starsteel); any wall block may be swapped for Fusion Containment Glass if you want to see the core — the two mix freely.
- Set the Fusion Reactor (controller) into the centre of one wall face, facing outward. It replaces that casing position and counts as part of the shell.
- Keep the interior strictly empty — any block inside (including fluids) invalidates the structure.
The reactor checks its structure automatically (largest shell first, so a 7×7×7 wins if several are possible). When the shell forms, the core lights up: a plasma torus spins at the interior centre, scaled to the shell and visible through containment glass. Breaking any shell block unforms the reactor — it goes dark and stops.
Fuel tiers
Fuel is matched by datapack tags, so packs can add their own: anything in
nerotech:fusion_fuels burns; membership of nerotech:fusion_fuel/tier2, /tier3 or /tier4
raises its tier. The shell size gates the tier:
| Tier | Fuel | Made from | Minimum shell |
|---|---|---|---|
| 1 | Fusion Cell (any nerotech:fusion_fuels entry not tagged tier 2/3/4) | Starsteel + Void Crystal (or the Advanced Fabricator) | 3×3×3 |
| 2 | Plasma Cell (nerotech:fusion_fuel/tier2) | Starsteel | 5×5×5 |
| 3 | Stellar Cell (nerotech:fusion_fuel/tier3) | Void Crystal + Starsteel | 7×7×7 |
| 4 | Antimatter Cell (nerotech:fusion_fuel/tier4) | two Stellar Cells collided at 12,000 J in the Particle Accelerator | 7×7×7 only |
Tier 4 is the one exception to "tier ≤ shell tier": the maximal 7×7×7 shell reaches one tier further than its own, which is exactly why antimatter is burnable there and nowhere else. Burning it also adds a flat +2 to the reactor's heat rate on top of the shell scaling — the meltdown risk is the price of the longest burn in the mod. See Exotic Endgame.
Higher tiers burn far longer per cell (fusionFuelTier1BurnTicks / Tier2 / Tier3 / Tier4,
the last defaulting to twice tier 3), and bigger
shells multiply output: the base rate (fusionReactorNePerTick) is scaled 1× / 4× / 12× for the
3/5/7 shells (fusionSizeOutputPermille). A 7×7×7 on Stellar Cells is the strongest generator in
the mod.
Heat, meltdown and containment breach
Power scales — so does the danger:
- Bigger shells run hotter (roughly ×4/×5/×6 heat rate by size), and an Overdrive preset doubles heat on top. The core's glow shifts from cyan toward red as heat climbs, and it strobes past the throttle threshold — that is your last warning.
- Meltdown: at max heat an unmanaged reactor melts down destructively, with a blast scaled to
the shell (radius 4/6/8, centred inside the shell). Servers can disable this
(
fusionReactorMeltdownEnabled=false), in which case the reactor just stalls until it cools. - Containment breach: breaking a shell block while the reactor is burning loses the entire fuel charge and vents a burst of pollution into the region. Shut the reactor down before resizing or moving it.
Cooling a big reactor is a genuine thermal-system exercise: ambient, coolant blocks and spacing all matter.