Understanding Fission and Fusion Reactors: What to Build First

Fission Reactor Basics

The Fission Reactor is a multiblock built from Fission Reactor Casing, Reactor Glass, Fission Reactor Ports, and a Fission Reactor Logic Adapter. Inside, you place Fission Fuel Assemblies surrounded by Control Rod Assemblies. It burns fissile fuel to produce heat, which is turned into power via a steam turbine setup.

Fusion Reactor Basics

The Fusion Reactor is a much larger multiblock built from Fusion Reactor Frames, Reactor Glass, Fusion Reactor Ports, and a Fusion Reactor Controller. It requires a Laser Focus Matrix and Hohlraum to ignite, and it consumes Liquid D-T Fuel (Deuterium + Tritium). It produces enormous power but is very expensive to build.

Which First

Build fission first. It's cheaper, uses simpler fuels, and teaches you the multiblock and steam mechanics you'll need for fusion. Fusion is endgame — don't attempt it until you have a large, stable power base and the materials for the frame.

Safety and Control

Fission reactors can melt down if control rods aren't managed. Use the Logic Adapter to monitor temperature and rod insertion. Fusion is safer but harder to start — you need a laser and a Hohlraum to trigger ignition.

Fuel Chains

Fission uses processed uranium. Fusion uses Deuterium and Tritium, both produced from water and lithium in dedicated machines. Set up those chains before you build the reactor itself.