"Powerful reactor unit. Takes more hull space and requires gas to function."
The Fusion Reactor is a large 4x2 reactor that is meant to provide more power to end game ships. The Fusion Reactor itself can reach a power distribution higher than one Small Reactor. However, it's large size makes it have a bunch of advantages and disadvantages.
The Fusion Reactor is similar to a Small Reactor; it cannot get EMP damage nor can it actually attack. However, if you plan on actually using the Fusion Reactor make sure you can actually hold it. Level 8-9+ should be the time you finally use a Fusion Reactor because power consumption will become crazy high.
The Fusion Reactor is also usually very sparsely armored on ships. This is because its high power count makes it a waste to target. However, be mindful that its large size can also cause a massive response from all your repair crew, potentially grouping them up for an easy kill.
The length of the Fusion Reactor can make it problematic to defend or repair. For maximum effectiveness it is best to ensure that crew enter from the left side of the room.
Fusion Reactors provide power while it is still upgrading.
Fusion Reactors have no functional AI Response.
You can remove all Fusion Reactors on your ship as long as you still have one normal Reactor onboard.
If you have no Reactors at maximum health, you will always have a 0% Escape Rate, even if you have a Bridge.