Here’s a design for a seriously large fusion rocket.
There are 36 living modules composing the centrifuge ring. Each module is 4 meters in diameter and 7.3 meters long. The “spines” are a belt cooling system for the nuclear power. Hot droplets are sprayed onto the belts and carried away and back again.
The front ring rotates to provide fake gravity, and there are large weights along the arms that support the habitation ring – these maintain the balance when crew and supplies move around the ring.
As usual, all done in Lightwave 3d.