For example here is my 3D model of The Prometheus the generation ship featured in the last phase of the campaign. The large sphere is all fuel. The smaller sphere is all hydroponics food tanks. The cube structures on the spokes are the living areas. I did my best to calculate how much fuel it would take to the system if you accelerated at a constant rate the first half of the trip and decelerated for the second half. Obviously it is a massive amount of fuel.

The journey took 180 years and by the end of the trip there were 10,000 people on board. Population growth was controlled so that the population grew smoothly over the trip.