Iganan Worldship

A class of very large worldships with no FTL capability built by the Iganan species.
Instead, the Iganan worldships were designed to travel to their destination at subluminal speed. As these ships were built before the invention of FTL travel and Graviton Wave Refraction, the engineers who built it relied on gravity from large rings and a centrifugal force. This is where most of the population on a worldship lives. Some rings are also taken up entirely by farms.
It comes mounted with ramjet fusion drives, which take hydrogen gas from space to generate power via fusion. Waste matter is then used as a heatsink and then expelled from the ship. A lot of the power generated here is also radiated towards the farm rings to grow food for the igarans.
The worldships also feature large heat radiators unlike most HF starships, with QEN heatsinks. The Iganan heatsinks are effective but large and heavy.
The worldships were designed to handle entire ecosystems. As such, they have been made very large and in great numbers. They can vary between 15 km and 20 km in length and contain enough farm space to house a population of almost 1 million each.