Science-fiction fleet design begins with setting and purpose

How do you create a science-fiction fleet that fits its universe?

Start with the setting's technology, communications, society, themes, and expected missions, because those conditions determine the fleet's ships and institutional habits.

Stewart's central rule is that the fleet cannot be designed in isolation from its universe. Faster-than-light travel, communications delay, civilian transport, economics, and the story's themes all shape what ships can do and why they exist. A navy accustomed to patrol, anti-piracy, disaster relief, or technology demonstrations will enter war with different ships and habits from a force built around peer combat. Historical peacetime fleets provide a model for showing capable people working with institutions and equipment that were never fully tested against their eventual mission.