The Universal Trinity of Vehicle Design
When building a world—or in this case, a science-fiction setting that probably involves many worlds—you must first define what kinds of warships are available to the setting’s nations. The discussion can be applied to warships at most levels of technology, even before the existence of efficient guns.
Any discussion of warship design begins with the Trinity of military vehicle capabilities:
- Mobility: Includes straight-line speed, maneuverability (changing direction, acceleration, deceleration), and range (how far you can go without needing to resupply). (The great basketball coach John Wooden famously wanted a more mobile player than the opponent at each position; the same principle applies to vehicles.)
- Offense: Anything you can do to physically harm the enemy, whether it’s ramming, fire (like “Greek Fire”), projectile weapons (rail guns), guided missiles, mines, blasters, or lasers.
- Defense/Survivability: Includes armor, defensive missiles, energy screens, and passive protections like anti-torpedo bulges. Maneuverability often functions as a kind of defense, as does stealth, exemplified by B2 bombers and F35 fighters.
There is generally an inherent trade-off: “Mobility, Offense, Defense (MOD)—you can have two out of three.” You cannot pile guns, armor, and powerful engines into one hull indefinitely; the ship will simply get bigger, making defense and mobility more costly.
The Logic of Size and Cost
This trade-off leads to a fundamental question of size: Don’t you want the smallest, cheapest ship that can do the job at hand? Light cruisers exist to perform jobs that don’t require a larger, armored heavy cruiser. Why pay more, and why “put all your eggs in one basket”? More ships are generally better than fewer for deployment flexibility. The only sound reason to build a super-gigantic ship is if that size somehow makes it immune to harm (size as a kind of defense in itself), or if the designer succumbs to the Rule of Cool (“10 mile long spaceships”).
Note that external factors, such as the need to build many ships quickly during a war, can also dictate design—as seen in the rapid production of merchant vessels like the Liberty and Victory ships in World War II.
Defining Warship Functions
Moving from generalized capabilities, we can determine what kinds of ships a navy needs by generalizing their intended functions.
Information Gathering and Protection
Scouting: This calls for ships with long range (which requires extensive living quarters, fuel, and self-repair capabilities). Long-range scouts are not intended to fight; their speed is their defense. Short-range scouts for a fleet, however, are built to fight off the enemy’s scouts, requiring less range but higher fighting capability.
Protecting Commerce: (Assuming interstellar trade is necessary, though advanced civilizations may be self-sufficient—a topic for another discussion.) Commerce protectors need the range of scouts but require greater fighting capability to defeat enemy raiders. Their strength must be sufficient to avoid damage that cannot be repaired by the crew on board.
Protecting Territories: This requires two types of ships:
- Far-flung territories: Ships here often provide a warning and warning system against common threats (like pirates). They may be intended to flee to a stronger force rather than engage.
- Major territories (The Core): Ships here are designed to defeat outright enemy invasion or attempts to destroy immobile assets.
Raiding and Battle Fleets
- Commerce Raiding: Historical raiders were usually medium-size to small ships on long cruises alone, with the objective of avoiding a fight while taking or destroying merchant ships. They need speed for the getaway and sufficient strength to brush aside small defending forces.
- Raiding Enemy Territory: Requirements here are similar to commerce raiding, but demand more fighting capability to brush aside defending orbital forts or small warships. Speed is critical for the “smash and grab” and getaway.
- The Main Battle Fleets: Fleet combat often involves a circular relationship where each ship class is countered by another, creating a strategic web. In WWI, for instance, destroyers were most dangerous to battleships, cruisers were most dangerous to destroyers, and battleships were most dangerous to cruisers. In a science-fiction setting, this circular relationship may be different—perhaps a more complex four-element relationship like “A beats B, beats C, beats D, beats A.” This relationship is critical, as it ultimately determines the fundamental functions and needs of every warship type in the fleet.
The MOD Trade-Off
Realistic fleet design requires applying the universal Mobility, Offense, Defense (MOD) trade-off to define a ship’s specific function—from scouting to raiding—and then modeling fleet combat based on a predictable, circular “rock-paper-scissors” relationship between classes to ensure strategic depth.
Your Turn: If you run Sci-Fi games with space fleets, how do you define your ship classes?
Read more at this site