Worlds of Design: The Warship Trinity

Picture courtesy of Pixabay.​

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:

1. 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.)
2. 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.
3. 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?

 

[doctorhook]

When i was going through my mother's things looking for the title to her car [1], I came across one of my first grade report cards. It had a handwritten note criticizing me for going to books to find information rather than asking someone. Today I'm a librarian and whoever wrote that note is dead.

[1] I never found it but I did find her divorce papers, which as it turned out I would need much, much more.

That’s lovely for you, but this thread is about spaceships. Thus far you’ve only made a cryptic comment about software, a terse assertion that that’s somehow relevant here, and then this anecdote about becoming a librarian.

I’m choosing to ignore the fact that you seem to using an allegory to say “look it up”. Why not just speak plainly and tell us what point you’re trying to make? Alternatively, why comment at all if you don’t want others to engage with your comment? If your next reply is equally opaque, I’m going to assume you’re a bot.

 

[dragoner]

I was there back then, eurisko was interesting, though more like "rules lawyering" kind of way, for what it did, exploiting loopholes such as self destructing it's own ships. EABA of space combat, probably not. High Guard, and Trillion Credit Squadron were fun supplements, not very RPGish, we called them "dice rolling madness." lol

 

[Vael]

I haven't really toyed with designing fleets from the ground up for a TTRPG, mostly just my own fiction (In the TTRPG space I'm using pre-existing settings, ie. Star Trek and Star Wars, really). So there is a change in perspective for a TTRPG ... where do the PCs fit in? A protagonist for a novel has different requirements than a party of PCs for a TTRPG campaign. In general, I'd assume PCs aren't looking to be basic crewmen doing laundry on a dreadnought, they'd be officers, movers and shakers. So you'd want ships that players can manage, ideally. So this, to me, tips the scale towards your corvettes, frigates and light cruiser equivalents. Ships large enough to have a full crew, but not have to manage the thousands of NPCs crewing the party's Dreadnought. Or not, you do you.

 

[dragoner]

You can do a "west marches" sort of hex crawl with a big spaceship, because it islike a floating town. I did that with a Traveller Kinunir from Adventure 1, a university bought a demobbed one, filled it full of mercs and sent it off to do research work.

 

[R_Chance]

You can do a "west marches" sort of hex crawl with a big spaceship, because it islike a floating town. I did that with a Traveller Kinunir from Adventure 1, a university bought a demobbed one, filled it full of mercs and sent it off to do research work.

The Leviathan class merchant cruiser from Adventure 4 was perfect for this. Four thousand L-Hyd tons displacement and designed for travel into the hinterlands. It had back up maneuver and jump drives just in case. A level of detail typical of British Traveller material.

Anyway, back on topic, before you can design warships / fleets you need to know the technology available. In Traveller I had three broad categories of ships based on weaponry. In Traveller, the three size / power categories of weapons were "turrets" (small, typically taking up 1-2 tons), "bays" (50-100 tons) and spinal mounts (taking up thousands of tons). Weaponry dominated my ship types.

Escorts were small ships (this includes destroyers, frigates, etc.) massing 1,000 tons or under. A ship could have 1 turret per 100 tons displacement. Cruisers (light cruisers, heavy cruisers, frontier cruisers etc.) massed 3-20 thousand tons and had bay and turret weapons. You could have one bay per thousand tons displacement. Capital ships (battleships, battlecruisers, etc.) were (literally) built around spinal mounts with bay and turret weapons supporting the main armament. A ship could only have one spinal mount. Capital ships tended to mass 50,000 tons plus. You could build ships up to 1,000,000 tons but still have only one spinal mount per ship.

The point is, my ship types were determined by the weapons available and the size of ship needed to carry them. Maneuver drives were not too different in capability and jump drives were similar in ability across ship types. The jump drives were capped largely by the tech level of the yard building the ships.

Different technology would have altered the ship types and sizes.

 

[Celebrim]

I strongly suspect that sensors and fire control are the dominant factor in space warfare. Can you see them before they see you? Can you calculate a firing solution? Can you predict how they will try to evade?

If you are doing the Yamato vs. Iowa comparison and you are focusing on shell size, maximum speed and armor belt thickness and not on the Iowa's integrated mechanical computers and sub-millimeter wave all weather radar then you've missed 90% of what differentiates the two vessels in combat. Fightability (how easily the weapon system can be employed and commanded) and information gathering and processing dominate over traditional "hard" metrics in real combat situations. If I know sufficiently more than you know about the tactical situation and I have faster decision making loops, then I have a near absolute advantage.

And we can see this in how WWII destroyer combat between USN and the IJN played out over time. The side with the better information gathering and processing dominated its era nigh completely.

Viewed this way, the events at Samar weren't actually surprising. If you view the two fleets by tonnage, weight of metal to throw, thickness of armor and so forth it should be a one sided IJN victory. But if you view the two fleets by speed of the decision making loops, their ability to collect accurate information, and their ability to act on that information because of the fully integrated mechanical fire control and stabilized gun systems then it was like one side with a bunch of muskets versus the other side with automatic weapons.

I suspect in space combat that is going to be even more true.