Starship hull classification is a very useful means to, roughly, gauges the capabilities of a given ship. Size alone says nothing about a ship's offensive or defensive capabilities. Likewise, most navies have little desire to publish the full specifications of their ships for comparison. However, generally speaking, what a destroyer can do versus what a cruiser or battleship can do is, in a very general sense, known.
Ship hulls are classified not just on their size and mass, but also their offensive and defensive capabilities as well as the role they were designed to fill. Specialty hulls, just as carriers or interdictors are entirely role based. Descriptors like 'light' or 'heavy' generally correlate to offensive or defensive capabilities.
However, when applied to specialty ships, descriptors are generally an indicator of how good at it's role the ship is expected to be. For example, a 'light carrier' would be expected to only field more fighters than would be typical for other ships the same size, but less fighters than a normal carrier.
These are the most common ship classifications. The are ordered from smallest/least capable to largest/most capable.
Note: The hull codes specified are League hull codes, but as they are used by both the League and Freelancers, they've been chosen as the class 'abbreviations' on almost all tactical interfaces. This means that while other races might not use these hull codes (or hull codes in general) they're ubiquitous enough to be known beyond just the League.
Note: These are both civilian and military.
Utility craft are things like tugs, maintenance ships, or anything not designed for moving cargo, people, or fighting.
Shuttles are small craft designed for moving a small amount of people and cargo. It is a smaller vessel that is launched from a mother ship, and has the ability to transport people or cargo between ships, or to and from a planet's surface without being damaged or destroyed. It has a secondary purpose as an evacuation ship if the mother ship is destroyed. Generally they have limited range and subspace capability, if any.
Fast an maneuverable, fighters are designed as small weapons platforms to get in close to lager ships and deliver payloads behind their defenses. Some fighters are also designed to target other fighters, acting as a line of defense for their mother ship.
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Unlike freighters, Merchantmen are commercial vessels designed to transport not just goods but also passengers. Most are able to be quickly converted to either haul cargo or passengers.
Another difference from freighters is that they are typically armed, at least minimally. Some are more heavily armed, being referred to as 'armed merchantmen', but they aren't recognized as a separate class.
Armed Merchant Cruisers are armed civilian ships designed specifically for defending other civilian ships in an convoy, or providing escort through dangerous space. They aren't generally suited for transporting cargo (though they can work well as limited passenger transport) and prioritize speed and armament over other concerns.
As these are still civilian ships, they tend to have (relative to military vessels) weaker armor and most governments have limitations on the weaponry they can have installed. In general, they're roughly about as well armed as a Frigate.
Auxiliary Cruisers are armed civilian ships designed to look like regular merchantmen or freighters, however they have almost no cargo capacity, instead using all that internal space for weapons or electronic warfare equipment. They are intended to be intermixed with a convoy, allowing them to provide support or scare off pirates with some surprise firepower. They often work best as a deterrent; simply knowing some might be mixed in with the other ships makes the convey less likely to be targeted.
These ships are designed to mimic normal ships, meaning they come with the ability to lie about their identity or spoof other ships, including being equipped with ECM to appear on sensors like the ships they're pretending to be. While the intended use for this is defensively, Auxiliary Cruisers are often used by pirate groups or criminals for their own purposes.
Because of the potential for abuse, Auxiliary Cruisers are heavily restricted and ownership is tightly controlled in most governments. Simply selling an Auxiliary Cruiser to an unlicensed individual is usually a serious crime. However, many manufacturers get around this by selling 'upgrade kits' for existing hulls.
Yachts are the most extravagant outward sign of extreme wealth, power, and privilege. The companies who build them often take the ancient line "We spared no expense" as a great place to start.
Super Yachts are, in essence, the capital ships of the civilian world. They're huge hotels in space. Most of them are armed in a limited sense but mainly with defensive weapons.
Originally named Littoral combat ships, LCS are a type of ship designed to operate with easy access to a base. They are relatively short range ship designed to be agile with a high damage potential compared to their size. Because they are small they are much harder to detect at long range and make for an excellent addition to most base defenses.
While most have subspace capability, their total endurance is generally limited due to lack of accommodations for longer journeys. Most LCS do not operate on their own for longer than a week at a time.
Frigates are the smallest ships to be considered true warships. They can operate on their own for weeks to months. Their facilities are limited, but they make for excellent patrol craft and armored couriers. They are, on average, not very fast, but they aren't required to be. They do, on average, have an impressive array of sensors to be used as advanced scouts for larger fleet groups.
Advanced Frigates are simply frigates with much improved speed, endurance and weapons capability. They rely on more complex, automated systems than more traditional frigates, meaning they end up being used for more specialized roles.
Corvettes are a specialized version of a frigate, designed primarily for speed. They are used as couriers, or advanced scouts. They tend to sacrifice armament or defense for their speed and maneuverability.
Destroyers are fast, maneuverable, long-endurance warships. They are designed to operate for long stretches on their own, and are generally tasked with escorting larger fleet assets or cargo ships. Destroyers, typically, carry at least one wing of fighters to act as scouts as well as increasing their effective combat radius significantly.
This hull class only belongs to the Archigos class. It was pitched as a new class of destroyers with experimental 'mold breaking' design decisions. They would only see limited production runs, unless something proved very useful. In truth, the poor reception of the Archigos class killed the idea.
Light destroyers are, in essence, frigates with longer endurance. They don't have the same type of offensive capability as a typical destroyer, instead increasing their speed an maneuverability without sacrificing endurance.
Heavy destroyers are a new type of destroyer. The idea is to fit near cruiser level offensive capability into something with the speed an maneuverability of a destroyer. In this role, the Archigos Class class performs very well.
Light carriers are destroyers that have had most of their armament replaced to make room for cramming more squadrons of fighters into them. They typically can field four to six full squadrons, but have the same speed and maneuverability of a destroyer. The main downside, however, is that they sacrifice most of their endurance, as their crew compliment increases dramatically.
Cruisers are large warships designed to operate independently, or as part of larger fleets. They are the the backbone of most militaries, offering the most versatility between damage, survivability, and multi-mission roles. Cruisers are well armored, well defended, and very powerful.
Light Cruisers are, in essence, oversized destroyers. They're a bit more survivable and better armored than a destroyer, but tend to operate and fight the same way as a destroyer would.
Heavy cruisers are, basically, miniaturized battlecruisers. They are focused on squeezing every ounce of firepower into a compact hull. Often they hit as hard or harder than their battlecruiser sisters, but only cost two thirds as much to build.
Logistics cruisers are designed to help coordinate military operations for an area. Most can handle a single star system, but the more advanced once can coordinate multiple star systems. They are, in essence, mobile bases, with repair facilities, advanced sensors, subspace radio relays, and often even manufacturing facilities.
Much like their ancient naval counterpart, carriers are cruisers designed to carry large amounts of fighters. Carriers rely entirely on their fighter screen for offensive capabilities (and the majority of their defense as well.)
Interdictors are designed to prevent ships from entering or leaving the interdicted area by subspace. While most are cruiser hulls that have massive gravity generators on them, some are built out of older hulls welded together. In either case, they are lightly armored, lightly defended strategic ships built for one purpose: interdiction. They carry very few weapons, and dedicate most of their space to their gravity generators and the massive super computers needed to successfully maintain an interdiction field.
Battlecruisers represent the cornerstone of modern military warfare. They are large enough to operate independently, capable of repairing or rebuilding any parts they need, but also the smallest class of ship that can provide support and logistics to an entire fleet. Their missions often include holding systems, or operating as a forward base for smaller groups of destroyers or frigates.
Advanced battlecruisers are heavy battlecruisers that have been refined though the usage of heavy automation. They field some of the most advanced technology yet invented, and are generally capable of trading blows with dreadnaughts or super dreadnaughts, while having maneuverability closer to that of a cruiser. For all their amazing feats, however, they're rare and difficult to build, with the Dante being the only current example.
Heavy battlecruisers are built with a single overriding goal: to wage warfare as efficiently as possible. While most battlecruisers have extensive logistical support built into their roles, heavy battlecruisers focus on putting as much destructive potential down range as possible, while being able to survive and repair anything that comes at them. They are some of the most destructive weapons of war every built.
While heavy carriers do carry more fighter squadrons than their smaller counterparts, their main focus is on not sacrificing their offensive or defensive capabilities, but still fielding as many fighters as possible. Unlike normal carriers, they can operate without their fighter screen if required.
Heavy interdictors are designed to be all in one siege weapons. Part Logistics Cruiser, a Heavy Interdictor is designed to hold star systems indefinitely. Unlike their smaller cousins, they tend to be decently armed, though mainly with defenses.
Battleships are an exercise in excess. They are large, excessive ships built entirely to be mobile stations. They have impressive firepower, but they are, in essence, siege weapons. They almost never operate independently, instead being the core around which a fleet is formed. When a battleship enters a system, the entire star system is considered part of the ship's operating sphere.
Super carriers are carriers that berth not just fighters, but LCS, frigates and even destroyers, if they're large enough. They're entire fleets in a single ship, usually deployed when a fleet needs to be moved quickly, as a whole unit.
Dreadnaughts are battleships that rely on other vessels for their logistics and support functions, instead using that space for more offensive and defensive capability. They are ships of pure war, designed knowing full well that they can't operate themselves without a fleet behind them. But that singular focus allows them to pour nearly unimaginable amounts of destructive power down on their targets. A single dreadnaught can easily devastate and entire world.
Super dreadnaughts are just dreadnaughts taken to the most ridiculous ends. They're literally small colonies in space, with the destructive firepower of a rather large fleet just to themselves. They are generally so large it's rare to ever see more than one in the same star system, and when you do, that's generally because someone either wants that system protected at extreme costs, or they want to extinguish all life in that system in the most extra way possible.