- Shuttles: The smallest classification of manned vessel is the shuttle. Primarily for carrying passengers or light cargo.
- Transport: Transports are the next size up in civilian craft. If they are just used to carry cargo or passengers, they are Transports. A variant: Industrial Ships, these vessels are used for a specific purpose, such as asteroid mining or mobile orbital production.
- Freighter: Massive cargo carriers which carry supplies to whole planets.
- Leviathan: The largest vessels in the galaxy, leviathans are operated exclusively by the Uendeshaji to transport entire fleets of ships, goods for billions of people, all the parts necessary to assemble a starbase, enough colonists to populate entire planets and can even house military carriers and dreadnoughts in their nigh-infinite holds. With no thrust of their own, they are specially designed to move via folding space with Psionic Teleportation. They are presently considered diplomatically neutral vessels by all Human stellar nations.
- Corvettes: Corvettes would be the smallest warships, designed for escort and patrol, anti-mine, or anti-stealth. They would be used where larger ships with more firepower are not deemed necessary (such as backwater worlds or low-risk areas) or where a larger ship would be unsuitable for deployment. Corvettes might be outfitted to have some sort of stealth or cloaking system for reconnaissance or spec ops missions; naturally it would be easier to cloak a smaller ship than a larger one (though plenty of examples of large stealth ships exist). In some series they are likely to be diplomatic vessels due to their small size and speed, particularly seen in Star Wars, and can commonly act as blockade runners (again; their small size and speed makes them ideal for slipping through a blockade, where a larger ship presents more of a target). They would, ideally, never be used for direct combat in large scale engagements due to their extremely light armor and weapons, but may be employed in a battle to lay down or destroy minefields, uncover stealth ships, act as stealth ships on their own (for whatever purpose needed), or for dispatching already crippled vessels.
- Frigate: Based on their history, space frigates would probably be best defined as smaller vessels with light armament and armor (but more powerful and larger than a corvette), suited for speed and maneuverability. They’d often act as patrol and escort vessels, whether for a merchant convoy, a single capital ship, or a fleet. Their agility and maneuverability means they can move to redeploy and protect other ships better than larger, slower moving vessels. You’d likely see a strength-in-numbers strategy with them. Frigates, unlike corvettes, would more commonly see direct battle and would probably not be found with stealth drives in most settings; they are simply getting too large by that point.
- Destroyer: Destroyers would be much like their naval counterparts; ships smaller than cruisers (and usually larger than frigates, though not always) but armed to the teeth with a multitude of weapons. They’d mostly act as escorts for larger fleets (and likely not for single warships, but exceptions would certainly exist) but can be seen operating in destroyer-only divisions as well. You could expect to find destroyers fulfilling all sorts of roles because of how multi-purpose they are, even roles that could be fulfilled by other classes that are designed for that purpose. It would, however, be rare to find a destroyer acting on its own in most circumstances; destroyers are not capital ships and do not operate as patrol craft. They do not operate independently as a rule, though I know of at least one case in fiction where a super-destroyer acted as an independent ship. Science fiction, as I mentioned previously, breaks a lot of rules.
- Cruiser: Cruisers are medium-sized vessels, able to operate independently but also commonly seen within a fleet. They would have the capacity to be used as anti-fighters, planetary bombers, raiders of enemy supply lines, and scouts. However, they would also be the class of ship most likely to engage in non-combat roles such as exploration or even colonization due to their ability to operate independently for extended periods. I would not expect cruisers to commonly be used in front-line assaults of an enemy fleet; that role is better left to other ships. However, they have the firepower, size, and better defensive capability to go up against other ships when needed and it’s not uncommon to see cruisers making up the bulk of fleets in some settings. It is however, in my admittedly amateur opinion, not the ideal choice; better to fill in that space with destroyers or battlecruisers and battleships. Cruisers can be considered capital ships in some settings (and in fact, some settings treat any ship over a certain size as a capital ship, regardless of role).
- Battlecruiser: Despite their unfortunate history, battlecruisers in space tend to operate similarly to battleships, and I would argue there is not much distinction between the two owing, partly, to the blurring of both vessels in our history. Battlecruisers and battleships, thus, often act as the heavy hitters in a fleet; they are the main combatants and are protected by other vessels such as frigates and destroyers. Being that they are capital ships, an engagement is usually won through battlecruisers and battleships. If a distinction is made between the two classes then battlecruisers would likely be quicker and less heavily armored than battleships, and in some settings are not even considered capital ships at all. But again; rules can be blurry and broken at the whim of any author. Regardless, battlecruisers and battleships are the truly massive, anti-“large vessel” ships in a fleet. They are meant to take a lot of punishment and dish out that punishment in kind. One particular term I see fairly often is “star cruiser.” In my mind, a star cruiser could either be the equivalent of a cruiser or a battlecruiser; that distinction is likely decided by whether or not star cruisers are considered capital ships, since that then determines the general capabilities of those vessels. As a general rule I would be bold enough to claim that star cruisers are equivalent to battlecruisers, and named as such because space.
- Carrier: Carriers tend to be some of the largest capital ships around due to the need to hold and transport large numbers of fighters, bombers, and other craft. Typically, though not always, their hull-mounted armaments are light; carriers usually rely on the large numbers of fighters they carry (when operating solo) or their fleet for defense and attack of other ships. The ability to carry craft does not make a ship a carrier by default; many frigates and cruisers, for example, will carry a complement of fighters or a few ground vehicles. In order to be considered a true carrier the vessel’s main role needs to be the transport and deployment of smaller craft (or troops; as far as I’m concerned not all carriers are extremely large and I would classify troopships and assault ships as small carriers).
- Dreadnought: Dreadnoughts are just about always gigantic ships; massive vessels that dwarf even the largest battleships or battlecruisers. The role they fulfill is exactly like a battleship or battlecruiser; complete dominance and superiority. Intimidation, even more so than with battleships, is the name of the game when it comes to dreadnoughts. When you have a multi-mile long ship bearing down on a fleet you know the enemy’s morale is precarious at best. Due to their large size they can often carry a large number of secondary craft, like a carrier, but their extremely powerful armament would tend to exclude them from that definition. A dreadnought carries a bunch of craft because it can, and this adds to its lethality. But its true strength is its overwhelming firepower, plus its usually resilient armor.
- Armored: Focus on defense.
- Assault: Focus on weaponry.
- Light: Generally, these vessels are more jack-of-all-trades combat vessels.
- Heavy: Generally these vessels are specialized in a particular arena of combat.
- Super: Bigger version with better attack and defense.