On the sea or in space, a battlecruiser is a cruiser putting on the airs of a battleship, and a fast battleship is a battleship cosplaying as a cruiser. This doesn’t become a problem until the types start to overlap.Admiral Brandel Tsurilen, First Shore Lord
So, in today’s piece of worldbuilding, have an analysis and explication of the different classes – or the different types, rather – of military starships operated by the Imperial Navy. (The basis for the ternary plot I’m using is, of course, Winchell Chung’s analysis here, so you might want to go read that first if you’re not familiar with the concept, then come back here.)
The chart on the right illustrates the differences between the various types and classes of warship in common use by the Imperial Navy by their P/D/W ratio – i.e., the relative trade-off between propulsion, defenses, and weapons (i.e. offensive armament):
“in common use” should be read as “not counting all the weird-ass specialist ships we build for special cases”; also, it doesn’t include auxiliary vessels (oilers, hospital ships, etc.) since they’re not operated by the IN, but by the Stratarchy of Military Support and Logistics.
Battleships, Dreadnoughts and Superdreadnoughts
“I am an Imperial Mandate-class dreadnought, and you are within a million miles of me. Ergo, you continue to exist solely on my sufferance.”
– an early experiment in AI captaincy
Battleships, dreadnoughts, and superdreadnoughts (B, D, S on the chart) are capital or supercapital ships mounting heavy long-range firepower as their primary function.
These types, the ships of the wall, are the kings of the outer engagement envelope, engaging each other with powerful weaponry at ranges of up to two light-minutes, and rarely closing beyond one to two light-seconds range (a zero/zero intercept at this residual range is considered a “set-piece” battle). They are the purest of all naval vessels in function, existing simply to counteract each other in the battlespace of major fleet actions, or to own the volume of space they can dominate if not opposed; the ultimate argument of star navies.
The principal difference between two of the three types is simply mass and volume; doctrinally, the majority of the ships of the wall of any given time should be of battleship classes, with their larger cousins the dreadnoughts providing heavier stiffening formations to the wall and occasional nasty surprises.
Because while it sure would be nice to build nothing except dreadnoughts, even nearly-post-scarcity economics doesn’t stretch to overbuilding everything just in case.
Superdreadnoughts, while sometimes referring to particularly large dreadnought classes, more typically refer to ships falling in the dreadnought type by mass, while using much of their internal volume for specialized systems: typical examples would include the command superdreadnought, the information-warfare superdreadnought, the anti-RKV superdreadnought, and so forth.
One example of this listed separately (L on the chart) since its P/D/W ratio moves it well outside the standard range is the mauler superdreadnought. In this case, the specialized systems in question are a very, very large mass driver or laser, with propulsion and defensive systems stripped back to accommodate it.
Mauler superdreadnoughts are not considered ships of the wall, but rather are specialized vessels used to attack specific hardened targets. Since their low speed and weak defenses render them vulnerable “glass cannons”, they are typically operated as part of a task force including close-in point-defense cruisers, and only brought up once opposing fleets and mobile defenses have been cleared away; however, in their specialty role of cracking hardened fixed bases, they’re unequalled.
The “hyperdreadnought” is a peculiarly unique version of the superdreadnought type, of which the Empire fields three, each unique within its class; Invictus, Imperiatrix, and God of War. In order, they are the home of Admiralty Grand Fleet Operations, the Imperial Couple’s personal flagship, and the literal embodiment of the archai/eikone of war. Any one of them turning up in the battlespace would have implications that, by and large, no-one wants to think about thinking about.
Battlecruisers and Cruisers
The backbone of the fleet, battlecruisers and cruisers (C on the chart) are middle-weight combatants, more heavily armed than destroyers and frigates, and yet more maneuverable than battleships and larger ships of the wall. Most cruisers also maintain limited AKV facilities. They are perhaps the best balanced (between operational aspects) of any of the Imperial Navy’s standard types. The distinction between cruisers and battlecruisers is simply one of mass and volume, with battlecruisers identifying the significantly larger and heavier classes of the type.
In fleet operations, battlecruisers and cruisers serve as screening elements and operate on the fringes of the close-in battlespace, maneuvering aggressively for advantage. For the most part, however, these middle-weight combatant types are intended for patrol operations and long-endurance “space control” missions, sometimes alone and sometimes in flotillas, as well as serving as the IN’s go-to types for independent missions of almost any type. In areas of heavy patrol activity, cruisers may lead destroyer or frigate flotillas into action.
Cruisers are also the type within which most variation exists, and cruiser classes may wander quite far from the indicated P/D/W ratio. Of particular note here is the point-defense cruiser (“pd” on the chart), the one type which you might see as a ship-of-the-formation, stripped of most of its offensive armament in exchange for point-defense enhanced to the point of augmenting that of other ships, but many other specialized varieties exist: the assault cruiser (optimized for planetary assaults, i.e., heavy on the ship’s troops and capable of launching drop shuttles and drop pods into atmosphere; some of these are aerospace cruisers, which atmospheric interceptors can sortie from before there’s an orbithead established); the diplomatic cruiser (a big stick to transport the softly-speaking); and the interdictor cruiser (specializing in the volume-security mission, which is to say, to chase down, capture and board other starships). The primary battlecruiser variants are the command battlecruiser (optimized to carry the admiral commanding a CC/BC task force) and the carrier-battlecruiser (which carries AKVs – see below – as well as its internal armament; this is the type of battlecruiser usually found operating alone, due to its significantly enhanced operational envelope and capabilities).
Due to their versatility, the IN maintains a greater tonnage of battlecruisers and cruisers in commission than starships of any other types.
Destroyers and Frigates
Destroyers and frigates (D, F on the chart) are small, fast, maneuverable ships used for screening larger vessels, as escorts, and for patrol work. On their own, their capacity is severely limited, for which reason they typically operate in flotillas assigned together.
As with the above two types, the most obvious difference between destroyers and frigates is their mass and volume. That said, the strict difference between these two types is that while a destroyer may possess very limited broadside armament, due to its limited volume, it does possess it. A frigate, however, possesses no broadside armament; its spaceframe is essentially constructed around its primary gun.
Like cruisers, destroyers and frigates are designed for the “close-in” battlespace – with the understanding that close-in, in space terms, means anything under one light-second of separation. Indeed, these types arguably dominate this battlespace, since they form the majority of the IN’s screening forces, whereas cruisers are largely incidental to “set-piece” naval engagements. In this area, they use their superior maneuverability to both engage each other with wolf-pack tactics and to swarm larger ships at close-in range. Their lesser defensive capabilities than their larger cousins reflects the intention that they should substitute speed and maneuverability, avoiding being hit, for the ability to withstand taking one.
Destroyers and frigates are also intended to serve in escort and patrol roles in relatively safe space, where antipiracy patrol is the main concern (a flotilla of destroyers or frigates is considered an effective counter to a single cruiser-class vessel, which would be a rare high-end encounter under such circumstances); and in small numbers and specialist classes as scouts, avoiding engagement entirely.
Some frigate classes, uniquely among naval vessels, are capable of atmospheric entry and landing. Such frigates occasionally serve an additional role with Imperial Naval Intelligence.
Autonomous Kill Vehicles (AKVs)
AKVs (A on the chart) – autonomous kill vehicles – are extremely smart multi-bus, multi-munition, multi-mission missiles. An AKV is, in effect, a small, stripped-down, AI-piloted starship – capable of much higher acceleration and greater maneuverability than a standard design, albeit with much less endurance – designed to act in multiple roles: as a mobile reconnaissance platform; as a “fighter craft” used to swarm and destroy larger starships from inside their own point-defense zones; or, when it loses all other fighting ability, as a kinetic energy weapon in its own right.
As indicated on the chart, AKVs have essentially no defensive weapons of their own; the intent is that they should substitute their vast advantage in speed and maneuverability for armor and point-defense.
A monitor (M on the chart), in essence, is a fixed base – an orbiting station or asteroid base – used for local defense. Their W/D ratio is skewed more towards defense than the ship-of-the-wall types, since unlike those, they lack even minimal maneuverability to avoid incoming fire or to retreat from the battlespace; on the other hand, their lack of concern for acceleration or other propulsive matters means that there is effectively no upper limit on the mass of the weapons or defenses that a monitor can mount, and asteroid-based monitors may make extensive use of the asteroid’s mass as armor and heatsink both.
Carriers (V on the chart) are battleship or dreadnought-sized vessels which eschew armament of their own in exchange for carrying a large number of AKVs, along with AKV replenishment supplies, strap-on AKV thruster packs, observation platforms, etc. Since they are not generally maneuverable enough or well enough protected (the massive flight deck of a carrier is essentially a corridor through the armor into the heart of the vessel) to survive heavy attack, they are usually held back from engagements, and as such their designs heavily emphasize point- and local-space defense over additional propulsion.
Assault carriers – i.e., those carrying dropships rather than AKVs – also fall into this category. The same general operational rules apply; they are held well back from any engagements, and do not move in to the target area until the high orbitals have already been cleared of the enemy.
Starfighters / Scouts
Starfighters (“sf” on the chart) are not manned fighter-class vessels. (The intersecting rules of physics, economics, and tactical effectiveness do not, in the general case, support a fighter-class of spacecraft in direct analogy to fighter aircraft. Rather, such craft can be replaced trivially by an equivalent vessel removing the biosapient pilot, their life support, and the ensuing limitations on maneuverability, acceleration, and computational performance, and replacing them with a computronium block; in effect, converting the spacecraft into an unmanned AKV.)
Rather, starfighters and scouts are essentially mini-carriers, suitable for operation by a very small crew, or even on occasion a single sophont, dedicated to the special operations and reconnaissance roles. They are small, no-frills starships designed to carry a limited, but still useful, number of AKVs or observation probes in exterior clamps. On arrival at their target, the AKVs or probes are then released to carry out the mission, while the starfighter itself serves as a command post, repair and replenishment depot, and coordination node in the tactical ‘mesh.
Couriers (“o” on the chart) are simply militarized (in construction standard) versions of the equivalent civilian type. While remaining, for the most part, “all engine”, military couriers add limited defensive and extremely limited offensive capability to give them at least minimal survivability in the event that they must pass through an engagement envelope; doctrine, on the other hand, demands that couriers should avoid engagement at all costs utilizing their superior acceleration and maneuverability to any other warship type.
Standard Sci-Fi Fleet: Well, most of these classes exist – although it is particularly important to realize that the Empire alone fields literally thousands of specialized class vessels that don’t fit neatly into any of these categories, and that to a certain extent, trying to shove everyone’s ship designs into the approximate same paradigm is an exercise in futility…
Ignoring the permanent city-ships, and starting with the military classes, we have, first, the regular fighting-ship classes. These begin with the frigate and destroyer (including the latter’s stealthy recon variant), small and fast ships used in “wolf-packs” for scouting, escorts, and screening elements, but which don’t themselves have the resilience or firepower to stand up in the wall of battle.
The middleweight combatants, and the most maneuverable/versatile, are the cruisers and battlecruisers, which also serve as screening elements for heavier ships, but are more often seen as the standard patrol and task-force element, often operating in flotillas (a cruiser wing with a battlecruiser or two thrown in for stiffening) or even independently (especially the battlecruisers). And since this type of operation (power projection, anti-piracy patrol, general keeping the peace of the spacelanes) is the bread-and-butter of the Powers and their naval forces, most navies, the IN included, field more cruisers and battlecruisers than just about any other type of starship.
These are also classes that come with a large number of variants. Most recognized among the cruiser classes are the assault cruiser (optimized for planetary assaults, i.e., heavy on the ship’s troops and capable of launching drop shuttles and drop pods into atmosphere; some of these are aerospace cruisers, which air fighters can sortie from before there’s an orbithead established); the diplomatic cruiser (a big stick to transport the softly-speaking); the point-defense cruiser (the one type of cruiser you might see in the wall, designed specifically to augment the point-defense of other ships); and the interdictor cruiser (specializing in the volume-security mission, which is to say, to chase down, capture and board other starships). The primary battlecruiser variants are the command battlecruiser (optimized to carry the admiral commanding a CC/BC task force) and the carrier-battlecruiser (which carries AKVs – see below – as well as its internal armament; this is the type of BC usually found operating alone, due to its significantly enhanced operational envelope and capabilities).
Then we come to the actual ships of the wall, battleships, carriers, and dreadnoughts. The battleships are the mainstays of the wall, large and slow vessels mounting heavy, long-range firepower for fleet engagements; and the carriers, even larger vessels, carrying an extensive complement of AKVs (autonomous kill vehicles, the missile/attack-drone fighter-interceptor hybrids described under Space Fighter, to swarm and destroy enemy starships at sub-“knife fight” range – i.e., hopefully inside the minimum effective range of their point defenses). The dreadnoughts are effectively “super-battleships” built on carrier hulls, used in relatively small numbers to stiffen the wall.
Superdreadnoughts are either dreadnought-class vessels built on even larger hull frames, or regular dreadnoughts with only battleship armament, using the extra internal volume to hold specialized systems; common examples are the command superdreadnought which houses the admiral in charge of a large task force or fleet; the information-warfare superdreadnought; the loadout-heavy mauler superdreadnought, the anti-RKV superdreadnought, etc., etc.
At the top end of the regular classes, we have the hyperdreadnought – taking the design principles of the superdreadnought classes even further – of which the Empire fields three, each unique within its class; Invictus, Imperiatrix, and God of War. In order, they are the home of Admiralty Grand Fleet Operations, the Imperial Couple’s personal flagship, and the literal embodiment of the archai/eikone of war. Any one of them turning up on the battlefield would have implications that, by and large, no-one wants to think about thinking about.
Less regular military classes include the starfighter, a frigate-sized mini-carrier with four to eight AKVs clamped to its outer hull, used primarily for covert operations and commerce raiding; the fleet carrier, a giant (and not itself offensively armed) lighthugger starship on the lugger model (see below) whose purpose is to ferry naval task forces to systems not connected to the stargate plexus; the fluffships – whose design is implicit in their name – that police systems for debris, ricochets, and misses after battles; and the relativistic kill vehicles for practicing MAD on an interstellar scale with giant lighthugger missiles capable of shattering planets, given a good run-up.
Among civilian ships, there are also various recognizable classes of starship for different purposes:
For freight transport, for example, one can recognize both the immense grapeships (from the appearance of the external cargo pods) or megahaulers, which transport vast amounts of containerized cargo along the largest and most dependable trade routes, and their smaller cousins the haulers, smaller freighters which handle more volatile but still regular traffic everywhere, and are willing to handle breakbulk as well as containerized cargo, and of course the volatiles-hauling tankers; and finally, picking up irregular and speculative trade and filling in the gaps, the thousand different classes of free traders (and their somewhat more combative overlapping variants beloved of smugglers and irregular commerce-raiding privateers, the blockade runner and corsair.) For routine transportation of volatiles, ore, and other such bulk and fungible cargo, fully automated slowhaulers often take up the task.
For passenger transport, likewise, we begin with the luxurious highliners and liners – analogous to the megahaulers and haulers in size and usage upon routes, and their express cousins the fastliners. And then, for those travelling off the regular routes or seeking a more unique experience, a great many free traders are just as happy to carry passengers as they are to carry anything else. Of course, the relatively wealthy and privacy-desiring have the option to travel in their private yachts, as ever, and at the other end of the scale, steerage-class transport is available to the relatively indigent on any number of iceliners, ships – often used as colonization transports – designed for the specialized task of transporting bodies in cryostasis or nanostasis, and minds recorded on data substrate.
In more specialized uses, dedicated classes abound: when messengers, mail, and packets need to get there really fast, within the stargate plexus at least, engine-heavy couriers are on the job; wrecks, debris, and flotsam are salvaged by debris recovery vehicles; hospital ships provide medical services (and reinstantiation services) to military fleets and disaster or epidemic-struck regions; logistics ships provide repair and construction services wherever they’re needed; oilers and tenders provide fuel, supplies, and other necessities to other starships; science, research, and exploration are done in the ubiquitous, customizable service/operations vehicles; smelterships render down asteroids into usable metal and other elements; and tugs and their larger cousins, the antimatter-torch equipped superlifters, move ships, modules, materiel – and in the case of the latter, entire habitats, asteroids, and even small moons – to where they’re needed to be…
…and if we’re willing to classify flying cities that are as much drift-habitats as starships, then we must include the civilization-backup ships, preserving archives, museums, and mind-states in the far reaches, ready to flee news of existential disasters; All Good Things, ICC, spreading the good word of commerce to underdeveloped regions with its skymalls; the empire ships, massive floating conferences/exhibitions/showpieces/parties flying endless loops around the Imperial Core and its many distant exclaves keeping population, culture, and knowledge well-distributed; and the embassy ships, similar exhibitions paying diplomatic calls on foreign polities and recently contacted worlds, bringing religiosity to the fuzzy-wuzzies and suchlike.
For local transport, small craft abound. For freight, lighters scurry about transporting cargo ship-to-ship, ship-to-station, and ship-to-ground; for passengers, pinnaces provide the same service, and in moving about between local stations or habitats in a cluster, the automated commutersphere provides rapid transport. Skydivers skim gas giants for fuel; maintenance and construction are carried out by the ubiquitous workpod; and other myriad local functions are served by the flexible, customizable cutter.
All of these, of course, exist within the framework of the stargate plexus. Outside that, a different type of ship entirely is required – lighthuggers need much more powerful engines (antimatter torch drives, for the most part) to reach the high fractions of c that make interstellar travel practical, sophisticated particle shielding to survive it, etc., etc. Let us leave aside for the moment the shardcruisers (not true lighthuggers, but hybrid ships built to service outposts in the outer cometary cloud of star systems, whose longest-range examples fade into slow, short-range luggers); and also the starwisps, ultra-light – a matter of pounds – light-sail vessels propelled by lasers at their point of origin, carrying information, tangle, or the smallest probes across interstellar space.
These then divide into clippers – high-acceleration, relatively low-mass vessels carrying premium cargo and passengers at the highest possible speeds, including, in the limiting case, the private staryachts of the very wealthiest; and luggers, their relatively low-acceleration higher mass vessels carrying passengers and freight in larger quantity. Specialized classes of lugger include the shiphauler (designed to transport docked starships rather than cargo directly; the military fleet carrier is an example of this type); the seedship (carrying ecopoesis packages and a startup colony); and the linelayer (transporting one half of a stargate pair to its destination system).