Fighter:

Length: 5-40 meters

Mass: 10-200 tons

The smallest spacecraft commonly used in combat, Fighters are used for patrols, escort, hunting small ships, and torpedo attacks on enemy vessels. Fighters are the smallest type of manned vessel that commonly has FTL capability, though many short range patrol or defensive Fighters lack FTL. Some Fighters are manned while others are unmanned, usually slaved to manned Fighters within their squadrons.

Fighters have been in use for millenia, but mostly in a secondary role due to their limited effectiveness compared to most warships. This left them mostly used in close patrol, ground support, and anti-munition roles. The paradigm changed with the introduction of the disruptor torpedo by humanity. While munitions had been in use for millenia on Fighters, none before proved as useful as the disruptor torpedo, having been forced to deal with the kinetic barriers of ships stopping munitions before they reached their target. This left them only useful at Fighter scales for finishing off warships already damaged in battle, a role filled by Frigates just as well. The disruptor torpedo turned Fighters from a support and cleanup unit, into a potential main strike weapon, equal in importance to the mass accelerators used for millennia. This started an arms race not seen in a long time, and gave the human defense companies, which already had high level knowledge of Fighters, a leg up that allowed them to survive in spite of the overall technological inferiority of humanity.

Interceptor:

Length: 5-80 meters

Mass: 5-500 tons

Built in the 2160s (post First Contact War) as a result of the rise in the perceived threat of Fighters, Interceptors are meant to intercept and destroy enemy Fighter and missiles before they can threaten friendly vessels or installations. Usually equipped with Mass Accelerators, anti-Fighter missiles, and Guardian Laser Systems, Interceptors are a deadly threat to Fighters, only held back by their, comparatively, high production cost. The 2170 saw smaller, less capable, Interceptors introduced at lower costs, but these craft are only marginally more combat effective than the Fighters they are meant to fight, leading to several navies operating two lines of interceptors, one cheaper but less effective, and another more effective but expensive. The mass of larger Interceptors gave grown over the years, with some classes nearing the mass of small Corvettes, which are often designed for the same role, though longer ranged.

Most high end interceptors are manned due to the fear of electronic interference, but it is not uncommon for cheaper Interceptors to be unmanned, either slaved to another Interceptor, their mothership, a supporting Corvette or Frigate, or even independently operated by a VI.

Gunboats:

Length: 40-100 meters

Mass: 400-4000 tons

Less an actual type of spacecraft and more flying fortresses, Gunboats are used for ground support within a planet's atmosphere, providing heavy (for ground engagements) fire support and overwatch for friendly ground forces. Some Gunboats are unable to escape their planet's atmosphere, restricted to operating on only a single world unless moved by a Dropship. Others are able to travel into orbit and travel between planets and stars, either through another transport carrying them or by their own power.

Some Gunboats are able to submerge themselves in bodies of water and operate like submarines (a feat far easier than some may think). Gunboats that can do this are very useful when the enemy has aerospace control, allowing for fire support to operate even with the skies under enemy control. After the introduction of disruptor technology, many gunboats were armed with such weapons, giving them a dangerous weapon against enemy warships that dare to enter a planet's atmosphere, threatening them with losing their ability to stay aloft, dooming the ship to a fiery demise on the surface.

Corvettes:

Length: 50-120 meters

Mass: 400-5000 tons

The smallest commonly accepted warship, Corvettes are primarily patrol ships, lacking the power to go up against larger vessels. Corvettes are unable to deal with warships or even larger civilian craft, but are perfectly capable of combating Schooners and other small craft, making them common police vessels, large enough to do their job, cheap enough to be mass produced, yet lacking the range or firepower to be any real threat. A planet's Police Corvettes will commonly be commandeered or commanded by its military in an emergency or war. Due to this and the potential suddenness of such an event, many governments require the crews of such vessels go through military training, make Corvettes all a part of the military like a Coast Guard, or encourage police forces to mann Corvettes with former military personnel. Corvettes lack the available mass to incorporate a sensor package sophisticated enough to be effective on its own on the modern battlefield, leading to them not being used alone, with them usually attached to a larger vessel and linked with that vessel's sensor package. If no larger vessel is available, Corvettes will always work in at least pairs, though larger formations are more common.

Corvettes lack the size to be of any use in ship to ship combat, and so are usually used for ground fire support, patrol, convoy escort, or to fill in holes usually filled by Frigates. Most large militaries do not use Corvettes in major battles unless absolutely necessary, seeing the loss of resources as not worth it for the minimal gain. The rise of fighters in promonance has led to corvettes often serving as fighter hunters, with many small corvettes being designed for such a role, or to fight alongside and support their own foghters.

Bomber:

Length: 40-200 meters

Mass: 60-5000 tons

The Bomber is a unique ship type, not meant for direct combat with other ships, but striking at the infrastructure of the enemy. To facilitate this, Bombers are some of the fastest ships in use, beyond the speed of even Frigates, the main predator of Bombers alongside Fighters. This allows Bombers to rapidly reach their targets while avoiding interception. Bombers are usually designed to operate well in atmospheric conditions, allowing them an advantage when nearing their targets compared to primarily space focused pursuers. The main strike weapons of Bombers are their expendable munitions, designed to be fired off rapidly, keeping the time a Bomber is forced to remain in an area short.

The largest user of Bombers is the Volus Protectorate, which has a large fleet of Bombers under its command. These Bombers serve as one of the Protectorate's primary contributions to the Hierarchy Navy.

After the introduction of disruptor technology, much effort was put into deploying it on bombers, to mixed success. It was found that bombers sit at the odd point of being large enough for secondary mass accelerators to effectively shoot down, yet small enough to be vulnerable to laser fire. While not an issue when avoiding warships, direct strike against them proved this to be a quite fatal flaw. Nonetheless, ambushes using bombers proved to be quite effective, leading to their proliferation, if not to the same extent as frigates or fighters.

Assault Landers:

Length: 25-300 meters

Mass: 0.5-120 kt

A rather common ship for planetary assaults, assault landers are designed to deploy large amounts of troops directly onto a planet's surface. While many assault landers simply drop off their troops, some stay around, supporting troops through fire support and surveillance.

Assault landers are vulnerable to enemy fire, leading to them often being heavenly escorted. Many assault landers are converted into civilian dropships after their service, with it being equally common for dropships to be turned into assault landers when needed.

Sloops:

Length: 100-250 meters

Mass: 3-25 kt

A type of intermediate range patrol vessel, Sloops are a cheap solution to patrolling vast areas of space, though lacking the ability to act against some of the illegal or hostile activities they may find due to their size.

Sloops fall into a similar size range as frigates and corvettes, but are instead designed for long patrols in desolate systems or areas of systems. They are usually used by powers with large amounts of space to patrol and a relatively limited budget to do so. Sloops are usually far cheaper than Frigates of the same mass due to not needing the large Eezo Cores of the more combative vessels. Many powers forgo the use of Sloops, having the funds to use Cruisers instead, lacking large patrol commitments, or wishing to ensure high levels of fleet combative capabilities. Those aiming for the latter option upgrade Frigates with long range capabilities nearing or equal to the Sloop to allow them to fulfill a similar role. While this increases their cost, groups like the Alliance believe that removing the need to produce large numbers of vessels that are near useless in large battles, alongside giving Frigates more versatility, is worth the price.

Sloops are rather common pirate ships, being large enough to outfight Corvettes, at least for a while, while also being small enough to be cheap, inconspicuous, produced at secret facilities, and, perhaps most importantly, able to fit in the small scale docking and repair facilities found at many small colonies, which are often the only facilities available for resupply or repair.

The use of sloops increased after first contact with the Alliance and the introduction of disruptor technology, serving first as a stopgap solution for increased escorts against fighter attack, and later as a cheap alternative to frigates and destroyers for escorting larger vessels.

Monitors:

Length: 80-800 meters

Mass: 1-1500 kt

Often called orbital or coastal defense ships, monitors sacrifice long range capabilities and operational endurance in exchange for increased firepower and protection. Per ton, monitors are more powerful than other warships.

The difference between monitors and orbital/coast defense ships is thin to nonexistant, with the terms generally being used interchangeably by most human organizations. The Alliance itself considers them two different, yet similar, ship types. To the Alliance, monitors are designed for stationary guard of a single, distant location, meaning they often designed for longer operation tkmes, though not full patrols. Coast/orbital defense ships are meant for the defense of an actual colony or similar site with the ability to support it, meaning they lack the endurance of monitors.

Patrol Carriers:

Length: 80-250 meters

Mass: 5-100 kt

Small ships, often converted from civilian vessels, patrol carriers, sometimes called picket or pocket carriers, allow for small formations and navies to deploy a notable number of fighters and interceptors without the expense of a larger vessel. They have become rather common patrol vessels among minor powers since the introduction of the carrier, hence the name. They provide a wide patrol area using their fighters, while also retaining some effectiveness in fleet actions, carriers not being as bad as direct combat ships when it comes to capability loss with size. The Alliance is a prolific user of patrol carriers after the First Contact War, often deploying them with a formation of corvettes to patrol vast areas of space for a lower cost than cruisers, saving those valuable vessels for more important locations or combat formations.

Patrol carriers generally lack full flight decks, insted using flight or hanger bays like are found on none dedicated vessels like cruisers. This leaves them easier to build or convert, but less effective than a traditinal carrier.

Frigates:

Length: 150-300 meters

Mass: 3-30 kt

Scouts, skirmishers, light escorts, close patrol ships, fast transports, insertion craft, pirate hunters, and much more, Frigates are perhaps the most versatile type of warship in service due to their high speed and reasonable size. Capable of fast FTL and STL speeds in excess of most craft outside of Fighters, Courier Drones, and Interceptors, Frigates can usually not be engaged by anything but one of the former or another Frigate unless it chooses to, using its high speed to evade and outrun any opponent.

Frigates are used to patrol settled systems, but rarely leave their systems, lacking the range or capabilities to be trusted beyond the range of its brethren and the system's defense forces.

Frigates gained a new prominence with the rise of Fighters and the disruptor torpedo, gaining the role as one of the fleet's chief defenders due to their high speed. While before, when the only major concern for point defenses were long range munitions, the mostly static Destroyer was the main defender of the fleet, but the rise of the Fighter, which can appear from anywhere due to their FTL drives, gave the rapid and cheaper, and thus able to be produced in greater numbers, Frigate a chance to shine. Production of Frigates has risen since first contact, and they have become a vital part of any fleet beyond their scouting duties.

The high surface area of Frigates compared to larger warships allow them to operate for longer in combat environments, dispersing their heat far faster than larger vessels. This and their speed make them good skirmishers and escorts. Most large fleets are surrounded by two spheres of Frigates: the outer sphere acts as an early warning system for the fleet, while the inner sphere defends the fleet from enemy Fighters, small ships, and munitions. It is a common tactic for the inner sphere Frigates of two opposing fleets to begin fighting each other, giving munitions and fast attack units a chance to strike the fleet.

When scouting for a fleet, a Frigate usually does not stray closer than long combat range to an enemy formation, allowing it to avoid fire from enemy Cruisers. If an enemy formation has a Dreadnought, such scouting Frigates usually remain at extreme ranges, fearing the fast rounds of the Dreadnought striking them down.

The limited amount of Guardian Emitters Frigates can carry compared to larger vessels makes their short term protective screens weaker, ironically making them more vulnerable to large waves of Fighters when alone. They also cannot afford to carry ablative armor as thick as most larger warships, making them vulnerable to laser fire, precluding their use against larger vessels at close range.

When Frigates manage to close with an enemy force, they are used to attack already wounded enemy vessels, taking down warships that are damaged from non-fatal mass accelerator rounds and those who lost their shields to disruptor torpedoes.

Assault Frigates are a special type of Frigate designed to deploy ground troops to a contested planet's surface, using their speed and maneuverability to land the force in spite of attempts at interception. The main assault force of an invasion is not usually carried in Assault Frigates, only the vanguard.

Destroyers:

Length: 240-450 meters

Mass: 40-400 kt

The heaviest type of escort in use, the destroyer once held the position as main escort used by almost all large militaries. This position was challenged with the introduction of the disruptor, increasing the prominence of munitions and unveiling the weaknesses of the destroyer. Destroyers are designed around large numbers of secondary mass accelerators and point defense lasers, providing a powerful defense against munitions and small ships. The greatest weakness of the destroyer is its comparatively high cost, and thus low numbers, and relatively low combat endurance compared to other escorts. The high cost of the destroyer means that all but the largest fleets cannot afford to deploy entire spheres of the craft without limiting their battleline forces, while smaller escorts are cheap enough to be built in great numbers. Additionally, while the destroyer is better at defending against single large attacks, repeated strikes, especially when damaged by said strikes, overwhelm their heat management systems, allowing subsequent strikes to make it through.

The destroyer evolved after the introduction of disruptor technology, decreasing in size and focusing more on hunting down corvettes and frigates than protecting the fleet from munitions. This led to them being equipped with oversized engines and eezo cores like frigates, effectively becoming oversized frigates, later even gaining the torpedo firepower of their prey. Hunter teams of destroyers surround a fleet, destroying groups of frigates that attempt to close with the fleet.

Assault Ships:

Length: 100-1000 meters

Mass: 3-5000 kt

The main difference between an assault ship and an assault lander is that an assault ship is designed not only to deploy a ground force, but also support it. Assault ships provide all the amenities for a ground unit as any planetary base, sleeping facilities, galleys, vehicle repair and even, in the case of some, replacement, and medical facilities. Assault ships often have armament designed for planetary fire support, large numbers of missiles, small mass accelerators, and fighters. Most have relatively minimal anti-ship armaments, relying on escorting vessels for protection. Assault cruisers are a variant of assault ship that do have powerful anti-ship weapons, giving them a level of independence far greater than most assault ships.

Most assault ships are too large to land on a planet, instead deploying their forces from orbit or high atmosphere. Some, however, can land on a planet's surface, often remaining there of mobile fortresses, impregnable to almost anything on the ground.

Light Carriers:

Length: 240-700 meters

Mass: 100-1400 kt

A smaller version of the fleet carriers introduced by humanity, light carriers sacrifice flight group size in exchange for a lower price far more affordable than the larger carriers, while still retaining the flight decks that make carriers so effective. The light carrier would spread across the galaxy with the introduction of humanity, becoming a relatively common sight within the navies of smaller powers like the Courts of Dekuuna and Illuminated Primacy.

The Alliance Navy divides light carriers into 2 subtypes: escort carriers and light fleet carriers. Escort carriers are smaller ships, most no bigger than half a million tons, often smaller. They are usually used to supplement the fighter forces of direct combat formations and provide them with more complex command, control, and coordination than is usually provided by non-carriers. Some are designed like other carriers, meant to stay far from combat, but others, specifically ones designed for the Turian Hierarchy, have protection sufficient to allow it to remain in formations even during combat.

Light fleet carriers are larger, most matching the size of light and heavy cruisers, and often serve as the flagships of smaller navy's fleets or entire forces, providing a safe location for command facilities.

Cruisers:

Length: 300-750 meters

Mass: 300-1229 kt

The main type of large warship used by most militaries, cruisers are vital to all larger militaries across the galaxy. Cruisers are used for power projection, having the range to deploy far outside of a powers core territory and support, alongside the firepower to deal with almost any threat it can be expected to face in peacetime. When used in larger conflicts, cruisers form the main battlelines of all powers, being powerful enough to take on most vessels, while being cheap enough to be fielded in significant numbers. Cruisers often engage in skirmishes, taking long range shots at smaller craft or dueling other cruisers, low risk attacks that more often end with the losing side jumping away to FTL rather than being destroyed.

The Treaty of Farixen, created in the aftermath of the Krogan Rebellion, puts a limit on the size of cruisers, and on the number of larger cruisers. According to the treaty, any warship with a mass accelerator over roughly 610 meters (609.3 meters or 150 of the asari unit of measure Tralint) to be a dreadnought. Additionally, any vessel with a mass accelerator over roughly 325 meters (324.98 or 80 Tralint) and a mass greater than roughly 1.29 million tons (100 thousand asari Urent) to also be a dreadnought. Many cruisers outside of Council Space have greater mass than allowed in the treaty, with the Hierarchy Warbook considering vessels over 1.4 million tons as grand cruisers instead of heavy cruisers. Cruisers of under roughly 980 thousand tons (978,320 tons or 80 thousand Urent) are not regulated by the Treaty of Farixen baring the mass accelerator limit.

Cruisers can generally be divided into four categories, heavy cruisers, light cruisers, patrol cruisers, and scout cruisers. Heavy cruisers are of between roughly 1 and 1.4 million tons, though some militaries consider vessels of slightly less mass to be heavy cruisers. They are powerful combatants and are regulated by the Treaty of Farixen, with the Turian Hierarchy allowed 300 heavy cruisers, the asari and salarians 200 each, and each associate race 120, a more even distribution compared to the division of dreadnoughts due to the greater use of heavy cruisers in peacetime. Nonetheless, no associate had a force reaching the limit as of first contact with humanity. Heavy cruisers often serve as the flagships of small formations or operate in units of multiple heavy cruisers.

Light cruiser is a category containing ships of between 980 thousand (978,320) tons and 600 thousand tons, though some navies consider vessels of slightly larger or smaller size light cruisers. These vessels are almost entirely unregulated by the Treaty of Farixen, but still have some use in major battles. They are rather common in most large and intermediate navies, often serving as patrol ships or flagships for small formations, alongside being used as raiders, being powerful enough to do some damage, but expendable enough to not be missed if destroyed.

Patrol cruisers are the smallest ships generally considered cruisers, vessels of between 300 and 600 thousand tons. They lack the offensive or defensive capabilities to compete with larger vessels in battle, so usually serve as patrol ships, or sometimes leading packs of frigates or destroyers.

Scout cruisers are relatively rare, being vessels of similar size to patrol cruisers, but with oversized engines and eezo cores more akin to frigates. Some larger militaries use these vessels for reconnaissance due to carrying far more equipment than any frigate could, but a far more common use is as a raider. Fast, yet far more powerful than any frigate, scout cruisers are often the banes of merchant fleets and supply convoys in all conflicts.

Grand Cruisers:

Length: 600-1200 meters

Mass: 1.4-3 mt

Larger vessels built along the lines of cruisers, grand cruisers are rare within Council Space due to them counting as dreadnoughts for the Treaty of Farixen, with only a few Asari Republics using them. Within the Terminus Systems, on the other hand, they are rather popular with those groups that can afford them, proving to outperform any other cruiser, while having greater operational mobility than dreadnoughts.

Sidge Ships:

Length: 700-1000 meters

Mass: 1-3 mt

A rather odd ship type, Sidge Ships are less warships and more mobile gun platforms, even more so than Dreadnoughts. Equipped with Cruiser, Dreadnought, or even Super Dreadnought scale mass accelerators on a ship of far lesser mass than most ships of those types, their main role is to bombard enemy warships and immobile targets at far beyond their ranges.

Lacking almost anything besides the main weapon in the ways of offensive or defensive systems, Sidge Ships are highly vulnerable to attack, particularly from Dreadnoughts, Fighters, and Frigates.

Sidge Ships are commonly used in Mass Relay defense, their extreme range allowing for ships to be destroyed while attempting to run blockades or assaulting a Relay.

The use of Sidge Ships is somewhat rare in Citadel space, the Treaty of Farixen making them impractical in their larger forms for any force wishing to field a full Dreadnought fleet. In the Terminus though, they thrive as an important part of the battlefield.

The divide between Dreadnoughts and Sidge Ships can be thin at best, arbitrary at worst. It is not uncommon for a bulky Sidge Ship or thin Dreadnought to have their classification change depending on the force observing it.

Dreadnoughts:

Length: 800-1200 meters

Mass: 1.4-6 mt

When the Rachni flooded into known space like an unending swarm, when the Krogan rebelled and tore a bloody scar across the stars, when the Hierarchy began to unify the disparate colonies of the Turians into one, when the Great Terminus League fell to ruin and the Five Kingdoms rose to try and take its place, the great fleets of the galaxy clashed with one centerpiece, one almighty sovereign of the battlefield, the Dreadnought.

Dreadnoughts are designed more around their spinal Mass Accelerators than the other way around. Their main guns reach anywhere between 70 and 90% of a Dreadnough's length, hundreds or even over a thousand meters long.

In any space battle, the role of the Dreadnought is to provide extreme range fire, using their main weapons to attack smaller ships far outside their effective ranges and with such force that a single shot can penetrate any non-Dreadnought. This comes at the cost of endurance. The large size of Dreadnoughts limits their surface area compared to their heat generation, limiting their combat endurance compared to smaller warships.

Dreadnoughts are extremely expensive and valuable, with only a few built by larger factions and those in existence limited to only the most important battles.

Groups that lack the resources to build full size Dreadnoughts make diminutive vessels, usually called second and third class Dreadnoughts. These vessels lack the ability to take on first class Dreadnoughts on their own, but are effective against Cruisers and can fight full Dreadnoughts, even winning if numbers, skill, or luck are on their side.

Most modern first class Dreadnoughts are nearing or beyond 1 kilometer in length and between 3 million and 6 million tons in mass, while most second class Dreadnoughts are 800 to 900 meters in length and mass 1.8 to 3 million tons, equaling the size of larger grand cruisers. Third class Dreadnoughts are even smaller, smaller than many smaller grand cruisers when it comes to tonnage and length, only holding the title due to their designs and the proclamations of those more minor powers who have them in their service.

Super Dreadnoughts:

Length: 1200 meters

Mass: Indeterminate

Super Dreadnought is less a designation and more a title for those vessels that far exceed the size of most Dreadnoughts of their times. The divide between a dreadnought and a super dreadnought is entirely arbitrary, more often made by politicians, the public, and the media than military officers. Few ships in history have been ever called a super dreadnought, and the only one active today is the asari dreadnought Destiny Ascension, a colossal vessel an order of magnitude larger than any other dreadnought ever built.

Fleet Carriers:

Length: 500-1200 meters

Mass: 1.4-5 mt

An invention of humanity, fleet carriers are designed to deploy large numbers of fighters, interceptors, and bombers, while also providing advanced command and control facilities to endure their maximum effectiveness. Most fleet carriers have extensive fabrication facilities, allowing them to create spare parts, munitions, and even entire small craft, making them useful support units for any fleet.

While fighters have gained a new prominence after the introduction of the disruptor, the fleet carrier has not received the same warm welcome, its large size and cost making it unappealing, most powers instead going for smaller carriers or just increasing the air groups of their other ships. The only groups outside of humanity to use full fleet carriers are a handful of Asari Republics and, ironically, the Turian Hierarchy, though even all those vessels combined would not match the number of fleet carriers deployed by the Alliance.