Mega-class Star Dreadnought

The Mega-class Star Dreadnought, also known as the Mega-class Star Destroyer, the Mega Star Destroyer and simply the Mega-Destroyer, was a class of Star Dreadnought utilized by the First Order.

Dimensions
The Supremacy was the sole Mega-class Star Dreadnought in the First Order's service with a colossal wingspan of 60 kilometers. Its construction was undertaken on an unprecedented scale. As the First Order's headquarters, the starship acted both as a command center and a battleship. Its size was gargantuan, easily outclassing all known ship sizes in galactic history, including the Star Dreadnoughts of the Galactic Empire, the trophy battlecruisers used by wealthy citizens of the waning days of the Old Republic, and even the various reconstructed versions of the flagship used by Xim the Despot.

Engines
The ship has approximately 32 sublight engines, which wae improvements upon the sublight engine system aboard the two Death Stars. It also possesses at least six fusion reactor complexes at the Starboard, allowing for redundancy and increased damaged resistance.

Complement and Crew Requirements
The ship is large enough to dock eight Resurgent-class Star Destroyers—six externally and two internally. It crews over 2,225,000 personnel, including officers, stormtroopers, gunners, vehicle engineers, factory workers, technical specialists, and communications staff. It possesses at least 10 military staging areas, each of which can accommodate a full corps of more than 36,000 stormtroopers. The operations decks have floors of workstations filled with highly efficient operators. The vast majority of the crew are Sub-Adults (i.e, too young for active combat deployment), and fully indoctrinated into the First Order myth of a chaotic galaxy requiring a strong, unflinching order to control it.

Because of its role as the First Order's headquarters, not only is the Supremacy able to carry stormtroopers into battle, but it is also capable of harboring, building, and conducting ship repairs for the First Order Navy in its onboard hangar bays, two of which are large enough to house and repair Resurgent-class Star Destroyers. Additionally, it carries production lines, shipyards, army training grounds, and even research and development labs. The Supremacy also acts as one of the premier research labs and factories in the First Order, possessing industrial capabilities rivalling the most productive worlds under the regime's control. Its armored decks house departments reserved specifically for the conception, research, and approval of new weapons and technology. It also houses well-stocked raw materials reserves, eight durasteel foundries, an asteroid mining complex for harvesting raw materials directly from asteroids fields, as well as state-of-the-art production lines. Training centers are present to indoctrinate young cadets into the military. As it carries all the supply lines, it also could not be cut off from supply lines. Its capabilities were such that its destructive power was comparable to that of a full fleet, its production capabilities comparable to that of a planet, and acted as a testbed for the various military advances of the First Order. It also possesses a detention center near the stern, a commons area, an assembly hall which could accommodate 200,000 personnel, as well as at least 346 laundry rooms. The majority of the crew quarters are placed within the various central "city" blocks of the ship.

It also possesses at least eight droid manufacturing facilities and a ground vehicle manufacturing zone. The tips of the wings are reserved for top-secret labs and dangerous weapons tests and possessed communications hubs. The starboard wing possesses a crew transportation causeway with an integrated tram system.

Bridge
The main command bridge sits upon a massive structure at the center of the ship, which has a similar design to that of the Mandator IV-class Siege Dreadnought, and to a lesser extent the Resurgent-class Star Destroyer. The bridge has access to displays allowing 360-degree views over everything within the city-scape-like structures on the main "wing" of the destroyer.

Hyperspace Tracker and Armaments
The Supremacy uses active tracking equipment that allows it to pursue its targets through hyperspace using a combination of technological advances and brute-force data crunching. The Shipboard Tracking Control Complex boasts the data-shifting power of a planetary intel hub, linking huge computer arrays to data banks loaded with centuries of combat reports and astrogation data. A static hyperspace field generated around the machines accelerates their processing power to unprecedented levels. A target's last known trajectory yields trillions of potential destinations, but the system can assess these locations with terrifying speed. This capability has its roots in the Tarkin Initiative. The ship, owing to it being the central command ship, forwarding base, and the proverbial brain of the First Order's entire forces, is also entirely self-sufficient, to the extent that its command need not be concerned about supply shortages. In addition, the vessel possesses thousands of heavy turbolasers, anti-ship missile batteries, heavy ion cannons, and tractor beam projectors. The bow of the ship possesses fifty ultra heavy turbolaser towers. Only the Death Stars and Starkiller Base rivaled its power. Its communication complex monitors the HoloNet traffic throughout the galaxy to identify trends and weaknesses that the First Order can exploit. As such, they also dispatch orders to various agents operating within both the New Republic and other faction's space.

Construction
The ship was built by the First Order at a staggering cost within the Unknown Regions to act as the official capital of the First Order at the order of the Supreme Leader. Although various officers and allies of the First Order argued for a planet to act as their capital, he insisted on using the Supremacy as the main capital, refusing to designate capital command to a world either under direct First Order control or in the Unknown Regions—at least until the restoration of total galactic control, as part of the Supreme Leader's aim to restore and further expand the territory formerly belonging to the Galactic Empire. Armitage Hux agreed with the strategy to keep the capital of the First Order aboard the Supremacy, seeing it as a way to mitigate the risk of it being destroyed in battle when mobile.