Multi-Layered Armor Schemes
The URN's primary passive defensive system is the use of a multi-layered armor scheme which is designed to stop, dissipate, and or deflect an incoming attack. This is achieved through the use of standard armor plating, electric reactive armor, and the effective use of double hulls and their resulting hull cavities.
Any warship's defensive scheme actually begins with the design of the vessel's hull itself. While the three-dimensional nature of space combat means that any surface may be attacked from any direction, sloping the hull along likely lines of attack is effective in deflecting some of an incoming projectile's energy. This is most effective for impacts from smaller mass objects, as larger rounds are harder to deflect at high speeds.
From this point, the first layer of armor is an outer layer, made up of solid metal alloy plating. The job of this first layer is to stop smaller projectiles from penetrating on to the next layer down and to slow larger strikes in order to reduce the damage they cause further within the ship.
On larger warships, the next layer down is made up of electric reactive armor, which is composed of standard, meter wide armored boxes. These boxes are filled with a conductive fluid and given an electric charge. When a projectile penetrates the box, the circuit is broken, and the projectile can be vaporized or turned into a plasma, dramatically reducing the damage caused.
Once struck, the boxed armor is expended, offering no additional protection and requiring replacement in order to plug the gap in the ship's defenses.
Those attacks which succeed in penetrating the first two layers enter into a hull cavity between the first armor sheathed hull and the second interior hull. This free space is effective at expending more of the attack's energy, especially for explosive ordinance. It can also be used to store raw materials for the ship's consumption, such as water, which add to the cavity's absorptive capacity.
What little energy is left over encounters the final defensive layer. The interior hull is sheathed in composite armor, usually in thinner quantities than the exterior hull armor.
These protective measures are scaled to the size and shape of the parent warship, and their effectiveness will depend heavily on the nature of the attack they're under. Escort and screening warships will suffer under the fire of capital ships, regardless of their armor scheme. However, the URN's multi-layered approach has proven effective in protecting their warships from peer-sized vessels, meaning that Umbrian warships have a fair degree of survivability in fleet engagements.