Titanium-A armor

Titanium-A armor is the most common form of battle plating used by starships constructed by humanity. It is employed on both civilian and military vessels as a general-use hull material designed to protect the spacecraft in question from damage ranging from micrometeorite impacts to hypervelocity projectile rounds and directed-energy weapons.

Characteristics
Titanium-A consists of high-grade Titanium-50, specially-strengthened and reinforced at the molecular level with stacked nanotubes, elastic polymer composites and intermetallic laminates - resulting in a plating material capable of withstanding hypervelocity projectile impacts and energy weapon attacks. The plates themselves are typically a dull grey in colouration, and are embedded with thermal superconducting radiators that work to radiate thermal energy from the ship into space. The space between individual armor plates is filled with shock-hardening fluids and encapsulated healing agents to reduce spall from impacts and automatically seal small hull breaches.

Titanium-A3 armor
Later during the Human-Covenant War, more advanced forms of Titanium-A were introduced, fitted with thermal superconducting elements to help strengthen against energy weapon impacts. One such example is Titanium-A3, a variant of Titanium-A battle plate developed by the Office of Naval Intelligence's Materials Group. Like Titanium-A, it is chemically altered on the molecular level to produce a stronger plate for ship hulls. It has only been noted to be used on the, whose hull is composed of 4.9-meter-thick Titanium-A3 battleplate.

Following the Human-Covenant War, some UNSC military vessels received energy shielding to allow the ships to absorb more damage.

Defensive capabilities
Prior to the Human-Covenant War, a single Magnetic Accelerator Cannon slug was capable of penetrating any vessel's Titanium-A armor plating. The armor took a newfound importance after the beginning of the Human-Covenant War: to contend with the Covenant's plasma weaponry, humans needed armor that would withstand the heat of the directed plasma. Despite its strength and resistance to heat, however, the Titanium-A plating is usually boiled away within seconds on contact with Covenant plasma torpedoes, and does not effectively dissipate the plasma. Energy projectors are able to pierce dozens of centimeters with relative ease. Pulse laser turrets can reduce the hull of a heavy frigate to about four centimeters in a single hit. Even energy swords can do significant damage to Titanium-A armor.

Titanium-A armor plating can be layered with tungsten for a radiation absorption rating of 5 and presumably grant greater protection against plasma weaponry. Unlike the Covenant's nanolaminate hull plating, Titanium-A plating is not effective during direct collisions with other vessels. After a direct collision with Proclamation's Tithe, the was heavily damaged, while the  was seemingly unharmed. When the destroyer collided with a Covenant stealth ship, the Iroquois lost all two meters of Titanium-A plating, although it did succeed to disabling the Covenant vessel.

Usage
Titanium-A, alongside other technologies such as Magnetic Accelerator Cannons, was developed in the 25th century as a response to the Insurrection. Since its introduction, it has served as the main hull material used on the warships of the CMA Navy and UNSC Navy. As much as a third of a given ship's mass may be composed of Titanium-A, with plate thicknesses often measuring dozens of centimetres thick. Frigates such as the may have up to 60 cm of Titanium-A plating, with destroyers like the  having plates as thick as 2 m. s, the standard line warship of the UNSC Navy, have plates with 191 cm of Titanium-A, while some carriers have armour plating thickness of 36 cm. Other carriers, such as, have multiple metres of Titanium-A plate. Outside of warships, Titanium-A armour is used as the hull material for support craft such as the D77-TC Pelican and GA-TL1 Longsword, alongside slipstream space probes and even drop pods such as Long Range Stealth Orbital Insertion Pods. Refit stations and construction platforms, such as Station Delphi, are essentially slabs of Titanium-A armor plating.

The UNSC uses Titanium-A for construction of military bases as well, to make them less susceptible to destruction. Underground facilities such as HIGHCOM Facility Bravo-6, CASTLE Base and Camp Hathcock used Titanium-A armor in their superstructures. Even lockers used by UNSC personnel are reinforced with a centimeter of Titanium-A armor plating. Eridanus Secundus, a United Rebel Front asteroid base located in the Eridanus system, was reinforced with a layer of Titanium-A armor which also helps deflect UNSC and Covenant sensors. On an infantry level, Titanium-A serves as the primary material layer for the armoured shell of the MJOLNIR Powered Assault Armor system, and is even used in infantry equipment such as the grappleshot.

In the civilian world, noncombat starships such as freighters may also be covered in a layer of Titanium-A, albeit much thinner and their military counterparts. These armour layers serve to protect the ship from regular space debris such as micrometeorites, as opposed to hostile projectiles.