Titanium-A battleplate

Titanium-A battleplate (Ti-A) is the brand name for an ubiquitous family of starship armor used by the UNSC during the 26th century. Titanium-A is not a single material but rather a trademarked series of proprietary alloys and cermet composites, the composition of which has changed dramatically with successive generations. More broadly, "Titanium-A battleplate" is also used to discuss the overall hull armor scheme of a ship, rather than just the material itself.

Characteristics and applications
Titanium-A armor starts off as plates of Grade-38 titanium-50, which are alloyed with various impurities such as carbon and aluminum. These are then compressed under extremely high pressure and face-hardened, and fine-turned machines correct deformations in its crystal structure to completely remove stress points. The final treatment of the surface layers takes place while the metal is cooling, further augmenting the armor and also applying the anti-corrosive protection if necessary. Taken as a whole, titanium-A is extremely strong, lightweight, and resistant to shattering and melting.

Although originally used to protect warships and fortifications from heavy weapons, Titanium-A armor has since been adopted by nearby all aspects of the UNSC. Armored vehicles, space fighters, slipstream probes, and even infantry lockers all utilize some form of titanium-A armor.

Much of the space-facing side of the titanium-A plating on UNSC warships is coated with carbide-ceramic radiator plates, which circulate a coolant fluid through the ship's systems to remove heat via radiating it to the surrounding vacuum.

Titanium-A1
The first generation of this family of armor plating, titanium-A1 was introduced during the 2460s as a replacement for graphene steels, but would not see widespread use until the 2480s. Though a vast improvement over older materials, later refinements are noticeably stronger and lighter per thickness, and A1 has proven particularly vulnerable to plasma weaponry. However, older pre-Covenant War warships have proven themselves to be better protected against missiles and naval coilguns than their later descendants due to their kinetic-optimized material properties and armor spacing.

Although no longer used on UNSC warships, this blend remains the most common form of armor plating in use, even into the Reconciliation Era. This is largely because it is easier to fabricate and acquire, as it is abundant in debris fields.

Titanium-A2
Developed during the Human-Covenant War, titanium-A2 battleplate is a variation that offers vastly improved resistance against energy weapons. The alloyed impurities have been changed for those better at combating thermal energy, along with a higher surface refractivity. It also features a cooling network as standard, which circulates a liquid coolant through the armor to mitigate thermal damage. It is also somewhat stronger and lighter on a per-thickness basis when compared to the original alloy, largely thanks to advances in fabrication technology. Despite these advances, the effectiveness of the A2 variant against Covenant anti-ship weaponry is limited and it was largely seen as ablative armor, giving plasma solid material to burn through before it reaches the vital sections of the ship.

Titanium-A2/C is a modified variation of the battleplate. By substituting in layers of insulating materials suspended in a shock-absorbing liquid, and layers left open to vacuum, this decreases the cost, weight and dramatically increases its resilience against plasma. However, it is even weaker than grapheel at resisting kinetic impacts due to the materials used being optimized against heat damage.

Titanium-A3
Introduced towards the end of the Human-Covenant War, Titanium-A3 battleplate seeks to combine the protective qualities of the original A1 mixture with the superior thermal protection of the rarer A2 formula. This is largely thanks to the adoption of techniques used in Covenant nanolaminate armor, which makes it up to 20% lighter than A1 and grants it superior resistance to thermal energies. This is paired with refractive coating and a dedicated thermal-control system integrated into the plating itself.