Titanium-A battleplate

Titanium-A battleplate (Ti-A) is the standard blend of armor adopted by the UNSC during the 26th century.

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.

Though titanium-A armor makes up the bulk of a UNSC warship's hull protective system, where it is made in thicknesses up to three meters thick, it is often supplemented with other materials for extra durability. Starting part way through the Human-Covenant War, titanium-A plates are usually sandwiched between layers elastic polymers and intermetallic laminates, which resist kinetic and thermal impacts, respectively. Between these are further layers of shock-absorbing fluids that carry suspended shards of ceramics and silica within them, which when compressed, dramatically increases the armor's ability to resist kinetic impacts. The fluid also contains a foam to seal small hull breaches from micrometeorite impacts, but large holes must instead be plugged by some sort of alternative sealing mechanism. As the UNSC had long embraced hull-mounted radiators, some ships also have a cooling system within the armor itself, to actively mitigate damage from energy weapons.

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 this armor in some capacity.

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, largely because their protective schemes use proportionally-thicker plates of this armor.

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 an early refractive coating on the surface. It also features a cooling network as standard, which uses refrigerated liquids that are then ejected from the radiators. 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.

Titanium-A2/C is a modified variation of the battleplate. By substituting in layers of insulating materials suspended in a shock-absorbing liquid, and vacuum-filled layers, this decreases the cost, weight and dramatically increases its resilience against plasma. However, it is even weaker than grapheel at resisting kinetic impacts, largely because of its laminated nature.

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.