Titanium-A battleplate

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

Characteristics and performance
Titanium-A armor is mostly composed of pure plates of Grade-38 titanium-50, which are organized at a molecular level into a single unified crystal. This removes the microscopic weaknesses normally seen, increasing strength. The outer layers are treated with thin insulating compounds, which protects the material from both corrosion and keeps out heat. Generally speaking, Titanium-A is extremely strong, ductile, lightweight, and resistant to heat, thanks to its high melting point.

On starships, Titanium-A armor is organized into individual 100mm sheets that are laid over some sort of dividing layer. These act as a firebreak for high temperatures, preventing the entire thickness of armor from being compromised by a single plasma hit. These are normally composed of elastic polymers and inter-metallic laminates on warships. 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 automatically blocks small hull breaches from micrometeorite impacts, but large holes must instead be plugged by some sort of alternative sealing mechanism.

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-A2
Developed during the Human-Covenant War, Titanium-A2 battleplate is a variation that is specifically engineered to resist plasma-based weaponry. It is alloyed with impurities such as carbon to increase its heat resistance at the cost of some mechanical strength and flexibility. To keep the plates cool, they are connected up to a thin layer of refrigerant fluids, which are expelled through the radiators when they get too hot. Finally, the material is treated with refractive coating reversed-engineered from the Covenant, lending further thermal protection. In spite of its superior performance against plasma weaponry, it was only found on a small range of starships, thanks to its cost, difficulty to manufacture in large numbers, and inferior performance against kinetic impacts.

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. The composition is improved, with some techniques used in Covenant nanolaminate armor being brought in to make the microscopic structure stronger and better able to resist plasma weaponry. This is paired with refractive coating and a dedicated thermal-control system integrated into the plating itself.