Armor

Armor is a material equipped to protect a spacecraft from debris and enemy attack. It generally comes in several layers of material (Silica Aerogel, Diamond, Osmium, Reinforced Carbon-Carbon, for example). Armor composition may differ according to the type of ship - a carrier may only have an anti-nuke flash layer, while a ship designed to fight other capital ships could have several meters of armor.

## **Types of armor layers**

### **Anti-nuke armor**

The anti-nuke layer, also known as anti-flash layer, is generally the outermost armor layer. It serves two roles: to protect the inner layers from nukes that don't detonate on impact and to bounce off sandblaster projectiles. It is a thin layer made of high safe use temperature ceramics, like tungsten carbide and titanium carbide. An underlying layer of diamond can be added to better dissipate the heat absorbed by the anti-nuke layer. These materials tend to have a brittle failure and the shattered pieces can damage the underlying Whipple shield, bulk armor or internal modules, so a spall liner could be used.

### **Whipple shield**

A Whipple shield is a layer of armor away from the underlying layers, set off by at least 25 cm, though 50 cm or 1 m are also commonly used spacings. They can be spaced by 1 m or more for increased performance, though this can cause the Whipple shield to increasingly impact the cross section and mass of a spacecraft, as more material is needed to cover the spacecraft from further away. Ideal Whipple shield materials are those that can melt easily, like platinum, tin and aluminum. Whipple shields should generally be between 1 mm (with denser materials like gold and platinum) and 5 mm (less dense materials like tin and copper) to stop most projectiles. Whipple shields are used to turn incoming projectiles into plasma, which causes far less damage because it's a gas and it spreads out inside the gap.

'Stuffed' Whipple shields can be created by filling the vacuum gap with graphite aerogel. This improves performance slightly.

### **Bulk armor**

Usually the thickest armor layer (with the exception of graphite aerogel), the bulk armor's role is stop kinetic penetrations. It can be made of one thick layer of a single material or more layers of different materials. Some materials that can be used are amorphous carbon (thermally resistant), boron filament (high strength to density and to price ratio), osmium (is the densest and has the highest ultimate tensile strength) and vanadium chromium steel.

### **Spall liner**

Spall are flakes of a material that are broken off a larger solid body, on the other side of where the material was hit. This makes spalling dangerous to inner armor layers (if present) and modules, and can damage or destroy them even if the armor itself was not penetrated. The spall liner is usually the innermost armor layer with an anti-kinetic role, and is meant to deform plastically to prevent the spall from ricocheting around. It should therefore be made of materials with a very high ultimate tensile strength and a large gap between this and the yield strength, like PBO fiber, spider silk and nitrile rubber.

The spall liner could also be the only type of anti-kinetic armor on a spacecraft or drone with a tight mass budget.

### **Anti-laser armor**

The anti-laser armor is made of a type of material resistent to the ablation caused by lasers. In the vanilla game there is an ablation cap in place, measured in cm/s, that is different for each material. Due to this, the best anti-laser materials are (ablation cap in parentesis): aramid fiber (0.16 cm/s), polytetrafluoroethylene (0.31 cm/s), nitrile rubber (0.44 cm/s), polyethylene (0.53 cm/s) and selenium (0.64 cm/s). A way to choose which material is best for a specific weapon turret, drone or ship is to calculate how many seconds the laser will need to ablate the armor thickness of each material, with the layer as thick as allowed by the prefixed mass and cost budget.

The anti-laser armor could also be the only type of armor on a spacecraft or drone, and often it is used to armor weapon turrets.

## **Sources**

* CoaDE blog post "Raw Steel" by qswitched
* Thread "need help on armor" on childrenofadeadearth.boards.net
* Thread "Laser ablation cap: bug or feature?" on childrenofadeadearth.boards.net