[douglas]

If a ship with emissive armor III is hit with a non-armor-skipping weapon, the damage to the hull is reduced by 30 before any other effect, to a minimum of 0. This does not affect damage done to shields - only the part of the damage that gets past shields is reduced. For this reason, I recommend using it only on ships that make heavy use of armor as their primary defense. It is particularly useful in combination with large amounts of crystalline armor and one shield generator. The amount of emissive armor on the ship does not matter, only the highest emissive ability is used. However, emissive armor has less structure than any other specialty armor and is much more easily destroyed, so putting multiple emissive armor components on a ship means you'll have the emissive effect active for more of the battle.

Edit: Wow, that was a lot of posts while I was typing. The shields from damage of crystalline armor works in a very complicated way that comes out to essentially equivalent to the emissive ability except that it stacks to a maximum of the structure of a single crystalline armor component or your maximum shields, whichever is lower. Emissive armor stacks with this effect beyond the limit, effectively allowing you to have 180 damage reduction as long as all 10 crystalline armors and at least one emissive armor remain intact. However, the emissive is weaker per component than crystalline, so you need backups. Spare crystalline armors are also important, but with the limited space on a dreadnought, I think two spare emissives is a better use of the space.