Hull Rating
Hull Rating is a number that tells the amount of armor a unit (ship or defense) has on its hull. Every unit has an base hull rating equal to one-tenth the sum of the Ore and Crystal required to build it. Armor Tech increases each unit’s hull by 10% of the base rating.
In combat, after damage in a given round is absorbed by a unit's shields, any remaining damage is then subtracted from the hull rating. A ship that has its hull rating reduced in combat by more than 30% has a chance of exploding equal to the total hull reduction.
For example, suppose a ship starts with a hull rating of 1,000. If at the end of the first round, it has received 250 hull damage (leaving 750), it will survive that round, as 25% is less than the 30% minimum for destruction. Suppose in the second round it receives 100 hull damage (leaving 650). It then has a 35% chance of being destroyed at the end of that round. However, suppose (65% chance) it survives to the third round, and further suppose that it is not hit in that round. Because it wasn't hit in the third round, it will survive that round.
At the end of combat, all surviving units are immediately restored to their full hull rating.