Armor

From NS community wiki

For Marines, each point of armor absorbs two points of damage. In other words, at any given time, the amount of damage a marine can take before dying is it's HP + Armor * 2. Armor on vanilla Marines and Jetpacks absorb 70% of damage dealt. Heavy Armors absorb 95% of the damage.

For Aliens, each point of armor is worth 2 points of damage at 1 and 2 hives. At 3 hives, each point of armor 2.5 points of damage. At 1 hive, alien armor absorbs 70% of damage - each additional active hive increases that by 10%.