From Growing Horizons

Modern Armor for combat spacecraft has been developed from early designs, utilizing multiple approaches to protect a spacecraft from an opposing forces fire. Usually the main armor of a spacecraft consists of a basic multi layer laminate of successive layers of high grade steel, followed by two layers of silica and graphite aerogel, a layer of boron, a layer of ballistic artificial spider silk and high density polyurethane. Usually multiple of these laminate layers are stacked and separated by empty space to make use of the Whipple Effect. Additionally, layers of artificial diamond mirrors may be added to provide additional defense against laser weapons.

Amoung all space going powers this armor is sloped to provide additional protection. Another measure as last layer of defense are the outer propellant tanks, where the propellant, water, is frozen solid at 150K. This layer of ice also increases the protection against radiation.

Sometimes a coating of EM absorbent material is applied on top of the armor to reduce the cross section of the spacecraft against active EM detection, but is usually deemed to be unneeded.