Cross Shielding is a property which is only noticable in Ion Bombers and Ion Frigates. It is not listed in either the weapons or shields statistics for these ships, however it is the reason for their effectiveness against capitol ships.
What is Cross Shielding?Edit
Simply put cross shielding allows some of a ship's power to pass through any shield. Usually the power amount is 1%, thus most ship's shields are 99% effective. However Ion Bombers and Ion Frigates have 50% cross shielding, and therefor are very effective against ships with high shield values.
How Does It Work?Edit
If a normal bomber attacks a dreadnaught the shields "absorb" or "deflect" 99% of the power. So while the Heavy Bomber has a power rating of 10 only 0.1 actually effects Heavy Cruisers, Dreadnaughts, etc. Using heavily shielded units against unshielded ships is called shield raping.
With Ion Bombers and Ion Frigates the cross shield effect is 50%, so half of their power gets through any shielding. So an Ion Bomber (with a power of 12) hits capitol ships with a power of 6. If your Ion Technology is high enough it is possible that almost all of the IB and IF power get through the shields and effects the armour.