Interplanetary missiles (IPMs) are designed to destroy enemy defenses. Tipped with an anti-matter bomb, they deliver a destructive force so severe that destroyed defenses cannot be repaired. The only way to counter these missiles is with Anti-ballistic Missiles (ABMs). In an IPM attack, only the attacker’s Weapons Technology level and the defender’s Armor Technology level are used in battle calculations, as IPMs penetrate shields, including Small and Large Shield Domes. Before an IPM can hit the defense itself, all ABMs on the target planet must be destroyed. Each ABM destroys one IPM.
The range (in number of systems) of an IPM is determined by the Impulse Drive level. Each level, of impulse drive researched increases IPM range. They do not use a fleet slot while flying. However they do create Activity on the target planet upon hitting, and the defender receives a combat report in his messages.
You can store 5 Interplanetary Missiles for every Missile Silo Level on your planet.