Mounted on a heavy tank chassis, the Ballistic Rocket has the longest attack range and damage, period. Even in its most basic form, it outranges every other weapon by a significant margin, which only grows larger with each upgrade, of which there are four. The last upgrade is the immensely powerful Nuclear Missile. This more than makes up for its long travel time, since the damage on impact is enough to instantly destroy structures and units in a large radius - and since it's a physical weapon, it ignores any shields. However, be warry of SDI Lasers and Defenses, as these will shoot the missile down before impact.
The Ballistic Rocket is the ED's major WMD and allows them to build a Missile Control Center from which 4 Missile Silos can be built. Each Missile Silo can carry 1 Ballistic Rocket, and can attack anywhere on the map.
in Escape from the Blue Planet each Ballistic Rocket costs 5000 resource, but may be reloaded immediately. in Lost Souls and Moon Project, Missile Silos must charge up similar to the UCS Offensive Plasma Cannon, and does not Cost 5000 resource
The Ballistic Rocket is researched from the Heavy Rocket Launcher, and aside from its own upgrades is not reqiured for any further research.