"Heavy barrel mass drivers that hurl very large kinetic rounds that do very heavy damage and can knock Destroyers and Cruisers off course."
Heavy Drivers unlock the weapons system of the same name, Heavy Drivers(weapon). This is the last node in the Ballistic Weapons tree which has a 100% chance of unlocking, it's dice from here on in. Also, this is the last node in the tree which links exclusively to Fission level technology. As a result, Heavy Drivers remain a quick and dirty option for a player who lags behind in technology.
Depending on luck, Heavy Drivers could cost as much as 67,500 or as little as 22,500 research points to unlock.