While it is clear the Zumwalt class is basically a test bed in the form of a possibly deployable vessel, they did build the infrastructure into the ship electronically to be able to drive a rail gun.
They have an integrated Power System (IPS) that can take 80 MW generated by four marine turboshaft generators, and distribute the power flexibly.
That is a huge amount of power, enough for a railgun, but I suspect they just couldn’t work out the bugs in time to put it aboard, so they have a 155 mm main battery.
so they have a 155 mm main battery.
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Isn’t that the battery for which they have no ammo?