[RainMan]

That would be my guess. The Gatling Gun was the original multi-barrel rotating gun, but rotation was based on mechanical intervention (turning a crank). I believe the genre is now referred to as either an autocannon (if based on the 20mm M61) or minigun if based on a smaller caliber and both use an electric motor. The Phalanx is completely automated with minimal inputs from the ship, so that it can continue to protect the ship even if the ship has suffered damage. The R2D2 houses its targeting radars. The Phalanx is an autocannon with the M61 using 20mm projectiles.

FWIW, the A-10 Warthog uses a bigger version of the autocannon ... the GAU-8 Avenger 30mm.

[Max in Utah]

The 20 mm autocannon was originally designed for use against human wave assaults, such as those launched by the Chinese during the Korean War.

[cport]

That is correct, RainMan. I was an FC on the USS Independence, and we had one on the starboard side of the island, one port side aft, and one port side on a sponson just below and forward of the waist cat. Those 20 Mike mike projectiles pack a hell of a punch being made of depleted uranium. The shells are fired electronically as well, meaning we had to go to EMCON in order to load the magazine. Back up batteries ensured operation even after losing ship's power. Approximately 3000 round per minute fire rate.

What was cool about R2D2 with a hard-on is that it was entirely self contained. Most fire control systems don't have a search radar. The continuous wave radar associated with the missile or gun system had to use either a saw tooth or step pattern to acquire a target if it didn't receive target designation from a search radar. Precious seconds when a mach+ target is coming at you. CWIS has it's own independent little search radar under the dome, which then sends it's own target designation to it's second CW fire control radar. Acquisition in less than a second. I loved my job.