4,500 rounds a minute: how the Phalanx defends a ship
Published
A Phalanx fires 4,500 rounds a minute, 75 every second, from a 1,550-round magazine[1]. That is about 20 seconds of fire before it is empty. It is a ship’s last line of defence: a 20 mm[3] Gatling gun for whatever gets through.
The last line
The Phalanx is a close-in weapon system: its maximum effective range is 1,486 m[2]. It is there for the threats that get past everything else.
In game
The carrier carries three medium point-defence mounts, sized for a full Phalanx:
| Mount | Where | Traverse | Elevation |
|---|---|---|---|
| Port pod | on top of the port engine pod, facing out | ±150° | −25° to +90° |
| Starboard pod | on top of the starboard engine pod, facing out | ±150° | −25° to +90° |
| Belly | under the hull, aft | all round | −10° to +90° |
In space an attack can come from straight above, so the mounts reach +90°. Tested against 1,200 directions, every direction is covered except one nearly overhead, and about 45 % of directions are covered by only one mount. Counting what the hull itself blocks, 4 directions are uncovered: thin cover, on purpose.
How it fires, in game:
- 25 rounds a second are shown. Each tracer stands for three real rounds; the 20 seconds of fire is real. Every shown round’s hit is rolled, which keeps the fight readable and the simulation cheap.
- Muzzle speed 1,100 m/s.
- It fires only when within 1° of the lead point, and leads with the target’s tracked speed and acceleration.
- It re-picks its target 4 times a second, the way a fire-control radar keeps its track, and picks the target it would hurt most.
- 500 rounds per mount: 20 seconds of fire, close to the real gun’s[1]. Reloading takes 5 seconds.
Range by tech level. Each weapon’s range in game comes from how tightly it groups its rounds. At Mk3, the carrier’s level, point defence reaches 1,250 m, a little short of the real Phalanx’s 1,486 m[2]. Lower levels reach 500 m (Mk0), 625 m (Mk1) and 833 m (Mk2).
Hits and damage. Point defence is +25 % accurate against small craft. Against a Mk3 fighter, which is hard to hit, a Mk3 mount hits about 45 % of the time; against a Mk1 fighter, 99 %. Each hit does 10 damage to a fighter, and a Mk3 fighter has 360 hull, so it takes about 36 hits.
Guns that hide
The game’s mounts can retract. Pulled in, a gun sinks into the hull under an iris cover: it can’t fire, and it can’t be shot. On Auto, a mount comes out when an enemy could be in reach by the time it is out, and goes back in 3 seconds after the last threat. It takes 1.5 seconds to come out, and it can fire, and be hit, from halfway. Each mount can be knocked out on its own.
The carrier starts with 20,000 light rounds in its hold, shared between its mounts and its fighters.
Related
- 350 m long, 80,000 hull: the carrier
- 74 to 78 aircraft: what a US carrier air wing carries
- 747 rounds, 146 hits: the same fight, watched or not
Sources
- Phalanx CIWS, Wikipedia.
The Block 1A and newer (pneumatic driven) CIWS mounts fire at a rate of 4,500 rounds per minute with a 1,550-round magazine.
- Phalanx CIWS: specifications, Wikipedia.
1,625 yd (1,486 m) max. effective range
- Phalanx CIWS: specifications, Wikipedia.
20 mm (0.79 in)