High-Tech Defense Gun Misses as Navy Accidentally Blasts Own Ship

People and tech screw up, big time—and Navy doesn’t want to talk about it

On Nov. 16, the Navy cruiser USS Chancellorsville was accidentally struck by a target drone during a training exercise off the California coast, resulting in some damage to the warship and injuries to two sailors.

In the incident’s aftermath, Navy reps tried to spin the story as a minor incident. “The ship remains capable of operations,” the official press release stressed. “However it did sustain some damage and will return to its home port of San Diego to have the damage assessed. The Navy is investigating the cause of the malfunction.”

But the official statement left out a key detail—one that could have serious ramifications for the world’s leading maritime force as it shifts to an increasingly tense Western Pacific.

The detail is that a Phalanx point-defense gun aboard Chancellorsville tried to shoot down the apparently malfunctioning BQM-74 target drone—and missed. The 270-pound drone, built by Northrop Grumman, is essentially an anti-ship cruise missile without a warhead. If the Navy can’t shoot down a BQM-74, it could be equally likely to miss a real cruise missile with a live warhead during some future shooting war with, say, China.

The Navy’s press release did not mention Chancellorsville’s reported failed attempt to defend herself. That critical bit of information was provided by an unnamed source to Raymond Pritchett, whose influential blog Information Dissemination has a strong Navy following. “This incident is a big deal,” Pritchett wrote.

Lt. Richard Chernitzer, a Navy spokesman, responded only briefly to our repeated inquiries. “We're still investigating what happened and because of that I'm not really able to give you more information,” Chernitzer wrote via email.

A BQM-74 drone being launched. Navy photo

Timeline of a screw-up

On the early afternoon of Nov. 16, the 9,800-ton Chancellorsville was off the West Coast testing its sensors and weapons—standard procedure before a months-long deployment to a potential conflict zone such as the contested Western Pacific.

Personnel on the ground at Point Mugu, a Navy facility in southern California, launched the 12-foot-long BQM-74 toward the cruiser. The goal, apparently, was to help Chancellorsville’s 300-strong crew practice with the vessel’s Aegis air-defense system, which combines radars and long-range surface-to-air missiles.

Navy regulations specify that the target drones, steered via radio signal by the operators on the ground, should never be directed straight at a warship. But someone or something screwed up and the drone set a course right toward the cruiser. It’s unclear whether the aiming error occurred among the people at Point Mugu or with hardware or software inside the BQM-74.

In any event, the drone was supposed to make a turn away from Chancellorsville at a distance of more than a mile but, for reasons that are unclear, kept barreling straight in. The vessel’s Phalanx gun reportedly opened fire—and missed. Flying at hundreds of miles per hour, the robot struck the warship’s hull, punching a hole in the metal skin and apparently igniting a fire that burned two sailors.

Phalanx firing. Navy photo

The never-miss gun

The Phalanx gun, produced by Raytheon, is a last-ditch “close-in” defense system. A fast-firing 20-millimeter Gatling gun fitted with a highly sensitive short-range radar, Phalanx automatically detects and shoots at incoming missiles, planes, helicopters and small boats. Fully spun up, the gun spews up to 4,500 rounds per minute.

Phalanx is extremely reliable, having shot down targets drones in hundreds of tests since the system’s introduction in the 1980s. A land-based version of the gun is used by U.S. ground forces to destroy insurgents’ rockets and mortars, again with a very high rate of success.

The close-in weapon is not perfect. In the past, Phalanx has been too accurate—actually hitting and severing the cables used by warplanes to tow gunnery targets for ships. That can cause the target to drift down toward the ocean, potentially placing nearby vessels in the gun’s line of fire. That danger has forced the Navy to rewrite the parameters of its live-fire tests.

It’s also possible for the stream of bullets from Phalanx to hit but not fully stop an incoming target. In 1983, a Phalanx aboard the frigate USS Antrim blasted a target drone, but debris from the ruined robot still struck the vessel, starting a fire and killing a man.

And most notably, Phalanx is programmed to shoot at only certain kinds of radar contacts—those moving in directions and at speeds and altitudes consistent with missiles, aircraft or boats that might threaten the warship. If a threat moves in a way that the Phalanx’s fire control does not expect, the missile, plane or boat could entirely escape the gun’s notice.

Weaknesses and liabilities aside, Navy officers still swear by the automated gun. “It really works,” says Pete Daly, a retired vice admiral who is now CEO of the U.S. Naval Institute. In 1995, Daly was in command of the destroyer USS Russell off the Hawaiian coast. An operator launched a BQM-74 from Kauai and accidentally steered it directly at Russell. The destroyer’s Phalanx shot the robot from the sky. “The close-in system worked perfectly,” Daly tells War is Boring.

The damage to ‘Chancellorsville.’ Via Information Dissemination

Accidental ship-killer

But that was then. Last month, Chancellorsville’s Phalanx allegedly did not work at all. And that should make the Navy very, very nervous. China possesses one of the world’s biggest anti-ship missile arsenals. With the Navy moving more warships into the Pacific, Phalanx can’t afford to miss.

Perhaps Chancellorsville’s crew activated the Phalanx too late for a successful engagement—in which case, it’s not the gun’s fault it didn’t stop the drone.

But there’s a more frightening possibility. BQM-74 drones are tailored to simulate different kinds of enemy anti-ship missile. If Chancellorsville’s Phalanx did indeed fully fire at the robot and failed to hit, it could mean the drone—either by design or by accident—found a gap in the gun’s fire control. Perhaps the drone was moving too fast, too slow or too low. Any enemy missile matching the drone’s physics could dodge American ships’ defenses.

Let’s be clear: this is pure speculation on our part. It’s impossible to say for sure what went wrong until the Navy completes its investigation. And that’s assuming the sailing branch makes its findings available to the public.

Pritchett, for one, seems to doubt the Navy will be forthcoming. “On the first day there [was] already a deception effort underway to conceal key details of the incident,” he wrote.

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