C-RAM: An Advanced Automated Point-Defense Gatling Gun

C-RAM is the US Army's answer to indirect fire from mortars, artillery shells, and missiles.
Christopher McFadden

Indirect fire from mortars, missiles, and artillery shells is a very serious concern for armed forces in battle. But, thanks to point-defense systems, like the C-RAM, indirect fire of this nature may have met its match. 


What is C-RAM?

C-RAM, standing for "counter rocket, artillery, and mortar," is an Indirect Fire Protection Capability (IFPC) weapons system developed in order to protect ground forces and forward operating bases from the threat of rockets, artillery, and mortars. C-RAM is not simply a single gun, rather it is made up of a variety of different systems which provide command and control capability, along with the ability to sense incoming rounds, warn, respond, and intercept.

C-RAM components include the Forward Area Air Defense Command and Control (FAAD C2), Land-based Phalanx Weapon Systems (LPWS), Lightweight Counter Mortar Radars (LCMR), Firefinder radars, Ka-band Multi-Function Radio Frequency Systems (MFRFS), Air and Missile Defense Workstation (AMDWS), and several other components.

A main component of the C-RAM system is the LPWS. This has been modified from the U.S. Navy MK-15 MOD 29 Block IB, Baseline 2 Close-In Weapon System. Another component, the M61A1 20mm Gatling gun, is capable of acquiring its target and firing at a rate of 4,500 rounds per minute. The Forward Area Air Defense Command and Control (FAAD C2) system integrates the sensors, weapons, and warning systems to intercept incoming rocket and artillery.

One major difference between the land- and sea-based systems is the choice of ammunition. The naval Phalanx systems fire tungsten armor-piercing rounds, while the C-RAM uses 20mm HEIT-SD (high-explosive incendiary tracer, self-destructing) ammunition. These rounds explode on impact, or on tracer burnout, reducing the risk of collateral damage if rounds fail to hit their target.

C-RAM firing
Source: Military Archive/YouTube

The C-Ram's naval equivalent, the Phalanx Close-In Weapons System (CIWS) was first developed as an automated weapons defense system in 1973, and incorporated a 20 mm M61 Vulcan Gatling gun autocannon, used since 1959.

The Navy Phalanx system was first appraised as a possible ground-based variant in 2004. Phalanx was selected partly because it could be readily interfaced with a multitude of sensors and systems designed to provide an overarching protection umbrella of sites on the ground.

In its land-based configuration, the LPWS system is mounted on a wheeled platform in order to provide enhanced stability on-site, and mobility for repositioning and deployment. 

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C-RAM test fire
Source: US Army

The Centurion C-RAM can, for example, be mounted on a trailer or the rear side of the Oshkosh truck. In October 2008, Raytheon and Oshkosh unveiled the Mobile Centurion, which mounts the system on a hybrid-electric HEMTT A3 heavy truck.

The first battle-ready C-RAM system was deployed to Iraq in 2010 in order to protect the "Green Zone" —  an area in Baghdad used as an Amerian embassy. Trials of this system showed that it was capable of knocking out 70-80% of rockets and mortar shells fired within its area of control. 

In fact, the system was used to defend the embassy just before Christmas in 2020. 

As of 2013, the Army Acquisition Executive (AAE) designated C-RAM Intercept an Army acquisition program and authorized fielding of LPWS guns and support equipment to the IFPC/Avenger battalions. Fielding is ongoing.

C-RAM on trailer
C-RAM on its primary mover. Source: u/PTRJK/Reddit

The C-RAM system has successfully intercepted hundreds of rockets and mortar shells fired at the "Green Zone", thereby proving the system's capability as a defensive system.

How does the C-RAM weapon system work?

Like its naval counterpart, the C-RAM utilizes advanced search-and-track Ku-band radar systems that feature closed-loop spotting technology to automatically acquire and track targets and engage them. Ku-band, in case you are not aware, is a portion of the electromagnetic spectrum in the microwave range of frequencies between 12 and 18 gigahertz (GHz)

Similar systems were installed on the Space Shuttle to help identify and track other spacecraft. 

The system can also be integrated with an array of other sensors and systems to help provide an overarching protective "umbrella" to protect a given location on the ground.

The weapon's primary armament is the 20mm "Vulcan" Gatling gun, it consists of six optimized barrels augmented with forward-looking infrared (FLIR) sensors. The barrels are secured together at the muzzle, mid-barrel, and breech to provide enhanced accuracy and enable fire to constrain shot dispersion patterns.

C-RAM and crew
Source: U.S. Army

The M61 is a hydraulically, electrically, or pneumatically driven, air-cooled, electrically fired Gatling-style rotary cannon that has been in used, in one form or another, on various fixed-wing military aircraft, tanks, and ships, for over 5 decades. It was originally produced by General Electric. 

The U.S. Army also uses the M61 in the M167 and M163 air defense systems as the primary gun system on the F-14F-15, F-16, and F-18 fighters of the USAF. The gun is also used as the tail gun on the B-52H bomber, while a lightweight variant is used on the F-22 Raptor fighter.

But all that firepower is also half the story. If you can't track and accurately put the cannon rounds in the right place at the right time, you basically have a fancy piece of pyrotechnics.

This is achieved through a combination of advanced sensors that enables the C-RAM to simultaneously search, track, engage incoming targets and prioritize targets and make kill assessments in both daytime and nighttime. 

C-RAM's Ku-band radar system enables the weapon system to detect potential threats early in their flight and then pass on their trajectory and vector data to the system's tracking algorithms only when it judges them to be a real and present danger.

C-RAM firing
Source: U.S. Army

Target tracking and engagement is further enhanced by a sophisticated thermal imaging system to help improve targeting. This system operates in the 8-12 micron wavelength range and is mounted on a stabilizing pedestal attached to the weapon's main antenna radome. 

It provides very reliable night-and-day passive search and tracking while also improving the overall anti-air warfare performance of the system in multi-path environments. 

Other tracking systems integrated into the Centurion C-RAM system include Northrop Grumman’s AN/TPQ-36 short-range Firefinder radar and the Lightweight Counter Mortar Radar, to detect and track fired rounds. This hardware is controlled by fire-control subsystems, like Northrop Grumman Mission Systems' Forward Area Air Defense Command and Control (FAAD C2) system, which ties together the sensors and weapons of the Army’s short-range air-defense battalions.

How much does C-RAM cost?

As you might expect, such a sophisticated piece of kit does not come cheap. Each C-RAM system costs somewhere in the region of $10 to $15 million depending on the final spec of the units purchased.

C-RAM closeup
Phalanx system installed on the USS Jason Dunham. Source: Paraxade/Flickr

But that is only the cost to initially acquire the technology. With such a massive rate of fire, this unit literally "burns through" bullets. Depending on the number of munitions spent, A typical engagement with a single missile could range from between $30,000 and $60,000 dollars

Some other estimates put the figure at around $40,000 per missile. This is not only costly from a material point of view but is also one of the main disadvantages of the system.

By spending so much ammo on a single threat, a limited ammunition supply will theoretically limit the number of threats that the unit can engage at a given time. By some estimates, this might mean that the Centurian C-RAM might have a maximum anti-RAM cap of about 5 incoming rounds before needing to be reloaded.

The system has some other perceived weaknesses too. For example, it takes around 5 seconds to acquire, lock on to, and engage a threat. It also has a fairly short effective range of between 109 to 1093 yards (100 and 1000 meters)

These weaknesses aside, it has shown itself to be one of the most effective anti-missile, mortar, and artillery defense systems in the world. For this reason, it will likely remain an important player for many armed forces around the world for many years to come.