Army Shows Off Awesome Automatic Mortar System That’s Still Too Expensive To Field

The Automated Direct Indirect-fire Mortar uses computer controls to manage recoil forces and make the weapon more precise.

byJoseph Trevithick|
Mortars photo


The U.S. Army is looking to invest heavily in upgrading its long-range artillery capabilities, including new howitzers, rockets, tactical missiles, and even railguns. At the same time, the service is working on a smaller, rapid-fire 81mm mortar with advanced computer-controlled features that reduce recoil, extend range, and improve accuracy that could offer extra firepower to smaller units.

On April 6, 2018, soldiers from the 2nd Brigade Combat Team, 1st Infantry Division, with help from the Army’s Armament Research, Development, and Engineering Command, experimented with the weapon, called the Automated Direct Indirect-fire Mortar (ADIM), during a multi-national training exercise in Germany. That event, known as the Robotic Complex Breach Concept, included a number of other advanced and prototype systems, including small drones, loitering munitions, and remote-controlled engineering vehicles. The main objective was to demonstrate how these various capabilities might enable a large mechanized force to break through various obstacles during a high-end conflict.

“The breach is one of the most difficult tasks that soldiers can be faced with on the battlefield,” Keith Briggs, the assistant engineering lead for the exercise, told Army reporters. “The ADIM was a great asset to our breach today and definitely increased our survivability,” U.S. Army 1st Lieutenant Cody Rothschild, a fire support officer from the 2nd Brigade’s 1st Battalion, 7th Field Artillery Regiment, added.

ADIM’s main components are the 81mm mortar mounted and a powered base that can rotate 360 degrees and elevate and depress the weapon’s barrel. As the name implies, troops can fire it indirectly like an artillery piece or straight at the enemy like a small infantry gun. The whole system sits on the back of a modified M1152A1 up-armored Humvee. But any similarities to a typical vehicle-mounted mortar end there.

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Most infantry mortars have no built-in recoil reduction mechanism, which is a feature generally more commonly found on larger howitzers and other guns. When Army soldiers fire their standard M252 81mm mortar, the force goes straight into the firing platform, whether it’s a vehicle or the ground.

ADIM has a so-called soft-recoil system that sends the barrel sliding forward before it actually sends a projectile flying down range. The momentum helps counteract the recoil.

The ADIM prototype moves into position during the Robotic Complex Breach Concept exercise., US Army

This arrangement means that the weapon can withstand more recoil, but remain relatively compact. In turn, it can shoot rounds with larger propellant charges and therefore increased range, but without making the entire system significantly larger to handle the additional strain of firing that ammunition.

On top of that, the mortar has a computer-controlled active recoil braking system that uses sensors to monitor the exact amount of force throughout the firing cycle. This further helps the system only accelerate and decelerate as necessary.

An official briefing slide highlighting ADIM's active-recoil components and offering additional performance details., US Army

A typical hard- or soft-recoil system has to be built to withstand the highest expected recoil by default, even if troops rarely employ the weapon in that way. ADIM’s active-recoil components mean it can better account for fluctuating variables, such as different amounts of propellant, temperature variations, and small differences in manufacturing tolerances without the need to make the system larger and more robust.

Army engineers say that, in general, a typical 81mm mortar would generate up to 10,000 pounds of recoil force, while the active-recoil enabled ADIM only produces a maximum of 2,000 pounds. This inherently makes the weapon more accurate, too, since there are fewer conflicting forces acting on the round as it leaves the barrel.

Another briefing slide with a cut-away diagram of the braking mechanism itself., US Army

In addition, there is a computerized fire control system that makes the weapon even more precise. This networked Automated Fire Control System-Mortar (AFCS-M) also means a centralized fire direction center can operate the weapon remotely, reducing the time it takes to go from a request for fire support to actually hitting the target.

ADIM is also semi-automatic, able to feed from a 20-round magazine and fire around 30 rounds per minute. In theory, this means, a small crew could position the weapon, have other troops operate it remotely, and then rapidly move to another location, either to better engage a new target or avoid counterattacks.

The heavily computerized nature of the system could make it readily adaptable to precision-guided mortar rounds in the future. The Army, along with the U.S. Marine Corps, is in the process of developing GPS- and laser-guided mortar bombs.

General Dynamics Roll-Controlled Guided Mortar (RCGM) GPS-guided 81mm mortar round., General Dynamics

These advantages don’t come cheap, unfortunately, and could explain why the ADIM remains largely a technology demonstration effort after nearly a decade. The Army first initiated the project in 2011 and has just the one prototype example. It had spent years before that experimenting with a weapon system known as Scorpion, consisting of a simpler Humvee-mounted Soviet-designed 2B9 Vasilek soft-recoil, semi-automatic mortar. That weapon feeds from four-round magazines and has a practical rate of fire of up to 180 rounds per minute.

The last time the service appears to have requested money directly for ADIM, in its 2015 fiscal year budget proposal it asked more than $1.8 million for continued development and testing. To put this in context, in its latest request for the 2019 fiscal cycle, the Army wanted just less than $12.5 million in the base budget to pay for the continued procurement of dozens more 60mm, 81mm, and 120mm infantry mortar systems combined.

The Army's Scorpion system, a Humvee armed with the Soviet-designed 2B9 Vasilek., US Army via HMMWV In Scale

In 2015, the Army acknowledged that the active-recoil system, in particular, had proven to be too costly in the past to make it practical for weapons, such as mortars, which are present in a large number of units. Though the service said the price point was coming down, there would still undoubtedly be increased sustainment costs associated with issuing ADIM and its computer-controlled firing mechanism on a wide-scale.

The added complexity of mechanical soft-recoil systems has proven difficult enough to make worthwhile in the past. The Army worked to develop a combination 105mm and 155mm soft-recoil howitzers in the 1970s before canceling the project and made a second abortive attempt at a similar system in the 1990s.  

The video below describes the Army's Cold War-era XM204 howitzer effort.

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There is the possibility that the research and development into soft- and active-recoil could apply to larger weapons, which might help spread the burden of certain costs. The Army is very interested in finding ways to squeeze additional range out of its existing 155mm howitzers and replace its 105mm types with an overall more capable system that is still lightweight.

Another option might be to pitch ADIM, or a derivative of the system, as a more effective, mobile fire support system for defending remote operating bases, which was one of the project’s original goals. Special operations forces are already employing a more traditional computer-assisted, fixed emplacement 120mm mortar system in combat with support from the Army logistics chain.

The business end of the ADIM weapon system., US Army

The Army could look to bring in other services, as well. The Marine Corps recently retired its towed 120mm mortars and is looking for new lightweight fire support systems that are still mobile enough to keep up with its expeditionary operational concepts.

There’s no doubt the new mortar offers impressive performance, but after almost 10 years of research and development, it’s not clear whether it will be able to succeed where similar past efforts have failed.

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