Enhanced grenade lethality: On target even when enemy is concealed

Army engineers worked to integrate sensors and logic devices to scan and filter the environment and autonomously airburst the fuze in the ideal spot. (U.S. Army graphic by Chris Boston)

Army engineers work to integrate sensors and logic devices to scan and filter the environment and autonomously airburst the fuze in the ideal spot. (U.S. Army graphic by Chris Boston)

By Eric Kowal, ARDEC Public Affairs

How does the warfighter launch a grenade at the enemy and ensure it hits the target, especially when the enemy is in what is known as defilade, or concealment, behind natural or artificial obstacles?

Steven Gilbert and a team of about 10 engineers within the Joint Service Small Arms Program are trying to solve that counter-defilade puzzle, which also doubles the grenade’s lethality in the process.

Gilbert is a project officer with the Armament Research, Development and Engineering Center. The engineering team is in the final phase of a project known as Small Arms Grenade Munitions, or SAGM.

The goal is to provide warfighters with the capability of shooting a 40mm low-velocity grenade out of an M203 or M320 rifle-mounted grenade launcher–with the certainty that if their target is hiding under cover or behind an object, damage will still be inflicted.

Staff Sgt. Nehemiah E. Taylor, of the Mississippi National Guard's 298th Support Battalion, fires the M203 grenade launcher during the individual weapons qualification weekend at Camp McCain, Miss. (U.S. Army photo)

Staff Sgt. Nehemiah E. Taylor, of the Mississippi National Guard’s 298th Support Battalion, fires the M203 grenade launcher during the individual weapons qualification weekend at Camp McCain, Miss. (U.S. Army photo)

In this case, according to Gilbert, the SAGM round more than doubles the lethality of the current 40mm grenade against targets in defilade.

The SAGM project began in 2011, and the solution it seeks is not expected to be in the hands of Project Manager Ammunition Systems until July 2015.

Two critical areas were identified in the request for the needed capability the SAGM project is pursuing. When the enemy is hiding, improper ranging and overshooting the target is not uncommon for Soldiers, since it is hard to locate the exact enemy position.

The first phase of the project entailed making the fuze component smaller while maintaining the same functionality. Engineers have taken a standard M433 grenade round and developed the SAGM.

Gilbert described the round as being complementary to the XM25. The XM25 is a Counter Defilade Target Engagement System, which has an onboard laser system that determines the distance to the target.

“SAGM is complimentary to that; we are not competing against it,” Gilbert explained. “The XM25 provides direct fire, SAGM is indirect.”

The second phase was making the fuze smart by including sensors. The round detonates in what is called airburst. It will detonate over and past defilade obstacles that are detected by the sensor.

During this phase, engineers worked to integrate sensors and logic devices to scan and filter the environment and autonomously airburst the fuze in the ideal spot.

40mm SAGM Grenade Prototype (U.S. Army photo)

40mm SAGM Grenade Prototype (U.S. Army photo)

“Its intent is detonate over defilade obstacles and filter out stuff you don’t want it to go off on or over,” Gilbert said.

The third and current phase includes optimizing the fuze sensor that was integrated in phase two to improve ballistic accuracy, as well as integrating the new fuze with a live high-explosive warhead.

“Warfighters currently lack the ability to achieve desired accuracy and incapacitating effects against personnel targets in defilade at ranges from 51 to 500 meters,” Gilbert added.

With this new capability, which is fully autonomous onboard smart sensors, much like a smartphone, the grenade can perform a task without being told to do so by the user. It is designed so that, when fired, it will recognize its surroundings and can detonate over an obstacle that might conceal the enemy.

The ballistic trajectory of legacy 40mm ammunition inhibits optimal engagement of personnel threats under cover. For these reasons, engineers are working to optimize ballistic trajectory and the overall accuracy and effectiveness of the grenade.

“There are three modes of firing,” Gilbert said.

“Air burst after detecting defilade is the first. The default is point detonation or when it hits the target. Lastly there is a self-destruct feature which decreases collateral damage and reduces unexploded ordnance left on the battlefield or training ranges.”

In addition to improved firepower, the SAGM round does not require the user to carry any extra gear or weapon accessories, advancing the goal of reducing Soldier load.

“We successfully demonstrated the Phase 2 sensor technology in November 2013,” Gilbert said.

“This technology demonstration was conducted at Redstone Arsenal [Ala.] and it was shown that the sensor correctly detected defilade and air-bursted the round behind the defilade. This capability will inflict maximum lethality to any enemy personnel seeking cover behind defilade,” he said.