Mortar Technology
MORTARS REPRESENT THE LIGHTEST INDIRECT FIRE CAPABILITY THAT A SMALL TEAM CAN HAVE. TECHNOLOGY IS MAKING THEM EVEN LIGHTER, MORE ACCURATE AND MORE LETHAL.
There’s a strange irony in the fact that, at the same time that some global terrorists are employing mortars to indiscriminately inflict civilian casualties, many U.S. military forces and researchers are exploiting the underlying technologies in order to deliver more accurate and responsive fires with minimum collateral damage. The irony becomes even stranger when one considers that at least one of those key efforts has fallen “below the funding line” at the very moment when it has started demonstrating its amazing potential.
Long embraced for their ability to provide maneuver force commanders with immediate indirect fire, mortars have recently demonstrated the continuing utility of their high-angle fires in modern combat operations from the mountains of Afghanistan to the urban battlefield of Fallujah, Iraq. Meanwhile, designers and developers are exploring and testing a range of technologies designed to make the systems lighter, more responsive and more lethal while simultaneously reducing collateral damage.
MORTAR FAMILIES
U.S. mortar inventories currently include three primary systems with a role of supporting fire control and ammunition subsystems. The three primary mortar weapon systems include the 120 mm M120/M121 mortar system, the improved 81 mm (I-81) M252 mortar system, and the 60 mm M224 Lightweight Company Mortar System (LWCMS).
The 120 mm mortar is fielded in both towed (M120) and self-propelled (M121) versions. Both versions use the M298 cannon tube.
The 81 mm M252 is a smoothbore, muzzleloaded weapon that replaced the M29A1 mortar. It features a high rate of fire, extended range and improved overall system characteristics and is capable of engaging targets as close as 80 meters and as far away as 5,700 meters. System components include: M253 cannon tube, M3A1 baseplate, M64A1 sight unit, and M177 bipod. The M177 bipod mount consists of a barrel clamp, two buffers, a traversing mechanism, a crossleveling mechanism, an elevating mechanism and two leg subassemblies. Both the U.S. Army and Marine Corps use the ground-mounted version of the 81 mm, while the Marine Corps also has a carrier-mounted version in its Light Armored Vehicle family.
The 60 mm M224 LWCMS is a groundmounted system that can engage targets as close as 70 meters and as far away as 3,500 meters. System components include the M225 cannon tube, M7 baseplate, M8 auxiliary baseplate, M64A1 sight unit, and M170 bipod assembly. The weapon and ammunition are currently fielded to the U.S. Army, Marine Corps and select U.S. Navy units.
SYSTEM DESIGN TECHNOLOGIES
Some recent mortar technology efforts have been directed toward “lightening the load” of portable mortar systems in an effort to expand their tactical application.
An example can be found within the Marine Corps’ Marine Enhancement Program (MEP). The program was created in response to guidance provided by Congress in 1989 for the Marine Corps to establish programs dedicated to improving the “lethality, comfort and survivability” of the individual infantryman. As described by MEP planners, “The primary intent of the program is to focus attention on low-cost, low-visibility materiel solutions that can be rapidly fielded and that typically do not compete well against larger, high profile items in the budget.”
The MEP achieves this goal through an accelerated acquisition process that utilizes commercially available technologies to quickly provide lighter, more improved “infantry items” to the Marines. Along these lines, the MEP’s FY07 prioritized initiatives included the 60 mm LWCMS.
As part of the MEP approach, lighter versions of the system’s major components—including cannon, bipod and baseplate—are reportedly being developed as a joint venture with the U.S. Army and managed as an engineering change proposal to the currently fielded system.
One representative M224 component is the M225 60 mm cannon tube/barrel assembly. The current steel tube assembly weighs 14.4 pounds.
However, under joint efforts between the Office of Naval Research (ONR) and the U.S. Army’s Armament Research, Development and Engineering Center (ARDEC), designers have been exploring a new cannon tube made from a nickel super-alloy called Inconel 718. In addition to weighing approximately 10 pounds (30 percent) less than a steel tube, the new super alloy offers superior strength at the elevated temperatures experienced by the system during sustained high rates of fire.
In early January 2007, the U.S. Marine Corps Systems Command, Infantry Weapons Systems, Quantico, Va., announced its intention to award a sole source indefinite delivery, indefinite quantity contract to Dynamic Flowform Corporation (Billerica, Mass.) for both prototypes and possible production options of the new M225 60 mm mortars.
The announcement went on to note, that “Program Manager Infantry Weapons, in conjunction with the Office of Naval Research and the U.S. Army’s Armaments Research, Development and Engineering Center, and Dynamic Flowform have jointly developed a process to flow form cannon tubes using high strength nickel superalloy 718. The flow form process is a highly specialized manufacturing capability with very specific applications to date. Dynamic Flowform is the only manufacturer possessing the requisite manufacturing capability to produce the M225 60 mm mortar cannon in the time frame required to be safety certified, tested and produced in quantities for Marine Corps operational commitments. The Marine Corps requires 18 production representative samples for testing beginning 4th Quarter, fiscal year 07 with the ability to begin production of the first mortar cannon production option [800 units] beginning 1st-2nd Quarter, fiscal year 08.”
In addition to the new technology tubes, other recent ONR/ARDEC 60 mm mortar system technology efforts have focused on examining a more compact bipod with special coatings to eliminate the need for lubricants as well as a new forged aluminum baseplate.
FIRE CONTROL TECHNOLOGIES
New technologies are also being applied in the mortar fire control arena.
The mortar fire control system (MFCS), for example, is described as “a revolutionary improvement in mortar fire control capability, linking mortar fires with the digital battlefield. MFCS combines a highly accurate weapon pointing device, an inertial navigation/position system, and a digital communications capability embedded in the fire control computer to create a highly responsive and accurate fire control system.” The MFCS allows mortar crews to send and receive digital calls for fire messages, determine the pointing and position of the weapon and calculate ballistic solutions.
Other fire control technology efforts range from a “dismounted MFCS” for the 120 mm towed mortar system to the lightweight handheld mortar ballistic computer being developed to meet U.S. Army and USMC requirements for a lightweight handheld ballistic computer to support dismounted operations.
The latter examples are representative of the expanding use of handheld fire control systems, which will be further explored in an upcoming issue of SOTECH.
AMMUNITION TECHNOLOGIES
But few aspects of the mortar arena have seen greater application of new technologies than ammunition. The best example, and the source of the greatest irony noted above, is the 120 mm precision guided mortar munition (PGMM).
The PGMM has been “a long time coming.” In fact, the U.S. Army “Mortar Plan” of July 1985, noted that a 120 mm mortar system would be a good replacement for the then-fielded 107 mm “Four-Deuce” heavy mortar, among other reasons, because “[T]he 120 mm mortar offers significant growth potential as munitions technology progresses over the life of the system. Although no programs are actively in RDTE, the Army is examining the possibility of development of a guided munition…”
Nine years later the U.S. Army Infantry School released a mission need statement for a PGMM with funding profile established for demonstration under the then Rapid Force Projection Initiative.
Just over a decade later, in December 2004, ATK received the initial $80 million system design and development contract “to give the Army an unmatched precision advantage in 120 mm mortars” through PGMM.
The 120 mm PGMM is a drop-fired munition, which flies a ballistic trajectory to the target acquisition basket. After reaching apogee, the PGMM’s semi-active laser turns on and begins looking for laser energy from the forward observer designating the target. Using control thruster firings, the projectile maneuvers to the optimum angle of attack with the warhead detonating after target impact.
In addition to ATK, major subcontractors on the PGMM program include BAE Systems in Nashua (for semi-active laser seeker) and Pacific Scientific, in Valencia, Calif. (for the rocket motor thrusters that are on the side of the projectile).
Initial end-to-end firing tests of PGMM were conducted in January of this year at Yuma Proving Ground, and were followed by a second series of test firings conducted at Yuma March 20-21.
Describing the results of the most recent firings, Dave Rathe, PGMM program director at ATK, noted, “We shot three rounds and hit the target three times. They [the targets] were about four kilometers (km) from the gun position. And this is the second time that we have really demonstrated the end-to-end capability of the weapon system. So this was a really good test for us.”
Although the earlier January test resulted in just one target hit out of four rounds, Rathe said that, subsequent to that test, “We corrected a couple of issues that we had. One was a hardware issue and the other was a software issue.”
According to Lieutenant Colonel John Lewis, product manager for mortar systems at ARDEC, the most recent test was shot off a 120 mm ground emplaced mortar system with the laser designator 1.5 km from the target.
Ironically, Lewis noted that the PGMM program “was officially terminated by the Army in February 2007.”
“We are conducting an orderly shutdown. So we are going to conduct a few more guide-to-hit series throughout the summer and then conclude the program in the August time frame,” he said.
“Given all Army programs and the funding required for them, PGMM just didn’t make the cut line,” he added. “Nobody said that it was cut for performance reasons or anything like that. That is not the case.”
In fact, both Rathe and Lewis noted the continued existence of a JROC-approved requirement for this type of capability for the 120 mm mortar system.
“ATK is actively pursuing trying to get funding restored,” Rathe said. “But that’s still to be determined as to whether we can do that or not.”
Noting hope for program revival, Rathe added, “We’re working really hard to do that. There’s a lot of interest generated in this weapon system; particularly when you go three-for-three in testing. And we’re confident that we’re going to do very well in upcoming tests as well.”
As of this writing, the next round of PGMM guide-to-hit testing was slated for mid-May at Yuma.
When asked about the type of capabilities that PGMM could bring to the warfighter, Lewis was quick to observe, “What this does is to provide the maneuver commander an organic ability to employ precision weapons without having to go through the artillery fire support system. These are his own weapons that are going to be very responsive to him.”
Clarifying the use of “prevision” in the program title, Lewis noted, “The requirement we have is to engage the target with two rounds or less. And to be able to do that we need approximately a 1 meter CEP [circular error probable].”
“I think they really change the battlefield too,” echoed Rathe. “Because they take a mortar system and not only make it a suppressive weapon but also make it a precision attack weapon as well.”
Rathe continued, “We’re really excited about this and we think we can get the program reinstated, because I really believe this is going to be a revolutionary weapon for the close fight out there. It’s particularly important in today’s situation that requires low collateral damage, which is something that PGMM can bring as well. When you have the capability to hit a target with precision you’re not just taking out a whole building. You’re taking out one room that you’re interested in.”
FUTURE CONCEPTS
While the future of PGMM remains to be finalized, other researchers and scientists are looking even further into the future at other ways to limit the collateral damage caused by mortars and other battlefield systems.
As an example of this future vision, one of the more interesting new technology approaches to limit collateral damage recently emerged from the U.S. Department of Energy’s Lawrence Livermore National Laboratory (LLNL). In late April 2007, LLNL announced the opportunity to “license and commercialize its selectable yield technology for conventional munitions.”
Noting that “Applying appropriate force on target is important for any conventional explosives such as grenades, mortars, artillery, mines and air drop munitions,” the announcement read. “Traditionally, munitions have a fixed explosive yield. In order to avoid collateral damage an appropriate choice in munitions is paramount.”
The mechanism suggested by the LLNL technology is to limit collateral damage by “deflagrating” some unwanted amount of explosive yield and detonating the remaining amount. The resulting effective conventional yield would be determined by the timing differences between the deflagration fuse and detonation fuse.
Although industry interest in the approach remains to be determined, it marks one more milestone on a clear path in which the combat utility and viability of mortar systems have never been greater, with technology attempting to make those systems lighter, more responsive and much more accurate.
It remains to be determined where various aspects of those technologies fall in relation to funding lines. ♦