Researchers, engineers work to improve safety of munitions
By William H. Ruppert, IV, P.E., Program Manager, Joint Insensitive Munitions Technology Program
It’s the year 2045 and your grandchild is deployed to the hot spot of the future, commanding a ground unit combating the latest terrorist group. The vehicle he is riding in is suddenly struck by two rocket propelled grenades. The vehicle interior is breached and the ammunition inside sustains a direct hit, but none of them explode and the crew has only minor injuries. They quickly assume their respective defensive positions from inside the vehicle and return fire on the aggressors, decisively defeating them. Their training and their equipment have not failed them. They will live to fight another day.
This may sound too farfetched or even impossible, but at the U.S. Army Research Laboratory, researchers lead and support the Joint Insensitive Munitions Technology Program, or JIMTP, to develop safer munitions with the goal of ensuring the safety of our future warfighters.
The JIMTP is a unique partnership of government, industry and academic partners. The Office of the Secretary of Defense has program oversight, but it’s managed by ARL, and laboratories within the Air Force and Navy provide technical management. The partnership is essential to ensure the maximum return on investment in a time of increasing fiscal constraint.
These partners are working together to reinvent the way munitions work – making them almost impossible to ‘go off’ when the warfighter doesn’t want them to – while at the same time improving the lethality, reliability, safety and survivability of munitions.
The ideas behind Insensitive Munitions, or IM, are not new; DoD has been working to improve the safety of munitions since their inception. After several incidents during peacetime and combat operations that destroyed entire depots of vehicles and munitions, and heavily damaged several aircraft carriers, military leaders approved research dedicated to developing less sensitive munitions. Ultimately, as a result, Congress passed the ‘Insensitive Munitions Law’ in 2001 that specifically requires “The Secretary of Defense [to] ensure, to the extent practicable, that insensitive munitions under development or procurement are safe throughout development and fielding when subject to unplanned stimuli.”
These unplanned stimuli take the form of rapid or slow heating events, such as a fuel fire on a vehicle or aircraft, or an adjacent fire in a vehicle or storage magazine; impact by fragments or bullets due to shrapnel from nearby explosions or small arms fire from combat or terrorist events; sympathetic reaction due to the detonation of adjacent munitions; and shaped-charge jet attack from rocket-propelled grenade or similar weapons used by enemy and friendly forces.
However, it was not until 2007 that the department focused its efforts on developing joint (Army, Air Force, Navy and Marine Corps) solutions through a centrally-managed program. The JIMTP Program Office funds projects led by investigators across the Services, the Department of Energy laboratories, as well as industry and academia through the National Armaments Consortium.
This partnership has been extremely fruitful in the pooling of knowledge from scientists and engineers who otherwise would never have worked together. As an example, the primary candidate explosive fill for the insensitive 500-pound general purpose bomb was developed under JIMTP leadership. The fill was developed at an Army laboratory, specifically the Armament Research Development and Engineering Center, tested at a Navy facility, the Naval Surface Warfare Center in China Lake, Calif., and supplied by industry, BAE-managed Holston Army Ammunition Plant in Tenn., with project management by Air Force personnel at Eglin AFB, Fla.
JIMTP also led the effort to ensure smooth transition once the fill is proved out by assembling the acquisition personnel from the Army, Navy and Air Force as part of a Joint team to plan testing and transition in a synchronized fashion.
Insensitive Air-To-Ground Missile Propellants
The path to developing stockpiles of insensitive munitions is a long, slow, deliberate journey of incremental improvement, whereby one or two IM attributes are addressed in a new formulation or mechanism. One example of this work is being conducted at the U.S. Army Aviation and Missile Research, Development and Engineering Center at Redstone Arsenal, Ala. Rob Esslinger, from the Weapons Development and Integration Directorate there, leads the Tactical Minimum Smoke Phase I IM Demonstration project. Esslinger is aiming to develop and demonstrate rocket motors for air-to-ground missile systems that are less sensitive to fragment impact and slow cook-off threats. Throughout the last six years, Esslinger’s team from AMRDEC, Redstone Arsenal Test Center, and the Naval Air Warfare Center at China Lake have joined with industry partners ATK and Aerojet-Rocketdyne and the Joint Attack Munition System Program Management offices to research various rocket motor configurations, seeking to improve the threat responses.
Using several venting technologies and rocket motor formulations in composite and metal rocket motor cases, the team has successfully demonstrated that various formulations and venting configurations combined with composite motorcases enable the rocket motor designs to pass the initial fragment impact and slow cookoff tests.
This year the team plans to conduct rocket motor test firings on articles that have undergone temperature and shock extremes to simulate the environments of the real world, such as transportation and handling, captive carriage loads, and thermal shock resulting from altitude fluctuations. If these tests are successful, they will prove that the performance of IM rocket motors can match or exceed those of the currently fielded motors. In addition, these new, safer motors will be qualified for future air to ground missile system applications.
Although the work was initially focused on air-to-ground missiles, it has also gained the interest of the Close Combat Weapon Systems Project Office for application on the tube-launched, optically-tracked, wireless-guided, Javelin and Griffin missile systems. With CCWS support, JIMTP has provided additional funding to have the team conduct testing that will serve as risk reduction efforts for the transition of technologies to system development efforts and planned product improvements. The specific technologies of interest are a low-cost composite motor case, less shock-sensitive propellant, and cookoff venting devices. While it sounds simple to have two programs interested in similar technologies under development, each has their own unique challenges. The differences in motor diameter, propellant mass, and performance parameters, such as the presence of a launch motor in the ground launched systems and flight weight considerations for the air launched systems, resulted in significant propellant formulation tailoring and careful attention to the venting considerations in order to provide solutions to the two very different operating regimes.
The leveraging of funds and assets between the JAMS and CCWS Program Management offices and the JIMTP-led project has resulted in real financial savings for each organization. This key collaboration has enabled all parties with a vested interest in the technology development and demonstration efforts to have input into the final designs and products. Final full scale IM and static testing of the various motor configurations for AGMS, TOW, Hellfire and Javelin are scheduled to be completed by the end of fiscal 2014.
Rocket and Missile Warheads
JIMTP is also working to improve the IM properties of the TOW 2B and Tomahawk Missiles in the project “Anti-Armor Warhead IM Technology Integrated Demonstration and Transition,” led by Nausheen Al-Shehab, from ARDEC), Energetics, Warheads, and Manufacturing Technology Directorate at Picatinny Arsenal, N.J. AlSehab’s effort focuses on improving the warhead response to impact, sympathetic reaction, and cook-off threats. The team is composed of scientists and engineers from ARDEC, Naval Air Warfare Center at China Lake, AMRDEC, Naval Postgraduate School, Program Manager Air-280, PM CCWS, and industry partners (General Dynamics-Ordnance and Tactical Systems, Dynetics and CGI Federal) that have worked to integrate, demonstrate, and eventually transition multiple IM technologies into new anti-armor warhead designs that increase operational survivability of the munition. For the TOW 2B warhead, the primary areas of focus are cook-off (both fast and slow) and impact (both bullet and fragment) through multiple shotlines; while sympathetic detonation and fragment impact are the primary and secondary focus areas for the Tomahawk warhead.
JIMTP is developing a TOW 2B warhead that utilizes proven venting technology and a particle impact mitigation sleeve to improve the IM response while still meeting the performance requirements. PIMS aids in reducing the shock transmitted to the explosive by distributing the shockwave over a larger area and reduces the shock as it passes through the material. JIMTP has successfully demonstrated the TOW 2B warhead to pass the initial fragment impact tests at high and low velocities using a composite PIMS. JIMTP has also shown that venting technology successfully mitigates the fast cook-off threat.
Integrating these technologies is not simple. It requires significant design, analysis, and test and evaluation, to ensure an improvement in one IM aspect does not negatively impact the performance or reaction in another IM threat aspect.
Modeling and simulation was used extensively to evaluate the various PIMS designs, by determining the pressure reduction within the explosive as a result of using the PIMS designs, with lower pressures providing increased shock protection. This design tool has enabled the review and revision of the PIMS liner thickness and optimization prior to testing. Modeling was also used to determine the effect of the PIMS design on the location of the pre-ignition hot spots within the explosive formulation of the warhead during exposure to slow heating in order to address any concerns. This year, the team plans to conduct IM tests to reduce the overall weight impact of the PIMS for the lower velocity fragment impact test.
Modeling and simulation was also used to predict the result of the Tomahawk warhead responses to a sympathetic reaction threat. The modeling results lead to the selection of a new PIMS technology and insensitive main fill explosive to be pursued to reduce the response to a sympathetic detonation. The shaped-charge liner was also modified for the explosive fill and reactive liner. One-quarter scale warhead configurations integrating the new technology were built and tested, to compare the models predicted performance and reaction severity with the actual results. The scaled warheads performance validated the model, enabling the team to move to the final phase of the project – down selecting the best configuration and moving to full-scale asset production and testing. The production of full scale assets has begun and testing is scheduled to be conducted in early fiscal 2014.
The DoD will continue to develop new munitions to meet increased performance requirements to respond to various threats and enable lethality overmatch in any scenario. Using today’s available technology to obtain higher performance typically translates to a worse IM response. As a result, the JIMTP has its work cut out to try to both improve performance and IM. Novel, high-risk approaches will have to be investigated. This may include ‘tunable’ munition response through materials that become propulsive or explosive by stimulating them with lasers, microwaves, electricity, or magnets, or it might include out-of-the-box concepts for initiating explosives or significant overall munition design changes. To optimize our limited financial resources and increase our chances of success, we must develop solutions utilizing a joint approach, tapping into the knowledge and skills of the scientists and engineers in all services, DOE, industry and academia.
Less sensitive munitions have been in development for many years, with each technology breakthrough increasing our ability to keep Soldiers, Sailors, Airmen and Marines safer. The incremental improvements we are making today as evidenced by the on-going work at the major Army, Navy, Air Force, Department of Energy and industry facilities for various weapon systems will improve the safety of future weapons as well. The JIMTP is committed to developing and transitioning these incremental improvements so our future warfighters, our children, grandchildren, and beyond, operate in an environment where their own munitions are not their worst enemy.
ARL, AMRDEC and ARDEC are part of the U.S. Army Research, Development and Engineering Command, which has the mission to develop technology and engineering solutions for America’s Soldiers.
RDECOM is a major subordinate command of the U.S. Army Materiel Command. AMC is the Army’s premier provider of materiel readiness — technology, acquisition support, materiel development, logistics power projection, and sustainment — to the total force, across the spectrum of joint military operations. If a Soldier shoots it, drives it, flies it, wears it, eats it or communicates with it, AMC provides it.
Editor’s Note: Rob Esslinger of AMRDEC, Nausheen of Al-Shehab of ARDEC and Jeff Brock of ARL contributed to this article. As the Program Manager, William Ruppert leads the Joint Insensitive Munitions Technology Program, which consists of five Munitions Area Technology Group leads, 11 co-leads, more than 50 primary investigators, more than 100 scientists and engineers from all services, the DOE and industry. The JIMTP supports the DoD acquisition community and is the centralized investment for the advancement of basic understanding of sensitivity, development of new materials and formulations with improved sensitivity characteristics, and integrated systems showing improved insensitive munitions response.