ARMY AL&T
On Sept. 12, 2009, a Mine Resistant Ambush Protected (MRAP) vehicle in Ng’s convoy was destroyed by a very powerful improvised explosive device (IED). The IED ruptured the vehicle’s hull and fuel tank, which engulfed the vehicle interior in fl ames—to include 16 M768 60mm mortar cartridges that were carried inside the cabin with the 7-man crew. Although several Soldiers were seriously injured in the ambush, all survived. Thanks to the IM features of the M768 cartridges, a much greater disaster was averted.
M768
The M768 incorporates several IM features, including new energetic mate- rials in the fuze and shell body. It also contains a plastic fuze adaptor that melts in an accidental fi re, allowing the fuze to separate from the cartridge. This relieves internal pressure and pre- vents detonation of the explosive fi ll. After the MRAP had stopped burning, Soldiers who examined the wreckage were amazed to fi nd all of the rounds’ shell bodies intact, proving that none of them had gone “high order” in the fi re. They also found the remains of the fuzes that had separated from the cartridges as designed, which allowed the PAX-21 explosive fi ll to burn rather than explode. The team members who
The team members who developed the M768 were
gratifi ed to hear that their hard work paid off for American Soldiers in such a real and dramatic way.
developed the M768 were gratifi ed to hear that their hard work paid off for American Soldiers in such a real and dramatic way.
The M768 cartridge, which received Full Materiel Release in 2006, is one of the early success stories in a larger IM Strategic Plan that Program Executive Offi ce Ammunition (PEO Ammo) is implementing to develop and produce safer ammunition throughout its port- folio. The PEO’s PMs have instituted plans of action and milestones for improving IM characteristics for their assigned munitions through improve- ments in packaging, explosive fi lls, propellants, and fuzes for all calibers, up to and including 155mm.
PEO Ammo, under the direction of the Army Executive Agent for IM, has long recognized that IM enhances war- fi ghter safety by preventing catastrophic accidents, such as the now-famous fi re in Camp Doha, Kuwait, in July
1991 that resulted in 3 deaths and 56 wounded. This incident started with a small heater fi re in an artillery resup- ply vehicle—loaded with propellants and projectiles—that exploded, spread- ing the fi re from vehicle to vehicle. In all, 102 vehicles were destroyed or damaged before the fi re was extin- guished. In addition, IM promise to reduce the logistics burden imposed by the requirement for large separation distances between highly volatile muni- tions, both in transit and in storage.
IM Testing and Improvements
Department of the Army Pamphlet 70-3, Army Acquisition Procedures, presents a total systems engineering approach to assist in meeting IM requirements, and specifi es IM testing based on Military Standard 2105C, Hazard Assessment Tests for Non-Nuclear Munitions. This standard requires subjecting munitions to six very harsh tests:
• Fast cook-off—rapid exposure to a liquid fuel fi re.
• Slow cook-off—gradually raising the temperature to above the ignition point.
• Bullet impact. • Fragment impact. • Sympathetic detonation—inten- tionally detonating one munition surrounded by several others.
• Shaped charge jet impact—similar to a rocket-propelled grenade.
Shown here is the interior view of the MRAP in Ng’s convoy after the Sept. 12, 2009, fi re. An unexploded shell body from a M768 cartridge can be seen in the lower left. (Photo courtesy of PM CAS, Picatinny Arsenal.)
Over the last decade, great strides have been made in shell design, propellant and explosive fi ll formulation, and packaging improvements. For example, the sympathetic detonation and shaped charge tests were once presumed to be impossible to pass, routinely requiring
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