Demonstration of Perchlorate-Free Projectiles
Perchlorates are powerful oxidizers found in solid rocket propellants, munitions, roadside flares, fireworks, airbag initiators for vehicles, matches, electroplating operations, and some disinfectants and herbicides. While existing as both naturally occurring and man-made anions, perchlorate is a persistent contaminant of concern for a variety of industries. The Environmental Protection Agency (EPA) determined that perchlorates can have negative health impacts on adults and children and detected its presence in public drinking water systems, especially around sites that manufacture solid rocket fuel.
The military is particularly responsible for monitoring perchlorate used in solid rocket propellants and munitions. Under DoD Perchlorate Policy, military services must follow the strictest perchlorate regulations, which are mandated differently at the state level and at the federal level by the EPA under the Safe Drinking Water Act.
Perchlorate-based ammunition poses a great risk of contamination through both the initial manufacture and final demilitarization processes. Training exercises also present the possibility of contamination when deployed munitions leave behind traces of this chemical as unexploded ordnance (UXO) or fail to function entirely. As a result, several training ranges have closed, and more are at risk of closure for non-compliance of environmental and water contamination policy.
To address this challenge, ESTCP funded projects aimed at identifying perchlorate-free formulations for incendiary projectiles. Dr. Jared Moretti demonstrated a perchlorate-free and barium-free composition ( Project Webpage) to replace IM-28, an incendiary mixture that is nose-fitted in the US Army and Navy’s M8, M20, and Mk257 armor-piercing incendiary (API) rounds. The results of this project were determined feasible through the work of research teams at the Combat Capabilities Development Command - Armaments Center (CCDC-AC, team lead), the Naval Surface Warfare Center (NSWC), and the Lake City Army Ammunition Plant (LCAAP).
Perchlorate-based formulations are used in most small arms ammunition to produce an incandescent flash that ignites the fuel vapors. The IM-28 composition used in API bullets contains 10 wt. % perchlorate, with 12 grains loaded into each round. This results in a heavy amount of perchlorate used in manufacturing over time, which exacerbates the risk of contamination.
The project team created perchlorate-free technology by substituting alternate oxidizers, like metal nitrates. Another SERDP project ( Project Webpage) explored sodium nitrate as a possible alternative, but its hygroscopicity was found to be an issue. Sodium nitrate absorbed surrounding moisture extremely quickly, which caused concern for lasting reliability and sustainable performance.
Instead, Dr. Moretti and his team deployed a composition made up of sodium metaperiodate (SMP), magnesium-aluminum alloy and calcium stearate – all commercially available ingredients that comply with Environmental Safety and Occupational Health (ESOH) standards. Once the armored target is penetrated, the nose of the deforming copper alloy jacket and the stainless-steel core compresses this composition, activating its combustion to create the same “flash” necessary for igniting fuel vapors. This perchlorate-free and barium-free composition was successfully demonstrated in three .50 caliber bullet platforms: the M8, M20, Mk257 APIs.
To prepare this composition for implementation, a few more actions need to take place. The Army and Navy will require further safety and stability testing, and SMP will require a military specification document (MIL-SPEC) and approval from the Services for proper quality control. For technology transfer purposes, final hazard classification (FHC) must be determined through system level testing that uses larger lots more closely aligned to the size of regular production lots.