A basic component required for the efficient and effective functioning of medium caliber rounds is the initiator, the Electro-Explosive Device (EED) that initiates the explosive event. The current standard device being used in these designs is the M100, which consists of separate initiating, transition, and output charges. The M100 performs well, but the initiating and transition charges are hazardous heavy metal compounds. An aim in developing initiators for explosive devices is to eliminate lead and other toxic heavy metals from the chemical compositions.
The objective of this project was to synthesize and characterize up to eight replacement compounds for lead azide and lead styphnate for consideration as new, initiatory type compounds that do not contain lead or other heavy metals known to be toxic or to contain carcinogenic materials in their manufacture. The thrust behind the project was proof of concept since no heavy metal-free compounds previously had been used in the initiatory categories.
The compounds examined fall into the following three categories: inorganics, light metal derivatives of organics (salts and Meisenheimer complexes), and metal-free organic compounds. Routes for the synthesis of these compounds were devised that avoided the use of toxic or carcinogenic reagents, intermediates, and solvents. The candidate compounds thus synthesized were characterized fully by spectroscopic and thermal analysis. After these analyses, the compounds were assessed for hazard (e.g., impact, friction, electrostatic discharge, and ignition temperature) before recommending which compounds would be suitable for the next phase of the project. Further, sufficient quantities of these compounds were synthesized to conduct preliminary characterization and hazard assessments of each during the project. The project duration was 12 months.
Three compounds in the detonant (i.e., lead azide replacement) class were evaluated and assessed for their potential utility in EEDs. The two candidates found to be suitable were both silver salts. QinetiQ has recommended that compounds in this category be put forward for larger scale testing (e.g., formulation and functionality) and ultimate incorporation into medium or large caliber ordnance systems for use by the Department of Defense (DoD).
In the primary explosive (i.e., lead styphnate replacement) category, four candidates were synthesized and evaluated. The characterization and hazard assessment process undertaken eliminated all compounds as EED replacements. Notably, several candidates were insufficiently sensitive to function in the primary explosive role; other candidates had syntheses too low-yielding to permit recommendation as lead styphnate replacements. Further candidates have been proposed to overcome the shortcomings of the compounds studied previously and thus meet DoD requirements. This project was completed in FY 2002.
The major benefits of substituting these initiatory compounds in EEDs for medium caliber munitions include: (1) reduced health risks to workers during production processes, (2) reduced environmental risks during the production process, (3) reduced health and environmental risks to operational users, and (4) cost avoidance through reduced cleanup at both manufacturing and operational sites.