More than one million rounds of high explosive (HE) medium caliber ammunition are produced each year. All of these HE rounds require a detonator to make the projectile function effectively when it reaches the target. The impact sensitive (stab) detonators used in medium caliber munitions currently rely on the compound lead azide as a transition material that quickly and efficiently takes a mechanical input from the initiating mechanism and creates the detonation wave that functions as the HE main charge. Lead azide is an environmentally unfriendly material and must be handled and disposed of safely throughout its life cycle. The availability of an alternate, environmentally friendly material to replace lead azide would significantly reduce the environmental footprint associated with HE medium caliber rounds.
The objective of this project was to evaluate and test environmentally benign compounds that could be used as replacement materials for the current lead azide transfer charges used in stab detonator devices for medium caliber ammunition.
Two primary explosive compounds were synthesized in the laboratory and tested as direct substitutes for the critical detonator transfer charge. These compounds were the polyazidocyclophosphazene compound 1,1-(N,N'-ethylenedinitramino)-3,3,5,5- tetraazidocyclotriphos-phazene (ENTA) and diaminoazobistetrazine-3.5-oxide (DAATO 3.5). These compounds were subjected to strong (steel) confinement testing at Pacific Scientific Energetic Materials Company in Chandler, Arizona. The lack of a significant witness plate dent in these tests showed that neither compound was suitable as a lead azide replacement. Additional strong confinement testing was performed on a third compound, Diaminotetrazole, Fe(II) perchlorate complex (DFeP). Tests indicated it was strong enough to be considered as a candidate M59 transition charge but had a somewhat lower output than RD1333 lead azide. The M59 is a representative medium caliber stab detonator that is used in the M430 40 millimeter high velocity grenade. Testing was subsequently completed at the Naval Surface Warfare Center, Indian Head Division in M59 detonator hardware with transition charges of both DFeP and a lower sensitivity silver azide manufactured by the Costain process. The tests were conducted under brass confinement with a variety of charge weights and loading pressures, and the results were compared to similar tests with RD1333 lead azide.
While silver azide slightly outperformed RD1333 lead azide, the DFeP produced only approximately half the indent of RD1333 lead azide. It is expected, however, that further refinement of the DFeP crystal structure would provide some improvement. The reduced sensitivity silver azide was found to be a viable replacement for RD1333 lead azide in this application, provided that it passes compatibility testing with the NOL-130 initiating charge and the RDX output charge. An environmentally benign, primary explosive replacement charge for lead azide has the potential to be applicable to all fuses that currently rely on azide as the detonator transfer material. Since lead azide is also used as an initiator material in many primers, successful performance of the new material in the detonator could lead to additional applications in the primer area. (Project Completed - 2004)