The goal of this effort was to develop technology, materials, methods, designs and verifications to improve the reliability of the Army’s metal Micro-Electro-Mechanical-Systems (MEMS) safe-and-arm device (S&A) as the basis for meeting the less-than 1% unexploded ordnance (UXO) rate required for submunitions after 2018, and to eliminate lead-containing energetics in the Micro-scale Firetrain (MSF). The improved MEMS S&A is to benefit the Warfighter not only with improved reliability, but also, by virtue of miniaturization, by reducing the size of the fuze to free up space in munitions such as submunitions and 40mm grenades.
The munition fuze is the part of the system that keeps the munition safe prior to launch, reliably senses launch conditions and arms the weapon, and then detects and functions on target. The freed-up space is to allow room for additional features that can improve reliability, functionality, and performance of the munition; features such as redundant arming devices, additional computational components, sensors and larger lethality mechanisms.
This project focused on developing novel miniature explosive initiation methods, improved energetic materials and initiation and actuation mechanisms for the Army’s ongoing fuze MEMS S&A efforts. It focused on increasing fuze function rate or reliability, which directly reduces the risk of UXO remaining on the battlefield. Reduction of UXO is particularly important in cluster munition type ordnances, which contain multiple munitions with individual fuzes within each ordnance. This effort also pursued the development and engineering application of lead-free energetic materials, which reduces the environmental and toxic impact of lead on battlefields and also in ordnance manufacturing facilities.
Several technical advancements were investigated that had the best potential to improve the reliability of MEMS fuze S&A device. First, three new technologies were investigated to increase the reliability of converting electrical energy into explosive initiation detonation energy. Second, a new explosive "flyer driver" microscale detonation transfer scheme was employed and matured to replace a quasi, direct-contact energetic transfer scheme. Also, alternative, reduced-corner-turning explosive propagation schemes were attempted to eliminate one observed failure mode of the current Army MEMS S&A. Finally, new gas generant inks were developed that would be capable of actuating a micro-scale mechanical lock more efficiently.
Experimentation with novel lead-free primary explosive inks and with lead-free gas generant inks demonstrated that primary explosives such as lead styphnate and lead azide could be phased out of future MEMS fuzing, as successful replacements were demonstrated. These energetics powders were synthesized and formulated into energetic direct write materials (EDWM) that could efficiently propagate energy in microscale cavities, whether that energy is an explosive shock wave or a gas generant pressure wave.
Overall this project provided critical contributions to improving the functional performance of the Army’s MEMS S&A device. The project demonstrated not only new initiation and new detonation transfer mechanisms in microscale devices, but also improved upon legacy mechanisms without the need for lead- or mercury-based materials. The new materials also provide the benefit of being more readily manufactured and assembled into MEMS based fuzing devices.