Nanoenergetic Materials for Micro-Scale Tactical Applications
Military missions require small energy-dense formulations to propel and power future generations of miniature autonomous systems and satellites, and to provide sufficient energy yields in small explosive payloads. Nanoenergetic materials such as nanothermites are generally formulated as an elemental metal combined with a metal oxide, the former being the fuel and the latter being the oxidizer. These have superior reaction rates and energy yield relative to their meso-scale formulations and to conventional explosives but pose problems unique to reactions at these small scales. Recent advances in understanding the physical-chemical properties of nanomaterials have begun to address these problems, and formulations with superior energy yields now show promise for applications in miniature military systems. Nanomaterials in general, and nanoenergetics in particular pose unique threats of human toxicity and environmental health which challenge traditional toxicological assessment, but which must be assessed if these materials are to be incorporated into military systems.
THE MILITARY PROBLEM
There is an increased emphasis on the use of autonomous systems such as unmanned aerial vehicles (UAV), unmanned ground vehicles (UGV), unmanned underwater vehicles (UUV), and other autonomous systems to perform surveillance, reconnaissance, search and recover, and search and destroy missions. There are advantages to miniaturizing these systems such as signature reduction, ability to penetrate very small spaces, and reduced logistics. In addition, the potential for such micro-robotic systems to be deployed as distributed, coordinated networks or swarms both increases mission flexibility and complicates an adversary’s countermeasures. Access to space is now largely a commercial activity and it is likely that space will be another theatre of war in any major future conflict. The logical conclusion is that U.S. space assets will be targeted, crippling GPS systems, and the ability to reconstitute those assets will be critical. To that end, micro- and nano-satellites are being developed which could be quickly put into orbit as distributed networks, complicating an adversary’s countermeasures. These will require equally miniaturized thruster systems and nano-electrokinetic thrusters have been tested in the laboratory.
The previously cited examples all require that power sources, propellants, and payloads will need to be miniaturized and modern weapons will require greater and controllable yields from energetic materials. There are a number of promising new technologies, known collectively as “nanoenergetics”, which could address these requirements. These materials are manufactured to have at least one dimension at the nanoscale (1-100nm), and the small size of these particles confer different chemical and physical properties than when manufactured at meso- or macro-scales. From an energetics perspective, rates of reactions and energetic yields are vastly improved from ~10 kJ/cm3 for monomolecular energetics such as TNT to ~85 kJ/cm3 for aluminum-based nanothermite. The field of nanotoxicology has emerged to address the novel effects of nanomaterials on physiological and environmental systems in a manner that traditional toxicology testing is inadequate to do. The scientific literature in this area is replete with contradictions, mostly a result of widely differing methodologies.
The workshop approach is to develop the technical framework with which to inform a comprehensive research program on Nanoenergetic Materials for use as military explosives, propellants, and pyrotechnics. Dual-use applications include welding, demolition, energy storage, and manufacturing processes. The scientists participating in this workshop are tasked with developing an enhanced whitepaper(s) focused on this important mission requirement. The expected outcome is a research team(s) which proposes research ideas and goals which have a clear path to a “deliverable” solution to the sponsor.