There are increasing demands for reducing the sensitivity and envelope of explosive warheads for purposes of decreasing life cycle vulnerabilities and to accommodate other valuable components necessary to meet challenging precision strike and low collateral effects demanded in futuristic weapon systems.
Basic and applied research focuses on developing technologies that can be exploited for meeting these demands. A prominent area of study concentrates on understanding the behavior of explosives and energetic materials at extremely high pressures. These studies have recently led to innovative initiation methodologies for achieving sustained detonation rates and pressures at levels far above conventional means for any explosive material.
The result opens windows of research opportunities for enhancing performance potential of directed (e.g., shaped charges and explosively former projectiles) and lateral energy (i.e., blast and fragmentation) devices, as well as decreasing the quantities of explosives (or energetic materials) required in a weapon because of the increased efficiencies of energy conversion to useful work.
Parallel investigations of the response of materials under severe compression are essential for theoretical interpretations detonation processes under these newly reached supra-pressure conditions. In order to exploit these developments, sustained efforts are also directed towards identifying and quantifying mechanisms governing coherent flow during shaped charge jet formation, and coupled mechanical and chemical interactions during hypervelocity impact of inert and chemically active projectiles.
Approximately 50 student researchers have contributed significantly to these advances. Efforts range from theoretical analyses, finite difference modeling and simulation, experimental planning, engineering design, coordination of services for supporting precision fabrication and instrumented explosive and hypervelocity impact experimentation.
Over the last ten years off-site experimentation has been performed at Indian Head, MD and China Lake, CA naval laboratories, US Army Fort AP Hill, VA, Lawrence Livermore National Laboratory, University of Illinois, and the Ernst Mach Institute, Freiburg Germany. Students have attended and presented technical papers at domestic and international conferences.
Excerpt from the Office of Naval Research Energetic Materials Program Issue 4, October 2012:
“Under the direction of NPS Research Professor Ron Brown, the physics department’s Energetic Materials and Explosives Research Group at the Naval Postgraduate School has completed a series of explosive tests at the Iowa Army Ammunition Plant. These initiation tests demonstrated detonation velocities and pressures at levels far greater than those that can be achieved under conventional processes. A patent application has been filed for the initiation system and another is in preparation for the shaped charge design technology. Team members include: Christopher Tilley, Andrew Gilchrist, CDR Jonathon VanSlyke, Stan DeFisher. This work was co-sponsored by Dr. Tam of ONR Code 31. Kudos to all of our outstanding performers, keep up the great work!”
The ultimate goal of research is directed towards enhancing potential terminal performance of weapon systems containing energetic materials (including explosives). Basic objectives include improving our understanding of the detonation process, the processes of explosively induced metal launching, and the shaped charge jetting process, energy coupling, and hypervelocity impact.
The Office of Naval Research, Naval Surface Warfare Center-Indian Head, Naval Air Warfare Center-China Lake, Fallon Naval Air Station, and Lawrence Livermore National Laboratory have sponsored much of the work and have included substantial collaborative efforts with the aforementioned DoD laboratories, US and European universities, the Ernst Mach Institut (Freiburg Germany), and private US establishments for supporting precision fabrications, explosive loading and high-speed diagnostic experimentation.
Many of the over 40 students mentored over the last ten years have had the opportunity of (i) participating in these collaborations, (ii) conducting off-site experiments, and (ii) participating in international forums and co-authoring and presenting technical papers. Several have received research and outstanding thesis awards.
Examples of Research Achievements:
The following are some of the headlines of these investigations:
- Technology exploitation for improving the TOMAHAWK warhead.
- Record breaking shaped charge jetting.
- Invented explosive initiation mechanism for accelerating and sustaining detonation rates far greater than conventional means.
- Improved methods for predicting initiation threshold
- Quantitative determinations of the effect of hypervelocity impact of combustible projectiles and jets against underwater targets.
- Theoretical treatment of the contributions of aluminum combustion during prompt- and post-detonation of aluminized explosives.
- Underwater blast enhancement by a process referred to as detonation merging”.
- Identification of governing mechanisms responsible for penetration termination of shaped charge jets.
- Lethality modeling of fragmenting systems.
- Development and successful demonstration of a 25mm shaped charge device, containing a non-explosive, for neutralizing buried unexploded ordnance (UXO): including a spinoff to industry.
- Shaped Charge Jetting: Current focus is directed towards understanding mechanism governing material flow coherency under super-fast jetting conditions so as to understand the degree by which advances supported explosive detonation can be exploited for meeting future demands in IM, warhead miniaturization, and precision strike. This involves novel experimentation, computational modeling and possible extensions to classical theory.
- Experimental investigations of super-fast jetting in support of the above.
- Deriving shock impact experiments and quantum mechanics modeling with collaborators for purposes extending equations of states into the megabar range. This will likely include estimating morphological and lattice re-orientations.
Ronald E. Brown
Mail Code: PH/Br
Department of Physics
Graduate School of Engineering and Applied Sciences
Monterey, CA 93943