IM Hazards Modeling & Simulation – an International Collaboration Abstract Number 22170 Co-author: Steven Collignon NSWC Dahlgren Division Co-author: Thomas Swierk (presenter) Hart Technologies, Inc., 2019 Insensitive Munitions & Energetic Materials Technology Symposium Sevilla, Spain 21-24 October 2019 1 Distribution Statement A: Approved for Public Release unlimited. Distribution unlimited. UNCLASSIFIED
Contents of Presentation What? • Background Why? • Goals and objectives • Focus on propellant types – HPP and How? MSP • Lab-scale Testing & Model Development What happened? • Pre-test Predictions for Analog RM Tests What was • Conclusions summarized for both nations accomplished? • Improved M&S capability applicable for Who benefits? future weapon development Who did it? • Principal contributors from each nation 2 Distribution Statement A: Approved for Public Release unlimited. Distribution unlimited. UNCLASSIFIED
Background • The US DoD and UK MOD both have a requirement to field weapons systems that are IM compliant. • Improved modelling and simulation (M&S) tools will reduce risk in the acquisition process and help weapon systems meet the IM requirements. • An IM Project Arrangement was established. • For the US, participants included the Army, Navy and the DOE/NNSA National Laboratories (LLNL, LANL and SNL), under the auspices of the Joint DoD/DOE Munitions Program. • In the UK, participants included Dstl, DOSG, AWE, QinetiQ, several universities and other government contractors. 3 Distribution Statement A: Approved for Public Release unlimited. Distribution unlimited. UNCLASSIFIED
Goals & objectives The goal was to develop or modify M&S tools and apply them to a technically challenging IM problem useful for future weapon system development and assessment activities. • Rocket motors have historically been vulnerable to many of the IM hazards with solid propellants being particularly vulnerable. • M&S tools have been successfully used to examine threats to explosive-filled munitions, but that capability was seriously lacking when applied to rocket motor propellants. The objectives of this work were to: • Develop M&S tools for system-level IM assessment. • Exercise these tools in a joint IM assessment of a weapon system analog. • Demonstrate the ability to integrate validated M&S into system-level design and quantification. 4 Distribution Statement A: Approved for Public Release unlimited. Distribution unlimited. UNCLASSIFIED
Propellant Focus • The initial focus for the modeling capability development was a “generic” high-performance propellant (HPP ). • Modeling was aimed at determining the propellant response to a fragment impact threat as described in STANAG 4496. • The technical challenge was to develop a predictive capability to determine the propellant response from the impact of a threat fragment as it traveled through the motor sidewall and into the internal cavity (bore) of the rocket motor. • A “generic” minimum signature propellant (MSP) was identified as an appropriate candidate for additional model improvement. • This candidate propellant and the modeling capability that was developed were the main components of the system-level demonstration. Case Propellant 5 Distribution Statement A: Approved for Public Release unlimited. Distribution unlimited. UNCLASSIFIED
Fragment Impact Response of Rocket Motors • Motors need to pass IM fragment impact requirements • Better understanding of motor reaction needed to foster potential IM improvements • Motors containing HD 1.1 propellant can detonate via • Shock to Detonation Transition (SDT) • Unknown Detonation Transition (XDT) [More prevalent problem than previously thought] Lab-scale test configurations Case Projectile Case Propellant Plexiglas Propellant ABVR tests Cylindrical tests 6 Distribution Statement A: Approved for Public Release unlimited. Distribution unlimited. UNCLASSIFIED
Conclusions from Sub-scale Testing by AMRDEC * [ To support Predictive Model Development] • ABVR can replicate the detonative behavior of a full-scale motor • SDT threshold differs by <350 ft/s for the fragment velocity. • XDT reaction region is the same for thinner web thickness. • Thicker web causes some deviation. • Insufficient data available to compare non–detonative region. • Motors can detonate at lower velocities than what is typically expected. • Non-detonative regions may exist that are bounded by detonative regions at high and low fragment impact velocities. * “ Validation of the Army Burn to Violent Reaction (ABVR) Test as a Tool to Predict Full-Scale Motor Response to Fragment Impact ” paper given by Dr. Jamie Neidert, 2018 IMEMTS. 7 Distribution Statement A: Approved for Public Release unlimited. Distribution unlimited. UNCLASSIFIED
Analog Rocket Motor & Test Setup • MSP-1 propellant (31.3 lbs.) • Web thickness of 2.41 in • Oriented vertically – nose down • Mirror allowed for internal viewing of motor • Pressure gauges set in circular patter or 45° offset from shotline 8 8 Distribution Statement A: Approved for Public Release unlimited. Distribution unlimited. UNCLASSIFIED
Predicting XDT in Rocket Motors Technical Challenge : Determine the role of the propellant debris cloud properties and second wall shock effects when modeling the delayed detonation of an MSP. • Problem : Rocket motors with MSP can undergo delayed XDT (detonation) modes at unacceptably low projectile impact velocities. • Hypothesis : Based on the hypothesis that delayed XDT is essentially SDT in a porous cloud, conduct a range of simulations on the shock compaction of MSP debris clouds. • Goals of Study : To examine (1) if initiation occurs in debris cloud and (2) if it propagates to the rest of debris cloud and/or underlying bulk propellant. Consider a range of debris cloud parameters and projectile speeds. XDT Phenomenon Does Penetration & Debris Cloud detonation Debris Cloud Compaction- Propagate in Formation Initiation? Cloud? XDT ? X X X X X X X X X X 9 Distribution Statement A: Approved for Public Release unlimited. Distribution unlimited. UNCLASSIFIED
Approach for Model Predictions • Problem : MSP rocket motors undergo XDT at unacceptably low projectile impact velocities. Validated models don’t exist for predicting XDT & deflagration in projectile impact scenarios. • Objective : Develop and validate the LLNL HERMES* model to predict the impact response of MSP rocket motors from SDT to XDT to deflagration. • Benefits : Munition designers can use the HERMES model in ALE3D to develop new rocket motors and barriers that eliminate susceptibility to XDT. • Use the XDT model to aide the design of new sub-scale experiments that screen new MSP formulations. • Develop methodology for XDT modeling that can be applied to other energetic materials. * Reaugh, White, Curtis, Springer (2018), Journal of Propellants, Explosives and Pyrotechnics 10 Distribution Statement A: Approved for Public Release unlimited. Distribution unlimited. UNCLASSIFIED
HERMES Model Mechanism • Validating modeling capabilities with sub-scale testing resulted in accurate predictions when extrapolating hazard response to full-scale systems. • HERMES model was calibrated to demonstrate model behavior in slab ABVR geometry. 11 Distribution Statement A: Approved for Public Release unlimited. Distribution unlimited. UNCLASSIFIED
XDT Reaction – when, where, how ? It was hypothesized that XDT is essentially SDT in the debris cloud where two things need to happen • INITIATION needs to occur in the porous debris cloud that is shock compacted by the projectile. • Most energetic materials show increased shock sensitivity with increasing porosity and projectile impact velocity. • The main reason for suppressing XDT at small gaps was the higher density debris clouds does not have sufficient porosity to initiate at lower fragment velocities. • Detonation needs to PROPAGATE into the rest of the debris cloud or bulk propellant. There isn’t sufficient material in the debris cloud to continue to propagate detonation. • XDT requires INITIATION + PROPAGATION to occur. Three parameters drive XDT conditions to create cloud density conditions: bore size, web/slab thickness and projectile velocity. 12 Distribution Statement A: Approved for Public Release unlimited. Distribution unlimited. UNCLASSIFIED
Pre-test Model Used For Test Predictions Setup for large-scale rocket motor analog design in ALE3D Pre-test modeling performed before live full-scale analog rocket motor tests. 13 Distribution Statement A: Approved for Public Release unlimited. Distribution unlimited. UNCLASSIFIED
HERMES model pre-test simulations of analog rocket motor Experiments 2400 ft/s: Deflagration HERMES Model 3800 ft/s: XDT XDT-SDT Deflagration-XDT threshold threshold 4400 ft/s: SDT Note: Pre-test simulations at nominal, not actual, fragment velocities. HERMES simulations demonstrate good agreement for XDT- SDT & XDT-deflagration thresholds. 14 Distribution Statement A: Approved for Public Release unlimited. Distribution unlimited. UNCLASSIFIED
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