Environmentally Benign Multi-Component Delay System with Tunable Propagation Characteristics

Dr. Zachary Doorenbos | Naval Air Warfare Center Weapons Division China Lake

WP-2519

Objective

This project will develop gasless delay formulations free of perchlorate, lead, and hexavalent chromium. The researchers will develop a multi-component delay system exhibiting a wide range of inverse burn-rates within the required temperature range (-65 to 160°F). All reactants and additives involved in the delay system meet current environmental standards. The main benefit of this environmentally acceptable reacting system is the wide-range tunability of inverse burn rates, by changing the concentrations of the constituents. This multi-component reacting system will provide inverse burn rates (IBR) in the range from 4 to 12 s/in. The selection of energetic composite materials for ignition and transfer charges will also be addressed and explored in order to eliminate currently used perchlorate and hexavalent chromium compounds. However, the focus will be on the development of the delay column formulation.

The main hypothesis of the project is related to the replacement of the currently used, but not environmentally acceptable, delay mixtures consisting of potassium perchlorate, barium chromate containing hexavalent chromium, and lead compounds. Based on the thermodynamic analysis of different reacting systems, expertise in the area of self-propagating high-temperature synthesis and gasless delays, and preliminary experimental results collected prior to this project, the researchers will use a direct substitution of BaCrO4 with SrMoO4. The key advantage of this replacement is that SrMoO4 is a similar oxidant to BaCrO4, but meets all environmental standards. The fuels Si, Al, Zr/Ni alloys and B also meet the environmental standards. Preference will be given to silicon as a fuel due to its long-term stability and chemical resistivity to oxidation in highly oxidizing environments.

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Technical Approach

A new tunable delay system will meet all environmental requirements according to ASTM E2552-08. Three selected end items (M201A1, M213A1 and M228A1) will be fully tested at -65°F, 70°F, and 160°F in a grenade subassembly test fixture. The researchers will conduct testing related to the determination of reactants compatibility, thermal, electrostatic discharge, friction and impact sensitivities, gas generation, thermodynamic analysis, as well as, 2-D modeling of combustion front stability and propagation characteristics in actual nonadiabatic conditions inside of a delay body. This study will require determination of the reaction kinetics for selected delay mixture compositions. The reaction kinetics will be determined using nonisothermal differential scanning calorimetry.

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Benefits

The main benefit of the research will be the development of a multi-component gasless delay mixture, which will be tunable in a wide IBR range through reactants and functional inert additive concentrations. This integrated approach and expected outcome will be beneficial in a selection of future delay systems by the Department of Defense. The testing of the fully assembled delay bodies in sub-assembly grenade configurations will provide data for the future scale-up of the developed technology. (Anticipated Project Completion - 2018)

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Points of Contact

Principal Investigator

Dr. Zachary Doorenbos

Naval Air Warfare Center Weapons Division China Lake

Phone: 760-939-0202

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