Manufacture of Ordnance by In-Situ Resonant Acoustic Mixing

Ms. Amy Luebbering | NSWC, IHEODTD



Current methods for manufacture of ordnance items such as rockets and warheads involve a multi-step process where the explosive or propellant is mixed in batches and cast into molds that are then cured and loaded into the item hardware, or cast from the mixer bowl directly into the final hardware for cure. Up to 5% of explosive product is typically lost in this process as residual material left in the mixing and casting equipment and tooling. These waste materials must then be treated as explosive hazardous waste. The equipment and tooling used typically require cleaning with solvents, which also must then be treated and disposed of as hazardous waste. Both the casting and cleanup processes are hands-on operations, where personnel are exposed to explosive, fire, and chemical hazards. The objective of this project is to develop and demonstrate an ordnance production process mixing the energetic fill directly in the end unit hardware, reducing energetic waste, solvent use, and personnel exposure to hazards.

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Technical Approach

Resonant Acoustic Mixing (RAM) is a novel mixing technology that operates by low frequency oscillation of the mixer platform in mechanical resonance. The vessel containing the material to be mixed is secured to the mixer platform. There is no requirement that the mix vessel be of any particular size or shape, so long as the mass does not exceed the capability of the equipment. Therefore, it is possible to mix the explosive fill directly in a casting mold or end unit case hardware.

In this project, structural, safety, and processing studies will be done in the development phase to evaluate the ability of rocket motor hardware and liner systems to withstand the forces experienced during RAM mixing, and down-select a motor for demonstration. Fixtures will be designed to secure the selected hardware to the RAM-5 and inert process runs will be performed to ensure the final configuration maintains integrity during the mixing as predicted. After successful completion of the inert in-situ mixing process runs and live propellant mixing, live rocket motors will be produced by mixing the propellant directly in the lined rocket motor case, using the same mixing process tested with the inert trials. The rocket motors produced will be inspected according to typical Lot Acceptance Tests (LATs). As possible based on the rocket geometry, propellant grains will be machined to obtain samples for burn rate and mechanical properties testing, to confirm acceptable propellant properties and uniformity throughout the rocket motor. If not already a part of the LAT, motor cases and liner will be inspected via x-ray for any signs of cracking or unbonding.

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This project will provide a demonstration of a new mixing process that will eliminate the current solvent use and explosive waste associated with the existing mix/cast process for manufacturing ordnance items. The project will confirm the technical feasibility of in-situ RAM as a viable production process for rocket motors. The initial screening studies will identify the rocket motor hardware and liner characteristics necessary for successful utilization of this process. (Anticipated Project Completion - 2017)

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Points of Contact

Principal Investigator

Ms. Amy Luebbering


Phone: 301-744-1853