At Naval Surface Warfare Center Indian Head Division (NSWC IHD), the objective of this effort was to develop and scale up a process to manufacture ordnance by in situ resonant acoustic mixing in units on both a small-scale resonant acoustic mixer and medium-scale resonant acoustic mixer.
Mixing in situ would eliminate the current method of multi-step process of batch mixing, casting, and curing. This not only promotes a shortened mixing and casting process, it promotes a decrease in explosive waste, reduction in hazardous chemical exposure to personnel, and reduction in overall solvent use.
Several rocket motors were chosen due to their size relative to the five-gallon medium-scale resonant acoustic mixer (RAM5) and current production demand which increased chance of a successful transition. Electrostatic discharge hazard evaluations were completed to identify possible ignition hazards including electrostatic discharge, electrical sparks, frictional heating, and frictional sparks both in a lab setting and on site at NSWC IHD. Testing resulted in low to negligible chargeability allowing the project to move forward.
Liner studies were completed to determine if the adhesion would remain intact during in situ mixing. All trials resulted in no tears or damages to the liners. There has not yet been an in situ mix on the RAM5 however, a mix was done to simulate the conditions of resonant acoustic mixing with a successful casting on end unit hardware. The mix resulted in a homogenous material with no voids and a reasonable cure, but mechanical testing resulted in failing the material specification.
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)
Although the results were not ideal, they did show that in situ mixing on resonant acoustic mixers has a high potential for success and future transition to qualification. To further understand the impact of in situ resonant acoustic mixing of rocket motors, additional mixing and testing needs to be completed. Initial results show that in situ mixing is a potential route forward.