Tribological issues in the implementation of a MEMS- based torpedo safety and arming device

NSWC-Indian Head Division is designing and prototyping a MEMS-based Safety and Arming device for deployment in the next generation of small, multi-platform torpedoes. Designs under consideration utilize either LIGA-Nickel, deep reactive ion etch (DRIE) or-thin optical lithography nickel barriers, actuators and other moveable, spring supported structures. Critical issues for these devices will be sticking and sliding friction, wear during use, and surface morphology induced "snagging" and friction. In both the nickel-based and the silicon-based structures, there will be a need to characterize and quantify surface roughness and surface films (both intentional films deposited during fabrication and unintentional films resulting from environmental exposure). Another issue will be the long term effects of transportation and storage on the these structures such as how they might suffer from vibration-induced fretting corrosion or surface wear, and how these tribological phenomena might degrade performance when the time comes for the device to be put to use.