Design, Testing, and Safety Considerations of an Optically Isolated Firing Set

Experimental investigations at the Air Force Research Laboratory's Munitions Directorate required a firing set to initiate detonators in ultra-high-voltage experiments, but commercial firing sets with adequate high voltage isolation could not be found. To resolve this issue a Directorate team designed, fabricated a new firing set, verified that it met all design requirements, and obtained safety board approval for its use. The patented design uses all plastic fiber optic cables, pneumatic controls, battery isolation, and redundant safety devices to withstand voltage differences of hundreds of thousands of volts between the operator and the experiment. This paper describes the efforts to develop a very reliable firing set that met the high standards required by explosive safety procedures. Design features include Faraday shielding, redundant lock out features, multiple safing circuits to handle a variety of fault conditions and fail-safe bleed down circuits to eliminate concerns with residual stored electrical energy. The high-voltage-tolerant firing set allows research in unexplored areas such as electro-explosive effects. Presented at the Optical Technologies for Arming, Safing, Fuzing, and Firing II - SPIE Conference held in San Diego, CA on 13-17 August 2006. Published in the Proceedings of the Optical Technologies for Arming, Safing, Fuzing, and Firing II - SPIE Conference, 2006. Prepared in collaboration with SAIC, Fort Walton Beach, FL.