Publications

Abstract not provided.

The lack of protection for semiconductor bridges (SCBs) against human electrostatic discharge (ESD) presents an obstacle to widespread use of this device. The goal of this research is to protect SCB initiators against pin-to-pin ESD without affecting their performance. Two techniques were investigated. In the first, a parallel capacitor is used to attenuate high frequencies. The second uses a parallel zener diode to limit the voltage amplitude. Both the 1 {micro}F capacitor and the 14 V zener diode protected the SCBs from ESD. The capacitor provided the best protection. The protection circuits had no effect on the SCB's threshold voltage. The function time for the CP-loaded SCBs with capacitors was about 11 {micro}s when fired by a firing set charged to 40 V. The SCBs failed to function when protected by the 6 V and 8 V zeners. The 51 V zener did not provide adequate protection against ESD. The parallel capacitor succeeded in protecting SCB initiators against pin-to-pin ESD without affecting their performance. Additional experiments should be done on SCBs and actual detonators to further quantify the effectiveness of this technique. Methods for retrofitting existing SCB initiators and integrating capacitors into future devices should also be explored.

The NASA Standard Detonator (NSD) is employed in support of a number of current applications, including the Space Shuttle. This effort was directed towards providing test results to characterize the output of this device for its use in a safe and arm device. As part of the investigation, flash X-ray was used to provide stop-motion photographs of the flying metal plate that is created by initiation of the detonator. This provided researchers with a better understanding of the shape and character of the high- velocity disk as it propagated across the gap between the detonator and next assembly. The second portion of the study used a velocity interferometer to evaluate the acceleration and velocity histories of the flying plate, providing a quantified assessment of the detonator’s ability to initiate the explosive in the next explosive.

For many years, explosive components have used hotwires to convert an electrical stimulus into the thermal energy required to initiate the device. A Semi-conductor Bridge (SCB) performs the same function, but with the advantage of requiring approximately 1/10 the input energy of a comparable hotwire, while retaining excellent no-fire characteristics. The SCB also demonstrates faster function times due to its inherently-lower thermal mass. This paper discusses the development and production of two SCB-based devices, the MC4491 Initiator and the MC4492 Actuator. The initiator is designed to shock initiate a linear shaped charge by accelerating a thin metal plate across a small gap. The actuator functions several different components, sewing as either an actuator by producing a rapidly expanding gas to activate piston mechanisms or as an ignitor by providing hot particles for initiating pyrotechnic mixtures. Details are provided on the construction of both devices, methods of assembly, and performance characteristics (function time, flyer velocity, pressure in a closed bomb, heat content, and no-fire and all-fire levels).