Using Safe, Proven Fuze Technology for Rocket Motor ISDs

Abstract

Fuze technology for rocket motor warhead detonation has advanced with safe, mature technology to allow inline initiation devices, commonly called Electronic Safe/Arm Devices (ESADs). These devices are based on the demonstrated safety of exploding foil initiator (EFI) technology. Low energy EFI (LEEFI) technology can be adapted to rocket motor Ignition Safety Devices (ISDs) to offer improved reliability and performance. ISDs are first event ignition devices that must provide exceptional safety to offset some of the traditional fuze benefits. For example, an ISD must function before missile flight, therefore no dynamic environmental force may exist as a safety feature. In-line ISDs need to account for this through the use of dual static switches and a dynamic switch (typically oscillator-based) that generates the source of the high voltage. Also, ISDs are tied to the real world through an electrical cable. Therefore, transient events from electrical sources as high as 440 vac must be mitigated, making the 500-volt official limit a very significant issue. Electrostatic Discharge (ESD) and Electromagnetic Interference (EMI) become real concerns, also, as access to the ISD is more direct than a fuze embedded in the missile frame. ATK has a long history in the fuze industry and has worked to integrate this fuze experience into the ISD area. ATK’s Tactical Systems Company (ATK TSC) has developed an electronic architecture that interfaces with an initiator based on LEEFI technology. The front-end electronics consist of command sequence protection, ENABLE and ARM logic, timing, and an oscillator-based “Safe and Arm Logic Set”. The high voltage “Fire Set” electronics from proven ATK fuze devices is compatible with the unique firing characteristics of the LEEFI initiation device. ATK’s design approach for MIL-STD-1901A compliance is based on a demonstrated high voltage electronic architecture combined with a demonstrated LEEFI-based initiator from Reynolds Systems Inc.