Arm/Fire Device (AFD)
Arm/Fire Devices (AFD) are commonly used on missile programs to provide safe initiation of solid rocket motors. AFDs are rotating mechanism that move electric detonators in-line (ARM) and out-of-line (SAFE) with downstream ordnance, preventing inadvertent rocket motor ignition while in the SAFE position and assuring reliable initiation when in the ARM position. AFDs are flight proven devices that are compliant to MIL-STD 1901A requirements. EBAD has developed and qualified AFDs for many missile programs and deliver thousands each year. Several AFD examples are shown in this data sheet, which can be customized to meet specific system requirements.
Principle of Operation
The AFD mount directly into the forward dome of a solid rocket motor and interfaces with the rocket motor ignitor basket. In the SAFE position the AFD is electrically and mechanically isolated from system inputs and explosive outputs. When arming voltage is applied, the internal electrical detonators are rotated and aligned with a pair of internal Thru-Bulkhead Initiators (TBI). When detonators are fired, the TBIs produce a time/pressure and caloric output sufficient to light the rocket motor. The TBI provides a pressure containment barrier after functioning to prevent leakage of rocket motor pressure. The AFD does not contain a mechanical detent to keep the AFD in the ARM state, but rather returns to the SAFE position via a passive spring once arming power is removed. The electric detonators are intended to be actuated within several seconds after arming, thus the assembly is called an Arm/Fire Device.
The AFD has a hermetically sealed stainless-steel body that houses the critical components of the device. The AFD contains dual electric detonators, and an electrically operated torque motor or rotary solenoid to rotate the detonators into the in-line (ARM) position. A passive spring rotates the AFD into the SAFE position once arming power is removed. Dual TBIs are used for redundancy and initiate a common pyrotechnic motor ignition charge. In some AFDs, a disk with a simple visual indicator is affixed to the common shaft turned by the motor. As the motor rotates the visual indicator moves with respect to a stationary window where the visual status can be viewed.
AFDs are used for solid rocket motor ignition on tactical missiles and missile defense platforms when a rapid ARM-FIRE sequence is needed for missile launch or actuation.
- MIL-STD-1901A compliant
- Used on multiple US and foreign platforms
- Installs directly into solid rocket motor dome
- Internal redundant electric detonators
- High speed ARM-FIRE sequence for rapid motor ignition
- Small, low profile package