Test for electrically fired munitions

Electrically activated primers initiate missile and gun rounds and must be periodically tested for effectiveness and readiness

Military Technology

An all-up-round (AUR) is an assembled missile generally comprised of a housing (cartridge), primer, projectile, and propellant shipped by the manufacturer to it’s launch site or platform. AURs are tested upon delivery and periodically thereafter. Current test systems for AURs include instrumentation that measures parameters associated with firing the AUR, such as case mouth pressure, velocity of the projectile, and action time (the time from when energy is applied to the primer of the bullet to when the projectile leaves the firing platform). Current test systems for AURs are also known to test the propellant. Some rounds – including missiles – include electric primers which are activated by an externally provided electric charge as opposed to a mechanical impact. The electric primer ignites the primary propellant. Existing testing equipment for AURs is unable to test the electric primer functionality. Furthermore, existing test equipment is unable to control an application of required voltages in varied durations to the electric primer of the AUR.

For primers used in AURs, as well as in ammunition for rapid-fire cannon guns (including guns having multiple revolving barrels), a need exists to detect the causes of a long action time that exceeds a maximum action (dwell) time. The dwell time varies depending on the gun and ammunition configuration, but nonetheless has very tight tolerances. An example of a maximum action time is 570 microseconds for a 20 mm gun (although other suitable maximum action times may be required). An action time lasting longer than the maximum action time may cause damage to the gun or a misfire.

Navy researchers have developed a method and apparatus that allows control of an applied voltage, duration, and resistance to initiate an electric primer; and monitor output characteristics of either the primer or the AUR. This is a test to identify potential causes of long action time. The system controls several key elements with high specificity, including the applied voltage magnitude, the length of time voltage is applied (microsecond pulse duration), the number of voltage pulses, and an in-line resistance applied to the primer. Test system analysis results indicate if the device used to trigger the tested primer contains dirt or debris affecting firing performance; the rounds or primer are defective; the firing pin area has a mechanical fault or misalignment; and the status of several other variables affecting action time.

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