Shock and impact sensors are devices that detect sudden movements, changes, or severe impacts at a predetermined level and indicate whether that level has been exceeded. Impact sensors are used in applications where it is desirable to know when an impact has occurred. In an ultra-high velocity impact, the relative velocities of the colliding objects can be about 5000 meters per second (m/s) or higher which is about the speed of sound in metal. The speed of sound through the metal construction materials of a projectile limits the propagation speed of the shock wave from an impact through the projectile. An example of an application that uses this ultra-high velocity is an anti-projectile projectile. During the final flight stage of the projectile, high velocities are used to improve the accuracy and the efficacy of a successful engagement. In the case where it is desirable for a projectile to send a notification that it has had an impact, this event must be sensed, analyzed, and transmitted after the impact has occurred, but before the sensor, transmitter, and projectile are destroyed by the impact.
US Patent Pub 2010/0307353 entitled “Ultra-high velocity projectile impact sensor” discloses an apparatus for detecting the impact of an ultra-high velocity projectile using an optical fiber located in the projectile. An optical fiber provides a predictable response under the conditions of an ultra-high velocity projectile impact. When the optical fiber is intact, it propagates light and when the fiber is damaged, the light decreases. In the case where the optical fiber is broken or destroyed or even under some conditions of shock and vibration, the light cannot propagate or propagation is decreased through the optical circuit. When a projectile strikes a target, the impact will be at a first area of the projectile. Depending on the design of the projectile, this first area will begin to crush, collapse, fragment, explode, or similar. Given the ultra-high velocity of the impact, high energies are involved and the materials at the first area of the projectile begin to transition to an indefinite and/or unpredictable state. The optical fiber in the first area is possibly deformed, then destroyed, resulting in an interruption to the light propagating through the optical fiber. The shockwave from the impact begins to travel through the projectile from the first area of impact toward the second area farther away from the impact. The velocity of light in fiber is significantly faster than even ultra-high velocity impacts of a projectile with a target. This difference in velocities allows the monitor to detect a change in the light at the second area before the shockwave reaches the second area and damages or destroys the monitor.
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