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Projectile Orientation Measurement During Flight and Just Before Impact

ERIK CARTON, , RE DIEDEREN

Abstract


The angle between the line-of-fire and the rotation axis of a projectile is called the yaw angle. For fin and spin stabilized projectiles the yaw angle changes continuously during flight. Normally the yaw of a projectile is measured by orthogonal flash imaging of the projectile. However, this method provides only the yaw at a certain position, often at a certain distance from the target. To better establish the yaw just before impact, two methods will be presented and discussed: a continuous yaw measuring technique and a technique using a small V-shaped mirror close to the target impact position. A projectile can be illuminated during its flight using a laser beam directed from the target into the barrel using mirrors. By polishing the tip of the projectile the tip will reflect the laser light back towards the target. A light screen at the target position is used to project this reflection from the projectile tip. Using a high speed camera the position of this spot on the screen is recorded. Together with the known position of the projectile versus time, this enables the total yaw of the projectile to be measured continuously during its flight. Another method uses a high speed camera in combination with a V-shaped mirror placed just in front of the target. The total yaw can be calculated from the two (orthogonal) yaw-components. Examples of both yaw measuring techniques will be presented and discussed.

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