Two sets of laser light "screens" at a known distance apart on the flight range can
be used to calculate the projectile velocity. A set of laser beams arranged in a row
are shown through the expected path of the projectile. Laser light detectors are
positioned on the opposite side of the path. As the projectile passes through the
laser light screen, the sensor detects a change in the light beam and the time of
the event is recorded.
We can also measure projectile velocity using light detectors, since light is usually
emitted during a hypervelocity impact event. Light is emitted when the projectile impacts
the target. Light can also be emitted when the sabot pieces impact the sabot stripper.
Since we know the distance and time between these two light emissions, projectile velocity
can be calculated.
High Speed Cameras
High-speed cameras can be used to estimate projectile velocity and to verify the integrity
of the projectile prior to impact. The constant frame rate of the camera can be used to
determine the time interval between frames. The position of the projectile in the image
can be used to determine the distance the projectile travels. Knowing the time interval
and the distance is used to estimate the projectile velocity.
Launching a projectile at hypervelocity is such an energetic event that occasionally the
projectile breaks up during the launch. Flash x-rays are used to take several pictures of
the projectile before it hits the target. Flash x-rays are also used to see how the impact
damage grows inside of an opaque target.
Measuring with Lasers
The horizontal blue tube in the image is the tube that the projectile passes through on it's way to the target. The pair of shorter vertical tubes are used to for the laser light "screens" with sensors on opposite side.
Measuring with Light
The image shows a light detector positioned on one of the flight range diagnostic ports.
Measuring with Cameras
High-speed cameras come in many different sizes, types, and speeds. Current testing uses several different types of cameras that typically shoot at speeds from 50,000 frames per second into the millions of frames per second.
Measuring with X-Rays
The three long blue and grey colored tubes sticking out of the blue chamber in the image are flash x-ray heads. These emit x-rays briefly during a test so that specialized images of the projectile in flight and/or the projectile impacting the target can be produced.