Application Note: Imaging Hypervelocity Impacts for Aerospace Safety

Study of hypervelocity impacts could aid development of housings that protect airplanes and satellites from flying debris.

Researchers at the Thiot Ingenierie Shock Physics Laboratory been studying such impacts in superslow motion with the help of a SIM8 ultrafast CCD framing camera from Specialised Imaging Ltd. of Tring, England.

Experiments involved firing aluminum spheres at 4000 m/s against an aluminum target using a fixed two-stage light gas gun.

The flight of an aluminum pellet fired at 4000 m/s at an aluminum target is captured at 200,000 fps. Courtesy of Specialised Imaging Ltd.

The shots were imaged at a frame rate of 200,000 fps. Exposures of 20 ns or less were needed to reduce motion blur to less than the size of a pixel in order to allow accurate measurements of the projectiles just before impact.

This required adequate light levels to fully define the edges and the corners of the projectile; the event was backlit using Specialised Imaging's SI-AD500 flash lamp.

The resulting images clearly show a cloud of ejected material thrown backwards on impact and also demonstrates that even though the projectile disintegrates on impact, the fragments maintain the original projectile shape ahead of the main fragment cloud. The test also showed that the remaining fragments do not have enough energy to penetrate a second aluminum plate when two thin layers were used instead of one thicker layer.

Interest in hypervelocity has traditionally been driven by the military community, but is increasingly of interest to the aerospace industry for areas of research such as enhancing the survivability of aircraft to in-flight explosions and in protecting satellites from stellar debris.

The Thiot Ingenierie Shock Physics Laboratory is a private company offering impact-related materials characterization, vulnerability assessment and numerical simulation services. For more information, visit www.thiot-ingenierie.com.