To design effective shielding for spacecraft and to evaluate the risk posed by debris and meteoroids, we must be able to perform tests in the laboratory. Hypervelocity Impact testing has some extreme requirements. How do we launch projectiles at speeds more than seven times faster than the fastest bullet? How do we know how fast the projectile was traveling at impact? How can we get pictures of an impact event that lasts only a few microseconds - that's millionths of a second?
The testing capability of the HVIT, provided by the 3 light-gas gun ranges, allow for 100 micron aluminum balls up to a 10 mm aluminum balls, to be launched at velocities ranging from below 2 km/s to over 7 km/s. The diagnostics for the HVI testing consist mostly of flash x-ray systems and ultra-high speed cameras. The ranges are also equipped with light flash photo-detectors and laser intervalometers, all of which allow for the projectile velocity to be determined.
The ranges use Cordin camera systems, which are capable of framing rates of up to 2.25 million frames per second using standard Kodak IR film cassettes. The camera is a rotating mirror system which exposes each frame of a static circular roll of film for a few microseconds. The mirror is driven by a turbine powered by compressed nitrogen or helium.
The .50 caliber range presently incorporates a 300 kV HP model 43733A and a 150 kV HP model 43731A flash x-ray system. The 300 kV head is used to obtain orthogonal soft x-rays of the target, projectile, and/or debris plume. The 150 kV head utilizes three stations to obtain sabot separation information, projectile integrity data, and projectile velocity.
Launching projectiles at velocities high enough to simulate orbital debris impacts requires some remarkable equipment called "two stage light-gas guns."The technology that makes these guns work is fascinating.
We can measure the velocity of the impacting projectile in a hypervelocity impact test using several different techniques. And there are other tools we use to ensure a quality test.
Cordin High Speed Shadowgraph Cameras that are capable of taking up to 2.5 million frames per second are used to capture images of hypervelocity impact events that last only a few microseconds.
Hydrocodes are used to investigate impacts beyond the testable regime. They are also used as a visualization tool, to help us understand the physics that occur during an impact.
The science behind impact testing can be quite extensive, and is required for mission success and the safety of our crew members. To learn more about the science behind impacts, visit our impact physics page.
Over the years, the HVIT team has been keeping an archive of impact images on Shuttle, International Space Station, and other vehicles. Visit our impact galleries page to look through the imagery.