An excerpt of the high-speed film produced in the SSRMS test #4 is shown here. In the first frame, the incoming projectile can be seen just prior to impacting the surface of the boom. In the subsequent frames, the formation of the secondary debris and ejecta clouds is clearly apparent. Analysis of the debris cloud velocity reveals that the cloud tip travels at approximately the same velocity as the projectile.

This graphic illustrates why the secondary debris cloud is a greater threat to the SSRMS booms than that of the primary impact.