Fragment Tracking in Hypervelocity Impact Experiments

This dissertation develops an experimental technique for measuring fragmentation initiated by hypervelocity impacts performed in the laboratory. Hypervelocity impact fragmentation is relevant for many applications such as monitoring orbital space debris or researching planetary impacts. Researchers typically use two-stage light-gas guns to recreate hypervelocity impact experiments in the laboratory. My goal in this dissertation is to develop a non-intrusive, time resolved, measurement technique to track and measure the positions, trajectories, and velocities of individual fragments in 3D. I accomplish this by using measurement setups and tracking methods from photogrammetry, specifically adapting approaches developed for fluid flow measurement, such as Particle Tracking Velocimetry. The basic fragment-tracking setup consists of multiple high-speed cameras with converging views to record impact fragments. The analysis algorithm can be separated into four steps: fragment detection, tracking, matching between views, and triangulation. I develop algorithms catering to the specific characteristics of hypervelocity impact fragments to efficiently and accurately accomplish each step. I examine both individual algorithms and the entire workflow in detail using synthetic data to determine optimal approaches specific to the hypervelocity setting. I quantify measurement uncertainties and analyze the characteristics of the tracked fragments. Finally, I present some example tracking results which demonstrate my method's capability to measure 3D fragment positions, trajectories, and velocities, as well as 2D sizes, in a wide range of impact materials and conditions.