Experiments on the separation of sphere clusters in hypersonic flow

In this work, we develop a new methodology for hypersonic multi-body free-flight experimentation and conduct several tests to explore the aerodynamic separation of equal-sized spherical fragments, which approximates the atmospheric disruption of meteoroids. A novel suspension design enabled by 3D printing is introduced, allowing for rapid, reliable release of clustered spheres into hypersonic flow, and high-speed stereoscopic imagery is employed to visualize the aerodynamically separating spheres. A new data-reduction technique based on synthetic image fitting, along with previous edge-detection and photogrammetric reconstruction methods, is used to track sphere motions; these motions also anchor a novel self-calibration procedure for the camera apparatus. To probe the separation characteristics of disrupted meteoroids with increasing fragment population, clusters of 4, 11, and 36 equal-sized spheres are subjected to Mach 6 flow. Strong dependence of trajectories on subcluster interactions is discerned for both 4 and 11 spheres, with two-body lifting pairs identified as critical arrangements capable of producing outlying fragments, whereas the initial stage of mutual repulsion is observed to exert greater influence as the cluster population is increased. Finally, terminal lateral velocity measurements are compared with other studies to synthesize a coherent picture of separation trends for equal-sized bodies.