Phred Petersen
Pop rocket, 2007

High-Speed Schlieren Photograph; Canon 350D camera with a 210mm lens and Hadland Microflash unit; flash duration approximately 5 microseconds (1/200,000 sec).

RMIT University, Melbourne, Australia

This photograph recorded the blast wave produced from a toy rocket that was tipped with a cap gun charge. The visibility of an event that would normally be invisible to eye is the result of contrast from the schlieren imaging system and high-speed flash. A perforated metal plate below the impact point partially reflects the wave, which allows multiple wave fronts to pass through the perforations and recombine below. The combustion gases of the small explosion are shown to move at a much lower velocity than the blast wave itself.

A three-color circular light source was used in a Z-type schlieren arrangement with two 300mm f/10 mirrors. An adjustable iris was used in the cutoff plane to control sensitivity of the system.

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