Drag Coefficient Estimation of Low Density Objects by Free Fall Experiments

The present article investigates whether the drag coefficient of low density objects can be determined by free fall experiments with sufficient accuracy. Among other things, the drag coefficient depends on the flow velocity, which can be controlled in wind channels experiments. Free fall experiments do not offer an experimental environment with constant flow velocity. Especially the later part of the movement gets relevantly influenced by air drag deceleration. We theoretically estimate an average sphere drag coefficient for the relevant part of the movement of falling spheres. The results are verified by examining the drag coefficient from experimental data. Finally, we determine the drag coefficient of a model rocket, which is compared to the result of the corresponding wind channel experiment.