Investigation of Stability in Skydiving by Derivation of State Equation for Body Behavior and Root Analysis

Abstract

The objective of this study was to investigate the stability during freefall in skydiving, in which the diver has to take various body position in order to control precisely their distance, velocity, and direction relative to the other divers for the group performance. For this objective, the state equation for a simple elliptic cylinder model was firstly derived, considering its equations of motion and the fluid force characteristics. Next, using the form of state equation derived for the elliptic cylinder and the input/output data obtained from the developed simulation method for the body behavior of the skydiver, the state equations of skydiver were identified for various body positions. Finally, roots of the state equations were obtained to investigate the stability. As the results, the causes of instability such as spin and spiral phenomena were clarified as an unstable natural modes, and the stable limit of body position was obtained as a value of parameter which is related to the arch magnitude of the diver's body.