Experimental research in opening overload of life-saving parachute and dummy high-speed airdrop

This paper examines overload data of dummy during ground impact and high speed airdrop experiments. The overload time series of the center of the dummy in the ground impact experiments were recorded and decomposed into different components using wavelet theory. The evolution of chaotic characteristics, correlation dimension (D₂), Kolmogorov entropy (K) and the maximum Lyapunov exponent (λ₁), under different wavelet components were studied as well. Results show that the energy of dummy centralized in a frequency range of 30~50 Hz and the soft dummy can buffer high frequency shock better than rigid dummy does. Higher frequency wavelet components behaves randomly, in which the magnification of error becomes higher. In the rigid dummy airdrop experiment, the overload time series of dummy center and angular velocities on three dimension satellite coordinates were recorded. Because of the complex aerodynamic shape of dummy and complex airflow environment, the overload data had intense fluctuations and poor reproducibility, even under the same experimental conditions. The relationship between center overload and the posture of dummy at parachute-opening moment was analyzed using phase plane method. It can be concluded that the overload time series have two peaks, corresponding to the pull-out and parachute-opening respectively, which present a negative correlation.This could be explained from the perspective of energy dissipation. Besides, the phase plane analyze shows that there was a strong dependence of parachute-opening overload value on dummy attitude angle (α) and angular velocity (α’) at parachute-opening moment. It indicates that there exists an advantageous parachute-opening area, where -4<α’<4rad·s⁻¹ and leaning towards II and IV quadrant. It can be concluded that the seemingly poor reproductive time series exist a good regularity on phase plane.