Dynamic responses to landing impact at different key segments in selected body positions

The purpose of this study was to observe the acceleration responses of the key body segments to the landing impact in selected body positions. 5 young male subjects in 45 experiments were voluntarily exposed to the peak from 4 to 10g and duration from 50 to 80 ms acceleration pulses at 20° supine angle and the peak 10g and duration 50 ms impact at the supine angles from 20 to 60°. The acceleration responses on the dropping platform of the impact tower, the seat, the subject's head, shoulder, chest and ilium, as well as ECG of the subject were measured. The results demonstrated that the acceleration peaks of these key body segments in the chest-back direction had a highly significant positive correlation with the impact level. But their correlation in the head-foot direction was lower than that in the chest-back direction except that of the head. The acceleration peaks of these key body segments in the chest-back direction had a negative correlation with the supine angle. But the acceleration peaks of ilium in the head-foot direction had a positive correlation with the supine angle, and that of the chest almost bore no correlation. There were nonlinear relations between acceleration peak and supine angle at the head and the shoulder respectively, and the acceleration peaks of the head and shoulder in the head-foot direction reached minimum at about 40° supine angle. It is concluded that the acceleration responses of the key body segments demonstrate different properties between the chest-back direction and the head-foot direction. It is recommended that the angle of the seat back be adjusted about 40° before the spacecraft landing in order to prevent potential head injuries.