Abstract: The drag of hollow hemispherical parachute models is measured by an one-component strain gauge balance, while the flow field is investigated by the hydrogen bubble technique. Based on the measures and the theoretical analysis, the relationship between the ratio of maximum drag Fmax to force Fa caused by added mass during uniform accelerations and nbn-dimensional parameter Umax2/ad is obtained. In addition the flowfield phenomena related to maximum drag is studied in the paper. The experiments will be helpful to realize the internal relation between the dynamic stability of parachute and the opening shock.

Key words: parachutes, unsteady flow, drag, measurement