Dynamic Load Characteristic of Parachutes at a Subsonic Speed

This paper concerns with the results of an experimental study on dynamic load characteristics in parachute inflation at a subsonic speed. The unsteady drag of the parachutes in the process of inflation is measured in a wind tunnel at M=0.2, and the opening shock load is examined in detail with emphasis on the effects of porosity and size of the models. It is shown that the circular vents near the edge of the canopy are more effective than the slit vents to reduce the opening shock load without considerable decrease of drag in the steady-state. Detailed examination reveals that the model geometry as well as descending speeds has no serious influence on the coefficients of the opening shock load Cm and the opening time Ct, if both Cm and Ct are defined by use of the effective references calculated from the concept of an equivalent parachute, which has a circular plane canopy with the reduced area obtainable by subtracting porous area from the geometric one.