Low-speed Free-flight Stability and Drag Characteristics of Radially Vented Parachutes

A drop-test investigation has been conducted to determine the stability and drag characteristics of radially vented (duplex) parachutes. Parachutes of two different designs were tested: a large parachute with high geometric porosity and a small parachute with low geometric porosity designed for the same descent velocity with the same load. The results of the tests show that the large high-porosity duplex parachute was very stable in descent, oscillations averaging about [plus-or-minus]3.40; and the average drag coefficient based on the total canopy area and based on the fabric area alone were approximately 0.38 and 0.55, respectively. The small, low-porosity duplex parachute was also very stable in descent, oscillations averaging about [plus-or-minus]4.50; and the average drag coefficients based on the total canopy area and based on the fabric area alone were approximately 0.62 and 0.79, respectively. The oscillations for the cluster of three solid flat circular parachutes, tested for comparison purposes, were [plus-or-minus]7.10. The average drag coefficients based on the total canopy area and the fabric area alone were approximately 0.64 and 0.65, respectively.