Nomenclature
D ab= ground distance from load release to system first vertical D bc = ground distance from first vertical to main parachute deployment D cd = ground distance from main parachute deployment to ground impact D bd = ground distance from first vertical to ground impact h c = altitude of system at main parachute deployment V c = system descent velocity at main parachute deployment V d = system descent velocity at ground impact V windbc = range of wind speed from first vertical to main parachute deployment V windcd = range of wind speed from main parachute deployment to ground impact r = mean miss radial distance for the operational field tests x , y = mean point of impact in Cartesian coordinates for the operational field tests r = standard deviation of the radial miss distance for the operational field tests x , y = standard deviation of the Cartesian coordinate of the payloads for operational field tests
Although round parachutes have been used for airdrop for over 60 years, damage to canopy fabric and suspension lines still occurs during parachute opening due to the rapid canopy opening and the associated high opening force. Continuous disreefing of round parachutes to slow down the opening and decrease the peak opening force has been discussed in the literature, but no viable continuous disreefing method has ever been developed. In this paper, we present a practical, effective, and low-cost continuous disreefing method that does not use any external electrical or power source, only the opening force and the weight of the payload. The method was successfully demonstrated in a full-scale test from an aircraft using a 10.7-m (35-ft) diameter round parachute. The kinetic energy of the payload at parachute deployment of that test was 11 times higher than that of the standard deployment that the parachute is designed for. In spite of the severe deployment condition, no damage to the parachute was observed after ground impact.
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