A 101 ft Cargo Parachute System Employing Modular Canopy Construction, Radial Reefing, and Inlet Control System

摘要

This paper describes the design and development of a 101-foot diameter cargo parachute for low altitude airdrop of heavy payloads, utilizing a drag efficient "modular" canopy assembled from fabric sections, along with a unique reefing system consisting of an inlet parachute integrated with radial reefing lines. The inlet parachute and radial reefing method promote faster inflation of the reefed main canopy because the inlet chute or "Skirt Spreader" located at the skirt of the reefed main canopy provides sufficient spreading force to cause the main canopy to inflate to the reefed diameter much more quickly. Once inflated in the reefed stage, the radial reefing lines maintain a circular shape at the mouth of the reefed main canopy. The Skirt Spreader is released at disreef, allowing unrestricted flow to the upper portion of the main canopy. This reefing method is particularly effective with clustered parachutes since it leads to faster reefed inflation, more uniform inflation of the individual canopies after disreef, and corresponding reduction in lead-lag load disparity. In this application, it permits the use of shorter reefing times, and ultimately results in reduced time to full inflation, with a corresponding reduction in altitude loss compared to similarly sized canopies with traditional reefing. Canopy modules of three different shapes are arranged to provide an inflated profile similar to that of a Hemispherical canopy. The modules include reinforcements that are tied to each other at multiple points along the sides to provide a continuous grid-like structure over the entire canopy. The relatively small open fabric areas formed by the structural grid limit the progression of damage within the module and to adjacent modules. In the event of damage, the affected module can be quickly removed and replaced. Repairs to a module removed from the canopy are more easily made than equivalent repairs to a one-piece canopy. The modular concept affords greater maintenance flexibility because the canopy may be quickly repaired with a replacement module, while the damaged module may be discarded or repaired at a more convenient time or location. With the modular concept and need to replace only damaged modules, severe damage is less likely to cause the entire canopy to be discarded, as could be the case for a one-piece canopy. All of this contributes toward a parachute that is more readily maintained and has a lower life-cycle cost. Given these potential benefits, the modular parachute with a Skirt Spreader reefing system was selected by Pioneer/Fox Parachute Services as our candidate for the US Army competitively contracted Advanced Low Velocity Airdrop System (ALVADS) program. Through extensive testing, the modular parachute system demonstrated improved performance as compared to the G-11 with regards to reduced altitude loss and reduced rate of descent Developmental Testing was successfully concluded in August 2016 and the program has since transitioned to operational evaluation.