Development of a Low Cost 10,000 lb Capacity Ram-Air Parachute, DRAGONFLY Program

Abstract

A 3,500 ft 2 , 10,000 lb capacity, low cost cargo Ram-air is being designed and developed by Para-Flite, Inc. for the U.S. Army Natick Soldier Center (Natick) under the JPADS ACTD program. The airdrop system has been designed for deployment from 25Kft MSL at speeds of 150 KIAS. Test drops have been conducted with the system in order to finalize the deployment process and generate trajectory data suitable for the development of an autonomous guidance algorithm, of which C.S. Draper Laboratory is the designing authority. This paper presents the design philosophy and outlines the aerodynamic, structural and manufacturing considerations. Being driven by cost reduction, the design focused on using conventional materials and manufacturing techniques while trying to maximize gliding performance. The main canopy uses a cutterless slider reefing method which eliminates a dependency for complicated staged openings. Drop tests indicated that the parafoil was extremely stable in flight and generated a maximum glide ratio of 4:1. This level of glide efficiency matches or exceeds prior performance characteristics for similarly sized systems. Guided tests showed that the parafoil is also reasonably responsive for it size, with maximum steady state turn rates exceeding 9.0 deg/s. Nomenclature

Three-Stage Model for Slider-Reefed Parafoil Inflation

“…-Beyond sail and pilot chute-controlled sliders New slider-reefed parafoils designed for carrying high-weight cargo have been tested by the US Army and other governmental organizations [16,17]. Typically, such systems are deployed immediately after being dropped from high-flying aircraft -a situation where high (true) airspeeds and thereby high opening forces prevail.…”

“…The second equation in (17) defines the stopping point of the slider-descent simulation, triggered here by the drag area reaching a preset value that is expressed in terms of the fully opened wing dimensions. Here F end is a non-dimensional parameter and is usually greater than unity, as shall be shown in the next section.…”

“…Finally, the ½ -factors appearing in (20) are cancelled out, a move demanded by the comparison with experimental data discussed in the next section. Combining (17) and (20), and defining the contents of the square bracket as being equal to the function Δ(t), one obtains: (21) with ψ ~ 1/5. As will be shown later, the value of the constant Φ is quite close to the empirically-determined value of K ipm , indicating that Δ(t) should of the order of unity.…”

Dynamical Model of a Controlled Parawing for Drop Tests Trajectory Reconstruction

“…Lately the Draper Laboratories developed ded-icated parawing systems [3,4] and collaborated to the Joint Precision Airdrop System (JPADS) program with the goal to develop an autonomous guidance, navigation and control system for precision airdrop capability of high payload capacity. NASA in paral-lel developed a controlled parachute system to test the technology for a Crew Return Vehicle for the International Space Station [5].…”

Estimation of Load on Control Lines of Ram Air Parachute Designed for Precise Delivery Using 9-Dof Model

“…They used 9 DOF model to carryout dynamic simulations for open loop, and closed loop with designed yaw controller. Berland et al [9] presented the derived load for control line deflection based on current and voltage monitoring of motor during flight test. Nathan Slegers et al [10] investigate control issues for a parafoil and payload system with left and right parafoil brakes used as the control mechanism.…”