SBIR-STTR Award

We propose to attack line drag reduction from 2 directions, both of which utilize round cross-sectioned lines. We have previously assisted in the development of high strength, low drag, minimal diameter round cross-sectioned lines using novel construction techniques, but with standard and high modulus materials which are already airdrop acceptable. We have found large reductions in line drag using these construction techniques. We base our second approach on the fact that line vibration, induced by the moving air itself, contributes greatly to line drag. We propose to continue past investigations and tests of several variations of line treatments designed to ameliorate and/or attenuate lines' tendency to oscillate while in flight (so-called Aeolian vibration), and especially, such oscillations' ability to form and reform resonant and harmonic vibrations. We propose to build a large scale drag testing jig and compare the drag of these lines to standard parachute suspension line materials, both in short lengths and in lengths too long to contain in wind tunnels. We propose to limit our investigation to techniques which minimize the need for specialized line braiding equipment or post-manufacture alteration of lines. We further propose to limit our investigation to anti-oscillation techniques which are inexpensive to implement and which don't appreciably alter normal and typical methods used to attach suspension lines to canopies, payloads, etc, for instance with knots, sewn loops, larksheads and the like

There exists an opportunity to significantly reduce the drag produced by parachute suspension lines; a drag which can account for as much as 20-40% of the system’s total drag. We will continue to explore methods for such drag reduction which are both relatively simple and inexpensive to manufacture and for which little or no special handling characteristics or unusual or custom terminations are required. Our approaches do not alter the essentially round cross section of the finished line. We are producing drag reductions as high as 55% through our Phase I, two-pronged approach: First the reduction in line diameter through the use of high modulus fiber in a construction matrix including strong consolidation of unidirectional core fibers into a small diameter, relatively very round, smooth-finished line; and second, several non-strength affecting alterations of the line’s outer covering in ways which acoustically attenuate the vortex induced vibration (VIV) due to Von Karmann vortex shedding behind the aerodynamically bluff body, “infinite” length of small diameter round line.

Keywords:
Line Drag, Parachute, Airdrop, Personnel And Cargo Parachute Systems, Autonomous Airdrop System, Decelerator, Kite, Textiles