Inferring parafoil glide slope by extending unsettled trajectories via simulation

Master Thesis


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University of Cape Town

A unique catapult has been developed at the University of Cape Town for launching parafoils from a hilltop or into a quarry. The initial objective to determine optimum glide slope of a parafoil using Design of Experiments via flight testing presented challenges. The flight tests and supporting simulations were carefully planned, and were to be conducted by making use of Design of Experiments to investigate the influence of factor effects on glide slope. The two factors to be investigated were the trim settings; plumb line length and trim angle. Each of these factors was to be tested at three discrete levels and it was decided that a 32 factorial will be used with the aid of Taguchi's methods. Due to serious flight test damages to the parafoil canopy, lines and payload, it was deemed necessary to revise the project objectives. The required repairs implied that testing could not continue within an acceptable period of time. The revised objective of this project was to ascertain if unsettled trajectory measurements could be extended by means of simulation to infer the steady glide slope. In order to conduct the simulations required, a rudimentary theoretical model of the unsteady parafoil motion was developed to investigate the influence of line length and trim angle on glide slope. The aerodynamic model focused only on the longitudinal motion of the parafoil-payload system, however the effects of wind and atmospheric turbulence were also investigated. The experimental flight tests in the quarry were unsuccessful due to flight test damages sustained and the focus of this investigation shifted to simulated results rather than experimental results. The simulated results suggest that increasing the plumb line length or the trim angle results in an increase in the settled glide angle of the system. On average, trim angle had a 2-3 times greater effect on glide angle than plumb line length. In addition, due to the lack of sufficient height in the quarry, simulations were run to extend the unsettled trajectory to a steady state in an attempt to estimate the glide angle. These simulations were capable of estimating a settled glide angle with reasonable accuracy in certain atmospheric conditions.

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