Determination of the Geometry for a Ram-Air Parachute Canopy in Steady Flight Through Numerical Simulations

This paper discusses the application of Finite Element-based simulations to examine the geometry of a fully inflated, MC-4 ram-air parachute canopy in steady flight using a prescribed pressure distribution. Time and cost is always a factor in any engineering design, and until recently much of the design for parachute systems involved costly physical testing. Although these physical tests are very effective, Finite Element Methods provide an alternative to obtaining fairly accurate results at a fraction of the time and cost. Computer simulated systems are constantly proving their worth, and refining the strategies and techniques can only propel them forward in terms of reliability, accuracy and ease of use. A novel approach for the inflation of the canopy from its cut-pattern was devised and implemented in LS-DYNA software suite. The effects of net pressure, pressure distribution, and material properties were explored by assessing various measures of the canopy geometry. Five specific measures considered were: maximum spanwise extent of the canopy, radius of a circular arc fitted to the upper leading edge of the canopy, radius of individual half-cell openings, distance from the top of the canopy to the slider, and the maximum vertical distance between the canopy center and tip at the leading edge. A set of mesh refinement runs provided guidelines for acceptable average element area of 4.33 in2/element. These same runs aided in defining the time taken to reach a steady state. Variation of net applied pressure over a broad range resulted in minimal, less than 5%, change in the specific measures of the canopy geometry. This shows that the indicated technique can be used to reduce the use of resources to reach the resulting geometry of a fully inflated, steady state, canopy. This technique can be used in industry for preliminary design purposes in situations where a modification in the canopy is considered. It will give a good estimate to whether or not a modification will change the final, steady state, structure of the parachute system.