Structural Verification and Modeling of a Tension Cone Inflatable Aerodynamic Decelerator

Abstract

Verification analyses were conducted on membrane structures pertaining to a tension cone inflatable aerodynamic decelerator using the analysis code LS-DYNA. The responses of three structures -a cylinder, torus, and tension shell -were compared against linear theory for various loading cases. Stress distribution, buckling behavior, and wrinkling behavior were investigated. In general, agreement between theory and LS-DYNA was very good for all cases investigated. These verification cases exposed the important effects of using a linear elastic liner in membrane structures under compression. Finally, a tension cone wind tunnel test article is modeled in LS-DYNA for which preliminary results are presented. Unlike data from supersonic wind tunnel testing, the segmented tension shell and torus experienced oscillatory behavior when subjected to a steady aerodynamic pressure distribution. This work is presented as a work in progress towards development of a fluid-structures interaction mechanism to investigate aeroelastic behavior of inflatable aerodynamic decelerators. Nomenclature

Estimating the Collapse Pressure of an Inflatable Aerodynamic Decelerator

“…Note, the IAD model considered here is similar to, but not identical to, the IAD model in previous works. 1,7,8,19 For example, inflation tubes are not considered in the model presented here. Nevertheless, the IAD model presented here is sufficiently close to the physical IAD model to evaluate our analytical methods.…”

“…and without A-T panels were found to behave very differently; we will discuss these differences in the following sections. Based on the published data and specifications, 7,8 we were able to able to develop a mathematical model 11,12 for the tension-cone IAD, including the membrane tension shell, torus, and A-T panels. See Figure 1(e) where membrane components are yellow, A-T panels are in green and seam reinforcements are shown in red.…”

“…In the case of the IAD, the answer to this question will help the engineer meet design requirements for a lightweight deployable structure that packs into a small volume, is stiff enough to maintain a desired aerodynamic shape and enable the landing of larger payloads at higher altitudes. Roughly speaking, if the aerodynamic loading is not too extreme and the torus pressure is sufficiently large, the previously mentioned research 7,8,10 have demonstrated through physical models and numerical computation that the tension-cone IAD shape is stable. However, if the aerodynamic pressure is maintained at a constant level and the torus pressure is reduced a sufficient amount, there is a pressure threshold where the torus will collapse.…”

“…While inflatable aerodynamic decelerator (or ballute) technology dates back to the 1960's, [3][4][5][6] in recent years due to the advantages offered by the IAD, this technology has garnered additional attention through NASA's Program to Advance Inflatable Decelerators for Atmospheric Entry (PAIDAE). [7][8][9] An inflatable decelerator known as a tension-cone IAD (see Figure 1) has received particular attention. The key components of a tension cone IAD are a rigid blunt aeroshell, a tension shell designed to carry tensile loads, a pressurized torus, and in some versions, anti-torque (A-T) panels.…”

“…7,8,10 In this model, the tension shell and torus were constructed from urethane-coated kevlar. The A-T panels were introduced because, initially there were concerns that radially compressive forces generated by the tension shell would cause the inflated torus to roll outward and forward.…”