Computational analysis of a tension cone supersonic inflatable aerodynamic decelerator

Abstract

The 2009 Mars Science Laboratory mission has brought renewed awareness to the difficulty of landing large payloads on the surface of Mars. As a result, a new suite of decelerator technologies is being investigated for future robotic and human-precursor missions. One such technology is the supersonic inflatable aerodynamic decelerator (IAD). Previous studies have shown that a supersonic IAD can provide sizable increases in landed mass versus traditional parachute based systems, particularly for near-term robotic mission. This is due to the ability of an IAD to deploy at higher Mach numbers and dynamic pressures than a parachute, thus allowing for greater deceleration earlier in the entry sequence. As part of NASA's program to advance inflatable decelerators for atmospheric entry, one particular configuration, the tension cone, has undergone a series of wind tunnel experiments designed to acquire a full characterization of the aerodynamic performance of a particular tension cone geometry. One test objective entailed the acquisition of a data set useful for validating computational tools for later IAD analysis efforts. This paper presents a summary of the work performed in investigating two separate computational fluid dynamics codes for their suitability in predicting tension cone performance. The first code, NASCART-GT, is a solution- adaptive, Cartesian grid code that is used for rapid inviscid analysis of axisymmetric geometries. The second code, Overflow was used for Navier-Stokes analysis of three- dimensional geometries. These codes were evaluated for their ability to match measured pressure distributions, static force and moment coefficients, and observed flowfield characteristics. Overflow is also used to investigate flow features that were not observed during testing, such as the aft body recirculation region. Additional investigation into the aerodynamic performance of a tension cone was performed through a parametric analysis of multiple tension cone geometries. Three primary shape parameters were varied with the goal of identifying undesirable flowfield characteristics such as shocks attached to the surface of the tension shell and to provide insight into the sensitivity of drag to tension cone geometry.

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