9 th International LS-DYNA Users Conference Impact Analysis (2) 9-1 A Mesh Refinement Study on the Impact Response of a Shuttle Leading-Edge Panel Finite Element Simulation Karen E. Jackson and Edwin L. Fasanella US Army Research Laboratory, VTD Hampton, VA Karen H. Lyle NASA Langley Research Center Hampton, VA Regina L. Spellman NASA Kennedy Space Center Cape Canaveral, FL Abstract A study was performed to examine the influence of varying mesh density on an LS-DYNA simulation of a rectangular-shaped foam projectile impacting the space shuttle leading edge Panel 6. The shuttle leading-edge panels are fabricated of reinforced carbon-carbon (RCC) material. Nine cases were executed with all possible combinations of coarse, baseline, and fine meshes of the foam and panel. For each simulation, the same material properties and impact conditions were specified and only the mesh density was varied. In the baseline model, the shell elements representing the RCC panel are approximately 0.2-in. on edge, whereas the foam elements are about 0.5-in. on edge. The element nominal edge-length for the baseline panel was halved to create a fine panel (0.1-in. edge length) mesh and doubled to create a coarse panel (0.4-in. edge length) mesh. The element nominal edge- length of the baseline foam projectile was halved (0.25-in. edge length) to create a fine foam mesh and doubled (1.0- in. edge length) to create a coarse foam mesh. The initial impact velocity of the foam was 775 ft/s. The simulations were executed in LS-DYNA for 6 ms. Predicted structural deformations and time-history responses are compared for each simulation. Introduction Following the Space Shuttle Columbia disaster on February 1, 2003, and during the subsequent investigation by the Columbia Accident Investigation Board (CAIB), various teams from industry, academia, national laboratories, and NASA were requested by Johnson Space Center (JSC) Orbiter Engineering to apply “physics-based” analyses to characterize the expected damage to the shuttle thermal protection system (TPS) tile and Reinforced Carbon-Carbon (RCC) material, for high-speed foam impacts. The forensic evidence from the Columbia debris eventually led investigators to conclude that the breach to the shuttle TPS was caused by a large piece of External Tank (ET) foam that impacted and penetrated the left-wing leading-edge panel, shown in Figure 1. As a result, NASA authorized a series of tests that were performed at Southwest Research Institute to characterize the impact response of the leading-edge RCC panels. Recommendation 3.3-2 of the CAIB report [1] requests that NASA initiate a program to improve the impact resistance of the wing leading edge. The second part of the recommendation is to “determine the actual impact resistance of current materials and the effect of likely debris strikes.” For Return-to-Flight (RTF), a team consisting of personnel from NASA Glenn