Grid generation for overset grids on complex geom-

A collection of computational fluid dynamics tools and techniques are being developed and tested for application to stage separation and abort simulation for next-generation launch vehicles. In this work, an overset grid Navier-Stokes flow solver has been enhanced and demonstrated on a matrix of proximity cases and on a dynamic separation simulation of a belly-to-belly wing-body configuration. Steady cases show excellent agreement between Navier-Stokes results, Cartesian grid Euler solutions, and wind tunnel data at Mach 3. Good agreement has been obtained between Navier-Stokes, Euler, and wind tunnel results at Mach 6. An analysis of a dynamic separation at Mach 3 demonstrates that unsteady aerodynamic effects are not important for this scenario. Results provide an illustration of the relative applicability of Euler and Navier-Stokes methods to these types of problems.

This paper provides an overview of the computational fluid dynamics analysis of the ascent of the Space Shuttle Launch Vehicle during the investigation of the STS-107 accident. The analysis included both steady-state and unsteady calculations performed with the Overflow and Cart3D flow solvers. The unsteady calculations include moving body, six degree-of-freedom simulations of foam debris shed from the region of the left bipod-ramp of the vehicle. Many such debris trajectories were computed, some of which impacted the vehicle. The analysis provided an estimate of the speed at which such a piece of debris would strike the wing leading edge of the Shuttle Orbiter. These results were supplied to the Columbia Accident Investigation Board, and guided the choice of the impact velocity and foam size selected for the foam-firing test done as part of the investigation. This testing subsequently showed that it was possible for a piece of foam debris to cause massive damage to the Shuttle Orbiter wing Reinforced-Carbon-Carbon panels and T-seals, creating a breach where hot gases could enter the wing structure during reentry.

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