Formulation of an Uncertainty Analysis Methodology for Computational Fluid Dynamics of External Flows over Launch Vehicles

Space launch vehicles are often engineered with large safety factors due to the scarcity and cost of ground tests. In addition, these vehicles often carry expensive and delicate payloads that must go through extreme launch conditions. Computational Fluid Dynamics (CFD) can be utilized to support the design of these vehicles but often have uncertainty and errors associated with them that are often not fully quantified. This paper provides a methodology and investigation for quantifying and estimating the uncertainty for CFD over space launch vehicles when no experimental data exists. A generic launch vehicle was used for this study. The primary output quantities of interest for the study are the aerodynamic coefficients. While there are numerous sources of uncertainty, this study investigates the impact of mesh quality, boundary conditions, and turbulence models. The largest uncertainty lies in the y-moment coefficient, where the y-axis is aligned with the angle of attack, and is due to perturbing the turbulence model for a zero-degree angle of attack configuration or perturbing the mesh quality for a six-degree angle of attack configuration. The smallest uncertainty is in the x-moment coefficient, with a zero percent uncertainty for all configurations.