Validation of SLS Ascent CFD Surface Pressure Databases Using Artemis I Flight Data

This paper discusses the validation of the ascent surface pressure database developed using Computational Fluid Dynamics (CFD) for the Space Launch System (SLS) Program with Artemis I flight data from the ascent phase of flight. The ascent phase begins shortly after the vehicle clears the launch tower and extends to the first staging event. This work compares sensor data from the successful Artemis I flight to point pressures extracted from the implemented surface pressure database for Artemis I and other available CFD data sets. The database is constructed such that the pressure at any location can be extracted a posteriori so that there is no need have the correct sensor locations while running the CFD. A final source of experimental validation is provided from steady pressure sensitive paint (PSP) data obtained during a force and moment test in the Unitary Plan Wind Tunnel at NASA Ames Research Center. Most extracted surface pressures from CFD data sets match well with flight data and with the limited PSP data available. The differences that do exist are mostly caused by the way flight data was calibrated. The flight instrumentation had significant drift, so the flight data at each static pressure tap was calibrated to have a pressure coefficient of zero at liftoff and at another instance approximately two minutes into flight. However, many sensors, for example those on conical surfaces, are not expected to have a pressure coefficient of zero at high Mach numbers. Changing the calibration to the Newtonian aerodynamics pressure coefficient greatly improves the comparison to CFD. Several points remain where CFD and flight data still do not match, and these are in locations near the core stage engines, where the thermal environment and geometry were not modeled with high accuracy in this work. Overall, the Artemis I flight data strongly validates the continued use of this or similar CFD methods for launch vehicle surface pressure databas