During the Artemis I test flight, the SLS rocket experienced higher-than-expected vibrations near the solid rocket booster attach points, caused by unsteady airflow between the gap.
One solution proposed for Artemis II was adding four strakes. A strake is a thin, fin-like structure commonly used on aircraft to improve unsteady airflow and stability. Adding them to the core stage minimizes the vibration of components.
The strake solution comes from previous tests in the Unitary Plan Wind Tunnel, where NASA engineers applied an Unsteady Pressure Sensitive Paint (uPSP) technique to SLS models. The paint measures changes over time in aerodynamic pressures on air and spacecraft.
It is sprayed onto test models, and high-speed cameras capture video of the fluctuating brightness of the paint, which corresponds to the local pressure fluctuations on the model. Capturing rapid changes in pressure across large areas of the SLS model helps engineers understand the fast-changing environment. The data is streamed to the NASA Advanced Supercomputing facility via a high-speed network connection.
“This technique lets us see wind tunnel data in much finer detail than ever before. With that extra clarity, engineers can create more accurate models of how rockets and spacecraft respond to stress, helping design stronger, safer, and more efficient structures,” said Thomas Steva, lead engineer, SLS sub-division in the Aerodynamics Branch at NASA’s Marshall Space Flight Center in Huntsville, Alabama.