A rocket is buffeted by a chaotic flow of air during flight. At high speeds, airplanes experience a similar, unsteady flow of air over their wings. A method to precisely measure these fluctuating forces uses pressure-sensitive paint (PSP), called Unsteady PSP, which emits a bright crimson glow in the presence of high-pressure airflow.
NASA is using Unsteady PSP to test effects of buffeting on the Space Launch System (SLS. Initial testing suggested the buffet loads that would affect the rocket during flight could be sufficient to require redesign of critical structural components. PSP works by reacting with oxygen to produce light. Differences in pressure result in variations in the amount of oxygen interacting with the painted surface, and, therefore, in the intensity of the light emitted. Cameras around the wind tunnel record images that are combined to determine the pressure everywhere on the model.