Modeling the SpaceX Falcon-9 Booster’s Triple Sonic Boom Using Multiple Models and Conditions

In the age of commercial spaceflight, many organizations are designing rockets for reuse. Most designs employ some form of propulsive landing either on land or at sea. The foremost among these organizations is Space Exploration Technologies Corporation (SpaceX) with their Falcon-9 rocket. As such rockets return, they produce audible sonic booms over the surrounding areas. The Falcon-9 booster's sonic boom signature is unique, consisting of three primary shocks instead of the two associated with traditional N-waves. This provides an opportunity to study sonic boom formation from a unique geometry and to see whether the triple boom can be physically explained. This paper considers F-function and computational fluid dynamics methods to model the booster's sonic boom under conditions ranging from Mach 1.5 to 2.5. Results support the conclusion of Anderson and Gee (2025) [JASA Express Lett. 5, 023601 (2025)] that the central shock is the result of a rearward-migrating rarefaction wave produced by the lower portions of the booster merging with a forward-migrating compression wave produced by the grid fins. Although it is clear that both the grid fins and the lower portions of the booster contribute to the central shock, the different models disagree on their relative importance in producing the final shock.