Unsteady loads on a descending launcher first stage demonstrator in the aerodynamic phase

Within the Horizon Europe Project SALTO, a demonstrator of a vertically landing first stage equipped with three Prometheus engines (T3) was investigated. The vehicle is designed for recovery using a downrange landing approach. This paper analyzes the aerodynamic phase of the descent trajectory based on the wind tunnel experiments conducted with the full launcher configuration in the Trisonic Wind Tunnel Cologne (TMK). Unsteady pressure fluctuations were measured using high-frequency pressure sensors. Significant fluctuations were observed, particularly in the base region of the vehicle. In this region, amplitudes reached approximately 30% of the dynamic pressure and occasionally increased to 40%. In the vicinity of the grid fins, the amplitudes were lower but remained on the order of 10%. The measured pressure signals did not exhibit distinct dominant frequencies and were predominantly broadband in nature.