Ali Gülhan

In the Horizon Europe Project SALTO, a demonstrator of a vertically landing first stage with three Prometheus engines was investigated, the so-called T3. It shall be recovered with a downrange landing approach. In this paper the aerodynamic phase of the descent trajectory was investigated using wind tunnel experiments of the full launcher configuration in the Trisonic Wind Tunnel Cologne (TMK). The grid fins proved to be efficient to trim and control the vehicle. Increasing the size of the grid fins by 10% does not directly transfer into a larger trimmable angle of attack range. Modelling the engine nozzles as closed surfaces instead of open cavities introduces a systematic offset in the axial force coefficient which vanishes at zero incidence and grows to approximately 0.05 at the extremes of the tested angle of attack range, and it affects the roll moment of the undeflected configuration at the supersonic Mach numbers. This simplification is therefore acceptable for low-fidelity databases, but the nozzles should be modelled as open cavities for high-fidelity databases and for the validation of CFD computations. A Reynolds number variation showed a small but systematic effect on the axial force coefficient and on the roll moment, while no discernible effect was found in the coefficients governing the trim and the static stability. A superposition approach defined in earlier work was validated with the wind tunnel data. During ascent, the increase in length of the configuration influences the pitch moment coefficient considerably more than the deployment of the grid fins, while the deployed fins increase the axial force coefficient by approximately 17% at Mach 3.0.

The long duration hypersonic flight experiment ATHEAt was carried out with a two-stage sounding rocket configuration from the Andøya Space launch site on 6th October 2025 in Norway. The first stage motor Red Kite combined with the Black Brant Mark IV motor as the second stage made it possible to fly a payload with a mass of 244 kg at Mach numbers between 5.0 and 9.46 at an altitude range from 18 to 31 km for 119 s. The forebody of the scientific payload features a thermal protection system (TPS) made of ceramic matrix composite (CMC) segments. The first part has an ogive shape followed by an octagonal shape and four flaps. The payload includes a transpiration cooling and an impingement cooling experiment. The initial 5 deg deflection of all four flaps was increased to 20 deg during the hypersonic flight phase. In addition to 370 intrusive sensors, additional nonintrusive techniques were used for the measurement of displacement and deformation of hot structures. Two infrared (IR) cameras and four pyrometers measured the surface temperature distribution of the flap rear surfaces. To minimize the apogee dispersion and enable precise science conditions for the flight experiment, a flight-qualified predictor was used.

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.

The main goal of this study is the investigation of the recession augmentation of cork-based ablators in a particle-laden Martian flow environment in the arc-heated facility L2K. The thermal response of the P50 cork-based ablator is assessed through recession and material temperature measurements. An innovative laser-based technique was employed to measure the in situ, time-resolved evolution of material thickness due to ablation, swelling, and erosion. The results were compared with 3D surface scans. Sample temperatures were monitored using infrared thermography and embedded thermocouples. In the tests, a slightly simplified Martian atmosphere (97% [ ] and 3% [ ]) was used. The high-enthalpy flow was loaded with micrometric magnesium oxide particles moving at approximately 2000 m/s. Flow conditions without particles were also studied for comparison. The particle-induced erosion was evaluated by comparing conditions with and without particles. In the presence of particles, the increased surface recession causes higher in-depth temperature due to material thinning. For this reason, the design of cork-based heat shields for Martian missions around dust storms requires increased safety factors.

A novel dynamic stability test device based on the free-oscillation measurement technique has been developed for wind-tunnel applications covering flow regimes from subsonic to hypersonic conditions. The device offers high versatility through interchangeable cross-springs, enabling free-oscillation tests in pitch, yaw, and roll, and accommodating models with a wide range of moments of inertia and aerodynamic stiffness characteristics. It is suitable for both capsule-type and lifting-body space vehicle configurations. The first application of the device was a dynamic pitch stability test of the ReFEx (Reusable Flight Experiment) model, representing a lifting-body space vehicle, where dynamic stability along the designed trajectory was demonstrated. Oscillation data were evaluated using both cross-spring sensor signals and Schlieren image analysis, showing excellent agreement and thereby validating the applied signal-processing approach. A second application involved dynamic pitch stability testing of an inflatable heat shield model within the EFESTO-2 Horizon Europe project. Measurements were conducted using two cross-springs with different stiffness values, resulting in tests at different reduced frequencies. Additional Reynolds number variations were performed, allowing the influence of reduced frequency and Reynolds number on the extracted dynamic stability derivatives to be systematically assessed.

Re-entry flights of reusable first or upper stages typically foresee phases in the hypersonic flight regime, characterized by severe aero-thermal loads which could become critical for the most exposed components, like the vehicle forebody or the fin leading edges. These require consequently dedicated thermal protection systems (TPS), whose design generally requires a multi-disciplinary approach. In this framework, a viable solution is the use of high-temperature resistant ceramic matrix composite (CMC) structures, but the implementation of such technology, especially for the manufacturing of complex components and its application in real flight conditions, still presents significant challenges. In this work, the design activities for the CMC-based TPS of the payload forebody of a hypersonic sounding rocket are presented, developed within the framework of the STORT project, whose mission includes in flight demonstration of multiple critical technologies required for sustained flight at Mach numbers above 8, corresponding to a significantly high integral thermal load.

This paper presents the development and application of a Transformer deep-learning model to fluid–structure problems induced by shock-turbulent boundary layer interaction. The model was trained on data from experiments conducted at a hypersonic wind tunnel under flow conditions that allowed for a Mach number of 5.3 and a Reynolds number of ∼19.3×106/m. The shock-wave turbulent boundary layer interaction occurred over an elastic panel. The Transformer was trained using panel deformation measurements taken at different probe locations and the pressure in the cavity beneath the panel. The trained Transformer was subsequently applied to unseen data corresponding to various mean cavity pressures and panel deformations. The capability of the Transformer to capture aeroelastic trends is promising, with interpolation accuracy shown to depend on the volume of data used in training and the location to which the model is applied. The practical implications of this study for aeroelastic research are significant, offering new insights and potential solutions to real-world aeroelastic challenges.