Long Duration Hypersonic Flight Experiment ATHEAt

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 4 motor as the second stage allowed to fly a payload with mass of approx. 244 kg at Mach numbers between 5.0 and 9.3 at an altitude range from 18 km to 31 km for 119 seconds. This trajectory is compared to the planned one more suppressed and leads to more severe aerothermal loads. The forebody of the scientific payload consists of CMC segments, where the first part features an ogive shape followed by an octagonal shape and four flaps. Two active cooling experiments, i.e. transpiration cooling and impingement cooling, are part of the payload. A pneumatically driven actuator system increased the initial 5° deflection of all four flaps to 20° during the hypersonic flight phase. The conical module between the payload and the service module was used for a structural health monitoring (SHM) experiment. In addition to 370 intrusive sensors (pressure, heat flux, temperature, strain) additional nonintrusive techniques were used for the measurement of displacement and deformation of hot structures. Two IR cameras and four pyrometers measured the surface temperature distribution of the flap rear surfaces. The flight-qualified predictor based on the 3 DoF trajectory simulation was used to determine the optimal ignition time for the second stage motor based on input from the flight-qualified new strapdown IMU to minimize the apogee dispersion and enable precise science conditions for the flight experiment.