A concise overview of the overall layout of an experimental powered high-speed flight vehicle including its subsystems is given. A mission scenario, the different flight segments and events to which the payload is exposed are described and justified. This allowed the definition of the aero-thermo-mechanical loads required to conceptually design all elements on board of the vehicle. The final vehicle configuration could achieve the different mission objectives. In particular an aero-propulsive balance, i.e. thrust ≥ drag and lift ≥ weight, could be established at a cruise Mach number of M = 7.4 on the basis of a hydrogen powered scramjet engine while guaranteeing a good aerodynamic efficiency L/D ≥ 4 in a stable, trimmed and controlled way. The experimental combustion campaign could last for at least for 3s up to 9s pending on the finally obtained flight level. This test time is very valuable as it is about 3 orders of magnitude higher of what can be tested in European ground facilities. The vehicle made maximum use of databases, expertise, technologies and materials elaborated in previously EC co-funded projects ATLLAS I & II and LAPCAT I & II.Based on this conceptual design, the consortium has arrived at a key point where they feel comfortable to go to the next step in establishing a detailed design of the vehicle and the preparation of the launch vehicle and flight campaign.

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The influence of localized nitrogen transpiration on second mode instabilities in a hypersonic boundary layer is experimentally investigated. The study is conducted using a 7 • half-angle cone with a length of 1100 mm and small nose bluntness at 0 • angle-of-attack. Transpiration is realized through a porous Carbon/Carbon patch of 44 × 82 mm located near the expected boundary layer transition onset location. Transpiration mass flow rates in the range of 0.05-1% of the equivalent boundary layer edge mass flow rate were used. Experiments were conducted in the High Enthalpy Shock Tunnel Göttingen (HEG) at total enthalpies around 3 MJ/kg and unit Reynolds numbers in the range of 1.4 ⋅ 10 6 to 6.4 ⋅ 10 6 m −1 . Measurements were conducted by means of coaxial thermocouples, Atomic Layer Thermopiles (ALTP), pressure transducers and high-speed schlieren. The present study shows that the most amplified second mode frequencies were shifted to lower values as nitrogen is transpired into the boundary layer. In some cases the instability amplitudes were found to be significantly reduced. The observed frequency reduction was verified to correlate with the change of the relative sonic line height in the boundary layer. The amplitude damping was observed to occur only until the most amplified frequencies were reduced to around 50% of their undisturbed values. When transpiration within this limit was performed shortly upstream of the natural boundary layer transition onset, a transition delay of approximately 17% could be observed.

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