Final Report Summary - HEXAFLY (High-Speed Experimental Fly Vehicles)
Performing a test flight will be the only and ultimate proof to demonstrate the technical feasibility of these new promising high-speed concepts versus their potential in range and cruise. This would result into a major breakthrough in high-speed flight and create a new era of conceptual vehicle designs.
At present, the promised performances can only be demonstrated by numerical simulations or partly experimentally. As high-speed tunnels are intrinsically limited in size or test duration, it is nearly impossible to fit even modest vehicle planform completely into a tunnel (Fig. 2). Therefore experiments are limited either to the internal propulsive flowpath with combustion but without the presence of high-lifting surfaces, or to complete small-scaled aero-models but without the presence of a combusting propulsion unit. Though numerical simulations are less restrictive in geometrical size, they struggle however with accumulated uncertainties in their modelling of turbulence, chemistry and combustion making complete Nose-to-Tail predictions doubtful without in-flight validation. As a consequence, the obtained technology developments are now limited to a technology readiness level of TRL=4 (components validated in laboratory).
The HEXAFLY project aims to achieve a first maturation and a proof of concept to experimentally flytest these radically new conceptual designs accompanied with several breakthrough technologies on board of a high-speed vehicle. This approach would increase drastically the Technology Readiness Level (TRL) up to 6 (System demonstrated in relevant environment). The emerging technologies and breakthrough methodologies strongly depending on experimental flight testing at high speed can be grouped around the 6 major axes of HEXAFLY:
1. High-Speed Vehicle Concepts to assess the overall vehicle performance in terms of cruiseefficiency, range potential, aero-propulsive balance, aero-thermal-structural integration, etc...
2. High-Speed Aerodynamics to assess e.g. compressibility effects on transition, aerodynamic vehicle shapes with high L/D, stability, etc…
3. High-Speed Propulsion to evaluate the performances of high-speed propulsive devices such as intakes, air-breathing engines (ABE), nozzles (SERN) including phenomena such as highspeed combustion, injection-mixing processes, etc…
4. High-Temperature Materials and Structures to flight test under realistic conditions high temperature lightweight materials, active/passive cooling concepts, reusability aspects in terms oxidation, fatigue, etc…
5. High-Speed Flight Control requiring real-time testing of GNC (Guidance Navigation Control) in combination with HMS/FDI technologies (Health Monitoring Systems/ Fault Detection and Isolation)
6. High-Speed Environmental Impact focusing on reduction techniques for sonic boom and sensitivities of high-altitude emissions of H20, CO2, NOx on the stratosphere.