New Concepts in High-Speed Aircraft Design
Designing high-speed passenger aircraft is very difficult: design processes differ from those for conventional aircraft, and pre-existing designs cannot be easily adapted. Designers need an entirely new approach for such aircraft. The EU-funded ATLLAS II (Aero-Thermodynamic Loads on Lightweight advanced Structures II) project developed the necessary multi-disciplinary design methodology. The work extended the achievements of an earlier EU-project (ATLLAS I). Results addressed unusual flight conditions such as high altitude, temperatures and pressures. The new method resulted into a design of a new 200-passenger Mach 5 aircraft that utilises kerosene fuel and has a range of about 9 000 km. The team also developed several high-temperature materials. Additional innovations, such as a nickel-based hollow sphere and a tube-stacking method, supported internal and external airflow paths. The group characterised the new materials at both high and low temperatures, and complemented the high-temperature materials developed in ATLLAS I. Researchers demonstrated the applicability of the new materials to functional geometries, including flight control panels and other aircraft components. The materials' functionality was extensively tested in environments representative of flight conditions. Results allowed an extended duration of exposure to testing conditions. Whereas ATLLAS I achieved durations of minutes, the new results allowed exposure of hours or more. The team also studied fundamental aspects of cooling and the aerodynamics of boundary-layer transitions. The high thermal fluxes in combustors and its control on the external skins need to be mastered in a clever way to avoid overheat while maximizing the overall propulsion and aerodynamic efficiency. Environmental impact assessment showed that the new aircraft's sonic boom level was lower than Concorde's, despite the higher speed, though the carpet width was higher. The team also studied the effects of wind, turbulence and caustics. Exhaust emissions depleted atmospheric ozone, but needed further testing to establish long-term impact. The processes used in ATLLAS II for designing a new Mach 5 aircraft can be adapted to other applications and speeds. The work has also paved the way for key technologies for a high-speed vehicle that is both commercial and environmentally friendly.
Keywords
Aircraft design, supersonic, Mach 5, ATLLAS II, sonic boom, high-temperature materials, stratosphere, emissions, ceramics, cooling, high-speed transition, MDO, structures
