ATLLAS II is a logical follow-up of a finalized FP6 project which has as objectives: the identification and assessment of advanced light-weight and high-temperature resistant materials for high-speed vehicles up to Mach 6.
The material requirements are first defined through an in-depth feasibility study of a Mach 5-6 vehicle. The consortium has this capability at hand as they can rely on a first set of validated tools, material databases and valuable experience acquired during ATLLAS I. Starting with a preliminary aero-thermal-structural high-speed vehicle design process, further multi-disciplinary optimisation and testing will follow to result into a detailed layout of an independently European defined and assessed high-speed vehicle. Special attention will be given to alleviate sonic boom and emissions at high altitudes.
Throughout the design process, the aero-thermal loads will define the requirements for the proposed materials and cooling techniques needed for both the airframe and propulsion components. The former will focus on sharp leading edges, intakes and skin materials each coping with different external aero-thermal loads. The latter will be exposed to internal combustion driven loads. Both metallic (Titanium Matrix Composites and Ni-based Hollow Sphere Stackings) and non-metallic materials (Ceramic Matrix Composites and Ultra High Temperature Composites) will be evaluated.
Combined aero-thermal-structural experiments will test various materials as specimens and realistic shapes at extreme conditions representative for high flight Mach numbers. Both static and cyclic tests at low and high temperatures are planned including the evaluation of their durability in terms of long duration exposure to the harsh flight conditions. The materials assigned to dedicated engine components will be exposed to realistic combustion environments. These will be combined with passive or active cooling technologies developed in ATLLAS I.
Technology for hypersonic aircraft
EU-funded scientists are assessing advanced lightweight materials that withstand high temperatures for aircraft flying at speeds up to Mach 6, or six times the speed of sound.
A few years ago, the EU-funded project ATLLAS I developed materials and simulation tools to prove the feasibility of high-speed aero-vehicles. It also concluded that the optimal cruise Mach number is around 5 to 6. Following in its footsteps, the latest such project, 'Aero-thermodynamic loads on lightweight advanced structures II' (http://www.esa.int/Our_Activities/Space_Engineering_Technology/ATLLAS_II_-_Project_summary (ATLLAS II)), aims to get beyond the idea stage and work on a detailed design of a flight-worthy high-speed vehicle.
In line with the reviewers' comments, ATLLAS II's detailed design study targets an optimised vehicle design with respect to aerodynamic, propulsive, structural and thermal layout. The validated tools developed in ATLLAS I should allow the project consortium to further improve the design process and testing. The study will also place increased focus on reducing sonic boom and emissions at high temperatures.
Throughout the design process, the aerothermal loads will define requirements for the proposed materials and the required cooling techniques for the airframe and propulsion components. New materials such as metallic hollow-sphere packings and ultra-high-temperature ceramics and ceramic matrix composites are under investigation. ATLLAS II will test these materials and airframe shapes at extreme conditions that represent high Mach numbers. Both static- and cyclic-stress tests will be performed to evaluate the component durability.
ATLLAS II will also experiment on cryogenic fuels with emphasis on reducing carbon dioxide and NOx emissions.
So far, project members have analysed the effect of venting an under-expanded exhaust into the base of the fuselage. Based on the findings of this configuration and the cruise efficiency, they defined the design of three vehicles. Aerothermal and structural loads typical for high speeds are reproduced experimentally to derive valuable data.
Project results will pave the way to developing viable hypersonic aircraft that could completely redefine civil aviation in the not so distant future.