One of the most challenging problems of modern engineering is undoubtedly the prediction of hypersonic flows around space vehicles in reentry conditions. Indeed, the difficulties are numerous: first of all, these flows are very difficult to model, since very complex physical and chemical phenomena take place during the reentry phase; secondly, temperature, velocity and enthalpy are very high and densities are very low, making the reentry process very difficult to reproduce in ground-based experiments. The past three decades have seen important efforts in computational fluid dynam­ ics relying on the use of supercomputers to simulate these very complicated flows. The numerical simulation based on imperfect models and methods which were es­ sentially designed for transonic and supersonic flows has still a long way to go in order to be able to predict these hypersonic reentry flows very accurately. This situation has motivated very strong international cooperative efforts with, as the most visible consequences, the EuropelUnited States Short Courses on Hy­ personics, which were held in Paris, in 1987 [1,2], Colorado Springs in 1989 [3], and Aachen in 1990 [3]. The workshop on Hypersonics whose results are presented and analysed in these volumes is also a direct consequence of this international cooperation. This scien­ tific event was an initiative of P. Perrier, Head of the Theoretical Aerodynamics Department of DASSAULT AVIATION, who played a key role in the identification of the critical problems and the realisation of experiments, within the Hermes R&D program framework.

These two volumes contain a detailed survey on various techniques of numerical simulation of the critical reentry phase of space vehicles. Eight test problems are compared with experiments and thoroughly analysed. The books address numerical analysts, engineers, and physicists.

Invited Lectures.- Inaugural Address.- Comments on Experiments for Computational Validation for Fluid Dynamic Predictions.- Hypersonic Stability and Transition.- Scattering Kernels for Gas¿Surface Interaction.- Computational Fluid Dynamics for Hypersonic Airbreathing Aircraft.- Similitude in Hypersonic Aerodynamics.- Gas-kinetical and Navier-Stokes Simulations of Reentry Flows.- Numerical Simulation of Boltzmann Flows of Real Gases ¿ Accuracy of Models Used in the Monte Carlo Method.- Intrusive and Nonintrusive Measurements of Flow Properties in Arc Jets.- CFD for Hypersonic Propulsion.- Experimental Simulation of High-Enthalpy Real-Gas Effects.- Problems for Analysis.- Problem 1: Flow over a Slender Cone.- Problem 2: Turbulent Base Flow.- Problem 3: Flow over a 2D Ramp.- Problem 3: Flow over a 2D Ramp.- Problem 5: Corner Flow.- Problem 6: Double (Simple) Ellipsoid.- Problem 7: Flow over a Delta Wing.- Problem 8: Non-equilibrium Flow in an Arc Jet or a Shock Tube.- Appendix: Non-equilibrium Model for Problem 6.