Progress in Aeronautical Sciences, Volume 6 reviews advances in aeronautical sciences and considers a wide range of problems related to aerodynamics, including some classical problems of fluid motion and those affecting hypersonic aircraft. Topics covered range from equations of gas flow at low density; nonequilibrium expansion flows of dissociated oxygen and ionized argon around a corner; and the role of spatially growing waves in the theory of hydrodynamic stability. This volume is comprised of five chapters and begins with a discussion on flows of gases where the density of the gas is too low for equations of continuum gas dynamics to be applicable. The kinetic theory of gases is used to derive the equations governing such flows. The second chapter deals with the nature of shock waves in flows of electrically conducting gases subjected to magnetic fields. The third chapter is concerned with the theory of two-dimensional flows of dissociated oxygen or ionized argon expanding around a corner. The fourth chapter goes back to the classical problem of hydrodynamic stability and the possible mechanics underlying the transition from the laminar to a turbulent state of the flow. The last chapter describes a future type of aircraft that can fly at hypersonic speeds. This book will be a useful resource for students and practitioners in the field of aeronautics.