Free Piston Shock Tunnels HEG, HIEST, T4 and T5

At hypersonic flight the kinetic energy of the flow is large enough that high temperature effects such as vibrational excitation or dissociation of the fluid molecules occur. Due to the extremely high power requirement and the severe flow environment, the required test conditions can only be achieved in ground based impulse facilities. The most successful types of facility which are able to generate high enthalpy and high pressure hypersonic flows are shock tunnels and shock expansion tunnels. The principle of operation of these facilities is to store the energy over a long period of time, therefore reducing the necessary power requirement and subsequently releasing the stored energy rapidly. In free piston driven shock tunnels, the conventional driver of a shock tunnel is replaced by a free piston driver. This concept was proposed by Prof. R.J. Stalker in the 1960th and the facilities are referred to as Stalker tubes. In the present article, four major Stalker tubes, the High Enthalpy Shock Tunnel Göttingen, HEG, at the German Aerospace Center, the High Enthalpy Shock Tunnel, HIEST, at the Japan Aerospace Exploration Agency, Kakuda, T4 at The University of Queensland, Brisbane, Australia and T5 at the Graduate Aeronautical Laboratories, California Institute of Technology, United States are presented. In addition to facility overviews, selected research activities are discussed.