The combustion temperature in an efficient rocket engine is around half that of the Sun’s surface, well above the melting point of structural metals. How can the combustion gases, under high pressure, be contained within a combustion chamber and nozzle that must be made of materials as light as possible? Over the years, engineers have found a variety of solutions to this puzzle, and choosing the appropriate one (or ones) is a key part of the art of rocket propulsion engineering.