China conducts ground test of hypersonic ramjet that can change shape in flight

At a test facility in China, a hypersonic engine that reshapes its internal airflow channel – much like a throat tightening and relaxing – has operated continuously from a relatively modest Mach 1.8 (nearly twice the speed of sound) all the way to Mach 6 without failing. And the material that kept superheated gases from escaping? Essentially the same black mineral found inside a pencil: graphite.