The production of NO by hypersonic flight

Behind the shock waves occurring during hypersonic flight, a large amount of kinetic energy is transformed into energy of the translational and rotational degrees of freedom of the molecules. For high Mach numbers temperatures of many thousand degrees may be reached immediately behind the shock front. Chemical reactions take place and nitric oxide is produced. For hypersonic aircraft the NO-production of the engines exceeds the nitric oxide production behind the shock wave as well as the NO-production in the boundary layers. Reentry vehicles entering into the earth’s atmosphere with high Mach numbers cause strong detached shock waves. For the Space Transfer Shuttle (STS) the NO-concentration in the wake averaged over a cross section of 106 m2 is up to 800 times higher than the background NO-concentration. In total, an amount of about 5000 kg NO is produced for each shuttle descent; nitric oxide is formed in the altitude range 50 km