The special set of conditions experienced by a vehicle on atmospheric entry is referred to as an aerothermodynamic environment. When the shuttle orbiter initially re-enters earth's atmosphere, i.e. when it is high in the atmosphere - pressure is low and altitude is decreasing rapidly. The surface temperature of the vehicle increases rapidly and peaks at about 1200 deg C, when it is moving several kilometers/second and the atmospheric pressure is becoming more appreciable. High temperatures are sustained for several minutes as the vehicle decelerates rapidly. A shock layer forms around the vehicle, with dissociated and partially ionised nitrogen and oxygen flowing over the surface and reacting with the surface treatment. This article is a copy of the Friedberg Memorial Lecture given by a research scientist in Thermal Protection Materials at NASA's Ames Centre.
