Absolute intensity of non-equilibrium radiation in air and stagnation heating at high altitudes

Abstract

The paper presents some attempts to obtain the magnitude of the non-equilibrium radiation behind a normal shock for velocities up to 25,000 ft/sec in air. It is noted that the high non-equilibrium temperatures force one to extend studies further into the u.v. and i.r. than required for equilibrium predictions of significant sources of radiation. For example, to ascertain that the total non-equilibrium radiation is less than 1 W/cm 2 requires measurements from several hundred angstroms to more than 10 μ. Measurements covering much of this region using (1) monochromator and photocells, (2) bolometers, (3) photoelectric detectors, (4) spectrographs and (5) i.r. photocells are reported. At 23,000 ft/sec the radiation integral normal to the shock is about 0.4 W/cm 2-steradian; in air initially at a pressure of 20μ of Hg most of the radiation originates within 5 cm of the shock front. We also report on calculations which show that the effect of ambient atomic oxygen at high altitudes does not introduce any pronounced changes. Application of the results to the problems of satellite heating is made.