The process of radiation transfer (emitting, absorbing, scattering and reflecting photons) stands alone among all other processes of energy transfer. This is because the photons propagate at the speed of light, faster than any other processes. On top of this, radiation strongly depends on the wavenumber and the direction of the propagation.
Extra-terrestrial missions, as well as the re-entry process back into the Earth atmosphere, are all subject to a severe heating, partially due to the emission of light from a shock-heated gas toward the surface of a vehicle. The fastest man-made object, capsule Stardust, has collected the star dust from the comet Wild 2 and some cosmic dust and returned to Earth at speed of 12 km/s. The radiation was responsible for 90% of the total heating upon re-entry!
Simulation of the radiation transfer is not a trivial problem due to the spatial and angular dependence of the radiative vector. On top of that, radiation intensity of heated air must be spectrally resolved. In the HTGD laboratory, we advance numerical methods of radiation transfer and couple them with state-of-the-art optical models of various gases.