A gas–surface interaction model for atmospheric drag evaluation of very-low earth orbit satellite

Abstract A new gas–surface interaction (GSI) model for atmospheric drag evaluation of very low Earth orbit is proposed. The variable-gamma (VG) and variable-gamma energy-transfer (VGET) models are proposed based on the data from thermal and hyperthermal beam scattering experiments. The VG model takes into account the incident angle dependences of the accommodation coefficient and the VGET model adds the translational energy loss of the incident atoms in the scattering event. The VG model is an empirical model applicable for real surface scattering of molecules with thermal velocities and VGET is for hyperthermal velocities. These models are expected to provide a more realistic evaluation of the shear drag at the side surfaces of a satellite compared to the Maxwell GSI model for non-reactive molecules such as N 2 in VLEO environment. A model calculation of the SLATS satellite indicated that the drag coefficient C d is evaluated 38% lower than that evaluated by the conventional Maxwell model with a constant γ = 0.9.