In this paper numerical analysis has been done at re-entry condition of Space Shuttle STS-2 flight during descent phase of the vehicle using CFD++ laminar solver. 7 species with 6 reactions step chemical kinetic model is used for CFD simulation. The reaction rate constants are from Park-87 model. Flow field details and laminar surface heat flux are computed for the windward symmetry plane of the Space Shuttle. Results are computed for both Equilibrium and Non-equilibrium flows and compared with the flight heat flux data derived from measured surface temperature. Non-equilibrium computations are done with non-catalytic and fully catalytic wall boundary conditions. In the present study heat flux is calculated over the windward centerline surface at M=23.4, α=39.4° and at an altitude of 71.3km. The overall result shows a good agreement with the flight data and is observed that for x/l<0.2 there exist a finite surface catalyticity and heating rates are close to non catalytic wall condition and beyond x/l>0.2, predictions from Equilibrium, Non-Equilibrium fully catalytic wall and noncatalytic wall converge and flight heating rates are close to fully catalytic wall condition.