The article deals with the aerodynamics of atmospheric re-entry of an object idealised as a flat plate corresponding to the re-entry conditions at hypersonic regime. The rarefied flow conditions corresponding to various altitude are simulated using dsmcFoam, an open-source solver. The methodology of the current work consists of validating dsmcFoam and then apply for computing the flow field over the flat plate for a range of conditions. Results are obtained for different altitudes where temperature and number density are varying parameters, isothermal wall of the flat plate with surface temperature as a variable parameter and for adiabatic wall condition. Effect of angle of attack is also presented for these cases. The data obtained from the DSMC simulations will be applied to develop a mathematical model for predicting the slip velocity over the flat plate surface as a function of the variable parameters such as variables number density, ambient temperature, wall temperature and angle of attack.