For Aerodynamic analysis of vehicle at altitude, 100km, the validity of governing equations based on continuum model, was reviewed. Also, as the preliminary study for the sub-orbital space plane development, a candidate geometry was suggested and computational fluid dynamic(CFD) analysis was performed for various angles of attack in subsonic and supersonic flow regimes to analyze the aerodynamic characteristics and performance. The inviscid flow analyses showed that the stall starts at angle of attack above $20^{circ}$, the maximum drag is generated at angle of attack, $87^{circ}$ and the maximum lift to drag ratio is about 8 in subsonic flow. In supersonic, the stall angle is about $40^{circ}$ and the maximum drag is generated at angle of attack, $90^{circ}$. Also, mach number distribution of re-entry vehicle was computed versus altitudes.