© 1995 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.The work presents a comparative study for cooling aerospace plane, using liquid H2, CH4, and Xe. The ascending optimized trajectory to minimize the heat load in the hypersonic part is used to perform the study. The amount of heat rate and the mass of liquid coolant needed for cooling are calculated. A design of minimum inlet-outlet areas for the amount of liquid needed for cooling, is made with the consideration of the coolant's physical constraints in liquids and gaseous states. The comparison shows that the hydrogen is a clear winner as a candidate for coolant and it saves mass as compared to the other two coolants. The study shows that there are no fundamental barriers for the cooling system of the vehicle in terms of its coolant mass and area size for coolant passage, especially, if H1 is used.