Comparison of hydrogen and methane for cooling hypersonic aerospace plane

This paper studies the active cooling for aerospace plane, using liquid hydrogen and liquid methane. The study includes the cooling for the stagnation point, the leading edges for wings and engine and other parts of the aerospace plane that are close to the leading edges. The amount of heat rate (total, radiative and convective) 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 study shows that the ratio of masses of coolant to the initial total mass (initial total mass of the vehicle including fuel and coolant masses) are in the limit of the reachable range. Comparison of liquid hydrogen and liquid methane shows that liquid hydrogen is a clear winner as a candidate for coolant.