Aerospace plane cooling with H₂, CH₄, He, Ne, N₂, and Ar

This article presents a comparative study for cooling aerospace planes, using liquid H₂, CH₄, He, Ne, N₂, and Ar. The ascending optimized trajectory to minimize the heat load in the hypersonic part is used to perform the study. 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 laminar case for the stagnation point and both laminar and turbulent cases for the leading-edge heating have been considered. 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 comparison shows that the hydrogen is a clear winner as a candidate for coolant and it saves mass as compared to all other five 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 H₂ is used.