Cooling of aerospace plane using liquid hydrogen and methane

This work studies the active cooling for aerospace plane, using liquid hydrogen and liquid methane. 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. Laminar flow for the stagnation point and both laminar and turbulent flow 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 liquid 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, which requires about 20% or less of initial total mass for cooling in the worst case. Comparison of liquid hydrogen and liquid methane shows that liquid hydrogen is a clearly superior candidate for coolant and it saves 10% of the initial total mass as compared to methane. 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.