Active cooling of a hypersonic plane using hydrogen, methane, oxygen and fluorine

This paper studies active cooling of an aerospace plane using liquid hydrogen, liquid methane, liquid oxygen and liquid fluorine. An ascending optimized trajectory to minimize the heat load in the hypersonic part is used to perform the study, which includes cooling of the stagnation point, the leading edges of wings and engine and other parts of the aerospace plane that are close to the leading edges. The laminar case of the stagnation point and both laminar and turbulent cases for the leading edge heating have been considered. The amount of liquid coolant mass needed for cooling is calculated. A design of minimum inlet-outlet areas for the amount of liquid needed for cooling is made with consideration of the coolant's physical constraints in the 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) is in the limit of the reachable range. The comparison shows that the hydrogen is a clear winner as a candidate for coolant and saves mass as compared to the other three 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.