Trajectory optimization for reducing coolant fuel losses of aerospace planes

Engine cooling demands of a hypersonic carrier vehicle propelled by a turbo/ram jet combination are considered for a three-dimensional range cruise with a return to the launch site. The fuel flow required for cooling the engine is accounted for an overall fuel optimization problem so that the flight phases during which more fuel is required for engine cooling than for thrust producing are adequately accounted for. It is shown that a significant fuel saving can be achieved when compared with the classical trajectory optimization approach which only takes the fuel required for producing thrust into consideration.