Reduction of coolant fuel losses in hypersonic flight by optimal trajectory control

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