Active thermal control for hypersonic vehicles

The authors present the design and evaluation of a thermal control system that provides cooling by controlling the fuel flow through a network of heat exchangers. The heat exchangers provide cooling for both airframe and propulsion components. It is shown that efficient use of fuel cooling throughout the vehicle´s operating envelope requires modulation of the flow splits within the network. Modulating valves are adjusted in-flight to provide optimal distribution of the coolant. It is also shown that this modulation cannot be accomplished through scheduling alone if off-nominal heat loads are to be tolerated. Local control of panel temperature provides some tolerance, but it is not sufficient. A hierarchical controller consisting of a central control algorithm to coordinate the local controllers as well as the turbomachinery control provides increased tolerance to off-nominal heat loads as well as efficient use of coolant