This paper presents results of work that has been done in developing use of the Second Law of Thermodynamics and methods such as exergy and thermoeconomics into a system-level analysis and design methodology. The application of these methods to the design of a complete flight vehicle is illustrated by considering an integrated airframe/propulsion system as a device to do work. This shows how system-level consideration of exergy applies to all vehicle systems in consistent terms. For the hypersonic inlet flow problem, it is shown that a thermal energy exchange with the inlet flow could be used to position the inlet shock in the optimum shock-on-lip position for off-nominal flight conditions. The thermal heat exchange analysis has been done for a full range of Mach numbers both higher and lower than nominal. It is shown that there is a potential benefit in terms of reduced exergy destroyed using thermal energy addition than by the shock at higher Mach numbers. The paper then discusses how a device to accomplish this result would have to be integrated into a complete vehicle design.