Burt Rutan's White Knight and SpaceShip One, Photo Courtesy of Scaled Composites
Thermodynamics and Propulsion

9.3 Propulsion is a systems endeavor

There are a multitude of other factors which a propulsion engineer must take into account when designing a device including weight, cost, manufacturability, safety, environmental effects, etc. Thus propulsion is truly a systems endeavor, requiring knowledge of a variety of disciplines:

Fluids + thermo + structures + dynamics + controls + chemistry + acoustics + ...