An aerospace vehicle is accelerated by a propulsion system to a given velocity. A nozzle is used to extract the maximum thrust from high pressure exhaust gases generated by the propulsion system. The nozzle is responsible for providing the thrust necessary to successfully accomplish the mission while its design efficiency translates to greater payload and reduction in propellant consumption. Specifically, the nozzle is that portion of the engine beyond the combustion chamber. Typically, the combustion chamber is a constant area duct into which propellants are injected, mixed and burned. Its length is sufficient to complete the combustion of the propellant before the nozzle accelerates the gas products. The nozzle is said to begin at the point where the chamber diameter begins to decrease. This paper exploits the De Laval nozzle, a convergent divergent nozzle invented by Carl De Laval toward the end of the 19th century, and it tries to give a practical procedure to design the nozzle of minimum length. The basic assumption made is that the boundary layer thickness is small compared to the characteristic length, i.e. nozzle radius, so that the nozzle flow field can be treated as inviscid for the purpose of designing the aerodynamic lines. Ones the aerodynamic lines are determined, a correction can be made to account for the displacement thickness of the boundary layer. This second step of the designing procedure is not treated in here. This basic procedure has been applied successfully to many supersonic nozzle
