SCRAM Jet Engines - Nozzle configuration question.?

Question

As I understand it, in a SCRAM Jet engine the speed of the craft is used to compress the air to be used as an oxidizer for the fuel. What is the angle or parabolic curve of the nozzle of the engine? That is, is there a formula or known constant that allows for optimum compression of air given a certain speed?

Answer 1

I am not sure there would be a constant as you would need different thrust levels for differnt type planes.  Meaning depending on the weight and operating speed of the aircraft the formula would change for every aircraft.  For example the SR-71 needed to produce enough thrust to keep above Mach 2 at the alt. it was flying.  For it's design mach 2 is about the stall speed at that altitude.  For something flying at a lower level with a less critical wing you would not need as much thrust.  This is an intresting question though and I would like to see what othe people say about it.