Engine Nozzels on spacecrafts

[irizarry]

I am interested in the dynamics of rocket engine nozzles. Unfortunately the references I have found do not discuss in detail the items I’m interested in;

(1) What decides the diameter on the bell-shaped nozzle?
(2) How does the length to the nozzle affect the focus of
the burn?
(3) Curvature for nozzles are different, what are the rules
(or physical laws) that decide optimum performance?

Of course, like many things in science there may not be a collection of well defined laws that govern burn behavior; it may just be alchemy, like many aspects of Solid State Physics, Antenna design, etc.

If anyone has some references or comments please forward. I’m not looking for the classical mechanics behind rocket science but strictly nozzle design theory.

[SEDShead]

These topics were covered during my BS in aerospace engineering at the junior level, in my "gas dynamics" class. I'd recommend looking for texts on that for the general theory, allthough I believe I've seen some specific to nozzle design.

The theory itself wasn't all that complex -- the main issues were combustion and ambient pressure, throat diameter (for supersonic flow at that point), and the expansion ratio of the exit of the bell to the throat. This ratio would be optimized for a particular point during the rocket-in-design's trajectory. A rocket designed for getting a launch vehicle off the ground is completely different than one designed for use in vacuum.