I was reading this question: Why the non-symmetric design of rocket nozzles?
Which got me thinking, have there been any nozzles that don't end in an ellipse? Even the one in that question ends in a conic section, which is an ellipse. Perhaps maybe a notched ellipse, or a square? I realize that these are impractical for various reasons, but I don't doubt somebody has done experiments with non-elliptical nozzles.
A couple short-comings I would assume with non-elliptical nozzles would be:
- Potentially difficult (impossible?) gimbal.
- Incorrectly vectored thrust.
- Less concentrated thrust (possibly?).
(Feel free to correct/add to any of the above assumptions, because they are indeed assumptions).
If the answer is no, can someone give a quick-and-dirty why about the elliptical shape of all nozzles compared to something like a square?