So I'm an amature rocket scientist. while having a conversation with a friend on a nozzles we though of a new nozzle:

my nozzle design

Its a double nozzle where it expands a lot and then compress. I want to put this to the test on a R-candy but is it work the time and effort? I think it will lose a good portion of its energy by the time it comes out. My friend says that the Bernoulli's principle will cause it to go faster hence the lost of energy doesn't matter. What do you think?

  • $\begingroup$ Its not worth the effort, except as a learning exercise. Have fun, that's what amateur rocketry is all about. $\endgroup$
    – user20636
    Apr 2, 2018 at 6:19
  • 4
    $\begingroup$ Possible duplicate of Why do rocket nozzles open near the end? $\endgroup$ Apr 2, 2018 at 10:12

1 Answer 1


Bernoulli's principle only applies to incompressible flow. Once you go compressible, especially when you go supersonic, things become counterintuitive. This design will limit you more or less to an exhaust velocity just barely above Mach 1.


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