In Part 1 of this post, I presented the math behind a rocket nozzle.

Here, in part 2, I’ll show you how I turned that math into a 3d model!

First, the fun stuff… I posted my code to Thingiverse at http://www.thingiverse.com/thing:280483 where you can play with it live via the Thingiverse customizer.

How does it work? Well, first, I built an OpenSCAD script, using the math from Part 1 to build a 2D shape like this:

full2dNozzle(Rinlet = Rinlet, Ain = Ain, Rthroat = Rthroat,
             Rexit = Rexit, Aout = Aout, pct = pct);

This shape is actually two half-nozzles, one a conic nozzle and one a parabolic nozzle. Here, the inlet arc is 1.5 * Throat Radius, and outlet arc is .382 * Throat Radius, as shown in Part 1.

Once I have defined a function ‘full2dNozzle’ to draw the 2d shape, it is a one-liner in OpenSCAD to twist and extrude it into 3d:

rotate_extrude() rotate([0, 0, -90])
         full2dNozzle(Rinlet = Rinlet, Ain = Ain, Rthroat = Rthroat,
                 Rexit = Rexit, Aout = Aout, pct = pct);