Just a note…
The setup doesn’t change the Y and Z axis. If using the ‘object’ coordinates, the radius of the thruster will be 1 blender unit (unless the object has scale transformations).
To change this, we can add two new math nodes, setted to divide or multiply, for the Y and Z (just like the division of the X component). This is mainly for the sphere gradient, as the noise can be tweaked just using the scale. For a circular section, the Y and Z should be divided/multipied by the same value. Different values will turn the section into an ellipse (which in some cases can also be usefull).
And if you’re wondering, choosing between ‘divide’ or ‘multiply’ is just a matter of preference. Division is the inverse of multiplication, so some number divided by 2 is the same as that number multiplied by 1/2.
It makes readability a bit easier… for example: x/5 is the same as x*0.2, so choose whatever looks better for you.