For a university project, I'm working on optimisation of a Falcon-9-like launch vehicle, and one element of that is varying expansion ratios of the engines. This will impact on the engine mass, but to calculate that I'd need the thickness (or mass per unit area) of the engine bell of a Merlin or comparable engine, and I'm struggling to find any sources.

Edit: it's been pointed out that my question lacked specifics, I was after the typical wall thickness of a regeneratively cooled nozzle - as opposed to radiatively cooled like Merlin Vac, and not including support structures or external piping

  • 3
    $\begingroup$ It varies enormously engine-to-engine. I believe it also varies with different parts of the nozzle; someone (I forget who) on this site claimed the very large nozzle expansion of the Merlin vacuum engine gets down to 1/64" thickness at the end, and you can see quite a bit of flexing happening in videos of Falcon second-stage burns. space.stackexchange.com/questions/22789/… $\endgroup$ Commented Apr 10, 2020 at 17:32
  • 1
    $\begingroup$ SpaceX once fixed a crack at the end of a nozzle by trimming it with a tin snips. So they can get pretty thin. naturallyfundamental.com/spacex-tin-snips-rocket-fix $\endgroup$
    – Greg
    Commented Apr 10, 2020 at 21:25

1 Answer 1


At the exit plane the Space Shuttle Main Engine (SSME) nozzle was about 2 inches thick. This was a regeneratively cooled nozzle built up of tubing with a manifold encircling the exit.

enter image description here

Source: SSME Orientation (annotation mine)

Three SSME nozzles in the engine shop at KSC and a closeup.

enter image description here

enter image description here

Source: personal photos

  • $\begingroup$ Surely the total outer diameter includes reinforcing rings and fuel feedlines for the regen, so would not give an accurate thickness? $\endgroup$
    – Talisker
    Commented Apr 10, 2020 at 20:25
  • 1
    $\begingroup$ @Talisker You asked for the "thickness of a rocket nozzle". If you want something more specific, please edit your question. $\endgroup$ Commented Apr 10, 2020 at 21:04
  • $\begingroup$ here's a fairly thin one that doesn't appear to have any reinforcement, though I don't know if it is used. $\endgroup$
    – uhoh
    Commented Apr 11, 2020 at 16:09

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.