I found it quite fascinating that the Shuttle External Tank was as thin as 2.5mm. That seems very thin for a structure over 40 meters tall and weighing as much as 760 000kg fueled.

I'm curious how this compares to other rockets. I know original Atlas had very thin "balloon" tanks — but how thin was it actually, and how much did it weigh? And what about other rockets in use, say Falcon 9 or Atlas V? Or something really big like Saturn V? How much thickness and weight you need in the tank to support the whole rocket?


3 Answers 3


Old school Atlas -- 0.1 to 0.4 inches (2.5 to 10 mm) thick -- so, actually, similar to the metal portion of the shuttle ET.

Centaur upper stage tanks -- 0.014"--0.016" (0.36 to 0.41 mm) thick (!).

Saturn V's 1st stage tanks varied in thickness from 0.170"-0.254" (4.32 to 6.45 mm).


Adding to Russell's answer, Falcon 9 apparently has 3/16''-thick walls (4.7mm). This is interesting, because it's more than Shuttle's ET and about as much as parts of S-IC, despite being a smaller rocket. Presumably this is for extra structural margins to make the stage survive multiple reuse.

  • $\begingroup$ The system won't let me suggest an edit for 1 character, so wanted to notify you that 4.7mm is 3/16''. $\endgroup$
    – jkavalik
    Commented May 22, 2016 at 12:45
  • $\begingroup$ This Wired article confirms wall thickness is "about 5 mm". $\endgroup$
    – Hobbes
    Commented May 23, 2016 at 8:19
  • $\begingroup$ Falcon 9 carries thrust loss $\endgroup$
    – Saiboogu
    Commented Aug 27, 2020 at 4:27

For ariane 5 the thickness is:

8mm for the solid boosters 4mm for the cryogenic main stage.

However both have an additional thermal insulation layer. I couldn't find data for the booster [see comments], but it's 2cm for the cryogenic one.

Considering this data I wouldn't be surprised if the insulating layer is missing from the other answers.

PS: the fairing is 3cm thick.


  • 1
    $\begingroup$ The insulating layer is not a structural component. $\endgroup$
    – Hobbes
    Commented May 23, 2016 at 14:35
  • $\begingroup$ Of course, but it's misleading not to include it $\endgroup$
    – Antzi
    Commented May 23, 2016 at 14:37
  • 1
    $\begingroup$ AFAIK, the Ariane 5 boosters only have thermal insulation on the bottom end of the booster, on the inboard side which faces the first stage main engine. $\endgroup$
    – Hobbes
    Commented May 23, 2016 at 14:41

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