If I understand correctly from this question, The SSME's nozzle is made of pipes into which cool propellant circulate. The nozzle is larger at the end than near the combustion chamber. Thus, it must require either less pipes or smaller pipes near the combustion chamber than near the end (due to the bell-like shape).

How it this geometry handle? Are the pipes smaller? Are there less pipes? Is there other technique I can't imagine?

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    $\begingroup$ Good picture of the tubes here: ids.si.edu/ids/deliveryService?id=NASM-SI-2006-401 $\endgroup$ Aug 1, 2019 at 13:14
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    $\begingroup$ In this question there's a building technique allowing use of constant diameter tubes, in an helical pattern. Pitch decreases as bell diameter increases. $\endgroup$
    – qq jkztd
    Aug 1, 2019 at 14:20
  • $\begingroup$ @qqjkztd sadly, if you look at the RS-25 pictures, the tubes are straight. $\endgroup$ Aug 1, 2019 at 23:06
  • $\begingroup$ Or possibly: greater spaces between the pipes. $\endgroup$
    – ANone
    Aug 2, 2019 at 15:08
  • $\begingroup$ @ANone no spaces exist between the pipes. $\endgroup$ Aug 3, 2019 at 13:06

1 Answer 1


The cross-section of the tubes increases from the front to the rear of the nozzle - they are "tapered".

Reference, but no details - just mentions that they are tapered.

  • $\begingroup$ Does it mean that the flow inside those pipe change from one end to the other? $\endgroup$
    – Manu H
    Aug 6, 2019 at 5:35
  • $\begingroup$ Not the flow rate - that can't -but the fluid properties. $\endgroup$ Aug 6, 2019 at 11:20

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