They are fitted on each of the first stage strap on boosters and on the second stage core and are all orientated the same way. Pipes and cables connect to the stages from the cylinders. I believe they are removed before launch after the vehicle is installed on the pad.

enter image description here

  • 1
    $\begingroup$ I took the liberty of adding a picture. If the indicated object isn't what you are asking about, you can edit your answer to delete it. $\endgroup$ Nov 17, 2018 at 17:42
  • $\begingroup$ There's an inconclusive discussion on them on the KSP forum. $\endgroup$ Nov 17, 2018 at 20:22
  • $\begingroup$ Thanks for adding the picture! At least everyone is on the same page now. I have read the blogs which have discussed the cylinders. However we have still not arrived at a conclusive answer. Thanks for all the efforts! $\endgroup$
    – Phil27379
    Dec 11, 2018 at 16:37
  • $\begingroup$ based on the vertical orientation; cup-holders? $\endgroup$
    – uhoh
    Dec 18, 2018 at 10:09
  • $\begingroup$ Oh, there's actually 5 in the picture, one for each thruster column. $\endgroup$ Dec 18, 2018 at 17:50

1 Answer 1


According to this poster (warning: 3600 x 7300 pixels, 12.23 MB), they protect the "turbine exhaust (water vapor + oxygen gas)". See bottom of picture, white 23 and tan 19 identifiers.

The red covers are probably to protect against damage during shipping. Many of the exhaust ports aren't covered, but they are also hidden away under other structures.

A small thermal exhaust port. Hmmmm.

  • $\begingroup$ Great poster! But I don't think this is it, the position of white 23 is different from the barrel: 23 is between the pair of vernier thrusters and the main thrusters. $\endgroup$
    – DarkDust
    Nov 18, 2018 at 8:59
  • $\begingroup$ @DarkDust: Look closer at white 23: There is a line from the label circle to the exhaust port. $\endgroup$
    – DrSheldon
    Nov 18, 2018 at 9:15
  • $\begingroup$ I see that. The line points to an object between the vernier thrusters and the main thrusters, not the location of the barrel-like object OP is asking about. $\endgroup$
    – DarkDust
    Nov 18, 2018 at 11:23
  • $\begingroup$ Don't think that's it. The cylinders have power supplies or hoses connected to them. Also, if you view the image in the question full size, you can see the turbine exhausts just fine (they have a red ring with three white star-shaped objects on it offset from the aft bulkhead). $\endgroup$ Nov 18, 2018 at 14:36
  • $\begingroup$ They are not. You can see the turbine exhausts distinctly in that image (uncovered) due to there triangular structure. you can also see a separate image of the underside without these mysterious objects here: i.stack.imgur.com/bDABJ.png Further they appear not to be just coverings as: a) they are wired up to the external electrical connectors b) they are not 'over' anything c) the one for the centre block is mounted on an additional truss. I am certain they are not flight hardware and guess they are not directly related to rocket function e.g. some form of telemetry for transport. $\endgroup$
    – ANone
    Apr 16, 2019 at 12:57

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