Pictures of the octaweb show that the engines are not placed at the center of each octaweb compartment---they are closer to one side than to the other.

See the picture below for an example. Focus on just one section of the octaweb---any of the white panels at the top will do. The engine is much closer to the right side of the panel than to the left of it. You can trace the same pattern all the way around the octaweb.

Why? Is this just to make space for other components that must go in the same compartment? If so, then what might those components be?

enter image description here

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    $\begingroup$ This is an odd, and I think incorrect, use of the word 'asymmetrically'. Clearly the layout has rotational symmetry. $\endgroup$ – Organic Marble Jun 5 at 11:56
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    $\begingroup$ I think you're confusing symmetry with "how the enclosing panels are designed for optimum assembly and strength" $\endgroup$ – Carl Witthoft Jun 5 at 12:13
  • $\begingroup$ Consider the radial centerline of an octaweb section. If the engine were on that centerline, then the right side of the section would have mirror symmetry relative to the left side. But the engine is offset from the centerline, so that symmetry is broken. This is splitting hairs, but you can talk about symmetry here. That said, you're right that I was casual about my terms, though I think you can still get the gist of the question? $\endgroup$ – Alex Jun 5 at 20:45
  • $\begingroup$ Keep in mind, these are bypass engines. Those 8 smaller circles also spit fire. $\endgroup$ – Anthony Stevens Jun 8 at 20:14

The engine placement looks symmetrically to mee in this image.

enter image description here

Image source: https://blogs.nasa.gov/spacex/wp-content/uploads/sites/227/2014/04/octaweb_small2.jpg

Outwardly, the biggest change is an arrangement of eight engines in a circle around the center engine. Previously, the nine engines were built in three rows of three. SpaceX says the octaweb reduces the length and weight of the Falcon 9 thrust structure and streamlines manufacturing of the first stage. While this is the first NASA mission with an octaweb first stage, the engine pattern flew successfully during several previous SpaceX missions launching commercial payloads.

To place each engine not in the center of each octaweb section would reduce the thrust structure mass and improves the access to the engines during manufacture.

This graphic shows the thrust structure for the offset version:

enter image description here

And this is the centered version:

enter image description here

The additional brown parts are needed for a stable centered mount of the engines. So the centered thrust structure weighs a little bit more.

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    $\begingroup$ There is rotational symmetry, but you can see that each engine is offset to the side of its octaweb section. The offset is clockwise so that the top engines are closer to the right than to the left of their octaweb compartments. You can see a smaller hole just below and to the side of each engine, which is the gas generator exhaust, so my guess is the offset is there to accommodate that---but it would be nice to know for sure! $\endgroup$ – Alex Jun 5 at 10:06
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    $\begingroup$ @Alex I don't think your downvote is justified $\endgroup$ – Carl Witthoft Jun 5 at 12:14
  • $\begingroup$ I didn't downvote, Carl. I appreciate all the comments and answers I can get, yours included. Why do you say I downvoted? $\endgroup$ – Alex Jun 5 at 20:40
  • $\begingroup$ Makes sense, Uwe, but how would this asymmetry reduce mass? $\endgroup$ – Alex Jun 5 at 20:49
  • $\begingroup$ But Uwe, the engines are gimballed. The gimbal joints attach to plates directly above the engines, as do the thrust-vectoring cylinders. There are no connections to the radial side plates anywhere in the octaweb. In fact, shifting the engines so close to those side plates limits the maximum gimbal angle you could apply to the engines. Very nice graphics, by the way :D $\endgroup$ – Alex Jun 8 at 20:54

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