We know our rockets from head to toe 
, but can you tell the difference between the"Cryogenic Upper Stage, the Solid Rocket Booster and the Cryogenic Main Stage ? #ArianeFacts #TuesdayTopicpic.twitter.com/wk5Ts7R45N
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That's a tough one, really, as there is no true equivalent in function & position. One could at best compare them to joints like knee, hip, and perhaps the (curved) spine - the stuff that allows you to jump and lift off. But even that would be pretty inaccurate and misleading. :)
Yes, we tried a different approach for this question, sometimes creativity helps to understand complex technologies, don’t you think? 
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