Currently working on getting my PhD, with a few precious breaks for my own creative efforts, usually science fiction and space-related. Where it comes to spaceships, orbital dynamics or astronomy, I can probably help you out. That being said, I probably put in a little too much effort into the engineering aspect relative to the art!
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It definitely takes a toll in productivity (there's a reason these things are so far apart - there are two more pieces for this that are still in the works), but I think the results speak for themselves! Thank you!

Hi Braineater97, I'm glad you liked this, and even happier if it motivated you to try the game! SMAC really does not get anywhere near the attention it deserves, considering just what it managed in terms of gameplay, story and worldbuilding.
So before going into any explanation, I should head this off by saying that a lot of design decisions were based around me trying to reconcile different things in the game and supplementary materials such as the canonical 'Journey to Centauri'. Trouble is, different materials disagree on certain things, and even if you look solely at the game, parts disappear and reappear between shots, and the rerelease menu has a completely different design from the introductory sequence as well.
So, first, the centrifuge; it is indeed the part with the hydroponics module. It is normally folded against the ship to shield it from high-velocity impacts during the long low-relativistic travel phase, and would only be extended once the crew was awakened. This was supposed to happen upon reaching Alpha Centauri when the ship had slowed down and so shielding wasn't needed, allowing the ship to sustain whatever crew stayed aboard the Unity to support colonization efforts from orbit (or even elsewhere in the system, if it got used for that long). However, it might also occur if crew were awakened prematurely due to some form of emergency, as indeed happened as elaborated in 'Journey to Centauri'. Featuring only one ring does mean that it would either cause the rest of the ship to rotate or require a counter-rotator inside the ship; having a second ring with another set of habitats would be preferable, but this better what depictions I was able to find.
So, where is it in the game? The centrifuge itself does not appear in the introductory sequence, but it does in the rerelease menu, and 'Journey to Centauri' specifically states that the Gaians holed up in the hydroponics bay there, which is what led to the final design here.
As for the first stage fuel tank, it is indeed at the front. I got the idea for that from the introductory cutscene actually. There's a whole section in front of the part that I labeled 're-entry shield' that appears during the Unity's first panoramic shot, then disappears for every shot thereafter - but got put back on in the rerelease menu. What was it? Where did it go? I reconciled this by saying it was the first stage fuel tank, which would have been separated once it was just dead mass. Actually, it serves a double purpose here - it also serves as an impact shield during the initial acceleration phase and long low relativistic coasting. Once the ship is ready to decelerate, it turns around so its engine faces the direction of travel, so the exhaust intercepts anything coming its way and the shield is no longer needed, allowing it to be ditched. This does require that the fuel be transported all the way down the superstructure to the engine, but considering that the very acceleration of the ship means it'll practically 'fall' down right to the engine the moment it turns on, the only hassle that means is building an extra long pipe throughout, which could probably double as structural support.
Hope that answers your questions!
