My setting is a standard rotating ring space station. I want some action to happen in the core, specifically for the hero to take down a "hypercom" system that is housed there. I'm trying to understand what else would be happening/functioning in the core itself.

This station is on the frontier of known human space, orbiting a planet where they are mining needed resources. There's a good-sized population on the station and it has 5 decks. The station has all the normal stuff you need to live - sleepovers, food joints, bars, stores for sundries, and even some luxuries.

I suppose I could just make up whatever - but I'm wondering for a structure like this, what would make sense to be in the center? I assumed communications equipment was one. What other functions might be there that even possibly benefit from the zero-g environment?


I just want to say I love this community. I'm a creative, and I write sci-fi, but I'm no engineer or science guy. I'm sure sometimes my questions seem basic, but they are vitally important to my story. I really appreciate the thought put into the answers and the discussion. Please know that it helps IMMENSELY. I wish I could put this where everyone would see it, but hopefully some folks see this at least. Cheers!

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    $\begingroup$ How are we supposed to tell you what can be in the core, if the only thing you have said us about this thing is that it is a space station? It's like asking "what can there be in a ship?". What is the ship meant for? You won't find a swimming pool in an oil tanker nor on a carrier... $\endgroup$
    – L.Dutch
    Commented Jan 19, 2023 at 17:54
  • $\begingroup$ Ok, fair point. I will add some context to the question. $\endgroup$
    – MajorTom
    Commented Jan 19, 2023 at 17:55
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    $\begingroup$ @BMF A station spinning to have a bit over 1G on the outer habitation/business ring and a bit under 1G on the inner habitation/business ring would have gravity due to spin so close to zero-G in a core of nearly any size that I believe it's valid to call it zero-G for the purpose of this question. In fact, the bigger the station (larger habitation/business rings) the bigger the basically-zero-G core. $\endgroup$
    – JBH
    Commented Jan 19, 2023 at 18:48
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    $\begingroup$ Actual zero G also makes some things much harder. 0.1G is still enough to keep stationary things on the floor, but in true 0G you need to really change your perspective on how to do every day tasks; so, the difference can still matter a lot. $\endgroup$
    – Nosajimiki
    Commented Jan 19, 2023 at 20:21
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    $\begingroup$ Things would tend to bounce off the floor if you push it there with even a little too much force. Even if you place it very gently any vibration coming from the station could push it upwards $\endgroup$
    – mousetail
    Commented Jan 20, 2023 at 10:56

6 Answers 6


Like any good building, all your maintenance and infrastructure doesn't consume valuable space

Look at today's high-rise buildings. Where do you find the HVAC, the fire suppression water storage, etc? Either in a basement or on the roof. That building is expensive! Every cubic inch of rentable office space given over to power panels and fluid controls is lost revenue.

All that stuff would be in your core.

  • Energy generation, storage, and control
  • Communications & computer processing
  • Sewer/recycling processing
  • Water storage (although in space that might be more valuable in the hull as a radiation shield, but you can never have enough water in space)
  • Atmosphere processing (HVAC on Earth, a bit more complicated in space)
  • Food/goods storage
  • Maintenance workshops (metal working, electronics repair, etc.)
  • Freight "elevators" (transport) between levels (much easier at zero-G)

I think you'd also find things not maintenance related that you simply don't want to waste simulated gravity space for.

  • Security, jurisprudence, & high-value safes/vaults
  • Medical (e.g., convalescence and anything else you can do at zero-G)
  • Administration

Finally, never sell the idea of zero-G recreation short! Nothing would be more fun than a game of Zero-G Laser-Tag or a roller coaster that takes advantage of the environment.

I think your protagonist would find a whole lot o' stuff in that core.

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    $\begingroup$ High-rises don't put it all in the basement, they have utility areas spread around to minimize how far things need to be pumped/carried. These areas include water tanks (because you need to used staged pumps to get water that high), HVAC because the longer your ducts are, the less efficiently they can heat/cool areas that are farther away, and even electrical/communications relays, because you don't want to split all of your signals at ground level and run a million wires up through the building. $\endgroup$
    – Nosajimiki
    Commented Jan 19, 2023 at 19:01
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    $\begingroup$ Also, medical, administration, workshops, etc. are all harder jobs to do under zero G. $\endgroup$
    – Nosajimiki
    Commented Jan 19, 2023 at 19:03
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    $\begingroup$ I can't imagine that convalescence would be in zero-G, simply because healing outside of gravity would probably be a very Bad Idea for people who want to go back into gravity. $\endgroup$
    – jdunlop
    Commented Jan 19, 2023 at 19:03
  • $\begingroup$ @jdunlop That depends on what needs to happen. $\endgroup$
    – JBH
    Commented Jan 20, 2023 at 0:38
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    $\begingroup$ @Nosajimiki We're testing zero-g medical procedures. This isn't physics-lite. I'm giving the OP options that rationally can be put in that area based on the idea that the most expensive space in the universe would be the simulated gravity space on a station. BTW, unless you can cite relevant work experience, you're merely assuming that medical, admin, and workshops would be harder. And I've worked electrical in large buildings. There's a difference between local utility substations and the actual works. $\endgroup$
    – JBH
    Commented Jan 20, 2023 at 0:43

Docking and Storage

Rotating station designs almost always assume docking is at the core to make lining up with the station easier and to limit disruption to the station's spin. Also, since you mention this is a mining station, we can assume that it's intended to store a significant mass of cargo compared to its living space. When you add weight to a spinning station, you increase the already powerful forces that threaten to rip it apart; so, there is no reason to waste ring space on storing the countless tons of materials that your station is holding onto waiting for the next space freighter to come and take it away. This could also be very helpful for loading and unloading if your core is under dramatically reduced apparent gravity.

Sensors, Antennas, and Other Outboard Systems

In general, the control rooms for these systems will still best be placed in the ring making them easier to use and service for human technicians, but the stuff on the outside of your station like the telescopes, antennas, and anything you would have to do a spacewalk to fix would be much better mounted to the core. Space walks are dangerous enough without the risk of being flung off into deep space... so while I don't think it makes since to make the control room for the Hypercom system in the core, it does make a lot of since to make the actual transmitter/receiver sticking off the core somewhere.

Maybe Certain Kinds of Refining

I'm generally of the opinion that if you are mining on a planet, it is way cheaper to make your refining facilities on world, and only export the now much lighter refined materials. That said, it is possible that if your civilization has a need for very precise meta materials, that it would be better to finish refining these materials in the vacuum and/or zero G of space. So, certain refining processes may be best done in the core depending on what they are mining.

Nothing Else of Importance

If you are using your core for docking ships, moving around massive cargo containers, and possibly running high-energy refining processes, this means that the core section is also the most hazardous part of your space station. A ship docking a bit too hard, a 1000-ton container drifting into a wall a bit too fast, a refinery explosion... these are all risks that could damage your core section killing everyone in the area, and disabling nearby systems.

It's also harder to use most tools in zero-G; so, maintaining any sort of critical inboard systems in the core becomes much harder than if they are in the ring where you can use your weight to control the tools you need to work on them.

In other words, if it does not need to be in the core, it's generally best to put in in the ring

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    $\begingroup$ Docking on the core line has reasons far stronger that lining up the incoming ship. There is no way to match the ship with the station's speed of rotation elsewhere: you would need to fly the ship in fairly small circles and cling to the outer surface of something that is creating a 1G centripetal force. So the whole earth-weight of the ship is added at a single point, which will destabilise the rotation and impose impossible stresses on the station. $\endgroup$ Commented Jan 20, 2023 at 12:33
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    $\begingroup$ Methinks you would NOT store the material in a spinning space station, but in a separate facility that has no spin whatsoever. To keep the material in the space station itself, one would have to impart momentum to all of the material, a wasteful expenditure of energy that has no purpose. Better just to keep it in its own lump in space, and just keep adding to and taking away from the lump. $\endgroup$ Commented Jan 20, 2023 at 14:30
  • $\begingroup$ @JustinThymetheSecond The core does not need to have any spin at all since the OP mentioned that it could be either microgravity or zero G. Instead of a giant rotating disc, picture something more like a bike wheel where the habitat spins, but the core does not. This could be preferable to 2 separate stations because it means your warehouse/refinery crews could just take an elevator to work instead of having to constantly shuttle crews back and forth via space ship between the two. $\endgroup$
    – Nosajimiki
    Commented Jan 20, 2023 at 16:42
  • $\begingroup$ @Paul_Pedant I agree, the only reason I said its "almost always" true, and not absolutely true is that if the ring is large enough (Like an O'Neill cylinder), and the ship small enough, these factors can become minimal, and it may prove more convenient to dock on the ring than to dock at the core and then have to take the 4km elevator ride down to the ring. $\endgroup$
    – Nosajimiki
    Commented Jan 20, 2023 at 16:53
  • $\begingroup$ Most important refinery processes actually strongly depend on gravity. Refining is all about separating the things you want from the things you don't want. Gravity is great for that. It's a super easy way to separate heavy things like metals from less heavy things like slag. $\endgroup$ Commented Jan 20, 2023 at 18:01

Zero G

These are systems that you'd want to put in a non-rotating section of the space station. For smaller stations, you might be able to get away with just the actual center axle, but for larger stations, you'd want a large non-rotating section (let's call this a "drum"), and trains that speed people up to rotational speed to transfer between them.

Pressurized vs. Depressurized

This is a tech level consideration. For barely space age tech, you may not be shipping cargo around enough to make large open spaces useful. For Star Wars levels of advancement, your air lock is a forcefield, so you'll be able to move your entire ship into a pressurized space, making the point moot.

For those in between, having a hatch or gangway that people use to board and exit the space station can avoid requiring passengers to suit up, and can avoid lengthy delays while people cycle through air locks.

This is not always practical for large loads, and you may not even want to put them in a pressurized area. For that purpose, you'd want big areas of depressurized space close to where ships can dock


The most important role of the hub of a spinning space station is the docking complex. It provides a place for vehicles to attach without having to deal with centrifugal forces trying to throw the ship off. This is always best done right at the gravitational axis for smaller space stations. For stations where you might want more than two ships docked at once, you need a drum to manage all of the docks.

Trans-shipping Storage

As soon as you have space-based manufacturing, you have space based warehouses. This was done really well at Tycho station in The Expanse, where they had huge immobile volumes filled with trans-shipping containers that just stayed in one place. This is just a reasonable place to store goods coming off of a ship, while they wait for the outgoing ship to be available.

While there is undoubtably plenty of space to put this kind of thing outside of the station, you would want it to be close to where the cargo ships can connect to the station via a gantry. Higher value space would exist inside a Whipple shield to protect from micrometeorites.

Light manufacturing

Most manufacturing facilities would want to be on a separate station/platform where they aren't in the way of docking and transportation, but there will always be some cases where a finished good is best stored disassembled, and assembly is done as close to the location of use as possible.

Low-G areas

These are things for which a gravitational bias is beneficial for giving people something to push off on, or for keeping things sitting on a surface, but for which you don't really want full G of the outer sections.

Environmental systems

This is partially water storage, but also the systems that provide atmosphere for the rest of the station. Just like on Earth, you always want to store your water uphill so that it goes where you want it on its own.

Local warehousing

This would be a pressurized area where goods are stored after they've arrived, but before they're distributed. It would be full of small appliances and vehicles, building materials, furniture, and other things that are used up in the normal course of living. Pressurization makes it easy-access, and light gravity keeps things from floating away.

Groceries and sundries

Let's face it, it's easier to push around a shopping cart if you can push against the ground, and the cart doesn't weigh too much.


You might want an area where the residents can do low-G obstacle courses and the equivalent of geriatric swimming.

  • $\begingroup$ If the core is spinning, you still have to impart rotational momentum to anything that you put in it, unless it is completely isolated from the structure and not itself spinning. Gravity is not the only force one needs to contend with in a spinning space station. You still have inertia, regardless of gravity. $\endgroup$ Commented Jan 20, 2023 at 14:35
  • $\begingroup$ I've updated it with clarifications. The objective is to have a non-spinning core surrounded by spinning inhabited zones, and some kind of public transportation to get things between them. $\endgroup$ Commented Jan 20, 2023 at 18:52
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    $\begingroup$ I think you meant for "Environmental Systems" to be under "Low-G areas". In Zero-G, you would not have any G-force to get your water flowing down hill. Also, you cant connect pipes/ducts between a spinning outer section and a stationary inner section; so, they might actually need separate environmental systems all together. $\endgroup$
    – Nosajimiki
    Commented Jan 23, 2023 at 16:25

Industrial Systems

Lets imagine this space station is a massive ring and the center is slowly rotating. We can compare this to most high-rise buildings, as just like an office tower, its key to make the most of the useful space, and not waste it on pesky things like air conditioning. (Or life support.)

The Systems

Life support. Lets check off an obvious one. Every station needs air, and by extension, lots of tanks of algae and probably some gas liquefaction and air circulation equipment.

Water and waste treatment. You'll need systems in place to burn waste, presumably with plasma torches, recyclers or just plain dumping it out the side of the station. Unfortunately, water is heavy and hard to import, so you want to reuse it as much as possible. The coriolis force might actually help with this.

Energy and information distribution. Every apartment building has some kind of power and fibre-optic distribution panel. You'll need the same on your space station. Unfortunately, you don't have a city grid in space, so you will need fusion reactors, fuel tanks and most importantly, radiators.

Refineries and cargo. Of course, your station orbits a mining colony. It would make a lot more sense to have a specialized station to handle all the cargo, but refining becomes easier with incredibly straight-forward access to hard vacuum and zero gravity.

You could do the heavy refining planet-side, but making advances super-materials usually require strange environments, and the processes usually need to be manned, even if the majority of the work is automated, so putting it in your station makes sense.

Communication and navigation. You'll need laser comms, radar, laser targeting and lots of other systems to keep orbital collisions to a minimum. You might also need it to connect to arrays of laser or kinetic close-in weapon systems around the edges of the ring to defend the station or shoot/vaporize incoming debris.

Engines and main propulsion bus. As your space station is in orbit, it experiences a tiny amount of drag and its orbit will slowly decay. To counter this, the station needs some kind of station-keeping engines, probably on the "walls" of the ring and in the core of the station.

Active shielding. Lastly, you'd want some sort of magnetosphere around your station to deflect solar wind and dampen cosmic radiation. Sure, a lot of metal between you and it helps, but putting dedicated superconducting rings around the core will give your station its own magnetic field and splash incoming charged particles to either side.

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    $\begingroup$ Industrial stuff (and life-support stuff) is mostly not going to be at the hub. Many industrial and life-support processes involve separating liquids from gasses, separating solids from liquids, and separating solids from gasses. That's a whole lot easier when you've got gravity to help you. $\endgroup$
    – Mark
    Commented Jan 20, 2023 at 22:00

Observation station.

At the hub from the top and the bottom you can see the entire sphere of the universe, minus a small nearby area where your view is occluded by the ring of the station. It is important for the station to track incoming objects - ships doing business, possible aggressors, as well as objects which might impact and damage the station. Observations from the hub are not complicated by movement of the observation equipment, as would be the case elsewhere on the station.

The hypercom is there too, for the same reason - it has a clean shot to receive and transmit from the rest of the universe. Equipment situated elsewhere on the ring is moving, has the ring occluding part of the field of view, or both.

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    $\begingroup$ To communicate with places that just happen to line up with the ring, an antenna spire sticks out from the core. One on each side, because it looks cooler. $\endgroup$ Commented Jan 20, 2023 at 12:44

Power Plant

The station spins to generate gravity. The middle of the station has zero gravity. It is where we make electricity, by shooting particles into each other with great speed and precision. The calculations are tricky. Best do them where sunuvabitch Isaac Newton cannot interfere.

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    $\begingroup$ I wonder why the downvote? This seems like a reasonable answer. Engineering challenges of sensitive machinery become more challenging in a non-inertial frames. $\endgroup$
    – BMF
    Commented Jan 20, 2023 at 0:49
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    $\begingroup$ @BMF I would think it's because it's not clear what the answer is actually referring to. It says the station spins to generate electricity like (a turbine) but then starts talking about shoot particles at each other. Seemingly unrelated. It's not clear how spinning has anything to do with particle accelerators. $\endgroup$
    – DKNguyen
    Commented Jan 20, 2023 at 5:38
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    $\begingroup$ @DKNguyen Hmm yeah, I think my eyes glossed over that part. It doesn't make sense to use the rotational energy of the station to generate electricity. (Unless the station is drawing rotational energy from elsewhere. Sounds dubious.) Having missed that first sentence, I interpreted it as using some kind of inertial confinement fusion. Under that assumption, having to correct for variable rotation rates would be a ridiculous design choice imo. $\endgroup$
    – BMF
    Commented Jan 20, 2023 at 6:45

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