Realistic, near-term, rotating Space Station

[Twark_Main]

As to the design, usually the next step for a lot of folks on this thread is to create a drawing to share. And the norm is that you'll iterate your idea over time to address things you have discovered need to be improved.

Don't worry if you can't (or don't want to) draw, however. There are, of course, plenty of designs that have been shared here on NSF without it being necessary to make a drawing.

[Paul451]

There is a phenomenon that you should be aware of, if you aren't already, that could affect cylinder type designs. It is called the intermediate axis theorem (aka tennis racket theorem) that must be kept in mind. Lots of math on this, but essentially if you have a long cylinder it will want to tumble end over end unless there is a stronger force at work. Which is not a problem if you built your station to tumble like that (see the VAST 2035 artificial gravity station concept), but it could be a problem for O'Neill cylinder stations.

At this point, I'm starting to think you're just trolling.

A cylinder spinning around its long axis switching to end-over-over tumbling is long-axis instability, not intermediate-axis instability. Once again, they are not remotely the same thing, they are not caused by the same mechanism, they are not solved with the same solutions.

Vast's original concept was intended to spin end-over-end, around its short axis, which is why it was prone to intermediate-axis instability.

[Habitant]

Yes, i'm familiar with the tumbling issue. That's part of the reason why I'm suggesting short cylinders (more like a disc really) to minimize that risk. Of course with the given radius, anything but a short cylinder length would be too big to build (currently) anway.

Regarding creating schematics, I think I'd rather work on an interactive visualisation.

By the way, are you aware of the Coriolis force simulator at https://ephu.itch.io/coriolis-force-simulator ? Done with the Godot engine. Really neat.

With regards to why we should build a rotating space station, i think just avoiding health issues is a sufficient reason. Having to exercise two hours per day to prevent muscle atrophy is a big issue. Also the ability to research partial gravity is sorely needed for undertakings like manned trips to Mars.

[Coastal Ron]

Yes, i'm familiar with the tumbling issue. That's part of the reason why I'm suggesting short cylinders (more like a disc really) to minimize that risk. Of course with the given radius, anything but a short cylinder length would be too big to build (currently) anway.

Yeah, any rotating space station of any really useful size is going to require a LOT of mass to build. No getting around that. And until we figure out how to do space mining and refinement all major space station construction will have to be done with material lifted from Earth. Much further out in time space stations will eventually leverage mining material off of Earth (Moon, asteroids, etc.) to some degree, but I think we will need to perfect to a great degree how to build and operate rotating space stations before that point.

By the way, are you aware of the Coriolis force simulator at https://ephu.itch.io/coriolis-force-simulator ? Done with the Godot engine. Really neat.

No, I wasn't. Yes, neat!

With regards to why we should build a rotating space station, i think just avoiding health issues is a sufficient reason. Having to exercise two hours per day to prevent muscle atrophy is a big issue. Also the ability to research partial gravity is sorely needed for undertakings like manned trips to Mars.

If the goal if to expand humanity out into space then from all we can tell from our human experiments on the ISS, we will need some degree of artificial gravity to allow humans to survive, and eventually thrive in space.

I think rotating space stations will be necessary for industry too at some point, but keeping people healthy will be the first need, and the first priority.

[Vultur]

If the goal if to expand humanity out into space then from all we can tell from our human experiments on the ISS, we will need some degree of artificial gravity to allow humans to survive, and eventually thrive in space.

I think rotating space stations will be necessary for industry too at some point, but keeping people healthy will be the first need, and the first priority.

Long term that makes sense, but I don't think this is necessarily a near term need. We already know from Mir and ISS that 1 year+ in microgravity is doable, more than long enough to reach Mars. I am not sure there will be a near term need or reason to have humans in microgravity for longer than has been done so far (14+ months on Mir). Going to the Main Belt asteroids isn't very near term IMO.

It's not clear whether Lunar gravity will be enough long term, but we may get that data on the Moon rather than from rotating stations, depending on the progress of Artemis and/or the Chinese lunar program (which are currently funded, whereas building a large rotating station is not).

The only near term (say next 20-30 years, even with optimistic assumptions about post-Starship-availability expansion of human space flight) purposes I can see for rotating stations are research (on gravity levels not available on Earth/Moon/Mars) or recreation (at reduced but non-microgravity gravity).

Once we are talking about human travel beyond Mars, then rotating stations may be necessary.

[Coastal Ron]

If the goal if to expand humanity out into space then from all we can tell from our human experiments on the ISS, we will need some degree of artificial gravity to allow humans to survive, and eventually thrive in space.

I think rotating space stations will be necessary for industry too at some point, but keeping people healthy will be the first need, and the first priority.

Long term that makes sense, but I don't think this is necessarily a near term need. We already know from Mir and ISS that 1 year+ in microgravity is doable, more than long enough to reach Mars. I am not sure there will be a near term need or reason to have humans in microgravity for longer than has been done so far (14+ months on Mir).

My interpretation is that those humans survived the missions, but their health was degraded and they needed to heal and recuperate back on Earth to return to their pre-mission health levels (or try at least). That is tolerable today, but if we are going to be expanding humanity out into space then I don't think that will be an acceptable baseline.

Going to the Main Belt asteroids isn't very near term IMO.

I would agree, but there is a lot of interest in going there for space mining, so keeping humans healthy while they explore and exploit is a potential business model that I'm focused on.

It's not clear whether Lunar gravity will be enough long term, but we may get that data on the Moon rather than from rotating stations, depending on the progress of Artemis and/or the Chinese lunar program (which are currently funded, whereas building a large rotating station is not).

So far the Artemis program is not "built" to answer that question, because of the limitations of the SLS and Orion. Maybe that will change, and I agree that the least expensive place to doing health research on lunar gravity would be on our Moon. However I suspect that Mars gravity will eventually be the default when traveling off of Earth.

The only near term (say next 20-30 years, even with optimistic assumptions about post-Starship-availability expansion of human space flight) purposes I can see for rotating stations are research (on gravity levels not available on Earth/Moon/Mars) or recreation (at reduced but non-microgravity gravity).

Sadly, I think you are right.

Once we are talking about human travel beyond Mars, then rotating stations may be necessary.

There may be a need for people to be in orbit around Mars, so it could be earlier than that. But overall I think you are right. I have never thought there would be much demand for rotating space stations in orbit around the Earth, beyond transfer stations (i.e. short stay, no one really living on them).

[Twark_Main]

Yes, i'm familiar with the tumbling issue. That's part of the reason why I'm suggesting short cylinders (more like a disc really) to minimize that risk. Of course with the given radius, anything but a short cylinder length would be too big to build (currently) anway.

Note that "spokes with a hab on the end" with N_spokes > 2 has the same stability as a disc or torus. Some people think you need 4 spokes, but actually 3 is enough.

This really helps when you want to scale to smaller pressurized volumes, but you still want to maintain an adequate spin radius.

You can achieve stability with N_spokes = 2, but then you need to fiddle with the mass distribution of solar panels and heavy equipment to maintain passive stability.

[Paul451]

We already know from Mir and ISS that 1 year+ in microgravity is doable, more than long enough to reach Mars.

With their health significantly reduced.

And we don't know what Mars gravity will do once they are there. Will their health continue to degrade for the entire surface mission. Will it recover, as it does slowly on Earth. Or will it plateau, until the return trip.

It's not clear whether Lunar gravity will be enough long term, but we may get that data on the Moon rather than from rotating stations, depending on the progress of Artemis

Like Apollo before it, Artemis doesn't seem set up for such research. Certainly you aren't going to see animal studies on the lunar surface. Ironically, it's going to be harder to get lunar-g research out of the lunar program than out of an AG station, but impossible to get funding for lunar AG research because of the lunar program.

[mikelepage]

So... rotating space stations full of server racks for AI?
Must admit that wasn't on my bingo card. 

I know that any initial attempts at orbital AI infrastructure will be an extension of Starlink capability, but recent events have me wondering if at some point one might expect space data center hardware will be more cost-effective as large, human serviceable space platforms, where new components can be brought in to replace the old, rather than de-orbiting whole spacecraft as they do with Starlink satellites.

If (?) there are forcing functions leading to much larger data centers in space - say there's some limiting function to how many laser-links you can have between every node in a computing operation - and say the servers are normally kept in 4º degree C nitrogen only atmospheres, but can be optionally shifted to a shirt-sleeve environment for servicing, then maybe that is what supports the business case to make rotating space stations into reality. The tourism/partial-g science applications would then be nice add-ons.

[Coastal Ron]

So... rotating space stations full of server racks for AI?
Must admit that wasn't on my bingo card. 

I know that any initial attempts at orbital AI infrastructure will be an extension of Starlink capability, but recent events have me wondering if at some point one might expect space data center hardware will be more cost-effective as large, human serviceable space platforms, where new components can be brought in to replace the old, rather than de-orbiting whole spacecraft as they do with Starlink satellites.

Yeah, not on my bingo card either, but not sure what the value of having gravity of any kind would be for AI infrastructure in space. If such an infrastructure was not rotating, it should make it easier for robotic (or tele-operated) servicing.

[mikelepage]

So... rotating space stations full of server racks for AI?
Must admit that wasn't on my bingo card. 

I know that any initial attempts at orbital AI infrastructure will be an extension of Starlink capability, but recent events have me wondering if at some point one might expect space data center hardware will be more cost-effective as large, human serviceable space platforms, where new components can be brought in to replace the old, rather than de-orbiting whole spacecraft as they do with Starlink satellites.

Yeah, not on my bingo card either, but not sure what the value of having gravity of any kind would be for AI infrastructure in space. If such an infrastructure was not rotating, it should make it easier for robotic (or tele-operated) servicing.

Convection. For cooling. Also, robots that roll.
One myth I would love to squash is the idea that gravity only helps biology.

[Coastal Ron]

So... rotating space stations full of server racks for AI?
Must admit that wasn't on my bingo card. 

I know that any initial attempts at orbital AI infrastructure will be an extension of Starlink capability, but recent events have me wondering if at some point one might expect space data center hardware will be more cost-effective as large, human serviceable space platforms, where new components can be brought in to replace the old, rather than de-orbiting whole spacecraft as they do with Starlink satellites.

Yeah, not on my bingo card either, but not sure what the value of having gravity of any kind would be for AI infrastructure in space. If such an infrastructure was not rotating, it should make it easier for robotic (or tele-operated) servicing.

Convection. For cooling.

Not sure if artificial gravity would actually provide this, and the amount of rotating mass you need to provide artificial gravity could be replaced by really small electric pumps on a non-rotating data center structure.

Also, robots that roll.

Cool as they are, not sure they solve any problems because they roll... 

One myth I would love to squash is the idea that gravity only helps biology.

I haven't heard that, so I wouldn't be someone you have to convince. 

[mikelepage]

So... rotating space stations full of server racks for AI?
Must admit that wasn't on my bingo card. 

I know that any initial attempts at orbital AI infrastructure will be an extension of Starlink capability, but recent events have me wondering if at some point one might expect space data center hardware will be more cost-effective as large, human serviceable space platforms, where new components can be brought in to replace the old, rather than de-orbiting whole spacecraft as they do with Starlink satellites.

Yeah, not on my bingo card either, but not sure what the value of having gravity of any kind would be for AI infrastructure in space. If such an infrastructure was not rotating, it should make it easier for robotic (or tele-operated) servicing.

Why though? What evidence is there that microgravity makes things easier to automate? I would have thought the space station has shown us pretty convincingly that it's not the case.

This isn't the same as your preference to have a co-orbital logistics station - I can see the argument for microgravity if you're moving a lot of bulky supplies to and fro. But hopefully with a server setup you're not going to need to be moving much around. And when you do, having friction via an acceleration vector will be useful as a basic environmental constant that robots can react against. I was a bit flippant earlier, but isn't having a constant g-force part of why we think rotating gravity space stations will be useful?

It could work pretty well with with a skinny torus setup actually, keep the "prime" gravity level for human applications, and all of the other structural components/tunnels (e.g. in radial struts) for server racks. That way they'll be closer to the main radiators too (assuming an edge-on-to-sun config).

[Coastal Ron]

Yeah, not on my bingo card either, but not sure what the value of having gravity of any kind would be for AI infrastructure in space. If such an infrastructure was not rotating, it should make it easier for robotic (or tele-operated) servicing.

Why though? What evidence is there that microgravity makes things easier to automate? I would have thought the space station has shown us pretty convincingly that it's not the case.

I don't know about for others, but for me the only reason to have artificial gravity in space is to support having humans in space. So artificial gravity would be needed not only for the humans themselves, but for the things that support keeping humans in space.

But if we're talking about AI data centers in space, why do they need humans? They should not need humans on-site to maintain them, so at most all you need is the ability for humans to visit to fix "stuff", whatever that may be.

However humans cost a lot of money to keep in space, which is why I think autonomous or tele-operated robotic systems would be able to do the maintenance.

This isn't the same as your preference to have a co-orbital logistics station...

It has nothing to do with that.

I can see the argument for microgravity if you're moving a lot of bulky supplies to and fro. But hopefully with a server setup you're not going to need to be moving much around. And when you do, having friction via an acceleration vector will be useful as a basic environmental constant that robots can react against.

I'm really not seeing what value gravity provides. Sure, robotic systems can work in a gravity, but they can work without gravity too. So not seeing the MAJOR difference - what the value proposition is for data centers in space.

[crandles57]

I'm really not seeing what value gravity provides. Sure, robotic systems can work in a gravity, but they can work without gravity too. So not seeing the MAJOR difference - what the value proposition is for data centers in space.

Moving an object with motor driven wheels in gravity works. Try it in microgravity and it doesn't work as well as object is prone to floating away on the slightest of obstacles and wheels ineffectively spin while not in contact with anything solid. You can get efficient movement with wheels held in rails but this isn't ideal or as flexible if there might be lots of slightly different positions you want to be in. For server rack maintenance, rails might work well enough if designed in.

[Coastal Ron]

I'm really not seeing what value gravity provides. Sure, robotic systems can work in a gravity, but they can work without gravity too. So not seeing the MAJOR difference - what the value proposition is for data centers in space.

Moving an object with motor driven wheels in gravity works. Try it in microgravity and it doesn't work as well as object is prone to floating away on the slightest of obstacles and wheels ineffectively spin while not in contact with anything solid.

Why would anyone try to move something using wheels in zero gravity?

You can get efficient movement with wheels held in rails but this isn't ideal or as flexible if there might be lots of slightly different positions you want to be in. For server rack maintenance, rails might work well enough if designed in.

You are aware that we have been maintaining a space station in zero gravity for 25 years?

We know how to do maintenance in zero gravity, and in the vacuum of space. Oh, and we do use a robotic arm that can move across the station like an inch worm, grabbing Power Data Grapple Fixtures (FDGF) so that it can reach many areas of the station.

So I would stop being fixated with wheels in zero gravity, we use arms. Very much like how monkeys travel through trees here on Earth.

[Paul451]

Canadarm also has its own rail system, the Mobile Transporter, on the ISS main truss. If you wanted to move a bot around a zero-g data centre, that would be an ideal option.

However, the nature of data centres lends themselves to modular disposable units. Trend seems to be towards single free-flying units as distributed systems, not single bulk stations. No maintenance. No robots.

[JulesVerneATV]

but with a damaged launch pad?

Russia Unveils Plans for Artificial Gravity in Space
https://greekreporter.com/2025/12/24/russia-artificial-gravity-space/

Russia patents space station designed to generate artificial gravity
https://www.space.com/technology/russia-patents-space-station-designed-to-generate-artificial-gravity

The radially attached habitable modules would be rotated around this axis to simulate gravity for the crew by producing an outward-pushing centrifugal force. These would need to rotate about five revolutions per minute, and have a radius of 131 feet (40 meters) in order to produce 0.5g. A space station of that size would require multiple launches with each module that would then be assembled in orbit.

[lamontagne]

but with a damaged launch pad?

Russia Unveils Plans for Artificial Gravity in Space
https://greekreporter.com/2025/12/24/russia-artificial-gravity-space/

Russia patents space station designed to generate artificial gravity
https://www.space.com/technology/russia-patents-space-station-designed-to-generate-artificial-gravity

The radially attached habitable modules would be rotated around this axis to simulate gravity for the crew by producing an outward-pushing centrifugal force. These would need to rotate about five revolutions per minute, and have a radius of 131 feet (40 meters) in order to produce 0.5g. A space station of that size would require multiple launches with each module that would then be assembled in orbit.

Some extracted images from the patent:

[Paul451]

Amusingly, no image of what I think is intended to be the actual "invention". The mechanism for a counter-rotating hub.