One thing many of these designs don't bring up is long-term growth. Is the plan to build it once and that's it? Boring, and too prone to failure if the project runs into trouble at any point in time.
What I'd prefer to see is a space construction that is continuous. Imagine a ring station, but one that is cellular in nature- lots of smaller modules that together form the huge station. This allows one to construct and add further modules over time, growing as needed.
The beauty of this design principle is that we could start today. Design the first iteration of these modules, with the intent to fit them into SpaceX's Starship (or whatever heavy rockets come next). Launch 10 or 20 of them, connect them, and spin them up to 1/5th gravity, something not too hard to do. Add modules in the centre of the ring that are zero-G, where zero-G things can be done- but allowing those who live on station to live in mild gravity at least.
All the while, you can dream big. You can plan for how this station goes from 10 or 20 small modules to thousands.
Connecting pressure vessels together is a challenge. Each vessel and each joint is a failure opportunity, and having to go through bulkhead doors all the time doesn't scale well beyond mission crews. Plus you have to get the location of those doors right during initial planning.
For modularity it might make more sense to use nesting. A building inside a building has no seams. Doors only need footpaths between them, not hard structures. The inner building can be used for shelter in case of an accident, and can be run at higher pressures than it could in hard vacuum.
In the tinker toy model you would tend to have to keep repurposing buildings because while the size may be appropriate, the older structures may get pushed farther and farther from the center of the action, rather than staying in the center of the action.
I'm not getting the nesting argument here. At least in the early days, a window to space will be a key selling feature. That means that the surfaces will have greater value, like with skyscrapers, but worse. Worse because pressurization demands that surfaces bulge out to contain the atmosphere. So while a large sphere might be the best engineering solution, funny shapes held together by weird superstructures might be the most profitable option.
When we get into the more utilitarian phase of space development, then I think you would want something like shipyards where there really is a big micrometeorite shield (yes, as a sphere) with the inside filled with scaffolding. Robots scoot around do work with old and new hardware.
If you think about nesting ROTATING structure inside of other pressure-envelope structures, then you're getting into some really crazy stuff. Are there designs that might make sense? Maybe, I don't know, I guess I wrote a blog about it
I think you're doing a lot of math there to determine pressure and the fact is that pressure in a space station is going to be dictated entirely by biology - partial pressure of oxygen, nitrogen, and carbon dioxide for mammal metabolism first, and comfort and plant metabolism later on. By the time logistics of managing or building out a real habitat, you're in a ±5psi range. Anything outside of that died on the design room floor.
Windows are at a huge premium on cruise ships. It'll be much worse on space ships. But it's possible that inside windows will eventually look out onto something more interesting than the black void of space, so an inside window may be preferable. One of the reasons we look out the window in a car or on a boat is to establish the horizon and fight motion sickness. If you look 'outside' of a rotating space station - especially a rotating space station orbiting a planet or moon - you'll head rapidly in the exact opposite direction.
Even cruise ships tend not to hand underwater window, despite how desirable they might be. For the same reason, I doubt a space-station will have privately owned windows.
They're not really desirable on cruise ships at the end of the day. They gunk up quick and don't really have a great view even clean since you're either in harbor with probably silty water, or at speed in which case it's just fairly dark turbulent bubbles that you can see.
You could build rings around rings. A couple of the designs on that page have multiple 'floors' in the same ring. I suppose those could be built incrementally in either direction (stacking new rings, or adding another floor to an existing one).
I think my train of thought makes a bit more sense for moon and asteroid bases rather than free-floating orbital structures. And asteroid bases - on the right asteroids - are probably going to house most of the people.
The ISS design definitely doesn't scale up. Everything off axis is a lever arm and the bigger you make it the more the whole thing tries to twist itself apart.
I find it interesting that so many people claim spinning stuff up to create artificial gravity in space is "not too hard to do" and yet it has never been attempted, for a series of pretty compelling reasons. Everything is hard in space!
The big obstacle for spinning artificial gravity is that it won't really work on a small spacestation. It has been not tried because we never had the option of a so large station where it would make sense to try - I'm not saying that it's not hard, however, the fact that we haven't attempted it is not evidence that it's hard, it's fully explained by the needs and restrictions of our size-limited spacestations like ISS for which each module is limited to a 4.5 meter tube because of launch vehicle limitations.
Another reason why it's not done is because one of the reasons why we have a space station is to do microgravity experiments, and having artificial gravity only hurts that.
There was a plan to have a 'spinning module' on the ISS, but NASA cancelled it. NASA has never really supported artificial gravity, likely because none of the NASA Centers is really focused on it.
> likely because none of the NASA Centers is really focused on it.
That's what I thought until I started looking into it. The module has actually been built (several versions in fact), but never completed and launched.
It turned out during tests and simulations that the station's structural integrity was at risk and so it was decided not to attach a centrifuge to it.
Whether these concerns were warranted I cannot say, but engineers at NASA deemed it too risky to try.
I'm wondering if aiming for less than 1G of artificial gravity would be sufficient to counter the ill effects of zero gravity environments? If you could opt for, say 0.3g, then the required speed would be greatly reduced.
You're not wrong. But I feel that like most things, it's only hard because it hasn't been tried. Once we've done it a few times, it's routine. That's human nature.
We've also done some experiments already. There was, I believe, a Mercury mission where they spun the ship up. If I recall, it didn't go super well. But hey, we've had 50+ years to think of how to do it bette!
It’s done all the time on Station inside machinery. We also can easily making spinning rooms on Earth. merrygorounds are playground equipment for children.
It’s don’t commonly on Earth. Most of the point of LEO space stations is to study microgravity so you wouldn’t even want it.
It is indeed pretty easy, but annoying to do for technical reasons (rotating joints, etc). Easier not to.
It would require the building of a large space structure, which has never been done (even the ISS is not that large). For that, we'd need to get materials into space cheaper, or even mine/refine/manufacture materials off-earth.
The first thing that comes to my mind is that you either have to commit to have the entire habitable portion of a station be rotating, or you have to have some kind of rotating joint that connects the rotating and non-rotating parts of the station. That joint has to not leak air and be very reliable (if it seized up, the station could tear itself apart from the sudden torque).
Having the whole habitable part of the station rotate may be fine most of the time, but it makes docking with ships more complicated. If the ship can't be spun, then you can either use some kind of rotating docking collar (which doesn't have to be perfectly airtight if it's only used once in awhile, but it still has to be pretty good) or you have put on a suit and do a spacewalk just to move things back and forth between the station and the ship which sounds kind of inconvenient.
(I guess there's actually another solution which is to stop the station spin whenever docking with a ship. That costs energy and/or reaction mass, though, and you'd have to deal with whatever disruption switching to zero-gravity brings.)
I can see why they might not have wanted to deal with this for ISS, but maybe for a bigger/more ambitious space habitat we'll want to do it.
Regarding your idea of stopping the station rotation: a simple way to do it would be to spin a flywheel contained inside the station. It wouldn't need to be very heavy if it spins very fast.
Another possibility is to have the docking station completely disconnected from the outer ring atmosphere, and to use small "elevators cabins" attached to robotic arms to go from the ships to the rings and vice-versa.
Speaking of "really huge" - Culture Orbitals are about the ideal: ~3,000,000 kilometres across, 1g at surface and rotation time of 24 hours so no need to stuff like the shadow squares of Ringworlds.
Sadly, they do rather require "magical" technology....
From a radius of ~300m onward you'll see green lights (= good for people) for all considered parameters. RPM drops from 1.7 to 0.5 for a radius of 3000m.
I've always been curious on this question because I don't have any physics background.
If you made something like a gravitron ride on the moon, would it take a slower rotation speed to reach perceived 1g than if you spun up a ring station in orbit? This calculator makes it seem like you could get pretty close to 1g with just a bullet train running on a 3.14 kilometer loop.
It seems like the main thing stopping earth trains from being faster is that most of our tracks were built a really long time ago and it's not worth the effort replacing them, but if metal is readily available and you're laying new track already, designing for ~300km/hr wouldn't be that much of a stretch no?
Yes, a little. In freefall, such as on orbit, you need 1 gravity of centripetal acceleration. a = v²/r; v = √(ar); if we assume a 3-meter radius (roughly Gravitron size) we need about 5.42 m/s tangential velocity to get one gee. The moon's gravitational acceleration is 1.62 m/s/s; to find the centripetal acceleration needed to get a Pythagorean sum of one gee, we take √((9.81 m/s/s)² - (1.62 m/s/s)²) = 9.67 m/s/s. That means that now our √(ar) tangential velocity is just 5.38 m/s, which is less than 5.42 m/s. Does that help?
The main thing stopping earth trains from being faster is politics, not engineering. Trains have been occasionally going over 300 km/h since 01955, decades before maglev. The Shanghai Maglev Train has been running at 430 km/hr since 02004. The Euroduplex regularly runs 320 km/hr on regular 1435mm standard-gauge rails and reached almost 575 km/hr in a test in 02007. 300 km/hr trains have been in regular service since 01989. There are several other train lines that run over 300 km/hr, in Taiwan, PRC, France, Belgium, Saudi Arabia, Japan, Germany, the UK, the Netherlands, Italy, Spain, Korea, and Switzerland. Soon India and the US will join them.
The big advantage of maglev is actually not smoothness or absolute speed but acceleration and deceleration.
4 rpm is about as fast as you can spin to avoid vertigo when turning your head. So for 1g that requires a diameter of 56 meters (about the size of the leaning tower of Pisa), which is big.
Other challenges include how to spin it up (and down) safely, how to dock with non-spinning things, how to deal with changes in mass distribution, and how to put thrusters on it for use when it's spinning. None of these is impossible, but together they create a serious engineering problem, and the size of the whole thing is ultimately the dealbreaker.
The ISS is 109m end to end so a 56 meter diameter isn't an impossible dream. I've toyed around with a design that uses basically a shell around Starship that would be bolted together in orbit to form the station. I was aiming for 2 RPM however.
Docking would be via a central hub. Ships would have to match rotation to dock, but it shouldn't be too hard. My conclusion is that if the money and/or political will were there we could start doing this today, but the project would be hugely expensive (even with SpaceX cutting launch costs to a fraction of what they were only a few short years ago) and once you have it built it will be looking for a purpose. It would be cool for people to basically commute up to the central part (via elevator) to do zero-g research stuff, then commute back to the ring to live and avoid the various health problems with long term zero-g living like bone density loss.
You can even build a simple starter station that has only two segments on opposite sides of the central hub. This is less cool since you don't get the jogging path around the station. If stability is an issue you could also include a computer controlled mobile counterweight on the ends. I also had the concept of building it as a double hull with a layer of water between the inner and outer to reduce radiation flux and absorb micrometeorite impacts.
But in the end you are still talking about a hugely expensive project that solves problems that aren't all that bad yet. About the only way I could see this being built is if Elon decides to go all in on space and liquidates his fortune to build it. The instant some annoying bean counters ask the question "is this the best way to spend this money" the project is dead.
Basically, we would need to make something hundreds of meters in diameter to have any hope of a comfortable living situation. This is a huge amount of mass to get into space, which is notoriously expensive, but getting cheaper every year. Maybe one day we'll hit an inflection point where this is reasonable.
Put in 3RPM and it spits out a 100m radius. This is big for sure, but in the same order of magnitude of the ISS. If you are willing to live with only 0.5g instead of 1g you can slow it down to 2RPM at that size and be safely within human comfort limits.
That would give you a circumference of around 628m. That sounds like a lot, but if you could build it in 80m segments by bolting each segment to the outside of SpaceX Starship (which is 120m tall) that would take 8 launches to get the ring in orbit. Plus some more launches for the hub and spokes and panels and everything else of course. Still, 15-20 launches is not outside of the realm of the feasible. If there were the political will (or personal fortune) to build this it could be done.
Not necessarily. Andy Weir's 'Hail Mary Project' describes a way you can get the best of both worlds: don't make a full ring, but spin two objects separated by cables.
Split the initial station into two stations with a large number of cables connecting them securely. Now on your calculator, put in a 70m radius and a gravity of only 0.3g. All green dots.
But how do you get between the halves?" you ask? I think there's a simple answer to that: have cables complete the circle. A small car riding those cables can carry you around the radius. Then over time, you add more cells until the circle is complete!
If you give one half of the station twice the mass of the other, you can test out living in lunar gravity and Mars gravity at the same time. Maybe only one of those will turn out to be enough to stop bone loss. Maybe neither one. It would be better to know that before building a base.
The zipline would be trickier to make work, then. Probably you have a gadget that walks up the tether, and then you flip around and it walks down to the other end.
You don't even need to complete the ring so that you can start with a lot bigger radius. The larger the radius the less the weird gyroscopic effects when people turn their heads in certain directions and the closer it replicates earth's gravity. Then you can expand the ring by increasing the arc coverage.
Right, start with three cans, two of them swinging at ends of a cable, one at the hub with a docking port. Add onto that, two cans at a time, lowered from the hub; link them up to existing cans. When the ring is full, tada! Then, extend the center can out a ways, on the axis, and start over, nestling new cans honeycomb-wise. Or maybe give the next ring a bigger radius; each existing can gets a pair of basement cans.
Or, just extend everybody's cable a notch so there is room to shoehorn in the next pair of cans. As you add cans, the radius grows.
"Cans" is the only practical way to think of building a rotating station. Of course, the cans are really Starships, hanging by the nose. Passageways between cans are fabric tunnels. Each can has a mass on a column that is automatically raised and lowered as people and things move around, to maintain rotational stability, and keep the hub centered.
> Of course, the cans are really Starships, hanging by the nose.
Realistically, you'd want to keep re-using the expensive parts of the starship rather than park them in space, which makes me wonder what's the best way to re-use a starship while leaving cylindrical body sections in space?
You could have a Starship body with sections that are removable -- like maybe you have a 50 foot section that unbolts from the nose and the tail which you leave in space, while the nose and tail get re-connected and return to Earth as a shorter version of Starship. Or maybe you could just launch two Starships, and in space remove the engine from one and place it inside the other as cargo, so you land one complete starship and the extra engine, but leave one complete body in space.
I doubt it's possible to have a disembodied engine land itself using its own thrust without a lot of clever and novel engineering, but maybe it can land by parachute? Or use thrust to slow its re-entry so it doesn't overheat, then parachute the rest of the way?
I could imagine unbolting the Vacuum Raptors and stowing them before you hang the can. (Once you have enough Raptors, you can redeem them for a free can!) They get packed as cargo in one of the non-can Starships and landed for re-use.
Maybe you vent the tanks and open a hatch on top, and there is a stairway inside with floors, ductwork, and places to clip on lights and electric outlets. Probably you roll out insulation onto the walls so you don't burn yourself or get frozen-stuck if you touch them, depending on what is going on outside.
The rings should be modular to ease building and to aid in compartmentalization. However, adding to existing rings could be difficult in terms of planning or engineering, since you'll be changing the balance of the entire system and you'll probably want the module to be in a particular position.
If you instead make the rings "super-modules", you can connect as many as you like along a central axis of rotation. As long as the individual rings are balanced you're good to go. If they spin freely relative to each other, you could even build a super-modular ring in place and only spin it up after it is complete.
If you plan to add more rings you're going to run into the Dzhanibekov effect https://en.wikipedia.org/wiki/Tennis_racket_theorem, which was still a Soviet state secret at the time space habs were being imagined, and might have still been a secret when they filmed 2010. That station would have been wobbling like crazy.
I'm pretty sure that phenomenon even kills the https://en.wikipedia.org/wiki/O%27Neill_cylinder, especially once you introduce liquids and soil to the interior. It's likely that we have to spin the cigar along the long axis to keep from killing everyone, which would greatly reduce the usable surface area and screw up the artificial lighting situation.
I think you got that backwards; the long axis of an O'Neill cylinder is the principle axis, and the only one that would be stable. The second (unstable) and third (stable) would both be unsafe because the issue with contents shifting making them potentially switch rolls. But that was never the plan, so no great loss.
If I understand correctly, the first principal axis has the smallest moment of inertia and the greatest kinetic energy. Anything that can dissipate the kinetic energy (like soil or water generating heat) will cause the ship to not be able to maintain that rotation and in order to conserve angular momentum it will instead rotate around the other stable axis—the third principal axis or end-over-end—since that axis has the greatest moment of inertia and minimum kinetic energy.
Space travel is surprisingly cheap and easy if you don’t have to overcome a planetary gravity well to get anywhere. The plan for growth is to build space habitats for the people who are living in space and working in space to build, among other things, more space habitats.
Exactly, only op does not account, that some Russian[insert the one that at that point is at lowest development capability] module on joining would create space colony quakes and add other hazards... maybe even huge hole in the structure.
What I'd prefer to see is a space construction that is continuous. Imagine a ring station, but one that is cellular in nature- lots of smaller modules that together form the huge station. This allows one to construct and add further modules over time, growing as needed.
The beauty of this design principle is that we could start today. Design the first iteration of these modules, with the intent to fit them into SpaceX's Starship (or whatever heavy rockets come next). Launch 10 or 20 of them, connect them, and spin them up to 1/5th gravity, something not too hard to do. Add modules in the centre of the ring that are zero-G, where zero-G things can be done- but allowing those who live on station to live in mild gravity at least.
All the while, you can dream big. You can plan for how this station goes from 10 or 20 small modules to thousands.