9 ms·

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

• idlewords 5y ago
  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!
  • mabbo 5y ago
    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!
  • rytill 5y ago
    What are some of the first compelling reasons that come to mind?
    • f6v 5y ago
      It has to be really huge or spin really fast? Sorry, my physics knowledge evaporated.
      • chanc3e 5y ago
        Seems right. Being huge means less inner ear dizziness, spinning small and fast is stressful on materials and makes humans sick. And docking would be a major POA. If we are talking km diameter structures holding station in system, making it rotate isn’t going to be a drama.
      • arethuza 5y ago
        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....
        • deleted 5y ago
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      • wruza 5y ago
        1km - 0.95 rpm. 100m - 3 rpm. 10m - 9.5 rpm. 1ly - 0.0000003 rpm (once in 6.2 years, tagential speed is around c).
        • Valgrim 5y ago
          Since mass increases near the speed of light, wouldn't it become a ringularity?
      • idlewords 5y ago
        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.
  • PeterisP 5y ago
    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.
    • phreeza 5y ago
      Not really, you can do it with a cable tether and a counterweight. I think Zubrins Mars Direct called for such a setup.
      • BrianOnHN 5y ago
        Counterweight might be good use for excess in the meteor capture & exploit industry.
    • nickff 5y ago
      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.
      • qayxc 5y ago
        > 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.
    • 5y ago
  • nradov 5y ago
    It was attempted in 1966, albeit in a very limited way. https://blogs.scientificamerican.com/life-unbounded/watch-the-first-artificial-gravity-experiment/ https://blogs.scientificamerican.com/life-unbounded/watch-th...
  • Robotbeat 5y ago
    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.
  • Chris2048 5y ago
    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.
  • pomian 5y ago
    I thought they managed it in 2001.
• kijin 5y ago
  That sounds like what they did with the modules of the International Space Station, only bigger. :)
  • Bobylonian 5y ago
    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.
• teawrecks 5y ago
  Calculator for creating artificial gravity via centripetal acceleration: https://www.artificial-gravity.com/sw/SpinCalc/ https://www.artificial-gravity.com/sw/SpinCalc/ 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.
  • zabzonk 5y ago
    The very first program I ever wrote (apart from hello world) was one to do this on a Research Machines 380Z, in BASIC, back in about 1979.
  • jandrese 5y ago
    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.
  • monocasa 5y ago
    To be fair, the ISS is already about 100m long, albeit not pressurized sections.
  • mabbo 5y ago
    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!
• optimalsolver 5y ago
  Space sprawl? Not in my cosmic neighborhood.
• cgriswald 5y ago
  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.
  • hinkley 5y ago
    If you plan to add more rings you're going to run into the Dzhanibekov effect https://en.wikipedia.org/wiki/Tennis_racket_theorem 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 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.
    • MarkusQ 5y ago
      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.
      • cgriswald 5y ago
        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.
• hinkley 5y ago
  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.
  • AlanSE 5y ago
    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 https://gravitationalballoon.blogspot.com https://gravitationalballoon.blogspot.com
    • hinkley 5y ago
      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.
• majjam 5y ago
  You might like this article if you haven't already read it. The author discusses using starship segments to create habitat rings: https://news.ycombinator.com/item?id=29305544 https://news.ycombinator.com/item?id=29305544
• 5faulker 5y ago
  Dream big. Aim small.
• davidw 5y ago
  Strong Towns...but for space! I like it!
• GeorgeOu 5y ago
  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.
  • ncmncm 5y ago
    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.
    • elihu 5y ago
      > 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?
• twobitshifter 5y ago
  Seeing these designs I thought about using a double helix, which would support growth, and be a poetic choice.
• abecedarius 5y ago
  The plan was to build more of them, of course. (And of course the first ones would be smaller than later more ambitious ones.) See e.g. https://en.wikipedia.org/wiki/The_High_Frontier:_Human_Colonies_in_Space https://en.wikipedia.org/wiki/The_High_Frontier:_Human_Colon... Non-popularized version https://space.nss.org/settlement/nasa/75SummerStudy/Table_of_Contents1.html https://space.nss.org/settlement/nasa/75SummerStudy/Table_of... (but that was the very first study iirc and made some known mistakes; I have no idea what the state of knowledge is now.)
• philwelch 5y ago
  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.