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Now I recently had an idea for a setting and villain backstory and thought might as well get it vetted.

Once, there was a mighty Empire that had conquered its home system and converted most of the planets into a habitable Dyson Ring. The other species that shared their system were reduced to slaves and those in charge were planning to expand to other systems.

Fortunately, they got the attention of an interstellar species that subscribes to a similar philosophy as the aliens from the original Day The Earth Stood Still. If you want to war, destroy, pillage and do other horrible nasty stuff to fellow sentient beings, you're free to do so, so long as you keep it to your home star system. Try to take it to other star systems, and then we’re gonna have words.

So they sent one ship to the Dyson Ring and basically offered a warning: do not expand beyond your star system and there won’t be any problems. Of course, the evil Empire being evil, they just laughed in the emissary's face wondering what the hell such a puny little ship could do to their impressive Dyson Ring. The only response that they received was a solemn, “It didn’t have to be this way.” Then the ship fired a single shot right into the sun.

The lucky ones died when atmospheric containment failed and they were exposed to space, others were incinerated by coronal mass ejections that ripped the Dyson Ring apart, others slowly suffocated as life support systems were fried by flares. Some found habitable pockets to cling to life within as the world literally crumbled around them.

They thought they could claim the stars as gods, and the true masters of the stars sent a single ship to punish them for their sinful pride.

So here is the setting, a shattered Dyson Ring with shards ranging in size from as small as a square mile to as large as a couple of Earths, with the remnants of an evil species ready to attack any space traveler who is unfortunate enough to check out these interstellar ruins.

But here is the thing I want to know.

As the Expanse demonstrated any artificial ecosystem can be prone to cascade failures that can lead to complete and utter collapse, so once those dominoes start falling there is no stopping it. So once the Ring is shattered, complete and total collapse of the system and the utter extinction of any lifeforms still on board is pretty much guaranteed. But I want to know how long can that inevitable collapse be put off?

So my question is this: After being shattered, how long can a Dyson Ring support the life on it?

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    $\begingroup$ Is your Dyson ring spinning to create artificial gravity? Is the "roof" closed or open? $\endgroup$ Feb 8, 2023 at 17:06
  • $\begingroup$ The roof is closed and there is some magic gravity. $\endgroup$ Feb 8, 2023 at 17:07

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I'm going to answer your question with a question:

"How quickly after hitting an object does a ship sink?"

Could be seconds, could be minutes, could be hours, could even stay afloat.

The question really is in two parts:

1: How long do I need the Dyson shard to remain habitable for the purposes of my story? and

2: What technologies/design do I need to achieve that?

The first thing you need to consider is the design of the Ring - a single continuous Ring wouldn't last long, but a Ring that had a degree of compartmentalization (like a battleship has watertight bulkheads) - now we have the basis for some degree of survivability. Next up is redundancy of critical systems - what are the backup systems for our backup system? We need, initially, atmosphere and (potentially) gravity, then heat, water, and food.

Let's assume, therefore, that there is a big enough fragment that has within its compartment structure maintained all of those systems, but it's been blasted away from its star.

Here's the estimate of what would happen if our Sun disappeared - which gives an estimate of 2 months for the removal of the atmosphere and radiation from space to kill us all - but we are assuming those still work as above they are artificially created.

With enough reserves of power and resources, it's possible a small group on a large fragment could survive for a long time (months to years) - however the longer it goes on, the more the resources dwindle and with no star to replenish them - any small issue is magnified.

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Indefinitely, provided there was a prepared place

A Dyson ring is quite a complicated device with quite a huge span, all sorts of smaller installations could happen on its surface. In fact, to support life for an indefinite amount of time three things are needed: energy, sealed volume and equipment. Let's assume there is an emergency hideout located on the (inner) side of the Ring, supplied with some solar batteries together with a standalone backup fission or fusion reactor, some adequate shielding from all sides, with abundant resources within, up to a Biosphere ready to accommodate inhabitants. When the Sun decided to misbehave (by the way, what level of misbehavior? It's not a supernova, or else everything would get disintegrated, and also not a black hole collapse. Perhaps that ship just caused major disturbance in their sun's upper layers that caused "just" destruction and not eradication, therefore the sun should still shine), the device was armed, some local folks got covered inside, then BAM and a significant piece of the Ring with a probably damaged but functional habitat is torn off. Then after external normalization of the solar activity the habitat's solar panels unfold or get fixed with spare parts, and start providing energy into the sealed environment. This, given the Evil Empire's tech level, could just do for the inner community to eventually raise a Super-Villain, in the meantime they could scavenge other parts of the Ring that might contain deactivated machinery, survivors, minerals, electronics, lost data, etc, that would help that community to eventually rebuild.

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  • $\begingroup$ Well you are right the star didn’t go Nova, so the star is still there. I was kinda vague on that point but what the ship did to star caused a lot of CMEs and solar flares that wound up breaking the ring. Though your fallout shelter section is a pretty good idea and definitely something for me to look into. $\endgroup$ Feb 8, 2023 at 7:58
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    $\begingroup$ I'd expect that anyone building stuff up in space include a large amount of backups. Given how adversarial space is to life, it's best to be prepared for the worse eventualities, as accidents and dissidents do happen. Thus I'd hope that the Evil Empire did in fact create their ring with a good amount of paranoia, partitioning the ring so that each (smallish) partition could be cut-off from the rest and use its own back-up generators, etc... until the issues were dealt with. $\endgroup$ Feb 8, 2023 at 16:04
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    $\begingroup$ Even if the Evil Empire didn't plan backups specifically in case the Dyson Ring failed, construction of the ring would presumably have taken some time, and they had to put their people somewhere while that happened. Those systems would've originally had to be independent and long-lasting, and might still be around: The original home planet now integrated into an arc of the ring? Some construction ships? Airlocked tunnels to store / move resources before the atmosphere was delivered? Solar sails to stabilize the ring pieces before they were connected? $\endgroup$ Feb 9, 2023 at 18:19
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As others have pointed out, a Dyson ring would be built with lots of redundancy. Perhaps like a chain, with every "link" being mostly independent - except for needing the other links to keep the chain intact, in orbit, and properly oriented.

So the chain broke. Some links were destroyed then and there. Many survived the explosion, but some parts drifted off to useless orbits. Mass death over hours, days and weeks, as broken or de-obited pieces runs out of air, energy or survivable temperatures.

Remaining people live on some twisted piece(s) of "broken chain" in a survivable orbit. But the links are no longer properly facing the star; they have to deal with unusual temperatures and perhaps even migrate seasonally to links with useable orientation. Population may have dropped to a very small fraction of what it once was, but is now stable.

Repairing the ring itself may be too much for the survivors, but they might be able to keep what's left working indefinitely. And they would surely remember what they once had, and hate outsiders a lot.

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  • $\begingroup$ Honestly, your “broken chain” comparison is probably the best comparison to what the end reluctantly would look like, because I pictured a massive ring shard in a tumbling orbit giving it a day night cycle lasting about four hours. And repairing the Ring is not an option, it’s too far gone for that, too much is damaged beyond repair, and there is not enough material left in the system to make replacements, even if they still had the ability to process it. $\endgroup$ Feb 8, 2023 at 21:00
  • $\begingroup$ And these answers are great because it sounds like that final bitter collapse can be put off for a couple millennia at least, leaving the locals to slowly forget how their tech works as their home slowly crumbles around them, which is what I wanted for the story. A broken down gothic local for explorers to stumble into that seems abandoned and left to decay for millennia, but the original tenants remain, once worshiped like gods now reduced to scavengers and beasts as their once shining palaces crumble around them like forgotten tombs, monuments to their ancient pride. $\endgroup$ Feb 8, 2023 at 21:06
  • $\begingroup$ I was actually worried I’d get a year at most which would’ve presented a lot of timeline problems. Still great stuff. $\endgroup$ Feb 8, 2023 at 21:07
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    $\begingroup$ A Dyson ring could be built with redundancy. The Ringworld wasn't. It depended on Protectors keeping it going. $\endgroup$
    – davidbak
    Feb 9, 2023 at 18:41
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Frame challenge:

It doesn't matter how long people on the individual pieces can survive, they will be killed when the pieces are sucked into the gravity well of the sun/star.

This isn't a planet that cracks open, yet the pieces still hang around each other because there's not really any other place to go. It's not even a moon that has a stable orbit and the pieces don't have enough change in direction to impact the plant they orbit. This is something that can't be roughly assumed to be a point mass, because it acts completely different. It would act more like a rubber band around a ball being cut, rather than the rubber ball having a section cut from it. But even the rubber band around a ball isn't a good analogy.

A Dyson ring may have some angular momentum if it was rotating around the star, due to it needing some way to help maintain a stable position. With this motion, some pieces may be flung away from the star and some pieces may be flung directly into it (or near enough) so that it melts and is destroyed.

A Dyson ring may not need to be rotating around the sun, so now you have pieces of debris that are relatively stationary to the star.

Even if pieces were flung away from the star, they will still be drawn back into the star because it's a huge mass and pulls things into it. The only reason planets, comets, and other natural debris isn't pulled into it is because they are moving at the correct speed and angle to avoid the star. Going the wrong speed or at the wrong angle, and the star adds more mass to itself.

The likelihood of a piece being ejected from a destroyed Dyson ring at the correct speed and angle to achieve orbit is nil. The likelihood of a piece being ejected from a destroyed Dyson ring at the correct speed and angle to achieve escape velocity is even less.

The best you can do is to send a rescue to each section/piece in order of how desperate and how likely they are to die soon. So this isn't just about individual sections supporting life, it's also about triage of who can survive to be rescued and what order they need to be rescued in.

Some of these pieces may not be pulled into the star for days, weeks, months, or possibly years, so yes, you still need to decide if those pieces remain habitable and for how long. But they will all be destroyed by the atomic fires of the star they once surrounded.

I realize this significantly changes your story, because now you have to decide if there's a civilization that wants to do the rescue, if this civilization has the ability to perform it's own rescue, if the interstellar community watches this evil civilization disappear with a sigh of "good riddance", or some other outcome.

Edit:

I didn't explicitly say it before, but I'm making the assumption that simply getting near the star is enough for the debris to burn up to a point on inhabitability. I will admit that I didn't realize that the "no-go" volume around a star was so large, but it kind of makes this answer a little more on point.

Current human technology lets us get within about 3.83 million miles to the surface of our sun before it gets too hot. I'm assuming that a civilization capable of creating a Dyson ring isn't making one ~12 million miles in circumference. That said, whatever material they are making the skin of the ring out of, I'm assuming they aren't making the interior in that same material, so any broken ends not protected by bulkhead doors will be incinerated.

Also, only a fairly sizeable section (FSS) of ring debris could be assumed to have enough self-sustainment equipment to maintain a livable atmosphere in the extreme conditions around a star. (What "fairly sizeable section" means is definitely subject to interpretation.)

One issue with these FSS is that they will have enough mass that maintaining the current orbit or finding a different stable orbit will be next to impossible being that close to the star. I'd have to assume that maintaining orbit of even a moving ring would be considerably different than maintaining orbit of an individual piece. So it would also have to be assumed that this FSS would also have maneuvering thruster(s) to even have a chance of not being pulled into the star. Not only that, but the thrusters would have to be in the correct position and orientation to be able to put thrust in the correct direction to push the FSS into a stable orbit. And now we finally have to worry if there's enough reaction mass for the thrusters to even matter. Given all that, we still have to worry if the thrusters are capable of producing enough thrust, producing that thrust long enough while not going beyond expected usage, and if the FSS is structurally sound enough to survive the firing procedures.

Another issue is that we can safely assume that even these FSS aren't 100% self-sufficient in that they will eventually have to bring in more air, food, repair parts, etc. Granted, they may be able to harvest some of this from the plasma around the star and use the energy from the star to extend their lifetime, but they will still likely run out of something they need, eventually. So, if the FSS doesn't also include some sort of ship, manufacturing center, facilities to harvest plasma, and more, survivors of the initial disaster will not be able to survive indefinitely. Granted, this isn't part of the issue of falling into the star, but it's still a significant issue of survivability.

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  • $\begingroup$ Hmm, the “we are on a shard that is about to dive into a star,” might add a nice ticking clock, especially for someone to say, “is it just me, or is the sun getting closer?” I think time might be giving with some directional thrusters, something that would be used to spin the ring and keep a habitable piece in a somewhat stable orbit, but again the theme is everything by this point is broken down and I like the image of that last vestige tumbling towards a fiery end. Interesting take. $\endgroup$ Feb 8, 2023 at 22:56
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    $\begingroup$ Also, my writing would likely be too technical and not dramatic enough, because "no, that wouldn't blow up" would be my mantra. Along with "there are too many safeguards which would prevent that from happening". And "no, physics/chemistry just doesn't work like that". Lol. $\endgroup$ Feb 8, 2023 at 23:25
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    $\begingroup$ I'd try to build the ring as rotating in along stable orbit. This would make construction easier since all the pieces would approximately stay near each other before getting bolted together. The necessary orbit would change a bit during assembly due to attraction between the pieces, but that's not a solid-vs-separated distinction, but a "distribution of mass" issue. So start with a couple chunks on opposite sides of the same circular orbit and use sails / thrusters to adjust orbits as you fill in the gaps. If the attack leaves the pieces' velocities alone, they'll continue to orbit. $\endgroup$ Feb 9, 2023 at 18:32
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    $\begingroup$ @SarahMesser, I think I see where you are going with that, but the attack isn't on the station itself, but rather the star, and the star breaks up the Dyson ring with coronal mass ejections and flares. The flare might not change the direction of pieces, but I can see CME's doing so. Also, manmade orbiting satellites require adjustments to keep them in orbit, and if those don't happen correctly, the orbit is lost. And balancing an orbit with a mass on the other side just means the center of gravity doesn't change, rather than an orbit is maintained. $\endgroup$ Feb 9, 2023 at 18:43
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    $\begingroup$ @SarahMesser, I didn't realize it at the time, but there's a very significant volume around a star that's very, extremely, and massively hot, so a piece of debris won't even have to directly hit the sun to burn up, or at least make it very difficult for survivors to maintain their "survivor" status. I've updated my answer with this info. $\endgroup$ Feb 9, 2023 at 20:53

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