I have an idea for a story I'm brewing but I want to know if such things are possible or even plausible.

The basic idea is that the O'neil cylinder was created after a failed attempt of colonizing a planet. The cylinder would house a generation of people eventually growing in size. Soon infighting within the O'Neil cylinder would escalate of various groups that try to take control the entire station in order to impose their will. I hope that is clear enough.

Seeing how the structure should be maintain at all cost and minimize damage, I'm thinking a rules of engagement is placed with a Neutral faction to enforce it. This faction could compose of engineers who keep the station maintained.

With this idea, what would war be like inside the Cylinder? What factors do they have to consider and what kind of weapons can they use?

  • 1
    $\begingroup$ Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. $\endgroup$
    – Community Bot
    Commented Jun 20, 2022 at 17:33
  • $\begingroup$ I edited the question. I hope it is clearer now. $\endgroup$
    – kreoss
    Commented Jun 20, 2022 at 18:02
  • $\begingroup$ Research human tribalism. Do you have more then one tribe/group? Then yes you can have conflict. The simplest way to war would be valued scare resources to compete over, and time to solidify group identity and inter group animosity. $\endgroup$ Commented Jun 20, 2022 at 18:08
  • $\begingroup$ "The theoretical reason to wage war": In a football match between the representative teams of the Blue Sector and the Gold Sector, the referee, undoubtedly paid by the despicable dishonorable thieving Gold Sectorites, allowed a goal from a blatant off-side position. The admirable honorable brave Blue Sectorites saw that the only way to avenge this heinous crime was to go to war. $\endgroup$
    – AlexP
    Commented Jun 20, 2022 at 18:20
  • 1
    $\begingroup$ Doesn't everyone have a MAD weapon - venting the cylinder? That should discourage people from going to war. In theory. $\endgroup$ Commented Jun 20, 2022 at 19:02

5 Answers 5

  • When I hear or read about an O'Neill Cylinder, I think of something a few kilometers in diameter and a few dozen kilometers long. About 100 or 200 square kilometers. Half of it might be windows. So you have a really limited area to wage war.
  • The surface is the inside of a cylinder, not the outside of a sphere. It might be possible that a few fixed installations have line-of-sight to all of the surface. That might be fixed guns, fixed sensors, fixed communications stations.
  • I'm assuming that there are several sublevel below the surface, containing machinery, stores, living spaces, and more.

Those three mean it will be very much like urban combat. There is a role for tanks and aircraft in urban combat, but if they were optimized for it they would look different.

  • It is possible to damage the outer skin, sublevels, and habitat surface so much that the air escapes and everybody dies. For that matter, any significant faction could sabotage the outer skin as a "doomsday device."
  • There will be infrastructure like water pipes, central lights, etc. that may be somewhat redundant, but it might still endanger the habitat if the infrastructure is degraded.
  • Unless you get frequent resupply, there is a limited amount of material that can be turned into armaments. How much tungsten for penetrators, how much nitrate for propellants?

That sounds like infantry, possibly with a few light vehicles or powered armor, and a bunch of relatively small drones. Equipment includes both "moderately unsafe" weapons for use on the inner surface, and away from critical infrastructure, and "safe" weapons for use near the inner surface, or near critical infrastructure.

Between that and the small total area, I'm not sure if there will two sides fighting along a line of confrontation, or if it is one side ("the government") trying to fight against one or more sides ("the insurgency" or "the gangs").

Social norms might develop which keep key infrastructure safe ("all the gangs gang up on anybody who tampers with the water supply"), but this sounds too small and fragile to make it work. You might not recover from the initial period where these norms develop by trial and error.

  • $\begingroup$ Hmm interesting. Thank you for your answer. I did plan on considering Rules of Engagements that were placed after a near fatal accident. Something like smaller engagements, neutral zones where no fighting is allowed or even banning of specific types of weapons. I do like the sound of different types of weapons used on the surface or bellow the within the sublevels bellow. Their weapons would most likely not be too destructive to avoid station wide disaster. In terms of conflict, I was considering taking inspiration from Battletech or dune, where things became a almost feudal society. $\endgroup$
    – kreoss
    Commented Jun 20, 2022 at 19:20
  • $\begingroup$ @kreoss, a ban would need a community to enforce it. Do you have that many separate kingdoms who could contribute? Look at the Russian attack against Ukraine. Russia broke international norms, but while there is support for Ukraine, there is no global war on Russia to restore those norms. Just sanctions. $\endgroup$
    – o.m.
    Commented Jun 20, 2022 at 19:25
  • $\begingroup$ Perhaps a neutral faction composed of engineers who shouldn't take part of the fighting, will enforce and maintain the station. Going against them could have serious repercussions. $\endgroup$
    – kreoss
    Commented Jun 20, 2022 at 19:48
  • $\begingroup$ @kreoss You can't really rely on a watch dog organization to prevent rules of engagement from being broken. Rules of engagement have more to do with politics than necessity, and typically go out the window as desperation grows. That said, desperation has its limits. Using heavy artillery in an O'Neill Cylinder is about as dumb as using Nukes in Urban warfare. You don't need anyone to force you not to use it because no one wants a weapon that will kill themselves; so, everyone should be smart enough to choose weapons that they at least believe will not cause a hull breach. $\endgroup$
    – Nosajimiki
    Commented Jun 20, 2022 at 20:06
  • $\begingroup$ @Nosajimiki, until someone says "see, you made me desperate, I'll do this, really, unless you back down. I can only die once, after all." $\endgroup$
    – o.m.
    Commented Jun 20, 2022 at 20:26

Every society finds a reason to go to war. Sometimes it's an argument about the relative value of resources, but more often, it's one group taking offense at something, or some ruler deciding that they need something for the young people to do, or someone trying to make other people behave the way they want.

Think in terms of gangs that wage war for the right to sell something in a particular territory, or the poor trying to force the wealthy (and in charge) to raise their standard of living.

The special considerations in an O'Neil Cylinder are that you don't want to use big bombs, or poisonous gas, or biological infections since that'll inevitably effect everyone. Territory might be defined in a different way, for instance, the farms vs. the manufacturing facilities. Even in large corporations, people will fight to build little fiefdoms. It just usually doesn't come down to bloodshed.

This is 100% inevitable if the cylinder has no near neighbors. You can see this dynamic in the United States or the fall of ancient Rome. In an absence of credible outside threat, the people will turn to infighting. Eventually you will get one belligerent side that absolutely doesn't care how much they hurt the other guys, and that's when war starts.

  • 1
    $\begingroup$ Hmmm I guess war within a O'neil cylinder is almost no different that of earth. My mind keeps thinking that wouldn't living such a structure would make people more careful. I guess the most likely thing that would change is the way they conduct war within the cylinder. And you are right, biological weapons are out of the question. I guess even overly powerful weapons are out of the question. What sort of vehicles are capable of fighting inside it? I don't know how flying vehicles will work in such an place. Would the people who maintain the cylinder be like the ruling body? $\endgroup$
    – kreoss
    Commented Jun 20, 2022 at 18:42
  • $\begingroup$ Biological weapons are not necessarily out of the question. For example, your cylinder might have a dozen separate water systems instead of a single one for better redundancy; so, you may be able to contaminate someone else's water system without contaminating your own. Or if only your faction has a vaccine, you could vaccinate your faction against a weapon before distributing it to kill off all other factions. There is also the possibility of biochemical weapons breaking down in the air limiting the possible spread of weapons before they become inert. $\endgroup$
    – Nosajimiki
    Commented Jun 20, 2022 at 21:00
  • $\begingroup$ @Nosajimiki, did you know that dentists who work in high-rise office buildings aren't allowed to use nitrous? That's because, unlike in a space where you can vent things to the outside world, the nitrous would accumulate over time in low spaces, and can even cause peripheral neuropathy. A cylinder with 1G, which didn't rip itself apart, would definitely have that kind of environmental limitations. $\endgroup$ Commented Jun 21, 2022 at 5:58
  • $\begingroup$ For the flying vehicles question, watch Episode 22, Season 2 of Babylon 5. (youtube.com/watch?v=pzBDhnWK6zg) I think that quaqdcopters could readily navigate the shifting gravitational influences, but they wouldn't want to actually fly for much. $\endgroup$ Commented Jun 21, 2022 at 6:07

Weapons will be chosen to minimize collateral damage

The goal will be to choose weapon systems that don't have to sacrifice stopping power in exchange for minimizing risk to the hull of the O'Neil Cylinder. While kinetic and explosive weapons can be modified to be weak enough not to risk a hull breach, such weapons are easy to armor against. It will generally be better to choose weapons that specialize at harming people while minimizing structural damage.

The biggest risk behind firing a gun in space is that typical space station armor is designed to stop hyper velocity kinetic projectiles from the outside-in, not ballistic velocity projectiles from the inside out. The International Space Station for Example uses thin spaced armor called wimple armor designed to break up hyper velocity projectiles as they contact the outer hull so that the energy is spread out against the thicker inner hull. Not only do slower moving ballistic weapons not break up on contact with wimple armor, but if you hit a space station's armor from the inside, you hit the thicker armor with the full and concentrated force of your slug, and if you pernitrate it, it takes very little to breach the thinner outer hull... so unless this is specifically a military installation designed with internal firefights in mind, nothing about the hull is optimized against being shot at from the inside.

So if you want to nullify kinetic weapons, you simply need to armor your troops as well or better than the space station against them. So, any sort of tank for example could easily be made to be to dangerous to attack with conventional weapons.

Kilowatt Range High Energy Lasers

While the materials that make up the outer hull of a space station are not super resistant to ballistic weapons. One thing they are specifically designed to do is insulate against temperature changes. Space is harsh. Your space station in orbit of a planet will see hull temperature fluctuations of hundreds of degrees every day as it moves in-front-of/behind the planet it orbits. In generally, most of the materials the hull is made up of are designed to resist temperature changes, and can survive temperatures over 600°C. In contrast, humans are very particular about our body temperatures. A weapon that can rapidly raise a target by 100-200°C will have a negligible effect on the hull of your O'Neil Cylinder, but prove devastating to an human it hits.

Even if a tank is armored enough not to melt from a laser, you can heat it up enough to kill everyone inside without risking damage to the station.


Electrolasers are a electroshock weapons that create a laser-induced plasma channel that acts like a wire through the air for directing an electrical discharge that can stun or kill a target at range. Rather than killing by heat like a traditional laser, electrolasers electrocute thier targets. While a missed shot by one of these weapons may fry some of the station's electrical components, it is highly unlikely to cause a hull breach. These weapons could also be useful against enemy armored vehicles by frying the circuitry.

Biochemical Weapons

While most Biochemical Weapons would be suicidal to use in the closed spaces of an O'Neil Cylinder, there are many ways to deploy these weapons that would not pose a significant threat to your own people. One possible use case would be if your O'Neil Cylinder has a segmented water or food supply. By poisoning the enemy's food or water, you could kill them off without endangering your own supplies. Another possibility is the use of airborne toxins that react with and break down in the air. Such a toxin could be releases on a battlefield and be rendered inert before spreading to poison the whole O'Neil Cylinder. A third option could be poison tipped dart weapons. A poison tipped dart will not have the kinetic energy to risk a hull breach, but could still kill or debilitate.

  • $\begingroup$ What I know about O'Neil cylinders is that there is an earth like environment inside the cylinder with mountains, trains, hill and such. Similar to Battletechs Ares Convention, factions inside the cylinder follow a set of guidelines when the conduct war That means fighting in specific areas only and using certain weapons. Would conventional weapons still work if such combat were held in specific areas to minimize the structure of cylinder? $\endgroup$
    – kreoss
    Commented Jun 21, 2022 at 19:27

Fighting in O'Neil cylinders are a staple in Gundam franchise. The rules both opposing factions obey--most of the time--is no heavy weapon that are powerful enough to blow a hole through the wall, do not shoot the engine of the robots (according to the lore, using beam weapons to shoot the robot's engines would create a nuclear blast that would easily blow a hole in the colony's walls).

Some more ideal works have specific "fighting zones" in the colony for those who had a grudge to duke it out. But no fighting in any other places.

But most of the time, it only took one mad man before people start shooting nuclear rockets, or worse, dump poison gases into the colony.


Really? Oh, really?!

There are quite a lot of options defining which shape things can take, depends on skills of both parties, so as design of actual structure, what can they produce, or which terms/agreements they can make politically wise.

As @o.m. correctly pointed out - it a city level figth, and there are examples in history of such events when ruling class was overturned or changed. From ancient time(Rome), trough modern time(orange freedome, yellow wests, capitoliy etc)

So it does not need that much of a fire power, like it hard to call it a war, it more like a rebellion, a coup.

It can be like a compeition between swordsmen, or all willing vs all willing a sword figth, or a fist figths on the streets etc

It can take all kinds of forms. Being in space adds aditional dimension to that city scenario, giving ability to do things by controling software(hacking) and some key point hardware, if there is any by design.

Or it can be just one(few) guy shouting promises on a public square for 3 month's and 1% active power hungry population, reluctance of the rest, making a win for new power.

There is really no rigth or wrong scenario, and weapons required(as displayed by examples) almost none in some cases, fists are enough - and it not something as not probable or a minimal set, but it quite working scheme in reality, so as it possible to say it has certain degree of be fair, a version of democracy - fist democracy.

what it means being in space, in O'Neil

mm, not sure I should word it that way, and good stuff can be written in the setting you presented in the q in the way you ask about, buuut, it smells like an old stuff, generation ships, degradation and conflicts there, not that good old is bad, but it was early time on thinking on all kinds of things, in time when a digital drawing was not known and wasn't a thing(in 50-70's)

Since then a lot has changes, and someone has to reinvent what such a conflict may be on a cylinder, what kinds of solutions there are, because of the goal of expedition(setting on a planet), what it means to set a self sufficient colony with modern tech thus defining what do they have.

  • in that sense your question lacks what do they have

I mean if you just need action scene of the conflict to be, some passing by event, you do not need much really - fists and handguns are well enough to start and achieve results in a coup - it all you really need - it easy, fast effective, no way to kill the station.

But if your whole story, half of, good portion of it - is about that conflict, or you investigate the potencial and possibilities of problems and solutions in this setting - then it would be a too shallow of a take on what's available to the guys, in a sense of options.

  • in a sense there is no limits - "that nuke we did carry to melt ice caps on the planet, remember?, so I did fix it and I have it, also I placed a random guy who constantly shouts allhuckhackbar next to it, locked in a room, on this optimistic note let's start our negotiations - you talk to me now, or you talk to him later if you lucky enough." There is no need for a random guy, it can be a detector and a random event - needs an open system which can be understood, and be verifiable and can be seen in action which places certain percent probability of total destruction, and is eash to understand. So you can use what you have - if it is a big gun which makes a big hole in the shell - it can be part of the cards one plays. So in that sense it pointless to ask what can or can not they use - it all about how do you play the cards you have - one can have nothing and win, one can have everything and lose.

Being in a cylinder, next to a planet which has some potencial to be inhabited(meaning it big enough, and has some sort of atmosphere, maybe some water), in a space it really changes what can be done, expands it.

In short, or a biggest thing is that they can expand, build more of cylinders.

And they can split without figth, for a start. And then they can attack each other and destroy cylinders if they like to do so.

Even if there are tensions, which go trough a whole population, like dems and reps in usa, they can work on common goal, like splitting, making second cylinder or few of them.

And being in space, next to a planet mass, means they have means to do so(not taking mass form surface of planet(but it can be an option), but taking mass from upper parts of athmosphere (atmosphere scooping) for reactive mass for their probes, which can bring asteroids if there are problems reaching surface of the planets because of some limits of what they can implement rigth now)

Heading to a planet to colonize it, it also means bringing technology tree in some form, of dravings, description of processes, how to manuals, a plans to enroll and later recreate that technological self sufficiency, seed installations(which even if destroyed can be recreated, they aren't thag big or complex compared to a cylinder).

Losing competences in the technologies in space means death - if one can't serve the station(if there is no smart matter) then sorry, your life line is out in a decade or few no matter what you do - you have to get some tech competence back in this time.

And having comptences means a lot of things can be done in space if materials are available.

Basically 6 out of 8 planets in our system have moons, which can be source of materials, even small moons of mars are actually huge chunks of materials technology wise and they are huge as what can be done from them.

Asteroids in a system they also can be such sources of materials. (Basically you can bring the whole asteroid of materials minus oxygen by means of that asteroid, what it has, to a planet, if you need it)

So answer your q is that there is no limits, but fists and guns is welle enough. But if you set just for that, it will be a waste of conflict in such setting, space gives you a new dimension, so as capacities of them which are result of their initial goal are way bigger than just that. But most likely it a coup which ends in few days, and regular people do not care or even do not know that much about it all.


Reading some of your comments, I can't comment so add some stuff here.

Really forget tanks airplanes vehicles and war action of bunch of stuff in this setting. A colony, what it need the stuff for, a colony is just a big city. It even hard to imagine a significant rupture of society in this curcumstances, when everyone understand that they depend on everyone, it a survivial situation. It easy to convince that conflict on large scale is death for them all, and hard to convince it to be a solution, if they understand the situation which they are in.

Power struggle happens behing close doors - it has benn so for ages, and coups are failsin that sense.

The system is not capable to support a war even if imagine they have few tanks for some reason. Few lucky shots and all the capacity to make or repair them is gone. Not talking that few heavy vehicles in a city, in a war setting, not a such a brilliant idea, nor does it bring something of value really. (But depends, killdozer did well enough)

As a compeititon of some sort of arena figths, with some rules it can be a thing actually, if you like to have archaic approach. In a sense one wanna risk his life and bring death to his opponents(or maybe it not death, maybe a lose of dice rolls is convincing enough and can quench his attitudes) - okay here is your chance, those who win and survive define this or that matter, rest of the public relictantly allows this on that matter, because we see your resolve and our resolve to oppose is defiently not that big.

It may become a system, a part of managment. But really it up to you to invent it to depict it, if you have what it takes, as it is your story and there are many ways. But yes, changes in societal norms and conducts may happen, there is nothing strange in that, people to adapt, and despite the wars majority of our systems are in place to prevent them, as wars are way too expensive and it a last resort, and letting steam out on constant basis can be a thing and was a thing in time when duels were more of a norm, so it not something unheard of, or not something which had not been done in a bit different way.

PPS Rules

A rule of good life - one devides, another chooses - you can do this or that, you choose.

Also another rule - when there are more than 10 cylinders, and it means it easy to have them, then you surrender, successefuly defend your self, or bust. In this situation a cylinder is not such a big commondity or big asset, or a value. There is no point to spare it, when you remove opposing actors. With a star system resources you can have them as many as you like, if there is no one who disturbs you.


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .