Space Colony Question: Rama vs O'Neil

[Crossroads Inc.]

The recent "Life inside an O'Neil Cylinder" thread has recently had me thinking a lot about the top of space habitat in general.
The discussion of the Rama Cylinder in the thread also raised some interesting points.

An O'Neil uses natural light from the sun for energy as well as lighting the colony. However because of how it is laid out, only 50% of the interior can be used for habitation, as the other 50% must be the massive expansion windows.

In a Rama Cylinder, 100% of the interior can be given over to habitation. However it is a closed surface and (in the book) light was given by three immense "light strips" that ran the corse of the interior. While Energy was produce by, well, 'other methods' that were linked to the big spikes at the one end, presumably where the star drive was.

If one was designing a space colony, and specifically one for both long term sustainability and maximum population. Which would be a better choice? Is it something where you could even say one is better then the other? Or just different?

[Peebo-T]

Though wouldn't the 'use' of windows be limited to the closer orbits of the Sun/parent star?

How much light would be useful the further out in orbits one's cylinder is/gets?

Also, wouldn't a single light strip running along the 'center' of axis within a closed cylinder allow for 100% of the 'walls'/'sides' to be used? Assuming LED's of sufficient size and luminosity could be made?

Cheers

[Starglider]

I suspect repairing micrometeroid damage to the windows would be a pain, and the risks of a significant strike doing major structural damage are much greater, compared to making the whole cylinder out of reinforced concrete. Certainly if you can cheaply mass produce solar cells, coating the whole cylinder with photovoltiacs will give you more flexibility, in both internal arrangement (e.g. you might want some of the length to be multiple concentric cylinders providing different gravities) and energy usage.

[Crossroads Inc.]

Saftey and resilience were the main things I was interested. I was considering recently a "Space Ark" concept and was trying to get the bext over all idea. O'Neils are at thier best when close to a sun, but a Rama can move around. I was thinking of some sort of hybrid, something that would move between stars and be closed up, but upon entering a new system could open up and take in solar energy again.

Not sure how something like that would work. My current idea was to have an enclosed cylinder like Rama, that still has immense solar 'wings' that would open up. Obviouslly instead of mirros to redirect light, they would simply be solar cells for power generation.

[Junghalli]

For a space ark a Rama-type design would probably make more sense. You're going to need an artificial light system while drifting between solar systems anyway, a system of mirrors and windows is needless duplication of effort.

[Crossroads Inc.]

One of the other things that bugs me about Life inside a enclosed enviroment is basically one of economy.

Orginally O'Neil said many space colonies would "sell" energy from space born powerstations and solar panels. But if you are drifting through space with a massive collection of people and cities and such. What do you do for economy? Manufactured goods? Industry?

Government could be worked out easy enough. But where would materials come from? Unless you came across dust clouds or random asteroids, and there is no telling what resources you may find. And recycling can only go so far.

I am wondering unless we had "Magic Tech" along the lines of energy to matter, is the whole idea of a space going people untenable? Would it simply be easier to freeze everyone and wake them up when they get to a planet?

[Junghalli]

Government could be worked out easy enough. But where would materials come from? Unless you came across dust clouds or random asteroids, and there is no telling what resources you may find. And recycling can only go so far.

If you're supposing a nomadic civilization moving between solar systems, they would probably periodically (i.e. every few hundred or thousand years) stop around a convenient star and gather resources from an asteroid or something, or maybe buy them from the locals.

Or if you want something really far out they might live off the interstellar medium, scooping up the diffuse hydrogen with a magnetic scoop and using fusion to transmute it to heavier elements.

If it's just a generation ship then it's simpler. You know the destination and how long it takes to get there, you figure out how much of a stockpile you need to last until then and take that with you.

[sirocco]

Saftey and resilience were the main things I was interested. I was considering recently a "Space Ark" concept and was trying to get the bext over all idea. O'Neils are at thier best when close to a sun, but a Rama can move around. I was thinking of some sort of hybrid, something that would move between stars and be closed up, but upon entering a new system could open up and take in solar energy again.

Not sure how something like that would work. My current idea was to have an enclosed cylinder like Rama, that still has immense solar 'wings' that would open up. Obviouslly instead of mirros to redirect light, they would simply be solar cells for power generation.

Well the problem with having windows is that they can't be used for anything else : you can't put crops or buildings on it. Hence in interstellar space they are a total waste of space. At best if your internal structure is sturdy enough you can try filling them with water and transform them into artificial lakes.

But now you have to:
- have at least 2 separate lake to contain the water for industrial purpose and the one for your population
- find a new purpose for your empty water tanks.

Since the trip between the star systems will be quite long, you should also invest into nuclear reactors (fusion if you can) and large warehouses (?). And it seems to me that you always have some kind of continuous dust cloud between 2 stars (space is never really empty) so some matter scooper and a good stellar map would be necessary too.


And finally, colonists would behave differently from space nomads.

Probably they would have some kind of modular Rama that could be disassembled once at its destination to build space stations/habitats (if they can't settle directly on the planet or their are other place of interest in this particular solar system), satellites, defense grid (if necessary) and maybe some other space stuffs.

They may leave the main systems so that later (when they reach full industrial capability) they can "rebuild" the Rama and sent some people to the next star system.

Personnally I like this plan. It would put some engineering issues under the carpet

[Crossroads Inc.]

As far as my over all idea, I am going with an enclosed "Rama" style worldship. It will still have a large body of water inside similar to the orginal Rama, but I am planning on all industrial nodes to take place on the outside of theship, so any pollutants that can't be recyled can be vented into space.

The problem Im having right now, and maybe I am over thinking this, is how a "spinning" colony, like an O'neil or a Rama moves in space.

As we all know, you spin to create the illusion of gravity inside an enclosed space. However you also feel "gravity" when accelerating. When a rocket shoots up, even in space, you are pushed backwards giving the feel of gravity.

If a very large object is already spinning, and then you begin to push it forward, wouldn't gravirty inside be affected? Also if you are moving, don't you need something spinning in the OTHER direction to compensate?

I remember countless times people telling me that the B5 earthforce ships needed a secondary rotating hull section, or else they would just spin around in one direction.

Is something like that needed here?

[Crossroads Inc.]

AHA! so THATS why all the pictures have two O'neils linked together. So all of those SciFi pics that show a single O'Neil by itself rotating are off? You need two together, counter rotating to keep things in Balance?

Well shout that just raises more questions about how Rama stayed balance.

You mentioned a second hull rotating inside, how big would that have to be to balance things out?

I was planning on having a long central axis running through the middle of the ship anyways where all the light would come from, and then spars would go up to it for transportation. If something like that would rotate would it balance?

Also, if you link two colonies together, did O'neil ever go into how they are physically linked? I mean, I can't imagine using something like "Ball Bearings" on something of that massive scale, if you linked two immense structures that are rotating, how do you hold them together?

[Junghalli]

As for rockets, you don't really need to worry about them changing the gravity. Yes, they will change the direction, but on something so massive, the acceleration from the rocket will be very small, probably too small for people to notice. So I wouldn't worry about it.

I'm curious, what would it feel like to be on an accelerating rotating centrifuge?

I imagine it would feel sort of like you were on a slope; stuff would fall to the side with a slower velocity as it would fall down. Does that sound about right?

Yea, otherwise they will tumble in weird ways over time.

Though the pictures aren't necessarily wrong - the cylinders would need a lot of space between them (to make room for the mirrors) so you might just not be able to see the twin cylinder.

Interesting, I didn't know about that. How big of a problem would a single cylinder have? Do other designs like spheres and tori have the same problem?

A lot of depictions show a torus around the station, for agriculture as I remember. Could you use that and/or the mirrors for your counter section?

Since the trip between the star systems will be quite long, you should also invest into nuclear reactors (fusion if you can) and large warehouses (?).

I think for an interstellar journey a nuclear power source is going to be pretty much essential; interstellar space is a very energy-poor environment. Hard to imagine where else you could get the energy to sustain your colony, unless maybe you have energy beamed to you from the home system in the form of a tightly focused laser. As for as warehouses go, maybe attach a bunch of asteroidal or comet material (maybe somewhat refined so you don't have to waste fuel accelerating any useless slag) to the front of your ship and between your habitat and the engines. That way it can double as impact and radiation shielding.

And it seems to me that you always have some kind of continuous dust cloud between 2 stars (space is never really empty) so some matter scooper and a good stellar map would be necessary too.

The interstellar medium varies between millions of atoms per cm^3 to 1 atom per thousand cm^3 or so, depending on where you are (it's pretty lumpy and uneven), with an average of maybe 1 atom/cm^3. We're in an unusually thin region called the Local Bubble which is something like a tenth to a hundredth as dense as the average. There's granules too, accounting for a small percentage of the ISM's mass compared to the gas and plasma (on average). It's there, but for the most part it's pretty thin. If you're just crossing from one solar system to another it might be easier just to take everything you need with you.

Also, the Oort Cloud stretches pretty far out, I've seen estimates that it goes past a light year from the sun. You might be able to island-hop across much of the distance between star systems rather than taking it all in one long hop, stopping off periodically to gather resources from Oort Cloud comets.

If you're planning to live off the ISM maybe you'd do most of your resource gathering in dense nebulae.

Probably they would have some kind of modular Rama that could be disassembled once at its destination to build space stations/habitats (if they can't settle directly on the planet or their are other place of interest in this particular solar system), satellites, defense grid (if necessary) and maybe some other space stuffs.

I don't see the point of disassembling it at the destination system. The whole point of the Rama approach is that the colonists have a nice comfortable home while they drift across interstellar space. You already have a nice comfortable habitat, why take it apart?

[Alerik the Fortunate]

In a short story in Gerard O'neil's 2081: A Hopeful View of the Human Future, the interplanetary passenger liner had I believe an ion drive powered by a laser station located in the inner solar system, which produced a constant acceleration of something like 2-5% g throughout the majority of the voyage. The passenger compartment of the ship, which rotated for gravity, was in the form of a tapered cylinder or beveled torus with the decks sloped at the same ratio as the thrust to artificial gravity, so that during sustained acceleration the resultant vector was almost always perpendicular to the floor.

[Crossroads Inc.]

The more I read about Space colonies, both here and elsewhere online, the more I come to realize they are in dire need of a technical “Update”

Much of the documents, outlines and “science” I find seem to be papers largely all done in the late 70’s. It seems there was a fairly large “futurist” movement in the 70’s, which spurred people like O’neil and others to dream up the lofty ideals for the various space colonies we now have.

However it seems that since then there has been a sad lack of follow up research or material written on the topic. One would imagine that, between the advances in computer simulations and engineering research, someone at some point would come along and do a new paper.

Exactly what sort of material tensile strength is required to build an O’neil?
How do you link two such massive structures together so they rotate in perfect balance?
What would be the air, food, water requirements for structure of that size and volume?

It is a shame there is not some new MIT student going through this with modern materials and computers to see just what it would take to engineer such a structure.

[sirocco]

Probably they would have some kind of modular Rama that could be disassembled once at its destination to build space stations/habitats (if they can't settle directly on the planet or their are other place of interest in this particular solar system), satellites, defense grid (if necessary) and maybe some other space stuffs.

I don't see the point of disassembling it at the destination system. The whole point of the Rama approach is that the colonists have a nice comfortable home while they drift across interstellar space. You already have a nice comfortable habitat, why take it apart?

Well when I am talking about "colonists", I mean people that will settle on another environment in another solar system. For that reason, they don't need a complete Rama ship.

First what will they do with the engine and whatever it uses as propellant? Once they arrived, even if it is a planet they have to terraformed they can always mine the surrounding asteroids.

And remember that we discussed earlier that if you are staying "stationary" (in orbit of a planet) an O'neill station would be more suitable and energy-efficient.

The Rama as described in teh book is more some kind of exploration vessel or even a line-cruiser between a homeworld and a far away planet for a pre-FTL race (or a pretty advanced race in a hard-scifi story). IF you want to use it to actually colonize a world, make it modular to provide the necessary ground and space industries to help the first settlers survive and prepare the arrival of the next batch.

On the other hand, if we are talking about space nomads, they would go the classic Rama design since they won't settle for a very long time. These people will probably travel too with a swarm of mobile factories and resource extractors.

[Junghalli]

Well when I am talking about "colonists", I mean people that will settle on another environment in another solar system. For that reason, they don't need a complete Rama ship.

First what will they do with the engine and whatever it uses as propellant?

Sure, they'd have no use for a dedicated interstellar engine except as spare parts and scrap, but there's no reason to take apart the habitat itself.

And remember that we discussed earlier that if you are staying "stationary" (in orbit of a planet) an O'neill station would be more suitable and energy-efficient.

It'd probably be more energy efficient but energy isn't really a huge problem in space if you're close to a star; you have plenty of uninterrupted sunlight and you can build very large solar collectors relatively easily.

[sirocco]

Well when I am talking about "colonists", I mean people that will settle on another environment in another solar system. For that reason, they don't need a complete Rama ship.

First what will they do with the engine and whatever it uses as propellant?

Sure, they'd have no use for a dedicated interstellar engine except as spare parts and scrap, but there's no reason to take apart the habitat itself.

Well what I meant is that you built a Rama ship to travel into space first and provide accomodation similar to the one on an Earth-like planet. which means that you will have system that only have use for space travel and other for life in harsh environment. If you are sailing to a place with harsh environment, it could be smart to use those systems.

They have the advantage of being 1- already built, 2- built by recognized engineers back on Earth and improved over the decades of the trip by the engineers on-board.

I guess there would probably core systems and anciliary systems, and every one of them would be doubled just for security. So you could make a lot of stuffs out of the Rama. =)

And remember that we discussed earlier that if you are staying "stationary" (in orbit of a planet) an O'neill station would be more suitable and energy-efficient.

It'd probably be more energy efficient but energy isn't really a huge problem in space if you're close to a star; you have plenty of uninterrupted sunlight and you can build very large solar collectors relatively easily.

Well you're right on that. And you can more easily adjust the intensity of artificial light. And use the energy for something else than lighting. But well it would be a 2nd type of space habitat, much closer to the O'Neill concept than to the Rama.