Author Topic: O'Neill Cylinder Mission - tech limitations.  (Read 13376 times)

Offline nestormakhno

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O'Neill Cylinder Mission - tech limitations.
« on: 01/25/2013 05:08 PM »
Hi there,

I am a video game developer and am interested in some background for a hard science adventure game set on an O'Neill Cylinder with some form of propulsion system. I would to get some background knowledge on the limitations (with current or near-future tech, and current or nascent knowledge) on the development of the following:

Quote
An O'Neill cylinder large enough to house a self-sustaining ecosystem during a mission to nearby candidate star systems with potentially exploitable/colonisable planetary systems.

For the purpose of this discussion let us assume that budget and project duration are essentially unlimited.

I understand that reading these forums there are a huge variety of users with knowledge in different fields possibly germane to this concept. I would like to categorise responses into the following areas:

Destination: Which star systems seems likely to have planets that are in any way exploitable by such a mission and are even potentially colonisable? Assuming best concepts for interstellar engines, how many years/generations would we expect a mission there to last?

Cylinder Specification: What materials would be best used for construction of such a cylinder? What propulsion system could, with current or near future tech, be used? What would be the optimum size for the population of this cylinder to be self-sustaining? What would be the optimum size for cylinder assuming such a population, if they are to remain sane and well-adjusted over a many-generation journey? How much of the cylinder should be devoted to hydroponics, industry, residence etc? What would be best used as light source for the cylinder interior?

Construction: What would be the cost of such a project? how long could it conceivably take to build a cylinder capable of interstellar voyages if a large enough corporation were set up? How long would the training of the population take?

I have already pored over the 75 summer study, I was just wondering what people here might have to add.

Thanking you in advance for your input.
« Last Edit: 01/25/2013 05:19 PM by nestormakhno »

Offline Tass

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Re: O'Neill Cylinder Mission - tech limitations.
« Reply #1 on: 01/25/2013 05:19 PM »
Destination:

Anywhere. If a civilization has the in-space industrial capabilities to build an O'Niell cylinder then it has no need for planets. Asteroids are much easier to extract materials from to construct more colonies. Teraforming is way harder, and still yields sharply limited living space.

Only interest in planets would be scientific - looking for life etc.


Offline nestormakhno

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Re: O'Neill Cylinder Mission - tech limitations.
« Reply #2 on: 01/25/2013 05:26 PM »
Thanks for the speedy reply. I had not really considered deeply the purpose of the mission.

For the back-story here I guess we would be thinking in terms of the cylinder being used to 'seed' other planets. Because a cylinder, no matter how well made, is potentially very fragile and prone to accidents.

If the purpose of the mission were to propagate humanity then I would expect it to colonise any terraformable planets it encountered on an indefinitely long mission, simply to increase long-term survival chances for somebody at least.

Offline Jim

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Re: O'Neill Cylinder Mission - tech limitations.
« Reply #3 on: 01/25/2013 05:45 PM »
O'Neill cylinder is not designed to support propulsion.

Offline Tass

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Re: O'Neill Cylinder Mission - tech limitations.
« Reply #4 on: 01/25/2013 06:13 PM »
O'Neill cylinder is not designed to support propulsion.

True, but he obviously meant it in a broader sense of "kilometer sized cylindrical habitat".

Thanks for the speedy reply. I had not really considered deeply the purpose of the mission.

For the back-story here I guess we would be thinking in terms of the cylinder being used to 'seed' other planets. Because a cylinder, no matter how well made, is potentially very fragile and prone to accidents.

If the purpose of the mission were to propagate humanity then I would expect it to colonise any terraformable planets it encountered on an indefinitely long mission, simply to increase long-term survival chances for somebody at least.

On the contrary. A million habitats spread across a solar system is much less vulnerable than a single planet. Of course once a civilization has reached that point it is likely that some idealist quadrillionaire will want to send a generation ship to another star to colonize that as well. There would be no economic incentive for it since it would be expensive and no one on board would live to reach the destination, but it would likely happen anyway for various idealistic purposes such as ensuring humanity's survival of things like a nearby supernova. (Still no terraforming, if people have lived for generations in a habitat, why start a several millenia project of terraforming when you can just build more cylinders).

It would be quite easy to do though with todays scientific understanding, if you have the industrial base of a civilization measuring trilions or quadrillions of people. Nuclear power and ion engines are easily able bring a habitat to another star as well as supply heat and light for the duration of the trip.

So my answer to your question of construction would be: At the moment the cost is prohibitive even for an Earth government, but the solar system allows for a million fold expansion of economy with todays tech if civilization manages to become space based. Eventually it becomes a "might as well".

Regarding specs: With known technology propulsion would be some electric ion drive, powered by fission. Material would probably be mostly steel due to irons abundance. Food production would as O'Niell envisioned be done in small individual cylinders. Plants tolerate higher radiation levels and don't care about Coriolis forces. Smaller cylinders make tailoring climate, light etc to the species easier and complete sterilization of a cylinder allows for easier pest control. The farm cylinders need only be suprisingly few and small. Year-round optimal growth is very effective. The big cylinders purpose would be to allow for the big open spaces and feeling of nature that people tend to enjoy.

I'd say about a million people. It is not much of a sacrifice to take off if you bring your entire country. Of course a much smaller ship of much fewer people could be build earlier, but with a larger chance of failure. 
« Last Edit: 01/25/2013 06:28 PM by Tass »

Offline Eer

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Re: O'Neill Cylinder Mission - tech limitations.
« Reply #5 on: 01/25/2013 06:58 PM »
A more appropriate forum to ask might be either Centauri Dreams (http://www.centauri-dreams.org/), the news forum of the Tau Zero Foundation, or folks at Icarus Interstellar, who are just trying to figure out how to build a fly-by probe.

In order to frame the question, just how realistic do you want to make your velocity for the duration of the transit?  And, are you willing to posit use of any unobtainium materials or technologies (e.g., fuel-less propulsion) to shorten the transit (e.g., increase velocity)?

At any rate, once you suspend your disbelief, you're free to do what you like.  If you want "realism" - calculate the transit time to, say, Alpha Centauri at, say, 20 kilometers per second, roughly 2 trillion seconds, or around 64,500 years.  20 kps is about 20% faster than the New Horizons probe presently on its way to Pluto, by way of comparison.

So, don't think in terms of millennia, but rather in terms of a time frame similar to the amount of time since we developed agriculture. 

On that scale, uploaded or purely artificial intelligences may make more sense - but again, it all depends on what you're willing to suspend in the way of disbelief.

Offline rklaehn

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Re: O'Neill Cylinder Mission - tech limitations.
« Reply #6 on: 01/25/2013 07:18 PM »
Hi. If you truly want to write hard sci-fi you have come to the right place.

An interesting option for propulsion would be the following: the spaceship is surrounded by a large magnetic dipole field created by a superconducting ring. This magnetic field gets inflated by injecting plasma, much like the magnetic field of earth or jupiter gets inflated by their ionosphere. Then, during a close flyby of the sun, you inject microscopic charged dust particles into the magnetic field that adsorb the light from the sun and turn the whole thing into a giant opaque cloud that serves as a solar sail. This is an extension of the magnetic sail concept that allows you to use a magnetic field to interact with photons and capture their much larger momentum compared to the solar wind.

You can find a bit of info about the concept here.

The good thing about magnetic sails or dusty plasma sails is that they also provide a way to decelerate at your destination. Just reinflate the magnetic field and brake against the solar wind of the target star. The magnetic field might also be useful as a shield during transit.

If you use a pure magnetic sail you are of course limited by the speed of the solar wind, which is about 0.1% of c. If you manage to turn your magnetic bubble into a solar sail you are essentially unlimited regarding the speed.

Of course you lose some dust and plasma while inflating the sail, but a very large magnetic field like for a full cylindrical space colony would contain the plasma/dust for a long time, probably long enough to leave the solar system.
« Last Edit: 01/25/2013 07:22 PM by rklaehn »
Try the ISS 3D visualization at http://www.heavens-above.com/ISS_3D.aspx

Offline KelvinZero

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Re: O'Neill Cylinder Mission - tech limitations.
« Reply #7 on: 01/25/2013 09:38 PM »
Destination:

Anywhere. If a civilization has the in-space industrial capabilities to build an O'Niell cylinder then it has no need for planets. Asteroids are much easier to extract materials from to construct more colonies. Teraforming is way harder, and still yields sharply limited living space.

Only interest in planets would be scientific - looking for life etc.


Or as some sort of art project.

Just wanted to agree. If you are building something like an O'Neill cylinder that can support a colony for the period of an interstellar voyage, and boost this thing to even a thousandth of light speed then it would now be trivial to build such homes for the much smaller task of just living in. Given you can do this, you could convert any solar system's asteroid belt to a thousand times more living area than the earth, giving much more safety to the species than a single planet.

Personally I think that long before we are ready to journey to other stars, we will have adapted ourselves to zero-g and looking back, be puzzled why anyone thought it was so important to reproduce the 1-g environment that only applies to the 25% of our home's surface where we cannot float.

As a destination, I suggest rogue planets. There are probably a bunch of jupiter planets with their own earth-sized moons between here and the nearest stars. They will be immensely cold but would have lots of fuel for fusion power. I bet you could even convert your colony ship's drive into a sort of spotlight sun that lights just a moon.

Probably more likely you would build something dedicated to the task. Once you have self sufficiency you can build pretty much anything. Scale doesn't matter any more. If it were not for the universal speed limit of light, exponential growth would let a single self reproducing colony convert the mass of the entire visible universe to malls and theme parks within a few thousand years. Perhaps it is a good thing we have that limit.

Offline 93143

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Re: O'Neill Cylinder Mission - tech limitations.
« Reply #8 on: 01/25/2013 10:21 PM »
If you want "realism" - calculate the transit time to, say, Alpha Centauri at, say, 20 kilometers per second, roughly 2 trillion seconds, or around 64,500 years.  20 kps is about 20% faster than the New Horizons probe presently on its way to Pluto, by way of comparison.

New Horizons was a chemical mission.  We could do much better with a very little development using solar or nuclear electric propulsion, and better still with near-term hard-sci-fi options like fission fragment rockets or aneutronic directed fusion product drives.  Realism doesn't mean a modest extrapolation of past achievements; it means a modest extrapolation of existing technology.

You could use nuclear pulse propulsion, but you'd have to be careful to keep the thrust level down and/or engineer your habitat to work in two axes...
« Last Edit: 01/25/2013 10:23 PM by 93143 »

Offline Andrew_W

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Re: O'Neill Cylinder Mission - tech limitations.
« Reply #9 on: 01/25/2013 11:41 PM »
The traditional approach is to fit the inertial confinement fusion system suggested for the BIS Daedalus interstellar probe to your interstellar ark, this gets you to maybe 1-3% the speed of light, you then head off to Epsilon Eridani which at 10.5 LY distance will take from 350 to 1000 years to get to. 
 Or maybe you could wait another century before leaving, pick the closer Alpha Centauri (as James Cameron did) and use light sails and antimatter annihilation to get to your destination way quicker (as James Cameron did).

http://www.projectrho.com/public_html/rocket/realdesigns.php
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Offline meekGee

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Re: O'Neill Cylinder Mission - tech limitations.
« Reply #10 on: 01/26/2013 01:43 AM »
You should pick up Clarke's "Rendezvous with Rama" - it has a nice description of an alien cylindrical habitat.

(A quick warning - From a literary viewpoint, Clarke's later works unfortunately take after Douglas Adams' Vogon poetry.  You'll find yourself looking for implements of destruction to impale yourself with.  Bear with it, however - the tech descriptions are worth it)

It is not an orbital habitat like an OC. No windows and mirrors, and it has an axial propulsion system, (Not too much of a spoiler) though the book never explains how it works.

It's a pretty quick read, too.
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Offline Patchouli

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Re: O'Neill Cylinder Mission - tech limitations.
« Reply #11 on: 01/26/2013 03:18 AM »
If you want "realism" - calculate the transit time to, say, Alpha Centauri at, say, 20 kilometers per second, roughly 2 trillion seconds, or around 64,500 years.  20 kps is about 20% faster than the New Horizons probe presently on its way to Pluto, by way of comparison.

New Horizons was a chemical mission.  We could do much better with a very little development using solar or nuclear electric propulsion, and better still with near-term hard-sci-fi options like fission fragment rockets or aneutronic directed fusion product drives.  Realism doesn't mean a modest extrapolation of past achievements; it means a modest extrapolation of existing technology.

You could use nuclear pulse propulsion, but you'd have to be careful to keep the thrust level down and/or engineer your habitat to work in two axes...

Even an Orion using nuclear bombs for propulsion can reach a good fraction of c.
http://en.wikipedia.org/wiki/Project_Orion_%28nuclear_propulsion%29

The traditional approach is to fit the inertial confinement fusion system suggested for the BIS Daedalus interstellar probe to your interstellar ark, this gets you to maybe 1-3% the speed of light, you then head off to Epsilon Eridani which at 10.5 LY distance will take from 350 to 1000 years to get to. 
 Or maybe you could wait another century before leaving, pick the closer Alpha Centauri (as James Cameron did) and use light sails and antimatter annihilation to get to your destination way quicker (as James Cameron did).

http://www.projectrho.com/public_html/rocket/realdesigns.php

I keep thinking one of these scenarios could happen on a several centuries long mission.





Oddly enough the Startrek one is somewhat realistic in that it was constructed out of a large hollowed out asteroid.
« Last Edit: 01/26/2013 03:28 AM by Patchouli »

Offline nestormakhno

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Re: O'Neill Cylinder Mission - tech limitations.
« Reply #12 on: 01/26/2013 05:12 PM »
Thanks for the food for thought so far, guys. I guess that the point is well taken about there being little need to colonise other systems when our own could be exploited far better using the kind of technology I am asking for.

Let's say, instead, as it is not too important to the main thrust of the plot WHY the mission is happening, that we were 'invited' to go visit [name of local, possibly viable for life system here].

Any thoughts on light and internal power sources? I like the idea of a central 'tube' of some kind of plasma that provides heat and light. Could anyone think of a mechanism for this, coupled, maybe, with a propulsion system?

 

Offline Tass

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Re: O'Neill Cylinder Mission - tech limitations.
« Reply #13 on: 01/26/2013 05:34 PM »
Thanks for the food for thought so far, guys. I guess that the point is well taken about there being little need to colonise other systems when our own could be exploited far better using the kind of technology I am asking for.

Let's say, instead, as it is not too important to the main thrust of the plot WHY the mission is happening, that we were 'invited' to go visit [name of local, possibly viable for life system here].

Any thoughts on light and internal power sources? I like the idea of a central 'tube' of some kind of plasma that provides heat and light. Could anyone think of a mechanism for this, coupled, maybe, with a propulsion system?

Maybe boring, but known and gets the job done: Straight up regular nuclear fission. LEDs. Electric propulsion such as Hall thrusters.

Offline nestormakhno

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Re: O'Neill Cylinder Mission - tech limitations.
« Reply #14 on: 01/26/2013 08:06 PM »
One of the things that concerns me is the amount of fuel required. Are there any currently proposed forms of propulsion where there is no necessity for carry large amounts of fuel to propel a cylinder potentially of many millions of tons?

Offline IRobot

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Re: O'Neill Cylinder Mission - tech limitations.
« Reply #15 on: 01/26/2013 08:07 PM »
O'Neill cylinder is not a very good design. AFAIK, small mass variations between areas could break it apart easily. A donut shape is much easier to handle.

Offline meekGee

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Re: O'Neill Cylinder Mission - tech limitations.
« Reply #16 on: 01/26/2013 08:29 PM »
Basically, you want to spin around the axis that yields the maximum moment of inertia.

The nice thing about the cylinder is the humongous volume and unique gravity effects...   (all explored in detail in Rama)
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Offline 93143

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Re: O'Neill Cylinder Mission - tech limitations.
« Reply #17 on: 01/26/2013 10:32 PM »
One of the things that concerns me is the amount of fuel required. Are there any currently proposed forms of propulsion where there is no necessity for carry large amounts of fuel to propel a cylinder potentially of many millions of tons?

Yes.

Unfortunately, not everyone agrees that the physical principle of the "Mach-effect thruster" is sound.  Same goes for the quantum mechanical variant, NASA Eagleworks' "Q-Thruster".  Experiments are underway...

If you're using a fusion product drive or a Super Orion or something that has a seven-figure Isp, you should be able to get past 1% of the speed of light and slow down propulsively afterwards with a total mass ratio of less than 2.  Fusion-based Orion starships have been proposed with delta-V capabilities as high as 8-10% of lightspeed (so ~4-5% if you want to brake).
« Last Edit: 01/26/2013 10:33 PM by 93143 »

Offline QuantumG

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Re: O'Neill Cylinder Mission - tech limitations.
« Reply #18 on: 01/26/2013 10:49 PM »
What's wrong with just using chemical thrusters?

If you can build an O'Neill Cylinder, you can build as many tanks as you need and fill 'em with fuel.

The whole point of the O'Neill philosophy is to use engineering to describe the possible with existing technology.
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Offline nestormakhno

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Re: O'Neill Cylinder Mission - tech limitations.
« Reply #19 on: 01/26/2013 10:58 PM »
OK - The suggestions about the propulsion system has given me some interesting avenues for research and reading. 93143  - I am going to have to follow up your comments about Isp and mass ratio.

I am intrigued by the comment of IRobot's about small mass variations breaking it apart. Clearly (at least with my long-lost pre-undergraduate knowledge of mechanics) the most stress put on the structure will be caused by rotation as the longtitudinal thrust, if I understand it, will be minimal.

I can see no need for the cylinder to have the long strip-like windows with mirrors to deflect sunlight as, in interstellar space, there would be none. I assume this would make the cylinder a slightly more viable configuration.

Another query... has anyone actually produced papers on the optimal size for self-sustaining communities which can perpetuate the skills needed, over the course of generations, to work on and maintain such a vessel?
« Last Edit: 01/26/2013 11:00 PM by nestormakhno »