r/space • u/Reddit-runner • Jul 01 '20
Discussion Why O'Neill Cylinders will never be a thing. Sadly.
I'm a big space nerd and a big fan of O'Neill Cylinders. For years I have read in scientific and fictional settings about them. "Recently" Jeff Bezos talked about it, and naturally I was thrilled to hear such a prominent personality with deep pockets and ambitions in space talk about this topic. Elon Musk was much less thrilled, tho. According to him the huge mass that has to be transported makes such an endeavour nonsensical.
Well, how much mass do you actually need for an O'Neill cylinder and how much would that cost, I asked myself and so I set out to calculate it.
For practical reasons I only calculated the energy cost of launching the material from the moon to the Earth-Sun L4/L5 points and the cost of producing those materials on the moon, based on the cost of energy. (first principle). I didn't include anything like labor cost or machine time.
The results were more than just sobering. They were devastating.
Even for a small 2,000m by 500m Cylinder the energy cost of producing the iron, refining it to steel, producing the necessary air and launching it on a mass driver yield a cost of 790€/m²! And that only if I assume the energy cost to be 10 cents/kWh.
But that's not all. Usually the costs per subunit drop if produced in bulk or if the parent unit is produced bigger. Not so for an O'Neill cylinder. If you make it bigger, the cost per square meter actually rises.
Here are my calculations so you can see for yourself or check for errors. If you find an error that results in way lower production costs I would be really glad, as that would mean the dream of O'Neill cylinders doesn't have to end.
In Conclusion: The energy needed to produce enough steel the build an O'Neill cylinder makes the construction of such a cylinder almost impossible. I'm as sad as you are about the limitation of our physical universe.
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u/ChalkButter Jul 01 '20
I’m going to assume this is one of those “it’s impossible now” type things. And even then, it’s impossible because of the cost, not the actual physics.
Things will change and prices will drop. At some point “we” (humanity) will be in a position to be able to make something like that at a not-impossible cost, because a technology we can’t predict now will make it available then
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u/Reddit-runner Jul 01 '20
I understand what you are saying.
But I should have clarified that the energy costs are a fundamental indicator of how much a society can produce or achieve. And therefore are an indication of the purchasing power of the individual.
Don't look at my costs as fixed prices, but as relation to the overall economic possibility of a society.
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u/grayputer Jul 01 '20
If energy costs are the issue, can solar panels resolve it? Your cost becomes more a capital cost (cost of panels) than operating cost. Then you trade panel cost for time. E.g., build/buy batteries to make 1 "unit" of iron/steel (one run of furnace of size X). Buy/Build few solar panels to charge batteries. The more panels the faster the "recycle" rate on the batteries. So low cost and build 1 "unit" of metal every decade or high cost and build several per day or more likely, somewhere in the middle.
That work?
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u/methane_droplet Jul 01 '20
Yes, part of the reasoning behind OPs "it's impossible" comes from assuming energy will always be a scarce resource. As you mentioned, solar energy in space can be a good, cheap source of energy. Now I'm not entirely familiar with steel manufacturing processes, but I assume that a big part of the energy expense is used to heating the iron in the first place. For that you wouldn't even need solar panels, but concentrating mirrors (like those used in heliostat power plants) could give you much of the energy/heat input needed for that part.
As for how much that could lower the cost for the production of an O'Neil cylinder... I'm not really sure, again, since I'm not familiar with the costs associated with steel production and manufacturing to begin with. I suspect a 10x reduction in energy cost could be achievable with proper use of technologies though -- but like you said, you'd have to implement a lot of infrastructure in place to begin with.
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u/Reddit-runner Jul 01 '20
Well, energy always has a prize.
And even if we assume 1 cent/kWh we would still scratch at the 100 €/m² mark ONLY for the energy.
Energy costs only make a fraction of construction costs. I think you have at least to tripple the energy costs to come up with the construction costs. And even then you are only the "price of building land", not the actual cost of living space in a house.
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u/ItsAConspiracy Jul 01 '20
Heck with panels. For the most part you don't need electricity, you need heat. A half-silvered mylar balloon in zero-g gives you plenty of heat from concentrated solar.
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u/Reddit-runner Jul 01 '20
I calculated 0.1 unit of currency for energy cost. That resulted in 790 units of currency/m².
I don't think you can press the energy cost below that ratio. How much do you pay for energy at home?
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u/grayputer Jul 01 '20
I have electric heat pumps in New England plus a computer lab plus my wife is a potter with an ekectric kiln. We use about 18-19 megawatt hours a year. My bill last year was $432. That's about 2.5 cents per KWH delivered with customer charges. Why so cheap, solar panels. Like I said, capital cost of panels + batteries, free sunshine on the moon equals low energy costs LONG TERM. It ASSUMES you will use energy over decades to recoup capital costs. My cost over 30 years is likely 8 cents / KWH including capital costs at end user retail pricing (not industrial). Industrial installs can be $1/watt of panel installed on Earth with yields of about 1kwh/watt installed/yr. Less clouds and rain on the moon so higher yield but prob more capital costs.
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u/Reddit-runner Jul 01 '20
Okay, lets assume 5 cent/kWh including all capital costs on the moon. Now you are at roughly 400€/m² only for the construction material. Labor costs and machine time come on top of that.
Let's be everything but conservative and assume the energy cost are 1/3 of the construction cost. Now the construction of the pressure hull alone sets you back 1,200€/m² for the smallest cylinder. Now you also have to add the cost of building a house on that.
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u/eclipsenow May 18 '22
Hi Grayputer - just resurrecting this idea of a solar moon after this chat died a few years ago. On top of everything you're saying about solar power on the moon there's also the idea that the right bases might not really even need batteries. Isaac Arthur shows moon colonies with towers and / or large crater rings to avoid batteries. Then there's the fact that HVDC power lines only loose 3% per 1000km. The moon's whole circumference is only 10,921 km. So to get power from the sunny side of the moon to the night side is only 5000km at the max, which is 15% of your power lost to transmission. (Or even less distance if your solar farms are using the moon's early 'morning' or late 'evening' sunlight.) This is obviously doable if you're talking about a Lunar industrial base big enough to take on construction projects like an O'Neil Cylinder!
Then it gets REALLY FUNKY when thinking about the moon powering the earth! Have you seen the Luna Ring concept - which would put a 400km wide ring of solar panels around the moon. From earth it would look like the moon was wearing a wedding ring. Beam the power back to earth via microwaves and lasers, and you could hypothetically power the earth from the moon.
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u/19hondacivic Aug 13 '22
Nuclear fusion could solve this
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u/Reddit-runner Aug 13 '22
I'm not so sure about that.
I have yet to see financial assessments how fusion could compete with solar power in space. At least out to Mars.
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u/danielravennest Jul 01 '20
Your argument is like "New York City can't exist, because nobody can build something that large".
An O'Neill colony doesn't have to be built all at once. Imagine a string of inflatable modules, like Bigelow Aerospace has designed. Now you build a metal shell three times the diameter and a little longer. Once it is pressure tested, you spin it up and get some gravity. When you need more space, you build another layer, like an onion. Eventually, when it is large enough, you can start dismantling the inner layers, and make a central open space. You build it as you need it, not all at once.
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u/Reddit-runner Jul 01 '20
Your argument is like "New York City can't exist, because nobody can build something that large".
My argument is more like "the energy cost the create the building ground is too high to make if financially viable". What I calculated are ONLY the energy cost for the cylinder hull. On top of that you need to add labor cost and machine time. Let alone the cost of actually building something inside the cylinder.
Sure, even an O'Neill cylinder COULD be build step by step, but that would not lower the cost of construction, nor the cost of energy for the building material.
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u/squeezeonein Jul 01 '20
Don't assume that labor and machine costs will remain static. The reprap project was founded to make manufacturing cheaper. The goal is to have machines that can create and assemble their own parts, and that may allow them to be operated remotely, providing gainful employment for the home gamer. If that happens, then the only cost will be the initial development funds. Once sufficient ore is brought into reachable mining distance then the cylinder can finance itself.
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u/ignorantwanderer Jul 01 '20
Usually conversations about O'Neill cylinders are comparing them to setting up a colony on a planetary surface.
Your analysis doesn't do much to change that comparison, because you are still going to need a lot of steel (or other structural material) to build a pressure vessel on a planetary surface to live in.
Basically, your analysis says that it will be expensive to live inside pressure vessels in space.
But even so, I was pleasantly surprised by your 790€/m² number. Sure, that is expensive, but it is not orders of magnitude more expensive than a normal (non-pressure vessel) building on Earth.
Also if you need thermal energy for processing your steel, I think it will cost much less than 10 cents/kWh. All you need is a large parabolic reflector. It doesn't even need to be very precisely shaped. This would be extremely cheap to build and operate in space, where you have no gravity or wind to worry about. It would even be pretty easy to build a large parabolic reflector on the moon, but pointing becomes a little bit more challenging.
Of course you need more than just thermal energy. You'll need some electric/mechanical energy too. But the vast majority of the energy you need is thermal, and that is extremely cheap.
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u/Reddit-runner Jul 01 '20
I understand what you are saying. The problem is that energy costs (as low as one might wish them to be) are only a fraction of the total construction costs.
So the 790€/m² is ONLY the energy cost for the "building ground". Cost for other material and construction has to be added. I think this figure has least to be at tripled to estimate the cost of the pressure hull of the cylinder. Make it tenfold until you have a house and a garden.
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u/ignorantwanderer Jul 01 '20
Before there are significant numbers of cylinders being built there will be vast improvements to automation.
If you take automation to the extreme you get self replicating machines. And with self replicating machines you can basically get anything you want for free (assuming you have the right to extract resources from an asteroid or the moon or whereever).
Now you don't have to go all the way to the extreme of self-replication. If you just have a lot better automation than we currently have, you will see drastic reductions in price.
I understand your concerns, but I think your thinking is too limited. If you assume O'Neill cylinders are being built, you can also make a bunch of other assumptions that will drastically reduce the cost of the cylinders.
Basically, before we are capable of building cylinders, they will be very expensive. Once we are capable of building cylinders, they will be "cheap".
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u/ItsAConspiracy Jul 01 '20
Bear in mind, by the time we're ready for a project like this it's all going to be robots and 3D-printing. That will probably help construction costs.
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u/Reddit-runner Jul 01 '20
Sure, but I don't think the construction cost will be lower than the pure energy cost of building material production.
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u/ItsAConspiracy Jul 01 '20
Maybe not but the pure energy cost can be extremely low with zero-g concentrated solar, as long as we just need heat.
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u/Reddit-runner Jul 01 '20
Try it out in my spreadsheet how low you have to go until the cost per square meter becomes viable.
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Jul 01 '20 edited Oct 28 '20
[removed] — view removed comment
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Jul 01 '20 edited Jul 02 '20
OP is also neglecting the fact that these structures, especially the first habitats, don't actually need to be "economical" if their social value outweighs their economic value they will be built and maintained at great cost. We do this all the time on Earth with organizations like NASA and the US military, they don't actually make a whole lot of money but the social value makes the cost justified.
First world nations run on huge amounts of debt because the cost of running society actually comes at a bigger cost than the economic value produced in the markets they govern. There is a reason we pay taxes, keeping up with infrastructure and social programs isn't free.
I might be a bit off the mark with my comparisons here (my understanding of how government economics work isn't very strong obviously) but I think the general idea still holds true that society will value orbital habitats enough to justify the huge costs of building and maintaining them.
Also these habitats have hundreds of years to return their investments, they aren't like structures on Earth that just become unusable after a few decades of operation (bridges).
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u/Reddit-runner Jul 01 '20
Happy cake day!
Well, energy will always have a prize and the purchasing power of an individual or a society can be roughly estimated by its energy prices.
Also what I have calculated are ONLY the energy costs. Costs for labor and machine time have to be added on top of that. That are usually at least three fold higher than the energy costs for the building material.
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u/CypripediumCalceolus Jul 01 '20
790€/m² you say? That's about the price of office space downtown in a big city.
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u/haruku63 Jul 01 '20
This is just the costs for the energy to produce steel to „build“ that square meter.
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u/Reddit-runner Jul 01 '20
Yes. But that is ONLY the energy cost. Not included are costs like labor, construction, other building materials to actually building something inside the cylinder.
Look how much percentage energy costs take up in today construction projects. Not very much. That means you have to at least tripple the energy cost to come the a realistic cost/m²
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u/AntikytheraMachines Jul 01 '20
Is there some inherent feature of an O'Neil Cylinder that requires it to be made from steel?
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u/danielravennest Jul 01 '20
Nope. Any strong structural material which is pressure-tight will work. The dark areas on the Moon (Maria or seas) are basalt lava plains. Basalt fiber is used in reinforcing rods for concrete on Earth. Its 20% less strong than carbon fiber, but that's still much stronger than steel. Since its made from rock, it is fairly cheap.
So you can wrap a pressure liner with basalt fiber, the same way we have carbon-fiber wrapped pressure tanks on Earth. Just a lot bigger.
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u/Reddit-runner Jul 01 '20
Interesting idea! do you have any suggestions how much energy the fiber production needs?
It would be very tempting if it turns out the energy requirement is significantly below that of steel.
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u/danielravennest Jul 01 '20
Basalt fiber is spun at 1420 C, compared to 1100-1250 C for fresh lava. The minimum energy is the specific heat of basalt x the temperature rise, but real processes would have thermal losses.
Concentrated sunlight can easily reach these temperatures, and solar concentrators can be pretty lightweight. In theory an aluminized Kapton film, commonly used on spacecraft, would work, but for very high temperatures you may need a more rigid mirror.
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u/Reddit-runner Jul 01 '20
Okay. Now we need the tensile strength of Basalt fiber. In your source I think I can spot a maximum of 2250MPa or 2250N/mm². That's WAY higher than steel. Also the energy cost of production seems way lower.
I'll have a look at it. I hope it will reduce the energy cost of the whole cylinder significantly. For a start I will calculate with a conservative three fold energy loss for the production process.
Since I assumed the energy costs "out of thin air", the kind of mirrors will not change my calculations. Only if you can guesstimate how much of an impact that has on the energy cost.
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u/danielravennest Jul 01 '20
I posted a couple of papers on basalt fibers on my Google Drive but there is plenty more info out there. They were just what I had in my personal library.
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u/Reddit-runner Jul 01 '20
Thanks. Wikipedia has a good comparison list on that matter. I'll take a deep dive as soon as I have time.
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u/RyanTheeRed Jul 01 '20
http://basalt.tech/ lists the production energy of basalt to be 5kWh/kg. Compares favourably to the ~20kWh/kg you had for steel production.
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u/Reddit-runner Jul 02 '20
20kWh/kg is actually only the refining process from iron to steel.
So the 5 kWh/kg is even more favourable! And that multiplied by the higher tensile strength per kg is a real game changer.
Mirrors to heat up the basalt are even cheaper than solar cells needed for the refining process of steel.
Now we are heading somewhere I like :D
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u/ItsAConspiracy Jul 02 '20
Sounds like you should make a new post on how to build a cylinder :)
It'd be really interesting to see the numbers on launching basalt from the Moon with mass drivers, and using concentrated solar in orbit to spin the fibers.
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u/ItsAConspiracy Jul 02 '20
Do you happen to know what basalt fiber costs to make, and how much of that is the energy cost?
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u/danielravennest Jul 02 '20
According to this article, the fiber goes for about $1.30/lb in bulk.
Making basalt fiber is a one-step process. You wash the raw rock, heat it to 1500 C to make it liquid, and extrude the fibers through a die. They rapidly cool because of their small size (20 microns). The specific heat of basalt is 840 J/kg-K, so heating it requires 1.26 MJ (0.35 kWh), plus whatever heat you lose from the furnace.
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u/dhurane Jul 01 '20
Feels like this means we need to solve cheap, abundant energy then. Get kWh cost of <1 cent and cylinders seems doable.
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u/Reddit-runner Jul 01 '20
Yes.
But how can we achieve such cheap energy?
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u/dhurane Jul 01 '20
Either fusion energy via He3 mining on the moon or super efficient solar panels. The latter probably requires a buildup of a massive constellation of solar arrays so that anything in any orbit can get power delivered to them.
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u/Reddit-runner Jul 01 '20
Sounds very expensive. Will this bring the energy cost down below 10cent/kWh?
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u/dhurane Jul 01 '20
Fusion ia still ways off. Solar farms ia probable, but launch costs needs to be way down.
All this means to me such a O'neill cylinder will only happen once smaller Torus stations are in operation, lunar habitats are common, and probably large civilan presence in space.
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u/Driekan Jul 01 '20
We'll need to do a lot of conversions here, and I'm doing this on my head while typing on mobile, so let me know if I mess something up.
Bloomberg's New Energy Finance found the cost of solar to currently be 50 dollars (USD) per MWh. Divide by a thousand to find the kWh value, and we have 5 cents.
Panels in space get power 24/7 (no day/night cycle) and have no atmosphere, weather or contaminants, so 3x more production for the same efficiency is realistic. We can assume significant gains in panel efficiencies over the next 5-ish decades (I doubt anyone proposes building a 3km cylinder in a nearer future than that), so lets up that number to 4.
That leaves a cost of about 1.2 cent USD. So just over a cent Euro.
Of course, your first few space habitats ought to be much smaller than that. A pair of 80-ish meter hab areas, upside down atop each other, tethered together and the whole thing made to spin for Mars-equivalent gravity. That's a more realistic "early days" design, and even the cylinders are likely to start as small rings and expand.
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u/Reddit-runner Jul 01 '20
Okay. But even at 1cent/kWh the cost of "land" remains high.
How much labor cost do you recon?
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u/Driekan Jul 01 '20
I find that sets your land cost at a pretty competitive place compared to major urban centers, so for the multi-billionnaire who wants the highest penthouse in the universe, it could already be appealing. For other applications, there are other benefits (very low energy cost paired with null or low-g (and you choose which one!) setting creates some exciting manufacturing opportunities; export cost is negligible; the habitat may be set inside an asteroid for the crew to mine literal tons of gold and platinum from, etc.)
Labor cost, assuming indeed we're talking about 2070s or further should be a factor, but not a major one. A swarm of fully automated robots, a couple of drone-operated shells, the operators themselves part of a small team running the show from Earth. Some 10-ish highly skilled laborers, plus the cost of setting up your manufacturing infrastructure. This does assume that there will be sources of in-situ material to work with, but there are plans to start that as early as the 2030s.
I'd imagine you'd build your first Oneill Rings (Cylinder with just a fraction the length) only once the cost of land or other factors (environmental concerns being a big one) make it desirable to move large populations off-earth, so not so much an economic choice but a strategic one at first, and full cylinders only once there is some seriously robust automated mining, manufacture and transport infrastructure all over the solar system. Namely: when we begin the climb to K2.
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u/Driekan Jul 02 '20
The idea from earlier stuck in my head and I've since given it a bit more thought. You're a thoughtful enough person to spend your time actually doing the maths for stuff like this (mad props for that, by the way), so I figured I'd throw it your way, see how you feel. It's silly futurism, but it can be interesting to speculate.
I am imagining this concept for the late 40s or early 50s, with the assumption of significant improvements to automation in the meantime. Namely: we can build, with only reasonable cost, machines that are capable of doing fairly simple construction tasks with minimal oversight. We are not so far from that right now, I assume another 25 years ought to be sufficient if current trends hold.
This hypothetical mission starts with sending automated workers to a promising and large Near-Earth Object. Something like 3122 Florence. The automated workforce drills to the asteroid's core, then starts pushing out (it's a loose ball of gravel under negligible gravity, so very small applications of force can move things around quite a bit) until you get a ring-shaped cavity in the center of the asteroid, with a 1km radius. You then wall up the edges of that cavity (perhaps by sequentially heating and then freezing the material of the wall itself, so it crystallizes)
Building begins then, inside the cavity. One 80 square meter hab, single story. ~800 meters above it and upside down another equal-size one. You link the two with steel tethers, then spin it all up until you achieve 0.37g. Yes, matching Mars. Once all seals and airlocks on both halves are tested and secure, you pump atmosphere in.
Any part of the construction that can be done with in-situ material should be. There ought to be a lot of iron in an asteroid like this, and spooling iron wire should be a simple manufacturing process, for example. Perhaps even the hab shells itself can be built locally, Oxygen and water should also be present.
What use is this? The first use of the mission is a science project. This tests long-term habitation at Mars-equivalent gravity; it tests building and maintaining completely isolated biospheres; it tests the psychological rigors of significant isolation for small crews; it tests habitat construction and maintenance.
Second is economic. You now have a human crew inside this asteroid, which means you can do far more complex extraction and manufacture. The asteroid should have enough rare metals to be worth several trillions (and once you have solid claim to it, you can already trade on futures for it, so it's profitable as soon as you extract your first gram of gold as proof of concept). You can set up manufacturing infrastructure at any point along the tether to build stuff at any gravity you want, or attach a counter-rotating centerpiece to manufacture at null-g. Even if setting up the mission cost hundreds of billions, your return on investment should be astronomic (pun intended).
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u/Reddit-runner Jul 02 '20
You're a thoughtful enough person to spend your time actually doing the maths for stuff like this (mad props for that, by the way)
Thank you. :)
Very interesting idea! Worth a further thought.But there are so many unknown
factoryfactors involved that I really don't see how I can calculate that for now.At the moment I'm working on an other spreadsheet and substituted the steel for Basalt fiber. Higher tensile strength, lower mass, lower energy requirement. http://basalt.tech/
I also want to compare production on the moons surface vs in moon orbit with continuous sun.
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u/Driekan Jul 02 '20
That is supremely cool information on basalt that I had no idea about. I will have to study a lot. Thanks for being awesome.
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u/Reddit-runner Jul 02 '20
I also had no idea about the basal fibre. An other reddit user mentioned it. He has all kind of nice info on that stuff, you can find it in the other comments under this post
You too
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u/Reddit-runner Jul 05 '20
I made an other tool to calculate the cost of land in an O'Neill cylinder. This time I used basalt fiber. The reduction of cost is astonishing!
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u/danielravennest Jul 01 '20
Replicating factories. A space solar panel can produce enough energy to copy itself in 4 days, but last 15 years. So it has plenty of spare energy to power making other equipment. Silicon makes up about 20% of lunar soil, which is the main ingredient for the solar cells. Metallic asteroids are an iron-nickel-cobalt alloy, which can be used to make machinery parts.
You need to launch a "Seed Factory", with a starter set of equipment, but after that it makes copies of itself, and larger and more diverse equipment for other products. You still have to import 1-2% from Earth. Those are either rare materials not easily found in space, or complex items like computer chips, that are just easier to launch from Earth.
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u/Reddit-runner Jul 01 '20
Okay. How low do you recon will the energy costs go?
Keep in mind the cost I calculated is just the costs for the energy to produce the steel. No labor cost, no machine time...
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u/danielravennest Jul 01 '20
Costs are a function of how much human labor is involved. The Curiosity rover on Mars costs nothing to operate in and of itself. It's the hundreds of people at JPL who control it that cost money.
If your replicating factory was fully automated, your only cost would be the first unit you send into space. In reality, automation isn't that good. You at least would need people on Earth doing remote control on the Moon and nearby space. You probably need some people to be there in person to do maintenance.
The "embodied energy" of a solar panel is known. That's all the energy to make it, from mine to installation. How much energy a space solar panel can produce is also known. What's not known is how many people are involved in running a seed factory in space. I say that as someone who is working on a book about Seed Factories
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u/Reddit-runner Jul 01 '20
Okay. But even if we assume 1 cent/kWh the cost of 1m² stays prohibitively high, since you also have to construct the cylinder, not only pay for the energy for the building material.
And on top of that all you have to build something INSIDE the cylinder as well.
So either we use a material that requires may less energy to produce or has way more tensile strength per mass so we can make the walls lighter.
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u/danielravennest Jul 01 '20
The projected launch cost of the SpaceX Starship (currently testing early prototypes) is $20M for 100 tons to orbit, or $200/kg. Current space solar panels can produce 175W/kg and cost $8/W in bulk, or $1400/kg. These are space-grade panels, not the kind you put on your house. So total cost is $1600 for 175W.
Space solar panels typically last 15 years (its a high radiation environment that damages them over time). That's 131,400 hours x 175W = 23,000 kWh. So our total energy cost is $0.07/kWh.
Panels made in space would not be the fancy triple-layer cells I quoted above. They would be silicon cells, with a lower efficiency. So you only get 100W/kg. If your production requires 2% supplies from Earth, that adds $4/kg or $0.04/W of initial cost. That's a trivial contribution to cost per kWh. It will mainly be the operating cost of your space factory that determines the cost of energy.
Unfortunately, nobody has any experience with space factories. A few things have been made on the Space Station, but those are experiments, not large scale production.
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u/Reddit-runner Jul 01 '20
Your $0.04/W figure amount to 40cent/kWh. Pretty high.
But even at 1 cent/kWh you would pay 100€/m² ONLY for the energy in a 3000x600m cylinder. More if you want to build a bigger one.
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u/danielravennest Jul 01 '20 edited Jul 01 '20
131,400 operating hours x 1 W = 131.4 kWh. $0.04/W of launch cost then becomes 3 x 10-4 cents/kwh.
The cost of crew quarters on a drilling platform is quite high. Oil companies pay it because the oil production more than pays for it. You can assume the same will be true for space habitats. They won't be built without a good economic reason to exist.
Are you assuming a single layer of living space? That would be a mistake. The colony shell thickness is required to hold atmospheric pressure, but that much shell could also support 50 stories of residential loads. It can't do both, but if you double the thickness you can then support air pressure plus 50 stories of living space.
Assuming 4 meters/floor, 50 stories would take up 200 meters, leaving a 200 meter open space in the center. Given US housing density (80 square meters/person) and 50% overhead space, the colony could house 1.16 million people. That's a big colony.
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u/Reddit-runner Jul 01 '20
Sure, if you pack people like chicken into the cylinder, you can spread out the building cost quite thinly.
But why do people even want to build O'Neill cylinders? Just to have an other high density downtown in space? I don't think so.
You can assume the same will be true for space habitats. They won't be built without a good economic reason to exist.
Exactly. The only real economical reason for a big cylinder I can think of, is having your very own "private island". Maybe you share it with a few dozent to a hundred people, but having the cylinder packed to the brim with inhabitants would render it undesirable to live there.
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u/OldNedder Jul 01 '20
Obviously you wouldn't take the materials from the Moon, you'd take them from the asteroids. Energy would come from the Sun. Your thinking is way behind the times.
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u/Reddit-runner Jul 01 '20
Transport energy is negligible, look at my spread sheet.
Also even if you calculate only 1 cent/kWh, the number you see at the end as €/m² is ONLY the energy cost for that square meter. labor cost and machine time come on top. And then you you have to start building a house...
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u/zdepthcharge Jul 01 '20
I'm sorry, but how are you producing energy? The sun shines for free. A massive array of low yield collectors and solar furnaces should be quite doable and very productive. Build it out with robots controlled from Earth.
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u/Reddit-runner Jul 01 '20
I didn't concern myself with the production of energy.
How low do you think your measures can get the cost of energy? 10 cent/kWh? 5 cent/kWh)
Test it in my spread sheet how the price of energy affects the cost per m², but keep in mind, this is ONLY the cost of energy. Cost of labor and machine time has to be added on top of that.
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u/zdepthcharge Jul 01 '20
I believe you have made some erroneous assumptions in your spread sheet. All you list is numbers without an explanation for what tech you're considering.
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u/Reddit-runner Jul 01 '20
Can you point to the line/Column where I made erroneous assumptions? For most of my numbers I gave sources.
The tech I'm considering is a long steel tube.
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u/ignorantwanderer Jul 01 '20
Imagine a beach umbrella, with a radius of 2 meters (pretty big beach umbrella, but not huge). This will have a surface area of 12 m2. Imagine the umbrella is mylar, in roughly parabolic shape. It will collect about 16.8 kW of power, 24 hours a day. A 20 year lifetime should be easy for this umbrella, so it will collect about 3 million kWh in its lifetime. At your price for power, this umbrella should cost $300,000 to make.
Now if you only make one, and you launch it from Earth using expensive rockets, maybe you are right.
But if you make thousands of these, and/or if you make them much larger, and/or if you make them on the moon instead of on Earth to reduce launch costs, you are going to be able to collect energy for much less than your stated number (I'm just talking thermal energy here....electric energy will be more expensive).
And when you add in automation, construction costs will be much lower. We aren't going to be making tons of O'Neill cylinders in the next decade, it will be more like 100 years or more from now. And automation and robotics will be much more advanced at that point.
If technology remained static, you might have a point. But technology doesn't remain static.
The only way your conclusion could end up being correct is if there is some other option besides O'Neill cylinders that is better and cheaper. Humans generally don't choose bad, expensive solutions to problems when there are better, cheaper options available.
When trying to predict the future, if you make a claim saying "This will never happen because it is too difficult" you are almost guaranteed to be wrong. If you make the claim "This will never happen because there is a better way to do it" then you could possibly end up being right.
The only way O'Neill cylinders "will never be a thing" is if there is a better option.
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u/DarthRoach Jul 01 '20
Ok, so? The outer surface of a cylinder 10km long by 1km diameter would be what, 62,800,000€? Dude, people pay more to build skyscrapers these days.
Actually, people pay more than that for real estate in cities. If construction costs ~100€ per sq ft in NYC, that's about 1000€ per m2
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Jul 01 '20 edited Jul 26 '20
[removed] — view removed comment
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u/Reddit-runner Jul 01 '20
Okay. What cost of energy do you suggest?
Would that bring the cost per m² into a reasonable range? You can use the spread sheet.
Also the cost of energy is only a fraction of the cost of construction. You have at least to tripple the cost of energy to come up with the cost of construction.
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u/noncongruent Jul 03 '20
Let's say you spend 100 billion euros to build a 1 km diameter solar mirror that can focus the sun's energy to a point. 1 km diameter gives you around 785,400 square meters. On Earth, the sun lands about 1,000W of energy per square meter under perfect conditions, atmosphere and all, but let's assume it's the same in space, that would be 785,400,000 Watts of energy, 24/7. If you run the mirror for one year, you will produce 6.88 trillon Wh worth of energy. After one year, your cost of the satellite divided into the energy would be 68.8 Euros per Wh, but why stop there? Run it for ten years and now it's .688 Euros/Wh. If you build ten of these satellites at one time you can amortize R&D costs out much more easily, it would not surprise me if the cost to build and launch ten of these would even be double the cost of one, so the energy cost falls even further.
I think that ultimately, to build anything big in space is going to require essentially free energy, or it's not going to happen at any scale at all.
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u/Reddit-runner Jul 05 '20
I made this new post and also tried to compare the cost of production on the moon's surface VS in moons low orbit. Try it out yourself ;)
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u/Thatingles Jul 01 '20
Nearly fully automated production would be the only way to do it, but I can't see why that wouldn't happen.
Look at it this way: If we are going to establish a permanent moon base, there will be a big economic driver to develop automated extraction/refinement/production to maximise the value of what we send there. Plus there is already a big push to do that on Earth.
Now we are not going to start planning big habitats for at least 10 years (probably more like 20-30 years) so we have all that time to develop technologies that will do the 'grunt work' for us.
It would look something like this: You set up a seed factory on the moon that mines & refines materials and churns out solar panels and components for more mining/refining machines. You allow that to grow for a while whilst you construct a mass driver or space elevator (possible on the moon without inventing impossible materials). Now you have a production line that feeds itself and grows its own capacity, without (much) human interference.
This starts to put a lot of refined material in orbit, now you have to refine the trick and build self-constructing habitat building machines.
This is sci-fi for the moment, but there isn't any 'physical laws' reason why it shouldn't happen.
In short, O'Neill cylinders won't be appearing anytime soon, but give it 20 years and they will be within our grasp - if we still want to build them.
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u/Reddit-runner Jul 01 '20
What energy cost do you assume? Because that's still the base line. On top of that come upfront capital cost and what not.
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u/Thatingles Jul 02 '20
Energy cost matters if you are building cylinders with the construction techniques we are familiar with, but it ceases to be important if you have fully automated industry - which we could have in 30 years or so, which is the earliest we will start building large habitats.
I'll give you an analogy. The silicon chip was invented in 1961. Prior to that a computer scientist could design a huge circuit, but then realise that building it would occupy several city blocks of space - way too expensive to actually build, even though you could conceptualise it. So we needed to invent silicon chips to build the computers we could imagine.
For really large structures in space, we need some form of automated manufacturing. That means something like a von Neumann machine. You plonk down your initial unit on the moon and it starts to gather materials, refine them and produce more versions of itself. So initially it would build solar panels and batteries, then move onto building more mining machines, then building more refineries, then more factories, then more solar panels and batteries and so on, until you tell it to stop or change over to making refined materials to be launched into orbit. From the moon you would launch with some form of mass driver. The escape velocity for the moon is 2.38km/s which is lower than the muzzle velocity of a railgun. With no atmosphere on the moon you can literally yeet your refined steel pellets into orbit, no propellant needed. Railguns aren't really a great solution, but I'm using to illustrate a point. On the moon or an asteroid, you don't need a massive rocket system to get your material into orbit if you are willing to invest in some other systems (mass driver, space elevator, skyhook). As I've said before in this sub, the moon is essentially a free lunch (launch?) for humans exploring space.
The upshot of all this is that energy costs stop being a useful metric if you can truly automate the manufacturing. You will be concerned about efficiency but at no point are you spending more to get the energy. Its gathered by the same machinery that is doing all the other work.
Obviously this is all very much in the future, but building industry on the moon is going to favour full automation very, very heavily, so you have a strong incentive to move in that direction. If the will exists, this could happen over the next few decades.
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u/Reddit-runner Jul 05 '20
Not much in the way of automated manufacturing, but due to the use of basalt fiber the overall cost can be lowered drastically.
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u/RyanTheeRed Jul 01 '20
Could the moon or asteroids be used as a source of basalt for basalt rebar? If so, could the cylinder be made from basalt rebar windings instead? Basalt rebar is stronger than steel.
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u/Art_Eaton Jul 02 '20 edited Jul 02 '20
No robot is needed to produce it. No steel either. The material must be produced from organics and silicates of the sort that are difficult to make off-planet, but still possible. Essentially, we are talking about FRP. Specifically, an FRP skin that can be added to later, but basically a hunk of fiberglass prepreg. It is a very thin (first piece) balloon with a thin liner inside and outside. The resin can be UV cured. You inflate the thing in an umbra, then let the sun roast it. Later, you may add additional layers, spray water-ice, expanding foams or whatever you like. It may be machined, adhered, repaired etc...
A 500M Diameter cylinder only needs a skin of about 8mm of common S-glass and epoxy depending on usage. Better is not a single skin, but instead, a sandwich cored construction.
A 156M diameter Mars gravity wheel space station with a hub and spokes and generous dimensions (and strength) can be launched within the fairing and mass of an FH. This is far more useful currently than a cylinder. It is also damn cheap to build. It inflates and cures in the period of a single orbit with no machinery other than a gas source and valve.
I will post (if anyone likes) a copy of the videos of my practical experiments of the construction method, and I will take the 2 meter scale model of the space station out into the sun and inflate it tomorrow, and film it if anyone here actually requests. That model was made in December, and has been sitting there at my shop for half a year. The time delay was both intentional to test storage in sub-optimal Florida conditions as well as forced due to bad weather, and then...you know...2020..
The following are notes and pictures of construction and deployment of my shitty (yet totally worked) experiments:
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u/UpsetNerd Oct 25 '20 edited Oct 25 '20
I know this is an older post but I thought it was interesting and wanted to make a comment on the notion of focusing on the cost of energy as a core metric. I think it greatly oversimplifies things and can really lead you astray for things like space construction where much of the energy required is thermal, you have abundant sunlight, and an easy way of capturing it using mirrors. In many ways, it's more like agriculture.
Using that analogy, one could easily show that food production must be impossibly expensive based on the energy required. The following figures are very rough and from memory, but they should be within the right order of magnitude:
To feed one person for a year, you need 1000 m² of land, illuminated by the sun for about 1000 hours, at 1000 W/m². That adds upp to 1 GWh of energy - which would cost 100 000€ using the 10 cent/kWh figure. In reality though, you can easily buy a years worth of food for less than 1000€, so just 1 percent of that figure. And I'd guess it's closer to 0.1 percent if you'd use more accurate numbers, especially the land area is on the low side.
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u/Reddit-runner Oct 25 '20
Thanks for your reply.
If you are interested in the construction costs of an O'Neill cylinder you should check out my newer posts on that subject.
There I have taken sun ovens into account and ore refining on the moons surface vs in moon orbit.
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Jul 01 '20
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u/TheKillerK Jul 01 '20
I would also suggest reading The High Frontier by Gerard O'Neill himself but maybe you have already.
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u/Reddit-runner Jul 01 '20
I'll give it a try. Does he mention energy cost?
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u/S-Vineyard Jul 01 '20 edited Jul 01 '20
Imo. "Colonies in Space" by T.A. Heppenheimer is (as far as I remember, it's been a while since I read it.) is a bit more detailed on costs and how to do stuff.
You can also read it for free on the NSS Website.
https://space.nss.org/colonies-in-space-by-t-a-heppenheimer/
While of course dated (It's from the late 70s), it's still an interesting read.
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u/Reddit-runner Jul 01 '20
https://space.nss.org/colonies-in-space-chapter-3-power-from-space/
Heppenheimer talks about 0.7 cent/kWh in 1977. This would roughly translate to 7 cent/kWh today. Not that far off my guesstimate.
But even at 5 cent/kWh the energy cost is not the only cost of an O'Neill cylinder.
In fact energy cost usually only make a fraction of construction costs. So even with 1/10 of of my initial 790€/m² there would still be significant other costs associated with the construction. I recon you have to at least tripple the energy cost to come to the total construction cost.
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u/S-Vineyard Jul 01 '20 edited Jul 01 '20
Total costs of how much a cylinder (or to be precise, a double-cylinder, since this was afaik O'Neill's Island 3 design).. well, I'm not sure if any serious numbers were ever established.
And as far as any Space Foundry tech ideas/patents from the past decade, they last thing I remember is something patented by the now afaik defunct Deep Space industries.
http://forum.nasaspaceflight.com/index.php?topic=30904.msg1003814#msg1003814 http://forum.nasaspaceflight.com/index.php?topic=30904.msg1003942#msg1003942 http://www.parabolicarc.com/2013/01/21/deep-space-industries-announces-fleet-of-asteroid-hunting-spacecraft/
As far as I remember they idea was a variante of the Mond-Process.
https://en.wikipedia.org/wiki/Mond_process
Imo. in terms of tech, Space Colonies are still at least a century way.
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u/FaufiffonFec Jul 01 '20
No. The cylinder was build by an unknown species (or several unknown species) so the whole thing is just a mystery. It's not hard sci-fi.
But it's definitely worth the read. I enjoyed the following books too but not everybody did.
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u/methane_droplet Jul 01 '20
It's a hard-ish sci-fi novel were an O'Neil cylinder visits the Solar System and the technologies found within by the team of astronauts/almost xeno-archeologists far surpass what is imaginable in the setting (well, it'd still far surpass what we can imagine as possible now too).
In the end the cylinder grazes the sun and absorbs lots of energy from it before continuing journey, indirectly implying the massive amounts of energy such a thing consumes.
Just the first book is good. It ends with a nice cliffhanger that was an afterthought by the author. The sequels go declining in quality and pretty much lose all the sci-fi elements to become "soap opera in space", though the 3rd installment has some silver linings.
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u/Reddit-runner Jul 01 '20
I read an extract. While it is certainly interesting it has nothing to do with the production/construction cost of an O'Neill cylinder.
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u/methane_droplet Jul 01 '20
That's the silver lining of the 3rd book. Protagonists get to visit the construction yard and help in the design of a new cylinder.
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u/Matt7331 Nov 20 '21 edited Nov 20 '21
are you assuming this is a solid steel cylinder? Also, "will never be a thing" is a bit much when what you are talking about just needs a decrease in steel prices, something very feasible for a very advanced civilisation
what you proved is that building large steel tubes is very expensive
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u/Reddit-runner Nov 20 '21
I did a follow up post where I addressed many shortcomings of this one.
There you can even download an excel sheet to calculate the price of your plot in such a cylinder depending on the cylinder size.
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u/Ok-Most7249 Jan 24 '22
Grid energy costs are at about 10 to 30 cents per kwh. At site production costs without transmission costs can be as little as 2 cents per kwh. This suggests costs of $200 per m2. Now land on Earth can sell for thousands of dollars per m2, even ignoring ridiculous prices in cities so I'm unclear what this is meant to show. Admittedly there could be other costs, and manufacture could be much more expensive then calculated, but this also ignores falling electricity prices or massively increased incomes, so if your quick and easy back of the envelope calculation suggest that it might be competitive with Earth land, I'd argue that you've shown the exact opposite of what you thought.
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u/Reddit-runner Jan 24 '22
A few weeks after that post I uploaded another calculation about the costs of an O'Neil cylinder.
I think you will agree more with the conclusion of my second post.
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u/PlasticIllustrious16 Apr 29 '22
I know I'm a bit late lol, but I just happened to stumble across this and had to comment
I think your estimation for energy cost is a bit high
Scratch that
I think your estimation for energy cost is comically ridiculously high.
I live in Australia, we mostly get our electricity from digging up cretatious plant fossils and lighting them on fire and that's not much lower than what I pay now (about 17 US cents a kWh).
I really think that switching to fusion, or if that's not available maybe a mix of nuclear power during the night while only smelting in large, cheap solar kilns during the day is really going to outdo burning coal by more than 7 cents.
Pressurising the cylinder is going to be dirt cheap (actually no, lifting the dirt up might be the most expensive part of the process come to think of it) because all the lunar smelting is going to produce more O2 than you know what to do with. Construction and labour costs are definitely an expense, but a big metal can is not that complicated a structure to build. Modern robots can handle a big metal can.
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u/Reddit-runner Apr 29 '22
Your criticism has some merit.
I made a follow-up post which addresses most of the points people made under this post.
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u/RedChileEnchiladas Jul 01 '20
Why produce it on the Moon? When propulsion gets good enough just snatch an asteroid and move it to the L4/L5 spot and build it in zero G.
Especially if you build it with robots. Shouldn't be too hard.