A Case for Orbital Rings

Part 1: What the fuck is an orbital ring? #

An orbital ring is, in its simplest form, a structure encircling the Earth, at an altitude of 100-400km above the surface. This means it’s a massive structure sitting in space, but the term “orbital ring” implies that it’s in orbit; it’s not. It’s actually stationary with respect to the ground, spinning just slightly faster than the surface it’s over.

This means that if you were standing on one, you would be feeling approximately the same downward pull you feel on the surface (you could be up to 12% lighter depending on the altitude). If you jump off, you’ll fall to the ground – hope you packed a parachute! – but you’re not reentering since you’re not at orbital speed.

So… how does it stay up there? Normally anything that’s up in the air falls down, and even if the ring were perfectly balanced around the Earth with all the force vectors canceling out gravity, it’d be under immense pressure and be wildly unstable.

Instead, we have a rotor inside it that is spinning above orbital velocity. That rotor provides us something to push off of, and our structure stays up! It needs to spin faster than orbital velocity to hold the weight of our ring. We’d actually want to have them in counter-rotating pairs to cancel out the gyroscopic effects, and we’d want to have multiple rotors for redundancy and to keep the load on any given rotor relatively low.

While it’s possible to make an orbital ring that’s actually a solid structure with a solid rotor, it’s a lot more likely to be a series of separate platforms that shoot metal slugs at each other, like a game of cosmic hot potato. Each one pushes off it while accelerating it toward the next platform. (This, by the way, makes it into an orbital particle accelerator, which is just unbelievably metal.)

The final piece of the equation is how you get to it. Because it’s stationary and not that far up, you can just drop a tether from the ring down to the surface. That tether is made of Kevlar (for strength), aluminum (for power conduction), and fiber optics (for communication). The tethers come out at an angle to provide lateral stability to the ring and you can just climb them with – in effect – a train-elevator hybrid.

Part 2: Okay, but uh. Why? #

Well, you can take a train into space! That’s pretty cool on its own, but not worth the hundreds of billions of dollars this would cost. Let’s cover a few examples of what these would enable:

A few of these may stick out to you as more important than others, and I agree wholeheartedly. Let me combine a few of these into one big, high-level point:

Orbital rings could cut CO2 emissions by half. Without even considering the potential for energy-intensive carbon capture that could be enabled by such cheap power.

Part 3: A HALF? That can’t be right. #

Actually, it’s even more than that! Let’s break that down:

Electricity generation makes up over 40% of worldwide emissions. In the next section I’ll show the cost reduction we could see for the solar power from orbital rings, and you’ll understand why that emission factor would quickly drop to 0%; we don’t use fossil fuels because they’re awesome, we use them because they’re cheap. We can be a hell of a lot cheaper.

Transportation is another 25%, but obviously we can’t drop that whole sector without a lot of people with gas-powered cars being very upset. However, we can cut it down substantially, so let’s subdivide transportation.

Aviation #

Air travel makes up about 11% of that 25%, or about 2.5% of worldwide emissions. It will get cut to nearly zero. This is faster, more spacious (you’d actually be able to have leg room!), and significantly cheaper. Getting from New York to Tokyo would be comparable in cost and time to a train ride to a neighboring city, with the advantage of a much nicer view.

That brings us to a 42.5% reduction.

Long-haul trucking #

Heavy trucks make up about 22% of that 25%, or 5.5% of the whole. While we still will need last-mile delivery trucks, long-haul trucking can be almost entirely replaced with travel via orbital rings.

That brings us to a 48% reduction.

Shipping #

Shipping is another area that is rife for replacement with orbital ring transport, providing faster transportation of goods for similar or lower cost. This makes up another 11% of the 25%, or another 2.5%.

That brings us to a 50.5% reduction.

Part 4: How can the energy be so cheap? #

This is – to me – the coolest part of the entire thing. Terrestrial solar power has a number of major issues:

Ignoring energy storage, to replace the world’s power generation with terrestrial solar you would need a land area of just shy of 500,000 km2. That’s twice the land area of Texas. Obviously, that wouldn’t all happen in one spot, but it’s still absolutely enormous.

Part 4.1: Okay, but putting them in space can’t be THAT much better #

How much would you need to do it with solar panels on an orbital ring? 20,000 km2; less than 10%. With these panels, half would be in direct sunlight at all times, allowing for constant energy generation that could replace the entirety of the world’s power generation. Note: This does not take into account transmission losses and other inefficiencies, which could be as high as 20%. As such, let’s bump it up accordingly and round up to 25,000 km2. That’s about the land area of Maryland.

That would produce 2.5TW of continuous power or 21900 TWh; slightly over the current worldwide consumption.

Part 4.2: That’s a fucking lot of solar panels. How much would that cost?! #

$1T, if you used the same exact panels we use on the ground and bought them at consumer rates. This is not the actual rate you would pay, by any means – the ring builder would be the largest consumer of solar panels in the world by orders of magnitude and would likely just build their own at that scale – but let’s go with it. $1T. A trillion dollars.

Part 4.3: But you said it was cheap? #

Here’s the thing: that’s nothing. It’s a largely one-time cost in order to completely replace every bit of power generation on Earth – a $4T per year industry.

Let’s assume each panel only lasts 10 years (which is almost certainly low, given the lack of weather damage and other terrestrial issues) and your orbital ring cost $500B (we’ll get back to that number, but let’s roll with it). Finally, right now the average cost for power in the US is $0.166/kWh; obviously the US isn’t the world, but it provides a good point of comparison.

If we wanted to pay off the entirety of the orbital ring and the solar panels in 5 years, you could sell the power at $0.091/kWh to break even. Make it $0.1/kWh (a 40% cost reduction to the US average!) and make a $190B/year profit.

After the cost of the ring is paid back and you’re just replacing about 10% of your solar panels per year, your costs would be $100B/year. You could drop your electricity price to $0.01/kWh (6% of the current US average) and still profit $119B/year.

Part 4.4: Oh #

… Oh. Damn.

Part 5: But how does this help with space travel? #

This is what most people want to talk about first with orbital rings – because it is super valuable – but it’s just not as interesting as the terrestrial implications for me, so I’ll give a really brief overview.

An orbital ring is in space, but it’s not in orbit, like we talked about. However, a spacecraft on a maglev track on the underside of the ring could accelerate itself up to orbital velocity over a couple spins around the Earth, then flip over to the other side and release from the ring. This provides a zero-emissions launch into orbit while accelerating at 2g or below; that’s comfortable for effectively every person on the planet, because 1g of that gets cancelled out by the fact that it’s happening upside-down.

This means that the only thing you pay for is maintenance of the track, the energy (cheap) required to propel it, and then whatever fuel you need to use to decelerate yourself at your destination. Zero Earth-side emissions.

Part 6: Okay, that’s a cool story. Is it feasible? #

In a word: yes.

Unlike some far-future tech like space elevators or a cat that doesn’t step on your laptop during meetings, there’s no major technological advancement required to build an orbital ring.

However, we’ve never built anything on this scale before. Not even close. We’re talking about – eventually – a ~13000km long structure in the sky. This would be the biggest construction project that humanity has ever undertaken and it would cost a lot.

Estimating the cost is hard for a number of reasons: 1) the sheer scale of the project, 2) there are a dozen different ways you could build it, 3) it would vary dramatically depending on whether it’s undertaken by private companies or governments.

I would put the upper bound on the first fully-functional orbital ring at $500B. I don’t think even optimistic estimates would drop below $100B. By “fully-functional” I mean: provides transportation and power for all areas within range and provide space launch capabilities. That’s not what we’d start with, but it’s likely what we’d be aiming for.

Part 7: Wait. “First”? You want more than one?! #

Yes, a lot more. Probably 12-15 depending on exact placement.

At the end of the day, a single ring can only be reached via tether (150-300km, depending on the ring altitude) and line of sight (1100-2250km) from a certain area on either side of it. While we can cover huge swathes of the population from a single ring, it’s impossible to cover the entire world with a single one.

Instead, we’d want rings at various altitudes and inclinations, with tethers from one ring to another. If you have a ring that passes through New York and London but you want to get to Tokyo, you’d go up to the ring that’s closest to you, then connect to the ring that brings you to your destination.

This is the orbital ring system, or ORS.

Part 8: How much would all of that cost?! #

Oh, an absolute shit-tonne. But once you’ve got a single basic ring up, it becomes a lot cheaper to put up new ones, since launch costs and transportation of mass (the major currency of orbital rings) would drop so substantially. I’d be shocked if subsequent rings cost more than $50B, with each one being cheaper than the last.

Depending on the level of vertical integration (e.g. owning the production of solar panels) this could be dramatically lower. Either way, it’d be much closer to a skyscraper than a city.

If you put a gun to my head and told me to give my best estimate of the total cost of a full-on ORS, I’d tell you $1.5T. That’s including all the materials, labor, bootstrapping system, R&D, overhead, government licensing, etc.

Part 9: This seems too good to be true #

Not everything is sunshine and rainbows. There aren’t many serious problems with the concept of an ORS, but these need to be solved to make it not just feasible but practical. A short list:

These are all solvable (some more easily than others), but they all make it harder and we should acknowledge that.

Part 10: With all that, does this even make sense? #

I’d say an enthusiastic yes, but it’s also my Special Interest, so I’m biased. At the end of the day, it comes down to the priorities of our society, governments, and/or the companies that decide that this is a worthwhile step.

An ORS would – without a doubt – change our world immeasurably. We’ve never had such rapid connections, such cheap and clean power, such easy access to space. There are a number of solutions that give us any one of those things, but I’m not aware of any solution that gives us all of them.

If all these things matter to us, then this is worth investing in. If they’re not, it’s not worth it. Simple as that.

I sincerely think this is the next big leap for humanity, but the sheer amount of investment, time, and cooperation required makes it a big ask. I hope we come together to make this happen.

Happy Hacking,

- Sera

 
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