Letting the imagination roam has philosophical as well as practical benefits. From the interstellar perspective, consider the Daedalus starship, designed with loving detail by members of the British Interplanetary Society in the 1970s. The mammoth (54,000 ton) vehicle was never conceived as remotely feasible at our stage of technology. But ‘our stage of technology’ is exactly the point the project illustrated. Daedalus demonstrated that there was nothing in physical law to prevent the construction of a starship. The question was, when would we reach the level of building it? For as Robert Forward frequently pointed out, interstellar flight could no longer be considered impossible.
We can’t know the answer to the question, but recall that before Daedalus, there was a lot of ‘informed’ opinion that interstellar flight was a chimera, and that all species were necessarily restricted to their home systems. Daedalus made the point debatable. If a civilization had a thousand year jump on us in terms of tech, could they build this thing? Probably, but they’d also surely come up with far better methods than we in the 1970s could imagine. Daedalus was, then, a possibility maker, a driver for further imaginings.
Fortunately, the Daedalus impulse – and the broader concept of thought experiments that so captivated Einstein – remains with us. I think, for example, of Cliff Singer’s pellet-driven starship, one that would demand a particle accelerator fully 100,000 miles long. Crazy? Sure, but a few decades later we were talking about slinging nanochip satellites in swarms using Jupiter’s magnificent magnetic fields, finding a way to do with nature what was evidently impossible for us to build with our own hands.
Robert Forward used to conceive of enormous laser sails for interstellar exploration, sails whose outbound laser flux would be amplified by an even larger 560,000-ton Fresnel lens built between the orbits of Saturn and Uranus. But I discovered in a new paper from Greg Matloff (New York City College of Technology, CUNY) that it was James Early who introduced another extraordinary idea, that of using a gigantic sail-like structure not for propulsion but as a sunshade. Early’s 1989 paper in the Journal of the British Interplanetary Society specifically addressed the ‘greenhouse effect,’ which even then concerned scientists in terms of its effect on global climate. Could technology tame it?
Once again we’re in Daedalus country, or Forward country, if you will. Imagine a true megastructure, a 2000 kilometer sunshade located at the L1 Lagrange region between the Earth and the Sun, approximately 1.5 million kilometers from Earth. The five Lagrange points allow a spacecraft to remain in a relatively fixed orbital position in relation to two larger masses, in the case of L1 the Earth and the Sun. But L1 is not stable, which means that a structure like the sunshade would require thrusting capability for course correction to maintain its optimum position in relation to the Earth. Bear in mind as well the effect of solar radiation pressure on the shade.
Image: Physicist and prolific writer Greg Matloff, author of The Starflight Handbook (Wiley, 1989) and many other books and papers including the indispensable Deep Space Probes (Springer, 2005).
Would a 2000-kilometer shade be sufficient, assuming the intention of reducing the Earth’s effective temperature (255 K) by one K? We learn that solar flux would need to be reduced by 1.5 percent to reduce Earth’s EFF to 254 K. 2000 kilometers does in fact somewhat overshoot the need, reducing solar influx by about 2 percent. That’s a figure that changes over astronomical time, of course, for like any active star, the Sun experiences increased luminosity as it ages, but 2000 km certainly serves for now.
But how to build such a thing? Matloff looks at two versions of the technology, the first being a fully opaque, thick sunshade which would be constructed of lunar or perhaps asteroidal materials. Think in terms of a square sunshade with a thickness of 10-4 meters, and a density of 2,000 kg/m3, producing a mass of 8 X 1011 kg. Building such a thing on Earth is a non-starter, so we can think in terms of assembly in lunar orbit, with the shade materials taken from an asteroid of 460 meters in radius. Corrective thrusting via solar-electric methods with an exhaust velocity of 100 km/s adds up to an eye-opening fuel consumption of 400 kg/s.
But we have other options. Matloff goes on to consider a transparent diffractive film sail (Andreas Hein has recently explored this possibility). Here the sail is imprinted with a diffraction pattern that diverts incoming sunlight from striking the Earth. This is a sail that experiences low solar radiation pressure, its mass reaching 6.4 X 108 kg. But thinner transparent surfaces are feasible as the technology matures, reducing the mass on orbit to 107 kg. Such a futuristic sunshade could be built on Earth and delivered to LEO through 100 flights of today’s super-heavy launch vehicles. Presumably other options will emerge by the time we have the assembly capabilities.
Either of these designs would divert 5.6 X 1015 watts of sunlight from the Earth, energy that if directed to other optical devices would offer numerous possibilities. Matloff considers powering up laser arrays for asteroid mitigation, an in-space defensive system that would work with energy levels much higher than those available through currently envisioned systems like the proposed Breakthrough Starshot Earth-based laser array. A space-based system would also have the advantage of not being confined to a single hemisphere on the surface.
Other possibilities emerge. A laser near the sunshade could tap some of the solar flux and direct it to power stations in geosynchronous Earth orbit, where it would be converted into a microwave frequency to which the Earth’s atmosphere is transparent. You can see the political problem here, which Matloff acknowledges. Any such instrumentation clearly has implications as a weapon, demanding international governance, although through what mechanisms remains to be determined.
But let’s push this concept as hard as we can. How about accelerating a starship? Matloff works the math on a crewed generation ship accelerated to interstellar velocities, with travel time to the nearest star totaling about four centuries. The point is, this is an energy source that makes abundant solar power available while producing the desired reduction in temperatures on Earth, a benefit that could drive development of these technologies not only by us but conceivably by other civilizations as well. If such is a case, we have a new kind of technosignature:
If sufficiently large telescopes are constructed on Earth or in space, astronomers might occasionally survey the vicinity of nearby habitable planets for momentary visual glints. If these sporadic events correspond to the planet-star L1 point, they might constitute an observable technosignature of an existing advanced extraterrestrial civilization.
When considering technosignatures from ET sunshades, it is worth noting that a single monolithic sunshade might be replaced by two or more smaller devices. Also, an advanced extraterrestrial civilization may choose to place its sunshade in a location other than planet-star L1.
There is a Bob Forward quality to this paper that reminds me of Forward’s pleasure in delving into the feasibility of projects from the standpoint of physics while leaving open the issue of how engineers could create structures that at present seem fantastic. That quality might be described as ‘visionary,’ calling up, say, Konstantin Tsiolkovsky in its sheer sweep. Matloff, who knew Forward well, preserves Forward’s exuberance, the pleasure of painting what will be possible for our descendants, who as they one day leave our system will surely continue the exploration of their own ‘Daedalus country.’
The paper is Matloff, “The Lagrange Sunshade: Its Effectiveness in Combating Global Warming and Its Application to Earth Defense from Asteroid Impacts, Beaming Solar Energy for Terrestrial Use, Propelling Interstellar Migration by Laser-Photon Sails and Its Technosignature,” JBIS Vol. 76, No. 4 (April 2023). The Early paper is “Space-based solar shield to offset greenhouse effect,” JBIS Vol. 42, Dec. 1989, p. 567-569 (abstract).
Well, this brought me
back as I ended up briefly discussing a related scheme in 2008 (of all places on a site called F1 Technical). It’s not a megastructure though, but a swarm of micro satellites achieving the same effect (alas, not enabling interstellar travel)
The paper is “Feasibility of cooling the Earth with a cloud of small spacecraft near the inner Lagrange point (L1)” by Roger P. Angel, Regents Professor of CAAO, University of Arizona, Nov. 14, 2006. Some alternatives to the technologies he proposes have emerged meanwhile, likely making his proposal (or a self-assembling megastructure variant of it?) even more feasible. Perhaps do a follow-up post on the subject here, incorporating some of the themes in Prof. Angel’s paper?
The paper:
https://www.pnas.org/doi/full/10.1073/pnas.0608163103
Where I discussed it back in the day among other climate change geoengineering proposals (my nic was “checkered”):
https://www.f1technical.net/forum/viewtopic.php?t=5207
We could potentially use sodium chloride as the lens material, simply grow it in space using a material that is very cheap and common on earth. We could also use metalens to concentrate the light we don’t want to hit the earth which will heat it and use it for power, perhaps as a halo of concentrated light around the earth. Satellites orbiting the earth could then direct the power to collectors on earth, other light that is useful for plants is allowed through to reduce carbon dioxide. It’s worth noting the size of the L1 point if used for a lens power supply device is enormous been millions of kilometers in diameter. I suspect a concentration of the light to a near by power station which then converts it to laser power which is sent to earth via a phased array would be better.
A while back a commenter indicated (with a web reference) that this was an idea by Greg Benford, at a conference in 2004[?]. I cannot read the JBIS article behind the paywall, but is there any confirmation of that claim?
The initial idea of an 8E11 kg mass needing a 400kg/s propellant use would mean either that another asteroid of the same mass as the shield would need to be consumed, or that the shield would be consumed for propellant in a little over a century. Reducing the shield/lens mass does not alter that calculation unless the diffraction reduces the perturbing effects on the shield/lens.
While the physics is not impossible, unlike Daedalus or similar for star travel, we really do not need to do such an expensive project to keep the earth cool. It is far less expensive to do geoengineering, and in turn far better to just stop adding carbon to the atmosphere, and actively remove what we have added. That we have singularly failed to do so, nor transferred the agreed pittance in funds to poor nations, there is no way I can see that such an expensive project could ever be achieved, even as the world boils.
If we are going to build such large space structures, it should be for the purpose of decarbonizing our energy use on Earth. Geosynchronous SPSs would be the better choice, and more maintainable approach rather than a device at L1 redirecting insolation away from Earth, even if the redirected energy can be used.
Alex, I’m pretty sure that Jim Early was out first with this, but Greg Benford did indeed explore the concept a bit later.
You can actually dispense with the use of propellant fairly easily.
First, go with deflection instead of blocking, and you dramatically reduce the light pressure felt by the shade/sail.
Second, hang a tether with a weight on it in the direction of the Sun. The tug from this can balance the average remaining light pressure.
Then you just use part of the deflected light for station keeping by adjusting the angle of deflection as needed.
Presto! No propellant consumption.
Yes, I’ve thought about this before. I would argue for a modular approach. Manufacture solar sails at a convenient NEO asteroid, add modules shipped from Earth to provide intelligence, and have the sails deliver themselves to L1. There is no need for a single solid sunshade, you just need to block sufficient sunlight.
Sails would place themselves slightly closer to the sun than L1 so they would effectively be statites, balancing gravity against light pressure. Position control could be provided by rotatable sub-sails as well as adjusting the main sail. Also, something like IKAROS’ variable reflectance liquid crystal panels might be used.
Mind you it would be hard to beat the graphene nano len mass wise, perhaps microwaves beamed back from earth could be used to stabilise it from falling to earth.
https://newatlas.com/optical-lens-one-billionth-meter-thick/41588/
Even if we had son of ‘Megalens’ which is equal to our current power useage it would only be around a hundred and ten kilometers wide, it would reduce a smaller amount of light but the power would offset pretty much all of our fossil fuel needs. If a graphene lens was used it would only weight less than a thousand tons.
Hi Michael
Unfortunately the Sun isn’t a point source so any lens smaller than the Sun won’t bring its light to focus. A Fresnel diffuser suffers a similar issue. Shades at L1 have to ensure the spot of shadow they cast on Earth is sufficient for mitigating global warming.
Sun Shades have been proposed for terraforming Venus. Placed in the Venus-Sun L1 position they have to be twice as big as Venus to blanket the whole planet.
A more modest proposal has been increasing the Earth’s albedo via high altitude particulates. A criticism of the concept is that reducing the solar flux that reaches the Earth’s surface only imperfectly matches the effects of increased atmospheric CO2; it might mitigate but not eliminate climate change.
As you state, there are cheaper ways of reducing insolation. The problem is that the increased CO2 has not only warmed the Earth, but acidified the oceans harming organisms that secrete carbonates for skeletons and shells. Reducing the heat trapped does not change this and may even exacerbate the carbon emissions as the problem is “fixed”.
We have built a large population civilization where our activities are rather finely balanced. Change the climate and its environmental effects and we will precipitate problems.
I’m reminded of Clarke’s “The Hammer of God” where the attempt to divert an ELE asteroid impact is sabotaged by a religious sect that wants the end of humanity. Imagine the scenario if the L1 structure is destroyed releasing an immediate increase in insolation after we have continued to release CO2 into the atmosphere. In any event, the structure must be maintained for hundreds of years while we try to eliminate the excess CO2, not just in the atmosphere, but in the oceans with millennia of turnover time. We seem incapable of taking a global view and as a result tribal game-playing just makes the problem worse.
Alex, we could prehaps store the CO2 in a large tube, say we build a large test tube in the Mariana trench so it reaches the seafloor and we build it up into air an equal amount. Due to the cold air and water co2 removal and storage would be much easier. Once we stabilise the CO2 produced on earth we could slowly vent out the CO2 over time to allow it to combine into rock.
I am not clear on how your proposed solution is to work. Carbon sequestration of fossil fuel combustion is best done at the source. Once the CO2 is separated it must be cooled below -78C to either liquify it under pressure or solidify it. The CO2 is then sequestered by pumping it under pressure into old oil/bas wells. A slower process is turning it into rock.
It is more expensive to extract CO2 from the atmosphere by machine. Trees and fast-growing plants are a more eco-friendly solution but currently even covering the planet with trees would not be enough.
The best solution is to stop using fossil fuels. Where we need chemical fuels we should be making them from water and gaseous CO2 so that combustion does not change the atmospheric and oceanic CO2 composition. However, converting CO2 to CH4 must be done with care so that inadvertent CH4 release does not happen beyond a minimal extent. Somehow we must also draw down much of the CO2 we have emitted since the industrial revolution.
Giving 8+ bn people on the planet the resources and power at a European level may not be feasible. This is a long-term problem that I don’t know how we solve in a way that maintains our biosphere. It may require the use of space resources, both materials and energy, requiring us to accept the costs to keep our planet biodiverse.
As the tube gets deeper into the ocean and higher co2 naturally compresses under its own weight and naturally settles to the bottom due to the cold. At high altitudes co2 is also easier to extract from the air due to cold temperatures. The tube will essentially float in the ocean storing co2, and it will give us time to get to a zero co2 economy.
Alex Tolley, reducing the heat does affect the solubility. Cold water always absorbs less carbon dioxide from that atmosphere. Warm water hold more carbon dioxide and warm water dissolves more carbon dioxide faster. This is a feedback process we see in the Milankovitch cycles. There is a tipping point to that when the water gets cold enough, that the ice ages begin. Less sunlight hits the northern latitudes over a long period of time due to the Milankovitch cycles. The problem is that it is not easy to reduce the heat of the oceans which take a long time to heat up and cool off. It would be easier to scrub the carbon dioxide out of the air which turn the carbon dioxide into bicarbonate put into metal cans. These carbon carousels could remove 135 ppm in less than three decades, but with high cost. The oceans would still take longer to cool off.
Another interesting conclusion we can draw is that we now have the technology to control our weather. With carbon capture machines we could keep the carbon dioxide levels between 240 and 280ppm so the Milkankovitch cycles would have no effect. During the ice age, the carbon dioxide levels were at their lowest point of the cycle at 180ppm and a ice age tipping point at maybe at 220ppm, a designer atmosphere or weather control.
Excuse me for the mistake.Cold water always holds and absorbs more carbon dioxide than warm water which holds and absorbs less carbon dioxide. with today’s technology we can engineer our atmosphere so we won’t have any ice ages or see level rise.
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Has this even been done at scale, or it is just a high cost proposal?
Yes, the ocean storage of CO2 and heat will take a long time to reverse. Worryingly, the Atlantic Conveyor is rapidly slowing as the Atlantic warms, making the cycling even slower, probably causing more hurricane damage, and already changing the distributions of fish populations. The oceans have acted as a huge buffer to our CO2 emissions and it will be a reservoir affecting our attempts to reduce atmospheric CO2 levels.
An interesting deep-time idea. However, human civilization is less than 15 millennia, and the ice ages responding to the various cycles are about 100 millennia apart. It would be heartening to think humanity could coordinate its global activities over such a long period.
If we are still around in another 15 millennia, I would hope our technology could not just control the climate and weather on demand, but optimize it for the biosphere and the diversity of life. It wouldn’t surprise me if we could extend the living area many times by building subsurface warrens and surface structures with multiple levels of habitats that could accommodate humans and wildlife on a re-engineered planet. It would be a massive undertaking, but we could build climate-controlled conditions that would work for the non-migratory species. [Migratory organisms might have to live on the top surface to have the needed freedom of movement, although they might be fooled in a virtual environment that makes it seem to them they have migrated long distances.] Think of this as not building O’neills in space, but rather using the concept of creating all that lebensraum on Earth instead. The ultimate arcology concept.
Oceanwide submersible had a small, portable, carbon dioxide scrubber onboard to get rid of the carbon dioxide build up from passengers breathing in oxygen and exhaling CO2 . The technology works. The cost to fix climate change will be expensive. There is no way to escape it. A large portion of our civilization is coastal cities near the sea.
Deep time atmospheric control is just an idea of course. Since we have the technology, an idea that certainly will be studied. I don’t know what the long term consequences of not have any ice ages would be. If we decide to keep ice ages, Woolly Mammoths certainly won’t be coming back, but polar bears might make a comeback.
Acid rain would only worsen with Sulfur injections—so that’s off the table.
Dear Michael,
Many geoscientists are somewhat aftraid of geoengineering. How long would the aerosols remain in the stratosphere? how might they affect the ocean floor upon Earth impact. How do we prevent an aerosol overshoot that might lead to an Ice Age? So astroengineering may be superior to geoengineering. But a lot of analysis is still required.
Regards, Greg
Your point about cautious geoscientists is well-taken.
I have to add: proposing advanced ideas like this – ideas that appear conceivable, albeit with shaky legs – is one of the charms of this site.
I suppose if we used graphene we could circulate a large current around it where we could funnel the solar wind towards a hole in the centre. At this hole we use some of the energy received from the sun to accelerate the particles so we can control the position of the lens via momentum exchange.
The light will not be focused at the earth but much closer to power stations say that allow 500 to a 1000 times concentrations, cooling will be an issue though. The concentration of light is focused on high temperature solar cells which can have quite high efficiencies, after that it’s converted into laser light and beamed to earth’s vicinity via a phased array.
The efficiency of solar cells at high concentration of light is quite impressive, If we could beam this laser light to satellites around the earth they could reflective or beam the power back down to power platforms at sea to produce hydrogen to be shipped around the world or use the power to combine co2 into hydrocarbons for disposal.
https://physicsworld.com/a/sunny-superpower-solar-cells-close-in-on-50-efficiency/
I think Alex is right. The key to this problem is to reduce CO2 emissions drastically in the next 20-30 years (and that doesn’t mean putting it off for another 10 years). Technical solutions bring about their own problems, many of which are unforeseen. A drastic reduction in emissions together with an attempt to begin a drawdown of greenhouse gases is essential. This should have already been underway for at least 20 years. We are coming very late to the game and oil and gas producing countries like Canada (my country) are fighting tooth and nail not to ramp down production. Greed is the main driver here. The amount of tax income produced is disturbingly small. Most of the profit disappears into a few pockets. Rex Tillerman might be an interesting case study on how not to tell the truth about CO2 emissions for more than 20 years. I’m all for learning what might be possible in the way of technical solutions but the problem is huge and still growing in impact and the time left is very small. Our global civilization produced 36.5 Gigatons of CO2 emissions last year. This is the path to disastrous further climate change. I don’t ask people to believe me but I would ask that people take an honest look at the data and come to their own conclusions. The time for denialism should be long over. The data is overwhelming. We are changing our own climate to something far more dangerous for us and millions of other species.
Work by W Strek indicted laser light on water with salt in it can produce hydrogen quite efficiently.
What efficiency exactly? Lasers are not very efficient in terms of power output to input. This may be just 5%. So even if the laser efficiency to release H2 was 100%, the overall efficiency would be just 5%. This is far lower than electrolysis which is about 70%.
It is very disturbing to see obviously intelligent people offer solutions that are at best sketchy (i.e. not well explained and not likely to be adopted by countries with an eye on maximizing profits for carbon sources), and at worst appear to be attempts to obfuscate about the problem and avoid the most obvious solution: rapidly decarbonize the economy. This won’t be easy or simple but is absolutely essential for the reasons Alex has outlined including acidification of the oceans, global sea level rise, loss of species diversity, loss of arable land and on and on. This means we will have to rely on intermediate technologies like batteries to drive cars and store power, and widespread use of many green power technologies such as solar, wind, ocean currents, geothermal energy and many more. Eventually we probably need a hydrogen economy with efficient fuel cells. This isn’t going to be solved by a tube in the ocean or a space lens. It’s going to be a rough ride and we’re probably going to learn the hard way, including a huge loss of human population as well as biodiversity before we get to work to overcome the problem. Forget about politicians, they only work toward their own short term desire for political power. Ground roots organizations around the world will probably have to do the heavy lifting here, together with some of the more sanely run countries. We have ignored this problem for decades and now the piper must be paid.
Gary if you are willing to pay for it good luck, America and China should foot the bill surely….not the rest of the world as that would be unfair…Hand in your cash and put your money where your mouth is so to speak. As for these ideas on this site good for them. I am more interested in power for space but the two can go hand it hand.
Everybody should pay their way Michael. Nobody said anything about America and China footing the bill. I’m deeply interested in space exploration too, so we all have a very obvious common interest. Ideas are great but we need to focus on what can be done in a very short time. This is not a linearly increasing problem. You could say we have accumulated a vast global debt called human caused CO2 increases in the atmosphere and the oceans. That debt must be paid down. We can either do it or continue to face an existential crisis. I’m all for any solution that actually works and does not cause other catastrophic side effects. Let’s think about the problem together as a global issue. If a sunshade works that would be great but the cost to lift a huge mass into L1 orbit would be enormous. Do we have the resources and money worldwide to commit to it as well as paying for all the other projects including de-carbonizing the world’s economy? We will have to be careful about that. Space exploration is exciting and I think essential but we have to have a home planet that can support all the things we want to do. The global ecosystem is not an enemy to be destroyed as quickly as possible. Nature won’t care about what happens to us if we continue wildly down the wrong path as we are doing. Politicizing a problem of this magnitude which is a threat to all living things is madness.
I forgot to add that I think the new layout is great Paul. It’s such a pleasure to come on here.
Always a pleasure to see you, Gary. And thanks for your comment. A lot of things still in progress behind the scenes but most of the visible changes are complete, other than some tweaking I plan to do (always the perfectionist!).
I second the comment!
Given that huge/mega structures in space are likely to be decades away, and we’re now at the stage that immediate action is needed, it probably makes more sense to decarbonise at the source(s) now, as much as we can.
Sure, continue research into space-based methods (SPSs seem much more doable than gigantic mirrors or lenses in the short term), but we need to get to work on more easily attainable projects now.
I also wonder how willing states, corporations etc, will be to pay for enormous space systems, if they often fight tooth and nail against far less grandiose contemporary schemes to reduce climate change. Of course the economics of this could change, if we get sufficiently desperate!
P.S. Paul – the new layout really does look good!
Many thanks, Michael! Good to hear that.
A large test tube construction at sea if deep enough would store co2 naturally from the cold, it would collect so long as air is passed over it, minus water maybe better. There are plenty of rocks that if added to the liquidified CO2 would start to form carbonate rocks at the high pressures locking up the co2. All the CO2 used in the construction of the tubes would be stored in it as well.
I don’t think this works as the CO2 has to reach at least 5 atmospheres of pressure to liquefy. Assuming the depth of the Marianas trench reaches 1000 atmospheres under the weight of 10,000 m of water and with a temperature of 0C.
CO2 has a density of ~ 2/1000 that of water, which suggests that at the depth of 10,000 m, it might reach 2 atmospheres, insufficient to liquefy it. This simple calculation suggests that at the bottom of the tube, CO2 will remain gaseous.
All you would need to do is spend some energy compressing the co2 in the tube until the liquid starts to form at the bottom. Once it forms over a certain depth it will keep the pressure at the bottom so the co2 is in a permanent liquid state. If the tube is extended up by say 5 to 10 km the temperature up there makes it a lot easier to compress. It would be a huge but simple construction many kilometers in diameter and at least 11km in height but there can be many smaller ones. It may be easier to organise and construct than getting all of the nations to control themselves and it will only buy time to get to zero carbon economies anyway, it would offer get views at the top if built high enough I would think. Perhaps we could generate our hydrogen at sea from natural gas and store the co2 in them for future disposal.
https://www.peacesoftware.de/einigewerte/co2_e.html
But consider that at the start, this tube will be under external pressure from the ocean. We have just seen how a small submarine imploded within milliseconds due to hull failure. This vast tube with low curvature walls will have to withstand these external pressures until it is filled with liquid CO2 whose density will counteract the external water pressure..
As the original purpose was to deliver a low temperature to the CO2, why not simply locate the CO2 liquefaction facility at one of the poles? The air temperatures are far lower than the ocean depths (4 degrees C) and there is no need for heroic engineering to liquefy the CO2.
In practice, CO2 processing is best done at the emission source, which is why sequestration is usually considered part of a fossil fuel power plant. Once CO2 is dispersed into the atmosphere (and ocean) it takes a lot of energy to extract it again.
Given all the benefits, biospheric and human health, what is to be gained by continuing to combust fossil fuels and trying to manage their CO2 emissions (and methane) rather than switching to other, zero-emissions forms of power generation?
The problem with co2 sequestration at source is the high temp of the gases and a place to move it and store it under pressure, that takes a lot of infrastructure and huge cost. The tube is not design to hold all of the co2 of the world that’s just too much for any structures, it does however show us how much co2 there is out there. As for the structure been built is that it will have water in it and that water is replaced over time with co2 so there is no pressure issues. I suspect a multi faceted approach is needed, reduce fossil fuel use as much as possible and remove the co2. As for the poles although cold they should be no build zones.
So to get the low temperature wouldn’t you need to inject the CO2 into the bottom of the tube to ensure it is liquid under the pressure of the water above it? That is injecting it at 1000 bar.
Does this really make sense when fossil fuel power plants have cooling towers and the CO2 is at high partial pressure to be separated out to be sequestered?
If the aim is to stop fossil fuel combustion and just extract the CO2 from the air to reduce its concentration, wouldn’t it be simpler to just place the CO2 extraction and liquefaction facility in a cold region?
Any method needs to be a low-cost method, preferably with a small footprint. It should also be scalable so that the extraction can be ramped up over time, rather than requiring a single facility to be scaled in size (cylinder dimensions) for its single task.
A cold region would be better but you also need great depths, there are regions in the north and south polar areas that are around 4000 m deep so could do as well. You don’t need a 1000 bar only cool it to a liquid and it being slighly densier than water it would sink normally to the bottom of the water column displacing the water.
So a simple test of this is to use a pressurized cylinder (5+ bar) mostly full of water at greater than 0 C. Inject the CO2 at the top and as it liquefies, it should sinn to the bottom. Questions:
How long would it take due to Brownian motion, and how much is lost as CO2 is soluble in water. Is this really better to use water-filled vertical tubes to generate the needed pressures rather than just having empty containers of arbitrary size filled with liquefied CO2 without water contamination?
It seems to me that the vertical column idea is a solution in search of a problem that has been solved by existing industries with pressurized CO2, as well as other means to directly convert CO2 to a stable mineral or organic state.
CO2 can be used for a variety of purposes including generating organic fuels where the specific energy of the fuel is needed, e.g. long-distance air travel. If one needs to sequester carbon to reduce the CO2 in the atmosphere (and the oceans) then stable storage as a mineral or organic material away from the biosphere seems to be the easiest mechanism to do so as they simply mimic what natural processes have already done, albeit at a slow rate.
For a really crazy idea, take the CO2 and send it to Mars to thicken the atmosphere and warm it as a start for introducing life to support eventual colonization. Win-win for Earth and Mars?
We would have very large sea water filled tube with a smaller tube inside it all the way to the bottom. The co2 is pressurized inside the smaller tube to the point of liquidfication by the pressure and temperature. The liquid CO2 simply drops to the bottom of the larger tube displacing the water inside the larger tube, the co2 fills the large tube from the bottom upwards, there is no great pressure difference between inside the tube and outside it bar the inner tube at the top. Tanks on land need pressure vessels the sea tube does not only a relatively thin shell. Co2 can also be used as precursor for many useful chemicals as you have stated having it in one place would be useful. Just saying we could produce hydrogen for a seaborne deliver system while tieing up the co2 in one place. It is only temporary until the zero carbon economy kicks in anyway. Maybe we freeze the top of the tube as cap to immobilise the whole structure. Mars is a non starter…
Interesting article on ocean co2 storage, it can form a solid hydrate in the right circumstances.
https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://www.ipcc.ch/site/assets/uploads/2018/03/srccs_chapter6-1.pdf&ved=2ahUKEwjHj8_cjICAAxVGPuwKHS2IBl84ChAWegQIBBAB&usg=AOvVaw1JrKDiGBL3OaoY8fxNX-PY
And how big a tube would be needed Michael? We need to remove at least 1 trillion tons of CO2 from the atmosphere (and that number is steadily increasing by tens of billions of tons a year). To have any impact at all your construct would have to be gigantic and as Alex points out probably wouldn’t work anyway because the pressure to liquefy CO2 isn’t there. We already have the technologies required to de-carbonize to a massive extent. The main obstacle is human beings set on maintaining the status quo such as those who own oil and gas companies. If we let them win everyone loses.
If the tube is to contain 1 trillion MT = 1E12 m^3 for liquid CO2 (about the same density as H2O) then:
height = 10,000 m. (depth of ocean trench.)
therefore diameter of cylinder = sqrt((1E12*4)/(pi * 1E4))
= sqrt(1E8*4/pi)
= 2*1E4*sqrt(1/pi)
= 1E4 m = 10km
diameter = 10,000 m or 10 km.
So a cylinder about as wide as it is high.
Global warming: on Earth and elsewhere…
A look at a bigger picture? Or perhaps something overlooked?
Whatever Dmitry Orlov’s value is in his idea of an ongoing economic collapse, the link you used is nothing more than global heating denial. He misrepresents what experts are saying, some claims have been debunked well before this piece was written, and at least one claim is preposterous.
The big picture is that the leaders of the big polluting nations are resisting change with the likely result that there will be significant harm to the biodiversity of the current biosphere, including humans. Major cities that tend to be situated on lowlands and at sea level will be flooded, and some will have to be abandoned. Southern Florida will be underwater. [I was just reading that the Thames Barrier that was built to prevent London flooding from storm surges will need to be replaced (or another built elsewhere) as it will no longer be able to prevent flooding. Britain is looking to build more airports despite the fact that there is no realistic existing technology that can be developed for transcontinental aircraft to be net-zero emitters.
The god of economic growth über alles is a problem that perhaps only a civilizational collapse can solve. This may be the collapse that Orlov thinks will be precipitated by other means.
‘To a man with a hammer, everything looks like a nail.’ Or the Law of the instrument, where the natural human tendency is to be over-dependent on narrow skill-sets and resources. To the cult of technology the solution of every problem is technical. Technical solutions can be bold or exciting and more so creative and fun. Political and cultural solutions might better address root causes, but tend to take us out of that comfort zone. But one could imaging a fantastic sci-fi novel where the story line revolves around cultural change and inner growth more than ‘gee whiz’ future technology. Or a story one where interplay of future technology – both advancements and failures – and the culture this change this generates become the plot points. We need to re-write the story about a future where people with widened human capabilities and expanded perceptions engage with, and solve our problems, with great personal joy.
Have you read Kim Stanley Robinson’s The Ministry of the Future? The proposed solutions are both technical and cultural. No “magic bullet”, but a set of actions that are implemented to try to change the global heating trajectory. At least one change is definitely criminal, but it has the desired effect. (The ends justifying the means?)
Whatever one thinks about the plot and the protagonists, it is a story that weaves multiple threads, both technological and social to try to achieve the goal, and therefore eschews the simple “one technological fix “approach.
Yes I’ve heard but now I’ll have to read. Considering the rights of future generations of humans reminds me of the Ecozoic movement where the rights of everything living in the biosphere count in the balance. Thomas Berry, the founder, had numerous taped lectures that are quite inspiring. He alluded to the nearly insurmountable difficulty of the work of culture changing and planet saving, but also the proportionate energy this work can liberate in one’s being.
It’s going to be a very long, difficult battle Project, what with the powerful vested interests attempting to stop progress. In a world full of national priorities that are detrimental to long term human survival it will be up to everyone that cares to put up a fight. Each person counts. I try to do something every day, such as fix even more carbon in my garden, use public transit, inform others about the growing crisis and what it really means for the future of their children (my neighbors now know a lot more than they once did a few years ago for example). I think a key part of all this will be to continue to spread the truth in the face of lies from people who appear to be growing increasingly desperate to shout facts down. Beware of easy, simple fixes as Alex says and don’t learn from random people in social media contexts without vetting the information. Be aware there are many lies and liars out there.
A good example of the deliberate abandoning of any climate action and even worsening the situation. Shell boss under fire for saying cutting fossil fuel production is ‘dangerous’.
The sooner Ecocide is established as a crime against humanity by the ICC the better.
‘Lavrentiy Beria, the most ruthless and longest-serving secret police chief in Joseph Stalin’s reign of terror in Russia and Eastern Europe, bragged that he could prove criminal conduct on anyone, even the innocent.’
“Show me the man and I’ll show you the crime”
Just as dangerous I would think of making ecocrimes because we are all guilty, maybe start those gulags in America for those past, present and future offenders….just incase. Will former president Trump be the first political victim for his stance on fossil fuels, it would not surprised me with the climate hysterists…
Climate change is an issue which me need to apply common sense to IMO and over time.
Going back to the sunshade been used for spacecraft power, if we can stabilise the lens against the solar wind and light pressure via active control using tethers/reflectivity or magnetic fields/ion drives using the solar wind as the free fuel. A way to use the power for spacecraft may be to say have the solar concentrator power plants produce laser light that is directed perpendicular to the lens construction. We could have a central laser system surrounded by another large lens, the laser light hits the spacecraft and is reflected back through the surround lens onto a much heavier dumb reflector. The laser light would be bounced back and forth taking advantage of recycling of laser light and importantly counter act the momentum destabilising effect of the laser light.
Not suggesting this as a counter to ecological solutions here on Earth, but want to go back to the topic of making use of L1. I suspect that hardware delivery solutions there will be / would be costly into the foreseeable future. [And the unforeseeable one is an even bigger bother.] But I would like to suggest that comets in this instance give some inspiration. When one considers how insubstantial a comet’s tail is and how efficiently it reflects sunlight, it would seem that existing space technology should aim for “specific reflectance” for the kilogram of fluid or dust released at L1. A ton of properly selected dust, fluid or both should be targeted to deflect or reflect sunlight away from the Earth. Even local illumination at L1 with local heating could end up as a net
flux loss in the direction of Earth.
An expanding or renewed cloud at L1 could deflect or reduce incident sunlight over the celestial arc width. If a cloud of dust and droplets covers an L1 domain about 20,000 km wide or high, that should be the region where it needs to do its job, cutting incident light on Earth. If the cloud disperses, send up another barrel full and pop it open.
This does not necessarily stop global warming – for a number of reasons. But it would interrupt its progression. Meanwhile, economic and energy transition, shoreline levies and everything else contemplated will likely have to continue.
But our capabilities to engineer in space will not be standing on the sideline either.
I was also thinking in this direction. The parameters in the article sound much like those for a cloud of dust. A trillion atoms per particle would be enough to keep it from dispersing thermally very quickly. Speculation: a dustcaster on the Moon might continually shoot silicon grains at L1 as the associated oxygen in regolith is extracted for other purposes. I wonder if it would be feasible to give the particles a small positive charge during launch, then stop them roughly at L1 by spraying them with an electron gun?
It would still surely be a colossal engineering project requiring industrial levels of space-generated electricity. And for our discussion, it doesn’t provide an interstellar space launcher. Or does it? The frontier of modern science is mostly a matter of efficiency. What if you could fabricate each grain of dust as a maneuverable spacecraft capable of responding to commands — a fleck of perfectly flat crystal “light sail” capable of rotating itself in space to precisely reflect in any given direction? I wouldn’t be overly surprised if some nuclear defense like this has already been attempted, as it recalls decades-old notions of “smart dust”. An enemy can’t blow up your space light weapon if it is spread out over hundreds of cubic kilometers. The toughest question to answer is how such a thing could be built, yet not soon abused for wicked purposes.
Hello, Mike.
One of the introductory astronomy books I read in grade school made the point that a comet’s tail spread out across the celestial sphere a la Halley’s, had about as much mass as a small automobile ( a VW Bug sticks in memory).
Similarly, zodiacal dust at the lead and trailing L4 andL5 serves as another example. For observing planets from interstellar distances, its presence, whether from Lagrangian points or annular distribution, poses a difficulty for observing planets from outside the solar system or around another star.
An Ariane V class payload on order of the JWST would provide about 10 x more than that.
The effectiveness of such a literal dump can be measured by direct line of sight opacity and scattering. These results can be obtained by a number of methods: absorption into a cloud and re-radiation at or scattering. But the overall effect is ( or should be) a reduction of direct light flux to the Earth’s surface. Solutions where there is an increase are possible, I would presume, but sometimes one would expect randomness to be courteous enough not to cause a stream to run back up a hill.
Spacecraft tend to draw Lissajous figure orbits about Lagrangian points. The velocity impulses need to maintain a trajectory in a Sun Earth Lagrange point or diminutive compared to other orbital operations. And quite possibly, if such a program of establishing a light fading operation in the Sun Earth LOS, other spacecraft or observatories could be steered clear. But if this is really a matter of terrestrial habitability, more drastic work arounds will be more than simply “admissible”.
Obscuration of sunlight occurs in many forms in the Earth’s atmosphere. The trick is to select the most suitable means in this environment. And I believe that comet tails give us a valuable lead on this problem.
Hello Paul – I think you’ll be intrigued to see the work of our research group at the Planetary Sunshade Foundation. We’ve developed some of these ideas quite a bit further, and we’d love to connect.
Will be glad to give your site a look, Morgan. Thanks.