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"Geoengineering" without saying which kind or at what scale is a bit too broad. Consuming less or putting solar shades in space may fit in that definition. I'm

"Geoengineering" without saying which kind or at what scale is a bit too broad. Consuming less or putting solar shades in space may fit in that definition. I'm more worried about taking intrusive measures (that probably have known or unknown yet disruptive side effects) to deal with symptoms instead of targeting the core problem. I don't know, like the solar shades of above or dumping iron in ocean instead of lowering extraction/burning oil/coal/gas or more or less harmless technologies of carbon capture. It may be too late to avoid some of the incoming damage that will cause what we emitted so far, but there is always space for worsening things even more.

PaulHoule 4y ago
I think the space sunshade is the optimal case for manufacturing with space materials. An asteroid like 24 Themis https://en.wikipedia.org/wiki/24_Themis https://en.wikipedia.org/wiki/24_Themis is rich in volatiles (carbon, hydrogen, nitrogen) and also in stony minerals. You'd need to send a factory that builds a larger factory, it is a lot like building a ship inside a bottle except it's the other way around, you're in the bottle and have to build the ship outside. What's funny about it is that you have to use the kind of chemistry that people use to capture carbon, make e-fuels, etc. on Earth. An asteroid like that has materials on it that are a lot like coal and you will have something that looks like a petrochemical plant that runs combustion processes but the carbon is too precious to vent into space so you will circularize as much as you can. There is also a large sail yard that makes something like https://en.wikipedia.org/wiki/IKAROS https://en.wikipedia.org/wiki/IKAROS basically large plastic films coated with layers of aluminum. it doesn't have to be high performance compared to other solar sails, in fact a heavier and less reflective sail will sit closer to Earth near the L1 point and be more effective at blocking sunlight. Some real headscratchers for me are: (1) Do you send people? If you don't you need to run the whole thing remotely and face a half hour latency when you're debugging problems. If you do then you have to build a habitat for the crew. (2) I think a good asteroid for this might be pretty gassy and if you start digging into it the gas will escape which is not only a precious resource but could be dangerous. You're going to have to do devolatilization at the very beginning when your stock of materials, storage tanks, and such are at the very lowest they'll ever be. The big advantage of this is that it won't have effects on Earth other than reducing sunlight. If I were going to write a science fiction story about this it might be a bit like Gundam in that the "Zeons" decide that sinful Earthers deserve to have their civilization fall and they send too many sunshades to L1 to drop sunlight and temperatures enough to crash agriculture. Maybe 1000 years later their descendants arrive on Earth... (One thing about Gundam is the giant robots are more plausible than the O'Neill colonies with large airspaces... I sketched out a minimum size Bernal sphere to be a really flashy destination in LEO and it needs 15 Starship loads of ammonia to make the atmosphere. It drives me nuts that some article gets published about making oxygen on the moon for people to breathe, which isn't really useful unless you can get 4 parts of nitrogen, helium or SF6 to go with it... If you try breathing pure O2 that's a sure way to "burn out" as opposed to "fade away" https://en.wikipedia.org/wiki/Apollo_1 https://en.wikipedia.org/wiki/Apollo_1)

PaulHoule 4y ago

I think the space sunshade is the optimal case for manufacturing with space materials. An asteroid like 24 Themis https://en.wikipedia.org/wiki/24_Themis https://en.wikipedia.org/wiki/24_Themis is rich in volatiles (carbon, hydrogen, nitrogen) and also in stony minerals. You'd need to send a factory that builds a larger factory, it is a lot like building a ship inside a bottle except it's the other way around, you're in the bottle and have to build the ship outside. What's funny about it is that you have to use the kind of chemistry that people use to capture carbon, make e-fuels, etc. on Earth. An asteroid like that has materials on it that are a lot like coal and you will have something that looks like a petrochemical plant that runs combustion processes but the carbon is too precious to vent into space so you will circularize as much as you can. There is also a large sail yard that makes something like https://en.wikipedia.org/wiki/IKAROS https://en.wikipedia.org/wiki/IKAROS basically large plastic films coated with layers of aluminum. it doesn't have to be high performance compared to other solar sails, in fact a heavier and less reflective sail will sit closer to Earth near the L1 point and be more effective at blocking sunlight. Some real headscratchers for me are: (1) Do you send people? If you don't you need to run the whole thing remotely and face a half hour latency when you're debugging problems. If you do then you have to build a habitat for the crew. (2) I think a good asteroid for this might be pretty gassy and if you start digging into it the gas will escape which is not only a precious resource but could be dangerous. You're going to have to do devolatilization at the very beginning when your stock of materials, storage tanks, and such are at the very lowest they'll ever be. The big advantage of this is that it won't have effects on Earth other than reducing sunlight. If I were going to write a science fiction story about this it might be a bit like Gundam in that the "Zeons" decide that sinful Earthers deserve to have their civilization fall and they send too many sunshades to L1 to drop sunlight and temperatures enough to crash agriculture. Maybe 1000 years later their descendants arrive on Earth... (One thing about Gundam is the giant robots are more plausible than the O'Neill colonies with large airspaces... I sketched out a minimum size Bernal sphere to be a really flashy destination in LEO and it needs 15 Starship loads of ammonia to make the atmosphere. It drives me nuts that some article gets published about making oxygen on the moon for people to breathe, which isn't really useful unless you can get 4 parts of nitrogen, helium or SF6 to go with it... If you try breathing pure O2 that's a sure way to "burn out" as opposed to "fade away" https://en.wikipedia.org/wiki/Apollo_1 https://en.wikipedia.org/wiki/Apollo_1)