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Comment by eloff | Hacker News Reader

That's got to be the cheapest solution to global warming I've heard of. I wonder what problems there are with it. The nice thing about it is if things start getting chilly (as we move into another glacial period one day) we can simply remove some of the shades again. The increased CO2 means more vegetation growth, which is nice. The only real problem at that point is ocean acidification, which I think won't be reversed by cooling things down again.

I wonder if we will one day regulate our climate on earth by shading hot areas and pointing mirrors at cold ones. There are all kinds of knock on effects of doing that, but it seems like a human thing to do. Modify the environment instead of adapting to it. That's kind of our thing.

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Stratospheric Aerosol Injection [1] for emergency cooling sounds relatively cheap too, and has the advantage of a) mimicking a well-studied natural process and b) being inherently self-limiting. Your "if things start getting chilly" fallback may not be viable if e.g. a Kessler cascade locks us out of orbit.

[1] https://en.wikipedia.org/wiki/Stratospheric_aerosol_injectio...

> The only real problem at that point is ocean acidification, which I think won't be reversed by cooling things down again.

From what I understand, it will help... eventually.

If ambient temperatures come back to normal, then the ocean won't absorb as much CO2.

Yes, I think so. I wonder by how much.

The bigger issue is the large amount of co2 that the ocean will quickly release back into the atmosphere as temperature and partial-pressure drop.

It would be better if we could come up with a way to neutralize / sequester the co2 already in the ocean.

That's Project Vesta: https://projectvesta.org/

Basically, artificial green-sand beaches which absorb CO2 as they weather.

That's the cheapest you've heard of? Have you heard of carbon pricing? https://www.reddit.com/r/worldnews/comments/bxgd5p/single_mo...

Carbon pricing sounds like a cheaper and a more direct solution addressing the cause of the problem (more greenhouse gases in the atmosphere) instead of its effect (temperature rise). What could go wrong?

A solution to warming? Maybe. A solution to ocean acidification? No.

Removing the shades would be quite hard, dare I say impossible to do in large quantities. Fortunately you don't need to do so; they will eventually drift away under solar pressure. So if you don't need them anymore, stop refreshing the pack and it will eventually disperse, whereas if you need more, launch more.

Or just orient them sideways to block less light. That shouldn't cost much fuel, if any (using reaction wheels). I think it would be best to keep those at hand, just in case.

If feasible at all, make a part of those shades photovoltaic panels, and beam the energy back using microwaves, as that would provide an extra incentive to launch that (GEO might be more useful for that kind of setup, I have no idea what deltav it would take to transfer to/from both, but you could use ion thrusters since you have on-board power).

How do you orient them? The dumb ones weigh 1g. How much will they weigh if they're smart, powered, and have reaction wheels for orientation? That's orders of magnitude again.

Better to send up 10,000X dumb shades with random orientation and spin. Not only are the dumb ones much lighter, they're proportionally much cheaper too, since they're basically just structured aluminum foil rather than needing thrusters, reaction wheels, computers, etc.

Is there any way to "bleed" more heat (other than making the atmosphere thinner, which is obviously a double-edged sword, and not feasible anyway).

Would be interesting to keep inflow the same and reduce outflow, but I have no idea what I am talking about.

Reflective roofs/walls of buildings, basically make more IR and heat energy get reflected away from the surface.

You don't really make the atmosphere thinner by removing CO2 or methane...they are trace gasses relative to N2 and O2, CO2 is less than a .05% of the atmosphere, IIRC. So, you mostly want to prevent heat from hitting the Earth, or decrease the absorption (increase albedo), or you want to remove the heat-trapping gasses that will continue a warming cycle by trapping the heat we do get.

I think space sunshade's a decent idea, but we still need very aggressive decarbonization, as CO2 is very bad for the ocean, nevermind the heat trapping.

I have encountered reflectors that actually reflected visible light. I think they were called "mirrors". Maybe you have encoutered them too.

Infrared radiation only comes from things that have been heated (mostly) by that visible light. Any light reflected back into space without being converted to heat is energy that is somebody else's problem.

It would suck to have a world not too hot, but with no sea life left.

Allowing CO2 to increase without bound would eliminate the fisheries billions of people rely on for their protein.

So our solution to polluting our planet is to pollute the space around our planet as well?

What happens when those space shades get hit by micro meteorites causing them to alter or de orbit?

That's not comparable types of pollution. If it's something we put there on purpose and provides us a benefit, I'd say even use of the word pollution is incorrect.

I don't think there's a big micro meteorite problem at the Lagrange point, but if there were for arguments sake, then you need to plan for it and have a way to replace shades that get knocked out of position. It's not like the whole system would fail if you lose one shade. That's what engineering is about, planning for all the likely eventualities.

> What happens when those space shades get hit by micro meteorites causing them to alter or de orbit?

"0.6-meter diameter and a thickness of about 5 micrometers. The mass of each disk would be about a gram..."

Absolutely nothing.

I agree space pollution is a problem but I would imagine that these are thin enough that they would burn up in our atmosphere upon reentry if they de orbit onto earth.

The issue isn't whether or not they'll eventually deorbit and disintegrate on re-entry -- that's a given. The issue is that while they're slowly approaching the Earth, they're a hazard to spacecraft. Slamming into even a gram of mass at orbital velocities could damage a spacecraft.

L1 point is around 1,500,000 km from earth, they wouldn't be entering earth's atmosphere (unless we would want them to), interfering with any other satellites circling us or anything similar.

I'm not an expert but I would think gravitational forces could move them towards other bodies like Earth?

they would burn up in the atmosphere - they have not much mass individually

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