5 ms·

A sunshade is also a strategic weapon, from the POV of those nations whose insolation may be blocked (or even increased, using reflectors) at the whim of the fo

A sunshade is also a strategic weapon, from the POV of those nations whose insolation may be blocked (or even increased, using reflectors) at the whim of the foreign policy of the national power that controls the sunshade. Not saying it's impossible or impractical, but the political consequences are non-trivial ... imagine being able to shave 10% off a nation's photovoltaic power capacity if they don't knuckle under to trade demands, or to mess with their storm frequency/weather patterns. It's a huge can of worms.

blkhawk 7y ago
not really because its so much hassle to even block the 2-4% of sunlight - there is no way to "focus" the shadow - reflectors are a whole different thing altogether
- raducu 7y ago
  Is there a reason why you couldn't close some shades and open others to roughly guide the shade on a specific area on Earth? ( besides the fact that you need to have much higher shading capacity if you want to be able to significantly shade just one region)
  - blkhawk 7y ago
    the shades aren't even visible from earth. they are like dust or fog that don't let 2-4% of sunlight through. To have "sharp" shadow like you are proposing you need to have a lot more shades (say 10 times as many) in a completely different (lower) orbit. they would also need serious station-keeping and control since they need to stay between earth and the sun. I think they would need at least hundreds of meters of delta-V a day
  - Tuna-Fish 7y ago
    That plan involves putting sunshades in L1, where most shades are visible from every sunlit point on earth. So you don't get to be picky, every shade shades everyone evenly. There are other suggestions for placing sunshades in MEO. Each shade there is ~60% less effective than it would be in L1 (because of the time it would spend not shadowing any part of earth), but it is much closer, so putting them up there would be easier and cheaper. Those could in theory be regional. However, it's been pointed out that sunshades would also necessarily be pretty damned good solar sails, so they might well make their own way to L1.
    - beerandt 7y ago
      >~60% less effective Is that strictly due to time when it's casting a shadow, or does that take into account the geometry of the shadow cast and the flux density of the sunlight at each point (watts/m2)? That'd be an interesting calculation to see.
    - peteradio 7y ago
      Why would they end up at l1? Wouldn't they get pushed away?
    - raducu 7y ago
      Yeah, I guess with very thin shades reflection is the only way, maybe if those were thicker and good heat conductors, you could shape them like very wide triangles and radiate the heat just a couple of degrees to the side, still protecting the Earth, but experiencing a lot less net force. If station keeping is needed, I would think you would want to make the shades as big as possible.
raducu 7y ago
A thing which costs trillions of dollars will probably not be overpowered -- so I presume at no point will it be able to dim the light by 10%, wouldn't that be overkill? Probably this will be governed by the UN. There could be some interesting implications if you do have active control -- like "should we cool this area to move this huricane". "Yeah, but we can't make it turn back over water, but instead of it hitting country A, it could hit country B".
- beerandt 7y ago
  If it's at the mercy of the UN, I doubt it makes it through the general assembly in any form, let alone past the security council. The nature of foreign policy would just make too many countries suspicious of ulterior motives.
marcosdumay 7y ago
> imagine being able to shave 10% off a nation's photovoltaic power While shutting down 90% of the agriculture output and completely messing with local climate.
toasterlovin 7y ago
Countries can just retaliate with nukes.
fragmede 7y ago
This has been the basis of my Elon Musk-as-supervillian plot. First, Tesla Roadsters and the batteries needed to power them, then SolarCity solar panels, and finally rockets? What is his plan? Tesla means a gigafactory’s worth of battery production, and the solar panels charge the batteries, but what are the rockets for? As discussed - a planet sized solar shade, casting the planet into darkness. Or at least into the shady side. Solar panels are mounted on the bright side of the solar shade, charging batteries on the shade. Those batteries get shuttled back to Earth on a rocket, and are replaced when the next rocket ship arrives. Musk becomes the primary provider of energy on Earth, selling energy where previously the Sun just gave the stuff away for free. Selling energy to all the nations of Earth, just to run LEDs in order to grow plants, proves to be very lucrative, but at that point, Musk has no need for money. All that’s left is for him to use this power to open a rift to the next dimension over to get power over life and death itself, and the SOE’s agents can’t stop him. Or are they? (Last part stolen from parent poster and isn’t the book I’d write. Big fan though!)
deleted 7y ago
[deleted]

blkhawk 7y ago

not really because its so much hassle to even block the 2-4% of sunlight - there is no way to "focus" the shadow - reflectors are a whole different thing altogether

raducu 7y ago
Is there a reason why you couldn't close some shades and open others to roughly guide the shade on a specific area on Earth? ( besides the fact that you need to have much higher shading capacity if you want to be able to significantly shade just one region)
- blkhawk 7y ago
  the shades aren't even visible from earth. they are like dust or fog that don't let 2-4% of sunlight through. To have "sharp" shadow like you are proposing you need to have a lot more shades (say 10 times as many) in a completely different (lower) orbit. they would also need serious station-keeping and control since they need to stay between earth and the sun. I think they would need at least hundreds of meters of delta-V a day
- Tuna-Fish 7y ago
  That plan involves putting sunshades in L1, where most shades are visible from every sunlit point on earth. So you don't get to be picky, every shade shades everyone evenly. There are other suggestions for placing sunshades in MEO. Each shade there is ~60% less effective than it would be in L1 (because of the time it would spend not shadowing any part of earth), but it is much closer, so putting them up there would be easier and cheaper. Those could in theory be regional. However, it's been pointed out that sunshades would also necessarily be pretty damned good solar sails, so they might well make their own way to L1.
  - beerandt 7y ago
    >~60% less effective Is that strictly due to time when it's casting a shadow, or does that take into account the geometry of the shadow cast and the flux density of the sunlight at each point (watts/m2)? That'd be an interesting calculation to see.
  - peteradio 7y ago
    Why would they end up at l1? Wouldn't they get pushed away?
  - raducu 7y ago
    Yeah, I guess with very thin shades reflection is the only way, maybe if those were thicker and good heat conductors, you could shape them like very wide triangles and radiate the heat just a couple of degrees to the side, still protecting the Earth, but experiencing a lot less net force. If station keeping is needed, I would think you would want to make the shades as big as possible.

raducu 7y ago

A thing which costs trillions of dollars will probably not be overpowered -- so I presume at no point will it be able to dim the light by 10%, wouldn't that be overkill? Probably this will be governed by the UN. There could be some interesting implications if you do have active control -- like "should we cool this area to move this huricane". "Yeah, but we can't make it turn back over water, but instead of it hitting country A, it could hit country B".

beerandt 7y ago
If it's at the mercy of the UN, I doubt it makes it through the general assembly in any form, let alone past the security council. The nature of foreign policy would just make too many countries suspicious of ulterior motives.

marcosdumay 7y ago

> imagine being able to shave 10% off a nation's photovoltaic power While shutting down 90% of the agriculture output and completely messing with local climate.

toasterlovin 7y ago

Countries can just retaliate with nukes.

fragmede 7y ago

This has been the basis of my Elon Musk-as-supervillian plot. First, Tesla Roadsters and the batteries needed to power them, then SolarCity solar panels, and finally rockets? What is his plan? Tesla means a gigafactory’s worth of battery production, and the solar panels charge the batteries, but what are the rockets for? As discussed - a planet sized solar shade, casting the planet into darkness. Or at least into the shady side. Solar panels are mounted on the bright side of the solar shade, charging batteries on the shade. Those batteries get shuttled back to Earth on a rocket, and are replaced when the next rocket ship arrives. Musk becomes the primary provider of energy on Earth, selling energy where previously the Sun just gave the stuff away for free. Selling energy to all the nations of Earth, just to run LEDs in order to grow plants, proves to be very lucrative, but at that point, Musk has no need for money. All that’s left is for him to use this power to open a rift to the next dimension over to get power over life and death itself, and the SOE’s agents can’t stop him. Or are they? (Last part stolen from parent poster and isn’t the book I’d write. Big fan though!)

deleted 7y ago

[deleted]