3 ms·

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 altoge

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.

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.