- #1
OwlHoot
- 9
- 1
- TL;DR
- Solar shield whose rotation cancels out net effects of photon pressure over the course of an orbit
It is widely accepted that global warming caused by accumulating greenhouse gases is happening and, as the late Isaac Asimov pointed out years ago, even if or when this is curbed, if the population remains at similar levels as now then just the waste heat from human activities will eventually be an equally serious and even more intractable problem.
One obvious way to reduce heat is to launch and install in near-Earth space large reflective mirrors to divert some sunlight away from the Earth. These could be either positioned at the L1 Lagrange point or closer in orbit round the Earth. But in either case, assuming the mirrors were large, for example a hundred mile wide disk of ultra-thin silver or the like, there's a problem: photon pressure, which will propel them away from where they need to be!
So (getting to the point) I wondered if it would be possible to design for an "unpowered" orbiting mirror a combination of rotation, possibly involving multiple moving parts, over the course of an orbit such that the photon pressure exerted toward the Earth when the mirror was between the two, or in what might be called the "near half" of its orbit, could be compensated by pressure exerted away from the Earth over the rest of the orbit such that it maintained stable, albeit perturbed, orbits over time.
Perhaps some design involving rotating slats like a steel blind, with offset "guide mirrors" at either end to turn the slats would work, analogous to the guide vane at the top of a windmill to keep it turned into the wind.
This might make a good undergrad physics project, if it hasn't already been done. The design would have to be pretty simple and, if possible, should not rely on powered propulsion (although perhaps a few solar-powered electric motors would be allowed, if that helps or turns out to be indispensable).
Regards
John R Ramsden
https://highranges.com
One obvious way to reduce heat is to launch and install in near-Earth space large reflective mirrors to divert some sunlight away from the Earth. These could be either positioned at the L1 Lagrange point or closer in orbit round the Earth. But in either case, assuming the mirrors were large, for example a hundred mile wide disk of ultra-thin silver or the like, there's a problem: photon pressure, which will propel them away from where they need to be!
So (getting to the point) I wondered if it would be possible to design for an "unpowered" orbiting mirror a combination of rotation, possibly involving multiple moving parts, over the course of an orbit such that the photon pressure exerted toward the Earth when the mirror was between the two, or in what might be called the "near half" of its orbit, could be compensated by pressure exerted away from the Earth over the rest of the orbit such that it maintained stable, albeit perturbed, orbits over time.
Perhaps some design involving rotating slats like a steel blind, with offset "guide mirrors" at either end to turn the slats would work, analogous to the guide vane at the top of a windmill to keep it turned into the wind.
This might make a good undergrad physics project, if it hasn't already been done. The design would have to be pretty simple and, if possible, should not rely on powered propulsion (although perhaps a few solar-powered electric motors would be allowed, if that helps or turns out to be indispensable).
Regards
John R Ramsden
https://highranges.com