Comments by "XSportSeeker" (@XSpImmaLion) on "The Russian Space Mirror That Lit Up The Night" video.
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Since Reflect Orbital was mentioned, and commenters already pointed out EEVBlog's video on the subject, I'll make the shortest possible explanation I can do for their idea being completely unfeasible.
It's pretty simple... for illumination, this could've been a good idea all in all. As in producing enough light to be similar to moonlight. Hard, but doable. We actually don't need that much light to see at night, as your blinking alarm clock will tell you. xD Or that weak LED from your charger you can't even see during the day, almost blinds you at night.
For solar power though, moonlight is almost the same as nothing. Even at perfect atmospheric conditions, with a reflector the size of the moon, the most efficient theoretical solar panels would only be able to produce very little power, not enough to ever justify spending as much as it would putting those space mirrors in orbit.
You might think this is a matter of efficiency, but it's actually a matter of the difference we cannot see with our own eyes, because of how flexible our vision is. If you measure with sensors though, then you get the difference. For instance, broad daylight in perfect conditions is something like 120 thousand lux. Moonlight in perfect conditions is bellow 1 lux. That's the harsh reality of it.
To make things worse for Reflect Orbital, their plans are about a constellation of small satellites.
The thing about putting any sort of reflector in orbit is that there is no secret or complex math about it - you can only reflect as much as the size of the mirror, again, given perfect ideal theoretical conditions that don't really exist in practice. You'll always have losses along the way - reflectance of the material, atmospheric conditions, light scattering, etc.
So say you have a 100 sq meter big reflector in orbit there. Being very generous, I think their proposed mirrors are way smaller than that.
You will only be able to reflect max 100 sq meter worth of whatever sunlight the mirror catches, minus atmospheric scattering, minus losses because of weather, material, warping, and so on. It doesn't matter if you focus the light to a single point, or open it up to cover 5 sq km worth of area, the amount of light reflected will still be at most 100 sq meters of direct sunlight. You cannot reflect more than what the mirror captures.
Get the issue there? It means that in order for you to produce significant power during the night, you'd need a mirror or several mirrors that are close to the size of a solar farm. Even at small scale, we're talking acres here, not just a few hundred meters.
Let's say you are ok with capturing very little power, so you don't really need impossibly huge mirrors or huge arrays of them - would that even be worth the price of launching all those satellites in orbit?
That's not even to mention all the worries about disrupting eco systems and whatnot.
You know what I think would be a still very hard but more feasible solution? A global interconnected power grid.
The Sun is always shining somewhere on Earth, and it's shinning mostly directly.
I guess mirrors could come into the fray when we're talking about the Pacific side of the planet, but that's something for the far future. Perhaps by then, we'll have already gotten to feasible nuclear fusion...
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