I’m no optical physicist, but based on empirical evidence of not melting due to light arriving from a huge ball of thermonuclear fire 8 light minutes away (and sure it’s not exactly focused), I propose a hypotesis that light-based energy transfer in atmosphere is very lossy and not feasible as a weapon.
Which is perfect for this community, of course.
Why do people claim the inverse square law applies? The light has already travelled 147 million km, another 500km from the earth back to the satellite is mathematically insignificant, it’s a rounding error.
It holds if the light spreads wider than the target. So also for directed light sources at large enough distances. Even a perfect mirror must spread the light in the same angle as it is incoming. Hence the beam would at least 3 km wide at the satellite. Therefore the satellite can only recieve a Illumination of ~65W/m^2 which is a few percent of the normal sun brightness of 1300 W/m^2 in space.
Another way to look at it, the mirrors cant make the sun seem brighter only larger. From the tower you see a large solid angle around you the mirror, therefore, it can seem like you are at the surface of the sun. However, fro. the position of a satellite, the power plant only takes a small solid angle, so it seems like a “smaller” sun. Assuming 400 MW and 1 kW/m^2 (at surface) solar power, it has an area of 400000 m^2, so a solid angle of 4.5e-6 sr from 300km while the sun has 70e-6 sr. So ten times smaller, therefore weaker. Note however here i did not account for attenuation in the atmosphere
Atmospheric attenuation of light is a real thing and the intensity of solar radiation is less on the surface.
https://pace.oceansciences.org/images/Solar_spectrum_en_v5.jpg
So, the light from the sun is very spread out. This is why it doesn’t hurt you. When you take almost all of the light from a large area and focus it to a point, it starts to add up fast.
You can test this with a leaf and a magnifying glass. The mirrors in this scenario are acting as a giant lens.
The biggest question is whether the mirror array is large enough to redirect enough energy to make it though the atmosphere.
It would likely be probable if the facility was specifically designed to do this.
