It seems to me that there’s a lot of math in the middle of this that just doesn’t matter that much: every photon hitting every part of the array is going to add energy. Whatever percent we transform into data doesn’t matter — all the energy from all those photons minus energy used for station keeping needs to be radiated away. I guess if some is used for station keeping so much the better.

I was hoping to read about what exactly these ‘heat pump radiators’ look like, but I guess ultimately they’re going to be lasers or flashlights or some such thing.

A relativity course question I recall from my youth asked how long an astronaut stranded 1km from a ship would need to point the flashlight away to return to the ship based on the mass of the photons leaving the light — spoiler - this can work in time to save an astronaut’s life — double spoiler: if you’re really accurate, it’s better to throw the flashlight if you’re in a hurry.

As I write this I realize my physics model is super weak, because I’m not sure what percent of the energy used to make a photon turns into the photon’s mass (and therefore is pushing against the laser), and what is in light and therefore just, you know, carries on for billions of years until it hits something else.