Comment by GistNoesis
13 days ago
It boils down to building big surface area mirror cheap enough. Once you prove there is business demand, and you have your cheap Mylar satellites working, you scale your system up with better technology.
Of course they don't reveal their neat trick now because from a strategic point of view it would be bad, because other people would copy them, and probably outpace them.
Once it's only a physics problem, it becomes quite easy. Here are two potential solutions to the physics problem : Liquid mirrors, and plasma mirrors. The easiest being the liquid mirrors so let's explain this one. In fact it's so easy, it's child play.
Have your kids ever played with soap bubble : It's the same thing but in space. You make a big ring (roughly of the same area of the spot you are trying to make on the ground) (thin circular wire that you fold so that it will unfold itself like these tents) and you flow liquid metal (like mercury) on top to form a thin layer, hold by surface tension (and eventually electric field to have finer control of the shape or the surface).
The mirror will be a few atoms thick, a design that must be fabricated in space directly. It's just that we are not used to thinking with low force zero gravity environment. You don't use motors to move your mirror, you use fields spawned from precisely positioned points (and you have to compensate for solar winds).
Of course there are still technological problems due to the harsh conditions of space, but it's not something unheard of : https://engr.ncsu.edu/news/2024/03/06/reflecting-the-future-...
> You make a big ring (roughly of the same area of the spot you are trying to make on the ground)
Unfortunately, this is not how the size of the spot on the ground is decided. Sunlight, even if reflected by a perfectly shaped mirror, spreads by approx 1 meter every hundred meters. At the "edge of space" at 100km, your spot already has a 1km diameter, in reality with a higher orbit and imperfect mirror & tracking it will be much larger. The size of your (ideal) mirror decides the brightness of the spot, not the size of the spot.
Liquid mirrors in space seem like a cool concept though!
The area comment was more relative about the power received : To be able to have the power on the ground you need to reflect it from space (pointing the obvious that with 100sqm of surface area, you can't collect more power than surface area * power density). You also don't want to overheat everything (otherwise you need sun towers instead of solar panels), so a ball park of around 1:1 is a good starting point.
To focus light, the ideal shape is a parabola, and it's a shape that occur naturally when you spin liquid in gravity. (Their are process to build big telescopes which only point up). Of course you don't have gravity anymore, but you can pull on your surface with fields, or you can have concentric rings that you align more or less along the axis to deform the surface. We don't need perfect focus just a rough spot.