[Robotbeat]

Launching a gossamer thin mirror in space is not very expensive. Broad strokes claiming anything launched to space is going to be a more expensive solution has to level with the fact that GPS and quite a lot of telecommunications and Earth observation seem to have incredible leverage if launched to space instead of just using ground based solutions.

[ben_w]

For this use, "gossamer thin" is unlikely. You want to control where you point the mirror, it needs a structure that not only doesn't flop around when you torque your spacecraft, but also doesn't have surprise vibrational modes that squeeze and expand the illumination zone.

(Things I'm learning while researching what is now looking like an eight thousand or more word blog post about why a different space thing, data centres, is also not a good investment; my guess is this would be less of a problem if you used mirrors like this to cool the earth by reflecting sunlight away instead of towards).

[Robotbeat]

I know for a fact it is gossamer thin. It does need structure, but there’s a fundamental limit to how small your spot size is anyway due to Conservation of Etendue, so small deformations aren’t a huge problem.

[ben_w]

You know "for a fact" anything about a tech which is currently in the experimental stage (or even "press release before first experiment" stage), in a field which has a famously large gap between theory and practice, confidently enough to assert it will definitely not suffer from the problems that mean the large sheet materials we already launch to space (space-qualified PV arrays) are much heavier than bare cells?

> Conservation of Etendue,

Sounds like you think I have in mind something like an Archimedes' heat ray. I do not see anything close to that for the presented satellites.

I would aver that the presented design is so far from being useful that making it useful requires solving enough engineering challenges to also enable an Archimedes' heat ray; but again: what is actually shown is not that.

The numbers I see from Reflect Orbital suggest they have an expectation of the apparent brightness fluttering by 5x from internal motion of the reflector. At the scale involved, may be easier to consider the imperfections/ripple as behaving the same as if some of the specular reflection becomes diffuse reflection.

[Robotbeat]

I know for a fact because I’ve dug deep into the field, colleagues work on it every day, and I’ve met and talked to the founders of Reflect, saw material samples of their mirror tech.

[Robotbeat]

I’ve physically touched the materials being used for solar sails and the lightweight mirrors.

[ben_w]

Unless you've also both massed the support structure (easy) and demonstrated that the support structure is sufficient in practice rather than theory (requires launching it), you're missing the point I was making by a mile.