FCC approves test of space mirror to light night sky • Hacker News Board

Re: FCC approves test of space mirror to light night sky

#161

Post by cyberax » Tue, Jul 14, 2026, 4:37 AM UTC

echoangle wrote: post #149

cyberax wrote: post #86

Earlier quoted context omitted.

You can't focus sunlight at the satellite distances. And this is a fundamental problem, the focal distance varies for each wavelength so your focus point will be smeared. You need monochromatic light for that (a laser). Edit: and also don't forget that the Sun is not a point source and has an appreciable angular size, further making it impossible to focus it with a reasonably-sized lens or mirror.

I see your point for lenses but how would that happen with mirrors?

Yeah, you are correct. The mirrors are not affected by the wavelength, though they are affected by the non-zero angular size of the Sun.

There are some non-linear effects that _are_ dependent on the wavelength, but not important to matter here.

Re: FCC approves test of space mirror to light night sky

#162

Post by Robotbeat » Wed, Jul 15, 2026, 12:18 AM UTC

Robotbeat wrote: post #157

ben_w wrote: post #156

Earlier quoted context omitted.

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? >…

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.

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

Re: FCC approves test of space mirror to light night sky

#163

Post by ben_w » Wed, Jul 15, 2026, 9:52 AM UTC

Robotbeat wrote: post #162

Robotbeat wrote: post #157

Earlier quoted context omitted.

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.

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

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.

Re: FCC approves test of space mirror to light night sky

#164

Post by kadoban » Fri, Jul 17, 2026, 3:35 AM UTC

kube-system wrote: post #159

kadoban wrote: post #116

Earlier quoted context omitted.

It's possible, it would just be _very_ dumb. It'd also turn into just...shooting them all down, restrictions of who anything is over wouldn't survive.

It wouldn't be an all-or-nothing type scenario -- and in fact there is already no common international agreement about where a nation's boundary extends to in the z-axis. The observed limit is "however high that country can detect and shoot something down"

Once you start getting shooty up in space, I think you fairly quickly get into https://en.wikipedia.org/wiki/Kessler_syndrome cascades of collisions and debris anyway, so it probably wouldn't matter.

> in fact there is already no common international agreement about where a nation's boundary extends to in the z-axis. The observed limit is "however high that country can detect and shoot something down"

That's the thing though, if you use that definition then 99.9+% of them are fair game, because _only_ ones around equator at a specific height are at a fixed point. Otherwise they migrate a lot and what country they're over would depend on what second you look.