Their brightness is a mixture of a lot of things, including the huge PV arrays and the angle they have with the sun when they cross the terminator between night and day.

Starlink have already put a lot of effort into their satellites being much less bright than most satellites, including tilting their PV away from earth during the terminator crossing, so from what I've read you'll mainly see them while they're being deployed and while de-orbiting.

(Part of my still-expanding draft blog post about space data centres is to work out how bright a million much larger objects would look. If they were in the orbit with the most sun, that's a terminator-following sun-synchronous orbit, which is maximum brightness).

Would the “datacenter” satellites be much larger? I thought each of them was only going to carry a rack or a cabinet worth of GPUs?

Much larger.

The compute part may be a rack or a cabinet worth of GPUs (though TBH the public designs are currently vague to the point of being artistic impressions), but they also need to come with a PV array big enough to power that, plus a cooling array that's going to be close to 25% as big as the PV array regardless of what unit size they go for in the end.

If they settle on making e.g. 120 kW satellites, that would be about 400 m^2 for the PV and another 100 m^2 for the radiator.

Have you seen Real Engineering's analysis? https://www.youtube.com/watch?v=_qpdUNMt2yg

Yes; their video pertains to two specific proposals for the data centres, unfortunately I am finding that *all* the various proposals fail to make sense but for different reasons.

Yes but would these need to be in LEO? I would imagine that they would aim for farther orbits to spend a smaller percentage of their time in Earth's shadow

Perhaps there will be communications nodes in LEO with high bandwidth directional links to heavy compute nodes in higher orbits? At some point I would assume that the jurisdiction of the FCC no longer applies? Or maybe you use laser links?

I still cannot believe it's economical to have "data centers in orbit" but I guess the truth will be seen in whether or not it actually happens.

> At some point I would assume that the jurisdiction of the FCC no longer applies?

The FCC has regulatory jurisdiction for communications on US objects in space, regardless of distance from earth.

Depends how cheap they can launch them.

Even very optimistic estimates (by people who aren't Elon Musk) say it will take a decade to get the costs low enough to be worthwhile for LEO; higher orbits are much more expensive.

They would be as large as your average hyperloop capsule.

I watch them come up over the horizon right after sunset. Only a couple specific trajectories are visible and they disappear pretty quick. Later on in to a clear night and after your eyes adjust to the darkness, you can find them all over the sky. They look like very faint stars speeding around. It's quite spectacular and hunting them makes for a fun activity with others while relaxing in a hot tub.

Out of interest, where are you on this scale? I don't think I've ever been better than a 6 from those star pictures, despite how I'd otherwise categorise where I live as suburban/rural transition: https://en.wikipedia.org/wiki/Bortle_scale#/media/File:How_l...

On a good night, around 5

Anything up there needs to reflect as much as possible to avoid building up heat. That which it can’t reflect is absorbed and needs to be emitted as efficiently as possible. Vantablack would likely make it absorb heat readily and glow in the near-IR.

This is a bit like suggesting we slather cars in vaseline to prevent traffic jams.

Maybe we could just blast Anish Kapoor into space on a one-man prison vessel instead?

Counterintuitively, the best way to make satellites less visible for ground observers is actually to make them MORE reflective. You want the reflection off the nadir side of the vehicle to be as specular (mirror-like) as possible so that the light reflected from the sun only makes it to a single point on the Earth's surface.

You can see that SpaceX (and probably other LEO operators as well) are already doing this: https://www.youtube.com/watch?v=rfJWli7YKPw

This video is a good visual illustration of that effect: https://www.youtube.com/watch?v=w8I25H3bnNw

It’s not the visual that bothers me. It’s the evidence of a monopoly that is being built that will dominate humanity for the benefit of literally one person

Lucky for us that he cares about humanity But others have similar ambitions and are making progress.