[ben_w]

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).

[leetbulb]

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.

[ben_w]

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...

[leetbulb]

On a good night, around 5

[throwthrowuknow]

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?

[ben_w]

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.

[smallerfish]

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

[ben_w]

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.

[largbae]

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

[SoftTalker]

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.

[toast0]

> 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.

[ben_w]

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.

[pyrale]

They would be as large as your average hyperloop capsule.