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Comment by whinvik | Hacker News Reader

I didn't quite understand what this meant from the headline. The introduction in the paper clears it up. The TLDR is that astronomers are concerned they won't be able to do space observations with so many satellites in the way, but SpaceX has optimized for some parameter the indicates this will not be an issue.

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The black paint also makes for stealthier capability in SpaceX's military satellites

https://wikipedia.org/wiki/Starlink#Military_capabilities

Guess they take "black projects" seriously!

There's an interesting question concerning why (most) US stealth aircraft are black. Black isn't the best color to make an aircraft invisible at night; a dark blueish gray is best for that. One possibility is that the radar absorbent material is inherently black so they don't have a choice, and indeed the U-2 was originally a dark blue color before it received a new black RAM paint. That is probably the real reason I think, but another possibility is that when missile and radar technology made visual intercepts less relevant, they were freed to paint these secretive aircraft a less optimal black, which everybody knows is the proper color for secretive aircraft.

Incidentally the new B-21 apparently won't be black. Maybe they have a new RAM paint formulation that doesn't force the choice of black.

Whatchu talkin' 'bout Willis? Neither the B-2, nor the F-22, nor the F-35 are black, they're all this bluish gray you mention, same as most non-stealth aircraft. The only stealth aircraft I can think of that was black was the F-117.

You're right that the F-22 and F-35 aren't black, but neither are they the blueish gray I'm talking about which is much darker: https://dragonladyhistory.com/2019/04/30/u-2-black-paint/ The B-2 also isn't very blueish, it's more on the dark gray end of the scale but I can see how that's subjective.

And you're forgetting the U-2 and SR-71, which lacked full blown RCS reduction geometry but were still fitted with the black RAM coating (the SR-71 also had some stealth geometry; that was the purpose of the chines.)

There's no stealth in space. Any sort of running electronics or photovoltaics will emit heat that can be easily picked up by spaceborne sensors. The strategic advantage for military satellites is going to be the fact that Starship can launch literal orders of magnitude more of them than the launch systems of rival countries, not the fact that they're painted black and thus marginally harder to spot from the ground with Mk. I Eyeball.

Is there a good reference on tracking satellites from their thermal signature? Couldn't find anything.

This is the most comprehensive debunking I’ve seen of the “stealth in space” concept: http://www.projectrho.com/public_html/rocket/spacewardetect....

This is one of the classic online nerd arguments, much of which is documented there. I’m a little terrified of reigniting the whole thing here and now to be honest, but if people want to get into it, have fun.

SBIRS is intended to use infrared to track ballistic missiles through all stages of flight, including decoys and debris released during the mid-course phase in space (so we know it's meant to be extremely sensitive, not limited to tracking hot rocket engines during the boost phase) Seems like a good bet that orbital systems with such sensors could be used to track LEO satellites too.

That’s weird, every ork knows purple paint makes it stealthy.

These will be still easily bright enough to be seen through a light pair of binoculars, so the claim that they won’t interfere with astronomical observations is a real stretch.

The problem with Starlink vs other satellites isn’t just the individual brightness but the vast number of them, and that they are often visible in a swarm.

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