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Decluttering low-Earth orbit: It's time to tidy up space

economist.com

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Re: Decluttering low-Earth orbit: It's time to tidy up space

#61

Post by sandworm101 »

crazygringo wrote: post #57
sandworm101 wrote: post #35

What people forget is all the natural junk up there. Space is not "clean". Something like 100 tons of rock, mostly dust, falls onto earth from space every day. That isn't stuff in orbit, but given the capture effects of our moon there is likely a significant amount that does achieve some sort of stability. That amount probably outweighs everything we have ever put up there. https://astronomy.com/magazine/ask-astro/20…

But there's an enormous difference between cosmic dust, which generally doesn't pose any threat to satellites or spacecraft, and the man-made "junk" that are essentially destructive whizzing bullets, cannonballs, and worse. The total mass is essentially irrelevant, what matters is the mass of individual objects. > Or, at least they are in orbits where danger from natural debris is vastly greater than from space junk.…

>> natural debris and space junk are tied 1-1

There are plenty of sats that have just stopped working, even broken apart, for unknown reasons. Telling the difference between a defect and a meteor impact is mostly impossible. Lots of spacecraft have just stopped working for unknown reasons. Until we start inspecting every failed satellite, as we do aircraft, we won't really know.

And note where the 2009 collision happened: over the arctic. This was one polar orbit colliding with a near-polar orbit, right in the danger zone I mentioned above.

Re: Decluttering low-Earth orbit: It's time to tidy up space

#62

Post by BurningFrog »

MauranKilom wrote: post #33
f-word wrote: post #19

Suppose you put a largeish amount of polyurethane foam in orbit, possibly around some scaffold to take up even more space, had it inflate when up there and had it absorb any wandering garbage for a while. How long would it take for the giant garbage mound to deorbit and burn?

I'm not exactly sure how you imagine the collisions to play out. If you think anything gets "stuck" in your foam, you're underestimating the speeds at which objects in orbit move. It's more like shooting a railgun at your impactor. I also recommend Netwon's impact depth approximation: https://en.wikipedia.org/wiki/Impact_depth For the purposes of deorbiting junk it may be sufficient to just impart some delta-v, but y…

I don't have a good feel for the numbers either, but surely if you make the Space Sponge big enough, things will get caught in it.

There is almost certainly a better material to use as well, but I don't think either of these practical concerns invalidates the idea.

Of course, big enough Space Sponges to make a practical difference would be very visible to the naked eye.

Re: Decluttering low-Earth orbit: It's time to tidy up space

#63

Post by jerf »

f-word wrote: post #28
jl6 wrote: post #21

Earlier quoted context omitted.

There’s a lot of junk but it’s spread out over a lot of space. You probably won’t catch much by accident. Also, it may be going dramatically faster than your catcher, in which case it would be less like a mitten catching a ball and more like a mitten catching a bullet.

Sure, but there's also a lot of uh mitten in this case, getting progressively denser as more stuff gets trapped in it. I don't think there's that many ways to trap all the tons of hyperfast shrapnel we've up up there, unless we can get starlink to just sporadically throw small nets around in hopes of catching enough junk on any given throw?

No, your "mitten" is getting blown apart, not getting progressively stronger. Your intuition is not tuned for space. Imagine trying to strengthen a structure by firing extremely high-powered bullets at it. "I have a tree near my house that is about to fall on us... how should I fire my high-powered rifle at it to reinforce it so it stays up?"

Re: Decluttering low-Earth orbit: It's time to tidy up space

#64

Post by Tuna-Fish »

gchamonlive wrote: post #39
copperwater69 wrote: post #13

Earlier quoted context omitted.

Imagine two objects hitting each other perpendicularly, as opposed to head on. Plenty of momentum could be conserved and thrown out in a median vector. Edit: Not only that, but even if 90% of momentum was lost - it only takes another satellite going in the opposite direction to supply all the energy. Here's what 2 ounces of plastic does at 15,000mph to a block of aluminium. https://imgur.com/gallery/8NwAhgK

It depends on the material. If they are flexible, and deform easily, a lot of energy would be converted into structural damage, I would presume. > it only takes another satellite going in the opposite direction to supply all the energy I see, indeed the next collision will supply a lot of external momentum.

Material properties essentially become completely irrelevant when things hit into other things at speeds that greatly exceed the speed of sound in either material. At that point, you get best results if you just model both objects as fluids.

Re: Decluttering low-Earth orbit: It's time to tidy up space

#66

Post by dylan604 »

crazygringo wrote: post #57
sandworm101 wrote: post #35

What people forget is all the natural junk up there. Space is not "clean". Something like 100 tons of rock, mostly dust, falls onto earth from space every day. That isn't stuff in orbit, but given the capture effects of our moon there is likely a significant amount that does achieve some sort of stability. That amount probably outweighs everything we have ever put up there. https://astronomy.com/magazine/ask-astro/20…

But there's an enormous difference between cosmic dust, which generally doesn't pose any threat to satellites or spacecraft, and the man-made "junk" that are essentially destructive whizzing bullets, cannonballs, and worse. The total mass is essentially irrelevant, what matters is the mass of individual objects. > Or, at least they are in orbits where danger from natural debris is vastly greater than from space junk.…

a rock the size of pebble or as small as a grain of sand will cause a very bad day when you realize that some of the objects have incredible amounts of kinetic energy due to the speeds involved (the speed of the rock or the speed of the thing to be damaged).

Re: Decluttering low-Earth orbit: It's time to tidy up space

#67

Post by SilasX »

tempest_ wrote: post #55
tomhoward wrote: post #17

Fun fact: A hobby satellite my father helped build as a way to justify procrastinating during university in the late 60s is now low Earth orbit space junk. He says he's rather embarrassed to have learned, post launch, that it would likely remain in orbit for 100,000 years. https://en.wikipedia.org/wiki/Australis-OSCAR_5 http://centralblue.williamsfoundation.org.au/oscar-5-the-fir... https://www.youtube.com/watch?v=hj…

And here it is! http://stuffin.space/?intldes=1970-008B

Wow, that’s a cool site! I’ve never seen orbiting satellites visualized like that. (But of course, also haven’t sought any out.)

Re: Decluttering low-Earth orbit: It's time to tidy up space

#68

Post by rocknor »

Noxmiles wrote: post #16

Meanwhile india: https://en.wikipedia.org/wiki/Mission_Shakti btw: The article is behind a paywall :(

Meanwhile USA has 25x the debris (as of June 2019). Glass houses...

https://orbitaldebris.jsc.nasa.gov/quarterly-news/pdfs/odqnv...

https://www.businessinsider.in/us-russia-china-and-india-sta...

Re: Decluttering low-Earth orbit: It's time to tidy up space

#69

Post by Zenst »

sandworm101 wrote: post #43
tomhoward wrote: post #17

Fun fact: A hobby satellite my father helped build as a way to justify procrastinating during university in the late 60s is now low Earth orbit space junk. He says he's rather embarrassed to have learned, post launch, that it would likely remain in orbit for 100,000 years. https://en.wikipedia.org/wiki/Australis-OSCAR_5 http://centralblue.williamsfoundation.org.au/oscar-5-the-fir... https://www.youtube.com/watch?v=hj…

Your father's satellite is very high (1400km, 1000km above the ISS) at the edge of what is classified as low earth orbit. It will be up there for a long while but the chance of it ever hitting anything is infinitesimal.

I wonder how the odds stack up against the odds of a human being hit by a meteorite? Those kind of odd's/statistics I can get my head around.

Re: Decluttering low-Earth orbit: It's time to tidy up space

#70

Post by gchamonlive »

Tuna-Fish wrote: post #64
gchamonlive wrote: post #39

Earlier quoted context omitted.

It depends on the material. If they are flexible, and deform easily, a lot of energy would be converted into structural damage, I would presume. > it only takes another satellite going in the opposite direction to supply all the energy I see, indeed the next collision will supply a lot of external momentum.

Material properties essentially become completely irrelevant when things hit into other things at speeds that greatly exceed the speed of sound in either material. At that point, you get best results if you just model both objects as fluids.

interesting insight! thanks
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