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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

#81

Post by MauranKilom »

BurningFrog wrote: post #62
MauranKilom wrote: post #33

Earlier quoted context omitted.

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.

Well, the reason why I brought up Newton's impact depth formula is that it quite clearly shows you have to have enough "braking" material up there. Distributing it over a greater area reduces the effectiveness proportionally.

The problem in the end is launch costs. Yes, we're getting better, but that doesn't mean we can shoot up a "visible to the naked eye"-sized impactor. Not to mention what difficulties an object of that size would bring for non-garbage that also occupies those orbits.

Lastly, I have no idea how much research there has been in containing the fragmentation of hypervelocity impacts. But presumably it would be an important part of the mission to not generate more garbage.

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

#82

Post by titzer »

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.

Suppose there are just two satellites orbiting at the same altitude, a bit higher, let's say 5 orbits a day (ISS orbits 18 times a day, roughly). The two satellites cross each other's path twice per orbit. Over the course of a year, that's 3650 potential collisions. Given the length of their orbit might be 50,000 km, then the average distance between these two crossings is 13 km. Over 10 years, that reduces down to 1.3 km. Over 100, 130m. Over 100000, it's 0.130m. They are gonna collide.

Of course, I am assuming a few things, like their orbits don't decay, they aren't exactly synchronized (i.e. they drift, and will eventually cross every point on the other's), but also that the uneven gravity of Earth doesn't corral them into narrower orbital paths (which it absolutely will, increasing the chances of collision).

That's for only two satellites. There are literally thousands. And when they smash apart, they can each generate hundreds more killer-sized fragments.

Kessler syndrome is a very real possibility on a long timescale.

We should be more careful the junk we put in space.

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

#83

Post by Triv888 »

4ggr0 wrote: post #22
ehnto wrote: post #12

Earlier quoted context omitted.

Check this site out, it's a catalogue of known stuff in space http://stuffin.space/ The ISS has regular enough operations required to dodge debris detected approaching for a near miss in space that I think it's definitely a concern for future operations. Consider as well that stuff in orbit is going ~25,000km/h or more and at that speed even a small bolt would decimate a spacecraft on impact.

What on earth...I did not know that there are sooo many thing floating around near us. Absolutely crazy.

In this visualization, they probably look a lot larger then they are in reality...

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

#84

Post by bluu00 »

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

what kind of black magic is that ?

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

#85

Post by Rebelgecko »

rocknor wrote: post #68
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...

I think the concern is that despite increased activity in space, most countries have slowed down the amount of dangerous debris being created.

Meanwhile, India created about as much space junk in a day as the US creates in 1-2 years. That's despite claiming that the the test was in an orbit that wouldn't leave any longterm debris.

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

#86

Post by eT8AZithxooKei6 »

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…

> "Passive magnetic attitude stabilization was performed by carrying two bar magnets to align with the Earth's magnetic field in order to provide a favorable antenna footprint."

Wow! I heard of this technique recently but I didn't realize it had already been deployed so long ago.

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

#87

Post by dr_dshiv »

sandworm101 wrote: post #58
simonh wrote: post #49

Earlier quoted context omitted.

Infinitesimal over 100,000 years? I'm not losing any sleep over it personally, but that's a long time.

The surface area of the sphere at 1400km is far greater than the earth's surface area. And satellites at that altitude are traveling much slower. Put together, the probabilities would akin to a handful of birds flying on earth, at random altitudes/places/directions, and two of them colliding.

This! How likely would collisions be on a sphere the size of the earth? How do the probabilities change from low earth orbit to higher orbits?

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

#88

Post by drfrank »

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?

A spherical Whipple shield might be able to capture debris. A 1 mm thick aluminum shell with a radius of 100 m would mass 810,000 kg. If SpaceX's Starship can achieve launch costs of 10/kg, that's $8 M per sphere.

But passive objects are only as likely to provide value as the ratio of the number of the total volume of the sacrificial objects to the total volume of assets, so you'd want a bunch of them.

Since the debris of interest is really just the material traveling in orbit, a cylinder might be more efficient, if some primitive attitude control could be included efficiently.

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

#89

Post by f-word »

jerf wrote: post #63
f-word wrote: post #28

Earlier quoted context omitted.

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?"

Right, so what's your solution then?
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