Decluttering low-Earth orbit: It's time to tidy up space • Hacker News Board

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

#51

Post by beerandt » Mon, Jan 18, 2021, 2:59 PM UTC

Cogito wrote: post #44

gruez wrote: post #40

Earlier quoted context omitted.

>and in denying the space to other classes of satellites. Is this actually an issue? The earth has a surface area of 500M km^2 so if want 0.5km between each satellite you can fit 500M satellites at one orbit level. A few thousand spacex satellites is a drop in the bucket.

Remember that, assuming circular orbits (which is fine for this discussion, I think), you have to fit satellites on great circle paths next to each other. For a single great circle you can fit a significant number of satellites in a chain, but turns out you don't want too many like that as all your satellites cover the same part of the earth. All great circles on a sphere will intersect in two places, which assures a…

But you imply those mitigations must be made to correct the "natural," initial orbital state, when in reality, the orbits were never truly circular or co-spherical.

It's not useful to make a simplifying assumption, if the solution to the problem is to reverse the resulting simplifications.

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

#52

Post by bgun » Mon, Jan 18, 2021, 3:24 PM UTC

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.

That makes the very big assumption that the density of other things to hit doesn’t massively increase.

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

#53

Post by im3w1l » Mon, Jan 18, 2021, 3:25 PM UTC

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…

> The real problem isn't that space is getting full of our junk, but that our junk is in a very narrow band of orbits that we use for very specific missions: Sun synchronous polar orbits used by imaging satellites.

What's the significance of these orbits?

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

#54

Post by BurningFrog » Mon, Jan 18, 2021, 3:29 PM UTC

simonh wrote: post #49

sandworm101 wrote: post #43

Earlier quoted context omitted.

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.

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

Yeah, that statement makes a lot of assumptions about the next 99,950 years.

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

#55

Post by tempest_ » Mon, Jan 18, 2021, 3:29 PM UTC

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

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

#56

Post by sandworm101 » Mon, Jan 18, 2021, 3:33 PM UTC

im3w1l wrote: post #53

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…

> The real problem isn't that space is getting full of our junk, but that our junk is in a very narrow band of orbits that we use for very specific missions: Sun synchronous polar orbits used by imaging satellites. What's the significance of these orbits?

A sun-synchronous orbit is a polar orbit where the satellite passes over each part of the earth at the same time every day. That is very useful if you want to photograph things at regular intervals using cameras (stable light, no nighttime) or if your satellite uses solar panels as these orbits can be such that the satellite never falls into the earth's shadow.

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

#57

Post by crazygringo » Mon, Jan 18, 2021, 3:34 PM UTC

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.

Are you sure? A quick online search reveals only two satellites appear to have been destroyed -- an Iridium satellite was destroyed in 2009 when it was hit by a junked Russian satellite, while in 1993 the European satellite Olympus was destroyed by a meteor.

So it would seem that so far, natural debris and space junk are tied 1-1. Why do you think natural debris is that much more of a risk?

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

#58

Post by sandworm101 » Mon, Jan 18, 2021, 3:36 PM UTC

simonh wrote: post #49

sandworm101 wrote: post #43

Earlier quoted context omitted.

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.

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.

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

#59

Post by londons_explore » Mon, Jan 18, 2021, 3:37 PM UTC

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?

I suspect if you did the analysis, you'd find rather than it getting denser over time, you'd find most bits of space debris (even tiny ones) would have enough energy to explode your catcher...

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

#60

Post by Chris2048 » Mon, Jan 18, 2021, 3:41 PM UTC

mdotshell wrote: post #23

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?

Because of orbital mechanics, anything that would be traveling faster than the scaffold would be at a higher orbit and wouldn't be able to be caught. The exception to this would be if the object were in an elliptical orbit, which would allow for contact to be made with the scaffold at its perigee, which be impossibly rare.

what if that thing had an elliptical orbit?