From the article:

> "Collisions are proportional to the square of the number of things in orbit," McDowell told Space.com. "That is to say, if you have 10 times as many satellites, you're going to get 100 times as many collisions.

Unfortunately, any collision also increases the number of things in orbit, by breaking up spacecraft. The collision between Kosmos-2251 and Iridium 33 generated 1,300 pieces of debris in orbit. The collision between Object 48078 from Russia's Zenit-2 rocket and China's Yunhai 1-02 generated 37 known debris objects, and likely a lot more smaller untracked objects.

This is likely to lead to Kessler Syndrome, a chain reaction of collisions once the density of debris fragments above a certain weight passes a critical density:

http://aquarid.physics.uwo.ca/kessler/Critical%20Density%201...

Unless satellites are brought back to Earth, the likely path of development is that Earth will get a layer of satellite debris which makes a a good part of satellite technology basically infeasible (and any spaceflight much more dangerous).

Stars in the Milky Way form a pancake-like disc 120,000 light-years across. In ~80 years our fastest space ships will hurl along around 900,000 kilometres per hour, assuming they can leave orbit. ;-)

That makes 144 million years to travel across the galaxy. Now space-faring peoples probably won't have evolved near the disc's edge. So let's say it takes about 100 million years to fan out and colonize most of the galaxy's habitable planets.

Our one data point on technologically advanced life indicates 4.5 billion years for it to find a foothold after the dawn of a new solar system. Depending on the values you put into an E.T. calculator[1], there are between 4 and ~200 advanced alien civilizations loitering about. We know of many Sun-like stars that are ten billion years old in the Milky Way, twice as ancient as our star.

One hundred million years barely registers on either a 5.5 or a 10 billion year scale. That scale affords aliens an enormous amount of time to have sown their seeds. Hence Fermi's Paradox and hence why a Kessler Cascade setback would be a footnote's footnote on these timescales. In short, a Kessler Cascade is important to avoid, but doesn't resolve Fermi's Paradox (it isn't a Great Filter).

[1]: https://www.omnicalculator.com/physics/alien-civilization

P.S.

I describe a novel solution for Fermi's Paradox in my hard sci-fi book. Am looking for beta readers; see my profile for contact details.

I have a dumb Kessler syndrom question, but I don't really have the physics to answer it myself.

I've been told that worrying about the longer-term implications of systems like Starlink aren't so terrifying because these satellites are in LEO. Specifically, the time for that kind of junk to de-orbit is on the order of 5 years, so the worst case scenario for this junk is to wait it out.

However, if we get a good set of bouncing space junk, how does that affect this? The vectors generated from the parts two colliding small object might be in any direction, including outward?

My physics isn't that great, so I am left with this question:

is it worth thinking about the small bits of junk re-orbiting other junk? Would that push out the timeline of being able to simply wait out a incipient Kessler syndrome?

Putting satellites in low orbits will help, since everything in those orbits will eventually decay.

It was reported this week that there was a catastrophic collision back in March,

https://www.space.com/space-junk-collision-chinese-satellite...

A sanguine take from Casey Handmer of the JPL: https://caseyhandmer.wordpress.com/2019/10/25/space-debris-p...

On a global perspective the interests of too many people don't align to reach any sensible consensus by conventional means. We see it with the pandemic, we see it with global warming and we saw it in general with every conflict and wars.

How can we make this happen?

Maybe this is the solution to the Fermi paradox: Advanced civilizations tend to create runaway space debris collisions, preventing them from leaving their home planets.

If I was writing a science fiction... space debris is a wonderful way of imprisoning a planet. Just put a bunch of junk in orbit, now no one can get out. Only a Han Solo type with asteroid avoiding skillz and a taste for danger.

Maybe a built-in step in the intergalactic civilisation process is launching a bunch of satellites, letting them crash, and forming an orbiting wall. This gives baby civilisations a few millennia to grow into their newfound power as the space debris forms into rings, allowing launches again.

Since space debris doesn't factor into the Insurance Underwriting pricing decisions at all of the space underwriters that I know it seems hard to believe this is a real problem.

My layman's understanding makes me wonder if we could solve this situation with a big-ass magnet in orbit, to slowly eat the debris.

OF course there would be complications from the simple fact that it would need to be very big, incredibly durable (as to not generate more debris itself), hard to launch (probably too heavy) and taken into account in all the calculations going forward.

> The world must cooperate

The world can't cooperate to block spread of covid, to end hunger, to avoid global warming, to end traffic of sex slaves, to curb nuclear weapons, to end chemical weapons and land mines, ...

Heck, even in some "civilized" countries people can't collaborate to achieve mass vaccination...

Do you really have any hope we will collaborate on organizing space traffic?

One science fiction thought is that inducing Kessler Syndrome on Earth would be a perfect way for a Moon or Mars colony to "declare independence".

If Earthlings can't get off the planet, it doesn't matter how much money, people and power they have.

>hundreds of e-mail alerts arrive each day warning of potential space smash-ups

Oh, so they could trow the Fax-machines out? Well done!

Is Email not a bit unreliable for for such a topic?

At this point I don't have much faith that there is any existential scenario that would unite the world in cooperation.

The fact that this isn't existential or even comprehensible to lets say 80% of the world's population, tells me we as engineers and designers need to plan for our technologies to be able to operate despite an inevitable cascading space collision.

> The Californian company SpaceX alone has launched some 1,700 satellites over the past 2 years as part of its Starlink network, which provides broadband Internet, with thousands more planned.

None of which are high enough in orbit for this to be an issue. They have a lifespan of 5 years or so before they fall and burn up in the atmosphere. Why was it included in the article? In the first paragraph nonetheless.

None of the other mega constellations are a problem either, they are mega constellations because they are in VLEO. You need more satellites to cover the Earth when they are lower, but they will also all fall back down, posing no long term threat.

Either the author is unaware of what he is writing about, or has malicious intent, either way, it doesn't instill trust in the article if there's no distinction of which type of orbit the satellite is in.

Sure we should be careful with satellites in more fixed positions, but the top paragraph seems like a hit piece against SpaceX, and slightly against the other companies wanting to do satellite constellations (although no name drop)

Could we have most things in space orbiting in the same direction? That would massively reduce the risk of collisions as their relative speeds would be lower, including any fragments resulting from a crash.

Why is everyone worried about all that junk? It's reaction mass for getting out of orbit or getting back to earth. It's mostly aluminum which melts easy. Just build a solar furnace in space that has a big 'catcher'. Make aluminum ingots. And shoot them off a spaceship which has a giant electromagnet. As you know, pulsing the electromagnet creates eddy current in the aluminum. This force has been used to weld metal

https://www.tandfonline.com/doi/abs/10.1080/0950711980945202...

The ingots fly back to earth and burn up in the atmosphere.

Seems inevitably we'll eventually get unsustainable levels of junk up there.

Anyone have creative ideas for how to clean all this crap up someday with "deep tech"?

Kessler syndrome is a real thing, but this reads like FUD.

We already can't work together to avoid catastrophic Earth problems like climate change, why would we start cooperating in space?

an interesting take:

https://www.colorado.edu/today/2020/05/26/solving-space-junk...

There is a YC startup from a recent batch that want to salvage and solve that.

I feel as though there are more clickbait headlines than usual on HN lately

Space is very, very big.

The smaller the space is (lower orbits), the faster any debris decays and burns up.

Whipple shields are a thing.

I really don't see much potential for a catastrophe.

Here's what I've learned: there is zero chance of the world uniting behind any cause. The solution to any of these problems will be economic and out of necessity and never because of altruism.

Want to reduce fossil fuel usage? It'll only happen when cleaner alternatives are cheaper.

Climate change? Nothing will change here until there's an economic reason for carbon sequestration.

This may seem depressing but there's an important lesson here: any sense of urgency is almost always overblown. Things really do have a way of resolving themselves.

Oh and as for space debris, yes it's a problem but space is also really big. Like the US also put a bunch of copper up in space [1] that's still there.

How could this resolve itself? It'll end up resolving itself when launch costs are sufficiently cheap. We've made a ton of progress in the last few decades. IIRC SpaceX cost of getting payloads into LEO is like 20x cheaper than 20 years ago but it's still north of $1000/kg.

But what does the situation look like when the cost gets below $10/kg? That's not as unrealistic as you may think. A lot of attention is given to space elevators. I think these are likely infeasible (eg they rely on discovering a sufficiently strong material that doesn't exist yet).

But orbital rings [2]? These require no magical material and would be completely game-changing. If you have something like that just hang things off them to pick up passing space debris.

[1]: https://www.wired.com/2013/08/project-west-ford/

[2]: https://www.youtube.com/watch?v=LMbI6sk-62E

When I read "avoid a catastrophic space collision", I thought about an asteroid hitting the earth and endangering life itself. Compared to that, a "catastrophic collision that knocks out one or more satellites key to their safety, economic well-being or both" sounds rather like an inconvenience. Of course, it could be "catastrophic" too, but there is catastrophe, and then there is catastrophe...

It is kind of funny how humans cannot exist without putting garbage all around the places they visit.

Orbits aren't stable.

If they were, worrying about "kessler syndrome" and "we cant pollute space!" would make more sense. But they're not. Stuff put in orbit will fall (or possible escape), and its a real job to find an orbit where that doesn't happen quickly.

Just like "COVID isn't smallpox".