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The current trajectory is that SpaceX proved the commercial and military viability of an LEO megaconstellation, repeatedly lowering their target altitudes and raising their satellite count because of debris and cell size concerns...

And now the rest of the world is trying to catch up in a sort of arms race, and not taking any care about debris concerns. The most tempting orbits are the ones in upper LEO that permit them to launch fewer satellites.

SpaceX are going to end up well under 500km (orbital lifespan: a decade) before things are finished, and they switched to very low orbit staging with SEP spiral out to reach final orbit a ways back.

China's newest constellation Thousand Sails is at an altitude of 800km (orbital lifespan: thousands of years), with a thousand satellites in the works over the next year or so and 14,000 planned, and they're launching them using chemical upper stages designed to explode into a thousand pieces at the target altitude. This is sufficient for Kessler Syndrome all on its own, without counting interactions with anything else up there. A catastropic debris cascade at 800km percolates down to lower altitudes over time and impacts.

We need viable treaties limiting development beyond 400 or 500km and we need them ten years ago.

I don't know how to sell the urgency of this predicament. You can have as many satellites as you want, a million uncoordinated bodies, at 400km because direct collision potential scales with (satellite count / orbital lifespan) ^2 . At 1000km, satellites decay so slowly we are already too crowded; we have already overused the space. We are speed-running the end of the space age and we are doing it to save a small number of dollars and to avoid a small amount of diplomacy.

This is not something we get a do-over on. There is no practical way to collect ton-scale debris at present, no way to track kilogram-scale debris, no practical way to shield pressure vessels against gram-scale debris, and even milligram-scale debris can hit with the force of a bullet. After collisions start occurring at a rapid clip, the mass of potential impactors quickly forms a long tailed lognormal distribution that denies us space for centuries.

Is Kessler syndrome the Great Filter (https://en.wikipedia.org/wiki/Great_Filter)?

As in, is it the thing that makes it so no one else has broken out of their planet to come visit us?

I could totally see it being the case that as soon as a civilization gets good enough at putting stuff into space, they start putting a lot of stuff into space and then things start crashing into each other to the point that they can’t ever launch any more things into space and become stuck. Trapped by the artifacts of their own progress

No. The space junk at a given orbit makes it unviable to put more satellites in that orbit, but launching beyond that orbit is still viable.

I'd consider it much less likely than e.g. nuclear or maybe chemical/biological warfare.

Kessler syndrome (if even achievable with current technology) would be a major bummer for science and the global economy for a couple of decades (no more Starlink, but we still have good old geostationary satellites, so no ships and airplanes would get disconnected as a result), or at worst centuries, but would otherwise not form any threat to civilization, whereas nuclear winter is already very capable of wiping it out.

I would guess that it would still be possible to send things beyond earth's orbit with only a low probability of collision with debris but perhaps I'm wrong.

"Low" is tough to say until someone does some proper sort of 'true mapping' of space debris in the range somehow. Protection would require a lot of complexity and cost due to the need for shielding and the delta-v to move it up there.

> until someone does some proper sort of 'true mapping' of space debris in the range somehow

You look at which satellites poofed and then figure out the maximum extent their debris could have drifted.

That works a little bit when we're talking about one satellite poofing in a year based on a collision with another satellite, and not at all when we're talking about thousands of events a year, many of which are satellite-debris collisions too small to track (you only get one orbital vector), or between pieces of debris.

Every collision generates hundreds, maybe thousands of pieces of debris, only the largest of which are trackable.

Not really. There are uncertainty bands. But based on the collision you know which orbits are spoiled for about how long.

Rather than protection on each rocket, couldn't you just send a bunch of fortified rockets that absorb the debris during a collision but don't emit anything. Do that a few times and then all other rockets just reuse the path that was cut?

Orbit is not a location. Orbit is a group of velocity-location vectors which form a stable loop around a body, without intersecting that body.

Imagine a bullet circling your head at mach 25. Now imagine a second bullet, circling your head at a slightly different angle, at a slightly different distance from your head. There's a chance that they could collide, and the resulting explosion would leave a great deal of dust... on a mixture of velocities, still circling your head. Now add a third bullet, also on a slightly different vector; Make sure that it doesn't collide with any of that dust!

The actual situation is we aren't dealing with 3 bullets or 100 bullets, we have ~170 million objects orbiting the Earth, and only around 50,000 are large enough to track. They are all moving fast enough in relation to each other that a collision would result in a sizable explosion, not an elastic agglomeration. We have no way of removing them.

The good news is that there is a large volume of space for them to exist in. The bad news is that as we continue to fill it up, odds of collisions increase, and every collision spawns many, many more objects.

You’ve explained what Kessler syndrome is but not why my idea doesn’t work.

I’m saying send reinforced rockets through the orbits that absorb the collision instead of generating more dust. That should let you clear a path through all orbits that intersect your path. It’s hard to do and the 3d aspect of it might make it expensive but conceptually it could be a solution. Or use super powerful lasers (potentially mounted on a satellite) to deorbit the dust

It takes about 90 minutes to complete a low earth orbit. A rocket can't hover in place for 90 minutes at the same altitude, then increase its altitude by its height and repeat. It doesn't have enough fuel for that.

Every launch failure will result in more debris and even lower probability of a successful future launch.

> don't know how to sell the urgency of this predicament

We need to start by understanding it. I'm having trouble finding this paper right now. But to date, all calculations have shown that Kessler syndrome as a generalised phenomenon is incredibly hard to trigger. Even intentionally. Especially in LEO. (Intentionally triggering it is of interest for strategic ASAT denial.)

> the mass of potential impactors quickly forms a long tailed lognormal distribution that denies us space for centuries

No, it denies certain orbits. (Again, barring some new orbital dynamic haven been discovered by this paper.)

If 800km impacts go asymptotic, it pollutes 700km and 900km orbits by virtue of having a distribution of resulting debris velocity vectors, and as drag pulls down all the resulting debris over the next thousand years, the 800km debris becomes circular 700km debris, and then circular 600km debris, and then circular 500km debris.

> as drag pulls down all the resulting debris over the next thousand years, the 800km debris becomes circular 700km debris, and then circular 600km debris, and then circular 500km debris

Circularisation isn’t the unexpected part. Sphericalisation is. One requires orbits to desync. The other requires plane changes.

There is percession of the perigee.

We are currently in a low-trust, selfish world where all hope of collaboration has gone out of the window, so we are on an unchangeable trajectory towards things like Kessler Syndrome and climate hell.

Humanity is a failed species. The engineers were right to send the xenomorphs.

Why would any of the US' adversaries agree to that? We have SpaceX, and they do not; lowering the altitude of megaconstellations is asymmetrically far more costly for them then it is for us.

Stopping China's (highly strategic, military) satellite constellations isn't a "small amount of diplomacy". It's an impossibility.

(It's even their declared planning that deliberate Kessler cascades are on the table [0]—to try to ground this discussion in diplomatic reality).

[0] https://www.scmp.com/news/china/science/article/3178939/chin... ("China military must be able to destroy Elon Musk’s Starlink satellites if they threaten national security: scientists")

Invite them in. Launch their satellites for them, at 400km. Give them cash or territory. Give away the farm. How doesn't matter. What matters is that we start coexisting at 300-500km, and we mutually taboo launching large amounts to altitudes much higher than that.

There is no stable Mutually Assured Destruction Nash equilibrium here, if either of us does this thing it causes dramatic harm to both.

Not regarding that as a worthwhile goal is "mineshaft gap" thinking - a zero-sum mentality entirely ignoring our collective advantage in order to pursue competitive advantage.

It is perfectly feasible to run a Chinese constellation alongside Starlink sharing the same space, orbitally. Very low orbits are self cleaning.

> Launch their satellites for them, at 400km. Give them cash or territory. Give away the farm. How doesn't matter.

That sounds not just expensive but unrealistic. I think it’s easier and more politically acceptable to just cripple their launch capabilities with cyberattacks or direct force. It’s not like the world trusts or likes the CCP, or looks favorably upon their aggression against Hong Kong, Taiwan, Tibet, Bhutan, Japan, the Philippines, Vietnam, etc. And this stakes are too high with orbital pollution

Or just destroy their rockets and launch complexes. It’s better than Kessler syndrome.

They, in turn, will destroy ours, and then you have basically caused the same outcome as Kessler syndrome: nobody can launch things to space.

There is no world in which giving cash or territory to the Chinese Communist Party would be acceptable to US taxpayers, regardless of the consequences.

i think you mean war-hawk capitalists, this taxpayer thinks cooperation is fine

I think OP is suggesting US concede to sharing 500km orbits that SpaceX has disproportionately squatted rights to, since current international law is first come first serve. Where concede is to rejigger international law to increase density of 500km so others wouldn't have to go higher, i.e. PRC mega constellations going ~800 because ~500 mostly taken. Or in ops suggestion, free for all. This is more costly for US since it saves entrants from going extra 300km, but imo proximity also greatly enhances chance for friction... i.e. if everyone chilling around same plane, and it's going to get magnitude more croweded, expect a lot more overt/hidden space war assets there to trigger kessler.

basically, it sounds like the U.S. should not treat China as a competitor and we should cooperate. this insane hypercompetition for literally no reason (other than US capitalists wanting to remain dominant) is going to destroy us all.

You think the Chinese capitalists aren't also trying to become dominant?

> upper stages designed to explode into a thousand pieces at the target altitude

By this do you mean at the 800km altitude?

Yes. In a lot of historical spaceflight programs, the stage used in the upper atmosphere stayed with you to the final orbit, and was detached at low speed there. This saved you from having to design your satellite with significant onboard propulsion. Some of the upper stages were able to vent remaining propellants or pressurants, some were allowed to heat up until the pressure vessel exploded.

Suffice it to say this is not sustainable for megaconstellations in thousand years orbits. The responsible thing to do with that kind of scale involves reliable, redundant, prompt de-orbit of upper stages, and ideally for high-thrust, high-mass, high-engineering-margin-of-error atmospheric upper stages never to make it that far into the mission.

One way is for the the US to be more politically stable again (some how). Every country with an army will want its own star link now for trust reasons.

For how long?

Because this thing is happening right now, it's happening fast, and it's happening without any effort to fight against the trend.

If your answer is "let's revisit this in 2050", then it isn't an answer.

And it will continue to happen and nothing can be done about it. Except global nuclear war, I suppose. That's not off the table.

Yeah well it means a lot of satellites are going to end up in space then.

The US is politically stable already (by historical and international standards), and has been since 1865. If you ignore the rhetoric and focus on actions there has been very little substantiative difference in foreign policy across the last 7 presidential administrations.

The US civil war is not the only time the US has been politically unstable. The civil rights movement, the labor disputes of the 1970s, the economic shocks every decade or so from market crashes all have been moments of instability.

What is January 6th if not a concrete example of recent political instability?

As for foreign policy consistency, 7 administrations takes us back to Reagan... The entire movement to sell out our industrial capacity to China and now the movement to try to reverse that have occurred in this time frame. This is just as important as our endless wars in the middle east, imo.

I don't disagree totally but I felt the need to put some nuance here.

Stability doesn't mean statis. The USA has been remarkably resilient to those minor shocks you listed. It continues to be the most politically stable of all the countries that actually count for anything in international affairs.

>I don't know how to sell the urgency of this predicament. You can have as many satellites as you want, a million uncoordinated bodies, at 400km because direct collision potential scales with (satellite count / orbital lifespan) ^2 . At 1000km, satellites decay so slowly we are already too crowded; we have already overused the space. We are speed-running the end of the space age and we are doing it to save a small number of dollars and to avoid a small amount of diplomacy.

This sounds like the most first-world-problem ever. It realistically affects practically nobody alive, nor would it ever. Most people will live and die on the planet's surface and never visit space, nor do they need to. There aren't too many space-based services that are really necessary to life on earth. Nobody really needs internet in the middle of nowhere. Sure, it's nice to have, but that's a first world problem that few people have.

Having satellites orbiting the planet is more beneficial than just solving the first-world problem of “knowing where you are” or “having Internet”.

NASA has done a large amount of work to use satellite data to forecast and then work to improve agricultural yields covering the entire planet. It definitely isn’t necessary, but to dismiss the improvement that has been made is crazy, and I’d hardly call “feeding people around the world” a first-world luxury given by space travel.

We can and should have satellites, but we can certainly be thrifty with how we use them.

The megaconstellation concept isn't necessary for most of the "cool stuff you can do with satellites." You might need a handful of weather or GPS satellites, and you can be more selective for orbits and lifecycle management if you're a responsible government operator.

The Starlink fiasco (and its clones) solely exists because we're abysmal at getting telecom projects built. If 80% of the country had the network connection you'd expect by 2024-- something like symmetric 10Gbps FTTH for $150 per month, and the other 20% was on a "real soon now" waiting list, there's precious little business case for Starlink.

Think about it: It was easier to plan out and deliver DOZENS OF ROCKET LAUNCHES AND A GALAXY OF SATELLITES than to tie down our existing telecom firms until they actually built a decent network, using technology like "backhoes" and "fibre-optic cables" that have existed for decades, cost next to nothing, and don't require literal rocket scientists to deploy.

The American telephone network under Ma Bell was almost a Wonder of the World for its scale, resilience, and universal accessibility-- and in barely one generation we ripped it out and failed to replace it with anything comparable.

I would argue the case there's a marginal case for one modest capacity public data constellation. The business case is basically Iridium warmed over-- for the places where there is no other practical option (ships at sea, completely undeveloped territories)-- you can pay $10 per gigabyte for 128k down, or to support some form of 911 outside of cell ranges. Arguably, we already had the infrastructure for that with the pre-Starlink satellite products (Viasat/Hughesnet)

But we hardly need every major power (and probably a bunch of private competitive duplication) blasting crap into space to make the deluxe version that's still not as good as a fibre running to your home.

> It realistically affects practically nobody alive

Do people in the Global South not use GPS or consume weather forecasts?

Sure, GPS is nice to have, but we lived without it for many centuries before it, it's also a "first-world-problem" if it goes down. GPS is also notoriously susceptible to ground-based jamming. And because of that there's also other ways to track position. Weather forecasts are nice to have, but often wrong. My original comment was framed more towards space travel.

The thing is that GPS doesn't just do positioning. If we lost GPS then we can just look at road signs (hopefully). GPS also provides time synchronization to a lot of very important telecom infrastructure. To prevent 4G base stations and digital TV transmitters from interfering with each other, their transmit reference clock frequency need to be disciplined to within 50 ppb and their time need to be synchronized to less then 1 us.

No GPS means no 4G and no digital TV. And technology leapfrog effect means that third world countries will be significantly affected, as they jumped directly to mobile phone: https://www.cio.com/article/194000/what-does-technology-leap... . And countries are moving toward digital TV from analog TV: https://en.wikipedia.org/wiki/Digital_television_transition because they want to free up the spectrum for cellular network.

This is bad. The transmitter towers aren't moving anywhere soon, so the obvious solution is to move them to fiber timing network. Wired is always more reliable then wireless anyway, ask Linus Tech Tips. Only China understands this though: https://www.gpsworld.com/china-finishing-high-precision-grou... and https://cpl.iphy.ac.cn/article/10.1088/0256-307X/41/6/064202 . EU is moving toward that: https://www.gpsworld.com/europe-moving-toward-a-timing-backb... . US is hopeless

And technology leapfrog effect means that third world countries will be significantly affected

Exactly that. In many parts of Africa the middle of nowhere is full of people. In many places mobile phones are the only way to get internet. I can't wait for starlink to be available here. Getting internet is not a first world problem.

> Weather forecasts are nice to have, but often wrong.

I think you are really, really underestimating the importance of weather forecasting to modern agriculture (and therefore global stability), shipping and transport, logistics, energy infrastructure, and on and on.

The paper in question is here: https://link.springer.com/article/10.1007/s40295-024-00458-3

It adds to a pretty large body of literature around this subject, the gist of which is "risk is going up, but we don't really have a good way of estimating what that means in terms of actual collision rates".

As long as it is militarily and commercially viable then the number of satellites will continue increasing, regardless of what academics have to say about collision rates. As per usual this is a coordination problem and in case people have not noticed nations are becoming less coordinated and more insular.

> in case people have not noticed nations are becoming less coordinated and more insular.

And what is your yardstick for measuring this? As far as I can tell this is the opposite of true. It's a popular national news meme but I don't believe it's been measured in any reliable way.

I won't comment on the broader point about how insular countries are becoming, but on this specific topic I'd say that the international reaction to global warming, which appears to be a very similar situation, shows exactly how little action is likely to happen.

I don't know about whether it is more or less common, but there has been international drama over conjunctions over the last several years

https://spacewatch.global/2021/12/spacewatchgl-share-chinese...

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> so you can greatly simplify your sentence

You didn't need to use "greatly" here because the suggestion you're offering without being asked is not particularly great or meaningful.

> I think that would greatly aid in your online communications.

I communicate online just fine, thank you, I'm also happy to be an individual and to allow that individuality to be expressed through my communications.

Thanks again for the unwelcome and unnecessary advice. Please don't use your time to police other peoples writing. It's rude.

I would recommend you take your own advice.

You are unwilling to adhere to your own standard? Interesting. What happened? Was it that someone else used this technique against you in the past to make you feel small? And now you've stored in some kind of quiver of ready to use insulting behavior to avoid any sort of confrontation or perceived failure? Then because of this you're made awkward and uncomfortable when it doesn't play out the same way as before?

In psychology that's called projection. I highly recommend looking into it.

"True" here is not a boolean, it's the truth of the matter.

The claim is that coordination is decreasing. Calling that "false" might mean coordination is steady. Calling it the "opposite of true" means that coordination is increasing.

That's a possible interpretation but the verbosity of the original statement hinders understanding the actual intent which is I why I recommended simplifying and removing unnecessary redundancies.

It's 40 words and makes three separate points in those words. I don't think it's too verbose, and I don't think your suggestion helps.

Everyone is entitled to their opinions.

The parallels to global warming appear to be close enough that this could be a good area to study what actually changes behavior on a global scale for a global environmental problem. I suspect this is easier to 'fix' mainly because there are fewer entities involved so not a total parallel, but it still might be informative to see when in the crisis arc action actually starts happening and what messaging impacted that timing.

There might be a cool storyline where we have to use enormous ground based lasers to clean up and start again.

Could even look a bit like the iconic Gibraltar WW2 search lights photographs.

What would zapping a satellite with a laser achieve? I suppose if you get it hot enough to melt everything, without anything flying off, then it would turn into a spherical drop of molten scrap... but then what?

You ablate part of it on the prograde side to create a small retrograde thrust which will deorbit it.

I think the right move is to merge this approach with goo blobs. We launch a large goo blobs or nets into a few strategic geostationary orbits and now you only have to ablate objects so they hit the goo then deorbit the goo once it is full (or just leave it there) as they would be large known orbits.

I assume the poster means to change its trajectory.

By adding energy (and momentum)? That seems unlikely to work. I guess you could try to shoot at things headed towards you over the horizon, to slow things down?

I was assuming it was to vaporize things to make the re-condensed remnants small and dispersed enough to be less of a problem. Though that seems like a tough problem if you have to stay trained on an orbiting bolt for any length of time, as the atmosphere wobbles your laser around.

Well the targeting angle could be low to the horizon, aiming into oncoming debris, reducing its orbital velocity, so that it deorbits faster. The vertical component of the vector would be minimized. A low angle reduces laser efficiency due to more atmospheric interference, but oblique enough it would work. Nearly all man-made satellites (and space junk) orbit in the direction of Earth's rotation because of launch boost, which makes this easier.

My understanding was always that LEO is much less of a Kessler risk due to atmospheric friction - ie: in the absence of active control and regular correction, LEO objects will gradually de-orbit themselves. It's the the higher geostationary orbits that pose the problem.

VLEO/LEO is the safest place to put satellites is it not? They'll eventually deorbit themselves if you do nothing, no?

The worst place for space junk is high orbits it would seem like. Earth was wildly visited by an Apollo rocket stage a few years back! That is pretty wild.

Paper: https://link.springer.com/article/10.1007/s40295-024-00458-3

Anyone have an open link?

I love Sabine Hossenfelder's videos but the audio effects on the transitions are killing me.

They're a little too similar to my phone's built in sounds I suppose. Nothing I can't get over though. What about them is "killing you"?

I would think newer sats will have collision avoidance capabilities and older ones will just crash. Maybe even clean up sats will be developed to collection them

Satellites fail (lost control, or spontaneously explode). Very small debris is everywhere and under 5-10 cm largely untracked, but some are working to fix this gap.

There is no incentive large enough for cleanup (it's expensive, nobody can/wants to pay, and there are a lot of objects)

Leo starts at 7.8 kilometers per second and speed plus secondary and subsequent collisions with very small debris makes it impractical. Also carrying fuel to react frequently would dramatically change the entire mission.

If your non refuelable sat is good for 6 months it probably no longer makes sense to launch it.

With currently deployed tech, most of the smaller orbital debris is not (usefully) track-able.

At orbital velocities, you gotta know it's coming to be able to avoid it.

And a orbital velocities, the untrack-able stuff can still kill a satellite.

Positioning a large, armored satellite in low or mid-Earth orbit significantly enhances its strategic value for both offensive and defensive anti-satellite operations. Such a platform could serve as a pivotal asset in maintaining orbital dominance, offering rapid response capabilities to neutralize threats and protect critical infrastructure.

In other words, welcome various "death stars" to keep order against malicious Kessler style attacks, etc.

What do you assume happens to a "neutralized threat" in terms of space junk?

Perhaps it is recycled aboard the large armored satellite or propelled into the Earth's atmosphere so it can burn up.

That helps nothing on the civilian side. Blowing up a sat will do nothing but raise long term risk.

Some sort of platform that can launch 'space drones' to deorbit a dead satellite before it crashes or if something else would happened to cause a collision, that could be useful, but, probably expensive.