Comment by ryankshaw
3 days ago
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.
How can you get past that orbit if there is all this junk destroying your rockets????
Ideally a satellite is in a given orbit for years. If junk is destroying it in weeks or even months you’ve got a massive issue.
However a rocket is spending in a seconds in that same orbit. Thus a rocket passing through may only have say 1:10,000 odds of a collision on its way to mars while satellites are getting shredded.
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integrate risk over time. if you have a high target orbit outside the "kessler belt" then you don't spend much time going through it. though this requires a fairly direct orbital insertion. slow orbit raising would have a higher risk, but even that would still be lower than for any satellite intended to operate for years and decades in an affected orbit.
It really depends on how much junk actually is there and in what orbits; especially at 500 km up, space is big. The surface area of the earth is 510.100.000 square kilometers, at 500 kilometers the 'surface area' is a multiple of that (I can't math), surely there's enough gaps or lower-density areas at that height even if there was a catastrophic Kessler Syndrome event.
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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 think it would be actually the other way around - Starlink orbits aee low enough to be self cleaning & Starlink satellites can be (and are) rapidly replenished. So even if something from up above hits anfew, the debris would deorbit soon & new ones could be launched.
With GEO sats, unless you go for direct GEO insertion, it might still have issues reaching the final orbit. And even at GEO, there could be a debris cloud as well causing issues, at least until the sun and moon gravity perturbs it enough.
The approximate-GEO belt involves far fewer satellites than projected megaconstellations, in a far larger volume of space, travelling at far lower orbital velocities, with a much tighter orbital plane distribution (so even lower relative velocities). Their orbital planes intersect every 12 hours instead of every 0.75 hours.
Targeted space junk disposal in GSOs appears to be quite practical. The easiest major orbital changes for an SEP stage to burn, structurally, involve lowering periapsis from high orbit.
On the other hand, there is just so much less stuff up there, as reaching that orbit is much more expensive in terms of energy expenditure, and it's all moving in pretty much the same direction and in the same orbital plane.
So unless somebody maliciously launches e.g. a bunch of ball bearings in the same orbital plane but opposite direction, the chances of "wrecking GEO" seem much lower (although the consequences would, as you say, probably be much more severe and long-term).
- "And even at GEO, there could be a debris cloud as well causing issues, at least until the sun and moon gravity perturbs it enough."
Not a satellite expert, but I understand GEO clears out relatively fast (~decades), because of those 3-body perturbations,
https://www.agi.com/blog/2020/07/geo-satellites-don-t-decay-...
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> if even achievable with current technology
Launching a nail bomb into orbit would've been possible as soon as we were able to get into space, the only question is motivation. A terrorist state, say North Korea, threaten the rest of the planet and demand concessions once they're able to get any significant mass into orbit.
I'd say intentionally destroying space assets etc should be considered an act of war (compare attacking another nation's ship in international waters), NK wouldn't have a chance and they could be put into space lockdown where any launches are intercepted.
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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.
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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?
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Every launch failure will result in more debris and even lower probability of a successful future launch.