The misunderstood Kessler Syndrome
aerospaceamerica.aiaa.org
aerospaceamerica.aiaa.org
Out of necessity, they have to display every object as at least 1 pixel. But that typically dramatically overstates the size of most objects in relation to the size or earth.
Most visualizations make it look like Earth is absolutely covered with satellites. Whereas in reality, those satellites are the size of a car or smaller. 8000 cars might not even fill up a good sized stadium parking lot, much less the entire surface of the Earth. And many of those satellites are orbiting at different altitudes, so they're even more spread out than just the surface of the Earth.
Any visualization that showed a full orbit in a visual field that a human can see at once, necessarily has to exaggerate the size of the satellite or it would be completely impossible to see the satellite at that same scale. By millions or even billions of times.
A GPS satellite in medium orbit has an orbital diameter of around 45, 000 km but is only a little over 5 meters in size. A ratio of roughly 10,000,000 to 1.
If you had a visualization a meter wide of its orbit, the satellite to scale would be less than a micron in size. Completely invisible.
The same problem comes up with those ‘topology of the earth’ maps that try to show how things like depth of the oceans, height of the Himalayas, etc. on a globe.
They have to dramatically exaggerate the actual altitude differences for them to be perceptible. [https://www.quora.com/If-Mount-Everest-was-on-a-globe-and-wa...]
The actual to scale difference in height of the Himalayan mountains vs sea level on a regular sized globe would be less than .001 inches. Completely imperceptible without precision measuring devices. Even producing such a globe accurately would be a feat of precision manufacturing.
Even on a giant (1 meter) globe, we’re talking less than 1mm.
Literally smoother than a billiard ball.
But they are the highest mountains in the world, and absolutely breaktaking if near them.
And space is even bigger, and satellites even smaller.
Great book on this:
>> the Earth deviates from spherical by only a third of a percent
https://en.wikipedia.org/wiki/Figure_of_the_Earth
>> For instance, the Anti-Friction Bearing Manufacturers Association (AFBMA) has a set of grades for bearing balls. A grade three ball has to be spherical within 3 millionths of an inch and the diameter must be accurate within 30 millionths of an inch. This means that for a grade three quarter-inch ball, the diameter would have to be between 0.24997 and 0.25003 of an inch and the smallest diameter measured on the ball has to be within 3 millionths of the largest diameter.
https://science.howstuffworks.com/transport/engines-equipmen...
If you stand at sea level at a pole you are much closer to the center of the earth than if you stand at sea level at the equator.
To anyone who's read the book with an existing background in precision engineering (i.e. and can independently vouch for its plausibility), is it still worth picking up?
According to ChatGPT, if the earth was the size of a spherical cow (approx 1.5m in diameter) then the space station would be about 8.5 micrometers which is roughly the size of some bacteria. It would be 46 millimeters away from the cow.
If earth was a spherical cow then a starlink satellite would be 0.31 micrometers, or 310nm which is about the wavelength of violet light. It would be about a large thumbtack away.
The orbital periods for these would be in the order of microseconds.
If the earth were 1.5m in diameter, the space station would be proportionally 12.83µm long[0], orbiting at a distance of 50.66mm (2 inches)[1].
[0]: https://www.wolframalpha.com/input?i=iss+length+%2F+earth+di...
[1]: https://www.wolframalpha.com/input?i=iss+height+%2F+earth+di...
Sometimes, it can help a little to convert to something vaguely human-scale, which probably doesn't fit on a screen. The surface area of the planet is ~500 million km^2, there's a large park near me with long, clear sight lines where I go for runs play disc golf that's about 5 square km. If I shrink the ~3x2 meter satellite dimensions by an equivalent factor of about 100M, it's an object with a size of 30x20 micrometers (unless I've screwed up a square-cube ratio somewhere), on the order of a grain of silt, the thickness of a Sharpie ink mark, or something a little smaller than a cross-section of a hair. My intuition approximates those dimensions and probabilities of two of those infinitesimal specs all the way to zero.
On the other hand, tens of thousands of satellites, those barely-palpable specs crossing that region of space once every 90 minutes, for hundreds of years? Then my intuition says it's a certainty!
Facing the multiplication of an impossibility with a certainty, intuition says they cancel out and it's a 50/50 chance, which is just not how it works.
Sometimes you have to just do the math and trust the numbers.
Both effects are misleading dataviz artifacts, but at least they're in opposite directions!
A great ESA video, linked from Don Kessler's website, shows a time-lapse simulation that better captures the seriousness of space junk. In the simulation @5:25, realize that each of those flashes represents an Iridium-Cosmos magnitude collision event: http://www.youtube.com/watch?v=RvZ3Lr-Tj6A
Depending on the assumptions you make, we could have billions or even trillions of Starlink satellites without triggering Kessler simply because
- Starlink satellites are actively controlled and steer to avoid collisions. Yes there are sometimes a couple of failed Starlinks in orbit, but since the active ones avoid the dead ones, you have to calculate the risk of one dead satellite hitting another dead satellite. And that's less than random because they quickly decay out of their crowded orbital plane to a different less crowded one.
- dead Starlinks are in a self-clearing orbit, deorbiting in under 5 years. As the article indicates Kessler is a decades-long process. Which can't happen if the satellites don't stay in orbit that long.
- most dead Starlinks aren't completely dead, or give alerts before they die, allowing SpaceX to actively deorbit them safely and quickly
- the vast majority of particles from a collision in a self-clearing orbit result in immediate clearing. If the original dead Starlink that would take 5 years to clear suddenly fragments, most fragments de-orbit within a single orbit (90 minutes). Elastic deformation reduces their velocity, lowering the orbit. Half of fragments are toward a lower orbit. The other half only boost apogee and either lower perigee or leave it unchanged. Being smaller, their surface area / mass ratio increases, reducing deorbit times.
Basically, Kessler is not a concern at VLEO altitudes. Unfortunately most proposed Starlink competitors cannot afford to launch the thousands of satellites necessary for a viable VLEO constellation and instead are launching dozens or hundreds into LEO orbits which aren't self-clearing and do pose a Kessler concern.
I think this is something that's not intuitive to othe average person. Basically: a collision can change an object that's in a circular orbit into an elliptical orbit with a higher apogee. But it can't circularize the new orbit higher without a 2nd "burn"[1].
Which means that if a satellite that would passively deorbit in a short amount of time is in a collision, it is necessarily true that all of the fragments will also deorbit in a small multiple of that time.
> Basically, Kessler is not a concern at VLEO altitudes. Unfortunately most proposed Starlink competitors cannot afford to launch the thousands of satellites necessary for a viable VLEO constellation and instead are launching dozens or hundreds into LEO orbits which aren't self-clearing and do pose a Kessler concern.
Thankfully, Kuiper will be just above Starlink. From what I understand, their passive deorbit times are ~10-20 years.
The real problem is with OneWeb and the upcoming Telesat Lightspeed which are both at 1000km+. It sounds like OneWeb was planning on a greatly expanded next generation constellation, but they've since scaled their plans back and are incorporating bandwidth from geostationary satellites into their offerings.
---
Huh?
My standard interpretation of "4D" in this kind of context is spacetime. But one doesn't "travel" through spacetime; one's entire journey "just is".
https://en.wikipedia.org/wiki/Slaughterhouse-Five#Tralfamado...
What have I misunderstood? Is this a 4D space in a 5D spacetime? Is "block spacetime" discredited? I thought the parent comment sounded weird, as if I'd missed some important context.
If you want to be technically correct, my understanding is that everything moves through spacetime with a constant vector - the faster you move through space, the slower you move through time and vise versa. We just don't notice (typically) because the effect isn't particularly pronounced below 0.01C. But I believe that GPS satellites do take this effect into account.
1. You can only go forward in time to varying degrees, never back.
2. Like I said above, we are technically always varying our speed through time. It's just that the effect is difficult to notice because the size of the effect is small.
That's what we seem to observe; but I'm not aware of any reason why that should be so a priori, and I don't know what kind of evidence would be conclusive, either this way or that.
This is my personal opinion, not an "official" physics opinion, but I think that the second law of thermodynamics creates a ratchet that prevents movement backwards in time.
There's this line about all the water molecules in a glass "randomly" jumping upward at the same time, leaving the glass empty. As far as I'm aware, this is completely possible; it's just so incredibly unlikely that it's never been observed.
If the Arrow Of Time is a result of the Second Law, maybe a similar ultra-unlikely circumstance could result in time going backwards. At any rate, I'm not aware of anything that derives the Arrow Of Time from any fundamental property of spacetime.
Let us imagine that there are 100 000 Starlink-sized satellites on the orbit.
At a given time, approximately 29 000 of them are over dry land and the rest over the sea.
29 000 car-sized object randomly moving across all 6 continents, including terrains such as the Himalayas. It would be pretty infrequent for them to come close to one another.
Douglas Adams nailed it. "Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space."
Very few people, even us nerds who are aware of the scale, and actually hold that scale in their minds properly. And that's just low earth orbit.
Geosynchronous, the Lagrange points, an Astronomical Unit, a Light Minute, a Light Year. It's one thing to understand what these things mean, but it's entirely another to put them into a human-scale context.
It's like the difference between knowing that there are 20 million people in the New York area and trying to name each one of them individually.
Luckily the reasons why we used to launch satellites into high orbit are mostly obsolete now. We did it for three reasons: firstly so the satellites would last longer because they are expensive, secondly to get higher land area coverage from fewer satellites again because satellites are expensive, and thirdly to make it possible to use stationary or slow-moving satellite dishes. Now that launching satellites is much cheaper and likely to get even more so, the first two reasons are obsolete. The third reason is made obsolete by modern phased array antennas that can be pointed without moving. So we don't need to take on the debris risk from high orbiting satellites anymore.
I would avoid the anime adaptation.
Personally, her aggravating her coworkers is hilarious, and if you've ever had a late-teens/early 20's intern/employee in your workplace, you've been there, and perhaps you remember being like her - very pure and simple in your ideology and worldview.
People who don't stick it out more than a couple of episodes don't get to see her character development and its message to both young idealistic folks who grow, and their cynical adult coworkers who help them achieve that growth.
It's a wonderful 'soft' scifi anime with good production values and a storyline that avoids the typical anime bullshit ("enemy bad, us good...but....SURPRISE, enemy not bad!", "teenager drama involving kids who are the only ones who can save the planet/japan from aliens", and "deep" plots that are mostly just the writers creating stuff that doesn't make sense and never explaining it, with random plot twists)
If I'm being honest the anime characters that really grate on me are the added office staff. They do slowly develop as characters also, but for a decent chunk of the show they are obnoxious comic relief.
(2022) https://www.smithsonianmag.com/smart-news/hubble-is-slowly-f...
I love these topics. While we might be nowhere near Kesssler Syndrome, the risks of space debris impacts are very real [2]. Some of the debris we've put up there intentionally and it's quite insane, most notably Project West Ford [3].
I believe that now anything put in space has to have a plan for how it will be decommissioned. For LEO probs, that typically means burning up in the atmosphere or, if it's large enough, crashing in Point Nemo [4]. For geostationary satellites, they're typically put in a disposal or graveyard orbit [5]. That doesn't solve the problem. It just kicks the can down the road.
People might think you can just accelerate a bit and leave Earth but that's not how orbital mechanics work. If you accelerate a bit you've just created a new orbit. You still need a lot of energy to leave Earth orbit. It's the same reason why dumping waste into the Sun (as some like to suggest) is completely unworkable. You can't just slow down a bit and fall slowly into the Sun. You just create a new orbit. It still takes a delta-V of ~30km/s to hit the Sun [6].
Fun fact: it requires less delta-V to reach Pluto then hit the Sun than it does to hit the Sun directly. Orbital mechanics are weird.
EDIT: fixed delta-V units.
[1]: https://www.youtube.com/watch?v=GCCKpI80V6M
[2]: https://www.space.com/9708-worst-space-debris-events-time.ht...
[3]: https://www.wired.com/2013/08/project-west-ford/
[4]: https://www.atlasobscura.com/articles/strange-maps-point-nem...
That number looks like it should be much much bigger to me.
But, you'd never actually do that, the calculations involved assume you have decided to specifically go towards the sun, maybe to get there quickly, but going to the sun is just a means to an end, so you'd actually pull shenanigans to get the same result indirectly for "only" a few km/s of delta V with carefully chosen launch windows. Which is like how it'd be easier to build a bridge from Greenland to Iceland than from Greenland to Spain. "We can't do that" versus "We can't do that either".
Another related fun fact from GP’s is that it’s way less delta-V to hit the sun from Pluto than it is from the Earth… 4.63 km/s according to wolfram: https://www.wolframalpha.com/input?i=hohmann+exit+delta+v%2C...
What happens if something like Starlink is intentionally targeted during an active conflict, maybe with something like a fragmentation warhead? The short deorbit time seems like a feature, if it can deny access to space for the duration of the conflict while minimizing long-term effects. Or is there enough... space... up there that it's a non-issue?
Also wondering about the impact on communications with higher orbits, eg GPS, assuming these satellites even remain intact. If LEO is contaminated, maybe with something like reflective foil strips / confetti, would signals still be able to get through? Or is that again a matter of sheer scale where it is unlikely to cover a large enough area to be a real concern?
Blocking access to space that’s about specific orbits not something like an ICBM or deep space probe which only needs a tiny window to be useful. Imagine the risk of collision is 10% per day, that’s going to quickly kill any satellite, but if you only need 10 minute window you’re down to 0.07%.
Communication would be basically impossible to block. 1g of matter per square mile isn’t going to achieve much of anything, but multiplying even that trivial amount by 200 million square miles of surface area = 200,000 tons or about 500 ISS’s.
Lasers shouldn't produce lots of debris. If anything, they would be good at destroying debris.
I'll rate it 8/10 in its category...but that's really not saying much.
LEO:84%, MEO:3%, GEO:12% (https://nanoavionics.com/blog/how-many-satellites-are-in-spa...)
Combine that with the increased volume at higher elevations, and you get much higher satellite density in LEO. So if there is any Kessler problem, it will likely happen in LEO first. And that is the place that is the easiest to deal with (or quickest to self-heal by orbit decay).
So I’m left with a question. Is the west just doing more in this regard while non western states are behaving recklessly/belligerently OR do those nations also sponsor efforts, but don’t get mentions because the article audience is western?
Basically a class act all round.
[0] https://en.wikipedia.org/wiki/Mission_Shakti#Space_debris
There's also an earlier Soviet program described in the article, with many space impacts, tho debris extent isn't noted.
https://en.wikipedia.org/wiki/Anti-satellite_weapon#United_S...
Something like how it's developing nations that didn't get benefits from early industrialization (or indeed were exploited as a result of it) sometimes push back against climate policies which they feel are shutting them out of all the benefits that the historical polluters have gained.
IMO, the west is a better steward recently, but has done some pretty questionable things in the past. For example: https://en.wikipedia.org/wiki/Project_West_Ford
There's even a potential business case auctioning off laser time to guard specific satellites. A typical satellite costs about $200 Million to build, plus many millions to launch, and a few million per year to operate. There are about 2000 active satellites in high orbits where debris could be an issue. If operators pay $100k per satellite per year, about a 5% increase in annual operating cost and a 0.3% increase in lifetime cost (assuming 10 year satellite lifetime), that's $200M per year revenue. Assuming 300 m/s delta V to lower an object's orbit to the point it will decay naturally, and a 0.01% ground based electric to orbital kinetic energy conversion efficiency, a bank of lasers consuming 2 MW of electric power (not beam power) would be able to deorbit 140 tons of material per year. There are about 9000 tons of material in orbit, about 2000 tons of which are in medium and high orbits, so that's about 1/14th of long lived space junk. Assuming a 5 cent per kilowatt hour average electricity price, that's under $900k per year to power the lasers. Assume that's around 5% of annual operating costs, call it $20M/yr for ops and maintenance.
For capex, assuming 10% laser efficiency, that's 800 kW of laser beam power, 1 kW of beam power is around $8k, though the optimal frequencies may be different, let's call it $30M. The optics and targeting system is likely to be the bulk of the cost. A university grade observatory, which is likely comparable in scale and complexity is around $500k, but this would be a custom build so it's likely substantially higher. The keck observatory cost $140M and is likely a good upper bound. Add another $30M for other technical components, and probably another $100M for non-technical aspects of the facility. Assuming capex is amortized over 5 years, we're looking at around $60M/yr for capex. For a $500M initial investment, in 10 years you're paid off and up an additional $1.5B, for an average annual return of about 15%. Not exactly the greatest investment as is, but within the realm of discussion. Further, these estimates are quite conservative and it's likely a decent portion of the initial cost could be covered by a government.
My fuzzy impression from [1] is even the high-order-100x density increase of solar/geomagnetic storms has limited impact on lifetime (above low-LEO where there's no need). Summer day vs winter night variability is already like 10x. I'm struggling to picture high-altitude explosions raising enough mass to do more.
[1] slide 12 on https://swfound.org/media/207065/02_bruinsma.pdf "THERMOSPHERE DENSITY AND UPPER ATMOSPHERIC DRAG ON SATELLITES IN LEO" Sean Bruinsma
In either case, it's likely to have unforeseen effects on atmosphere and thus climate.
A Falcon 9 can put ~20,000kg into LEO for ~$40M - so $2/g.
The cost of deorbiting little space junk is many orders of magnitude higher than that. And deorbiting is far cheaper than capturing and recycling.
https://en.wikipedia.org/wiki/Fermi_problem
No point to looking up the current exact price, nor payload, when removing orbital junk is multi-million-dollar ante game, and state-of-the-art is "a few engineering prototypes exist". The bottom line (that we're many orders of magnitude away from economically recovering small space junk as raw material) would be true whether the cost of launch was $20/g or $0.20/g.
Again, that's cost not price. That's what the state of the art can do in a best case, but probably highly repeatable and reliable scenario, today.
Everything else is in the realm of science fiction.
The way economics is supposed to solve this sort of problem is via liability (and probably insurance). This doesn't require solving the space mining problem, just an actuarial problem.
But of course, the problem is that certain international actors wouldn't accept any sort of rules-based accountability for damage when it's caused by their space junk.
“The curious task of economics is to demonstrate to men how little they really know about what they imagine they can design.” ― Hayek
While it's true that plastics recycling is mostly a joke, in most places, companies manufacturing plastics aren't required to bear the cost of recycling in the first place (i.e. there has been no attempt to internalize the externalities in the first place), so I'm not sure it's even possible to invoke plastics recycling as a counterexample.
If there had been a push to make plastics manufacturers bear the cost of recycling, then the fact that recycling doesn't adequately cover the full externalities might be an example of the problems with this process (certainly there is an incentive for companies to try to downplay the negative externalities resulting from their products if they will be forced to bear the cost of dealing with those externalities).
The real way to make this process work would probably just be to tax plastics heavily based on their negative externalities and use that money to dispose of them.
However, this would likely make goods using plastics prohibitively expensive for consumers, so it might be unpopular, but it would likely cause people to use alternative materials that are more expensive than plastics are currently, which would be beneficial.
Even if they only kept up with inflation, bottle deposits would be at least 25¢ today. The federal government should treat the microplastic tsunami like it did the hazard of drunk driving: tie federal highway funding to states adoption of universal plastic deposit laws.
Just my 50¢
[0] https://www.alternet.org/2005/10/the_hidden_life_of_garbage
This is already a major problem with long-tail risk activities (industrial plants, mines, oil wells) or those with numerous small operators (shipping, itself the origin of the modern insurance industry). Established operators sell off or otherwise divest high-risk operations, units, vessels, etc., to smaller entities which can extract remaining value then walk away from the ultimate costs.
Add in to this problems of international law (and its even more problematic variants, marine and aerospace law), and you've got problems poorly addressed by market-bases solutions.
This is a giant "if" that generates enough gravity to pull all the space junk into a ball.
"If you can get your ship into orbit, you're halfway to anywhere."
https://en.wikipedia.org/wiki/True_anomaly
but other orbit changes in LEO can be about as expensive as launching a rocket up from Earth. There is no point, for instance, in sending a cargo to the space station and then launching it in a polar orbit. The space station we have has no potential as a staging area to go to the Moon or Mars because it is in the wrong orbit. The cost of moving things around is one reason why Terra is the low-cost source of resources throughout the solar system still.
Now you can move space junk around without using fuel, instead you can hit the space junk with a laser which will evaporate off a bit of the surface and push it:
https://arxiv.org/abs/1110.3835
the usual idea is that you use this to deorbit space junk but you could also use this to change the orbit of a piece so maybe you could gather a bunch of them in one place or maybe somebody could use such a laser to engineer collisions. The laser they describe in that paper is almost like a tractor or pressor beam from science fiction.
https://space.stackexchange.com/questions/2046/delta-v-chart...
IMO Orbital mechanics is very unintuitive, and one of the results in people asking things like "why not shoot all of our trash into the Sun?"
What’s the probability of a major collision? What’s the probability that ISS significantly damaged?
It says there’s no consensus from the models, so we can’t know what any of them predict?
according to Grok: https://www.reddit.com/r/ChatGPT/comments/1dgyujd/comment/l8...
It's Greek for "wanderers", and it's where we get the word planet.