[HN Gopher] The misunderstood Kessler Syndrome
___________________________________________________________________
The misunderstood Kessler Syndrome
Author : throw0101a
Score : 103 points
Date : 2024-06-18 10:58 UTC (12 hours ago)
(HTM) web link (aerospaceamerica.aiaa.org)
(TXT) w3m dump (aerospaceamerica.aiaa.org)
| bell-cot wrote:
| The article has a nicely sober sub-title, and at least talks
| about people doing actual calculations & simulations. (Vs. the
| usual dramatic doom-mongering.)
|
| I'll rate it 8/10 in its category...but that's _really_ not
| saying much.
| h2odragon wrote:
| Atmosphere rarely gets mentioned, in "space pollution" stories.
| It can be a factor in "the sky is falling!" stories:
|
| (2022) https://www.smithsonianmag.com/smart-news/hubble-is-
| slowly-f...
| delichon wrote:
| Economics could solve it, if orbital manufacturing finds it
| cheaper to collect space junk for raw material than to boost it
| to orbit or mine it from asteroids. If we can defer it long
| enough to get to that stage an incipient orbital buzz saw may
| have a silver lining.
| exe34 wrote:
| collecting objects at orbital speed from any direction is a
| tricky engineering challenge.
| bell-cot wrote:
| Understated.
|
| 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.
| sebzim4500 wrote:
| Not sure where you are getting the $40M. That's much less
| than the sticker price, and probably much more than the
| actual marginal cost of a launch.
| bell-cot wrote:
| You are correct (as far as I know), but:
|
| 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.
| simiones wrote:
| I'm pretty sure that collecting objects from a field of debris
| where every object is moving at speeds of up to 30,000 km/h
| relative to other objects, in random directions, is much more
| of a scientific challenge before even looking at economic
| incentives for it.
| Me1000 wrote:
| Exactly. People forget (or simply don't know) that orbital
| plane changes are incredibly expensive from an energy
| perspective. It's not like you're walking down the road
| picking up trash in a row, you have to adjust your orbit,
| canceling out movement in one direction while adding movement
| in another. And it takes an incredible amount of energy even
| for minor plane changes.
| lazide wrote:
| Especially since most of the debris is widely spread, and
| often as small as a pea.
| ooterness wrote:
| Exactly. It's like mining lead from the bullets flying
| through an active battlefield. There's material there, but
| it's moving in different directions.
| bsder wrote:
| I thought that the only effective way to clean this is
| ground-based focused energy. And even that has absolutely
| absurd energy requirements.
|
| Everything else is in the realm of science fiction.
| schiffern wrote:
| People are focusing on the technical challenge, but there's a
| deeper issue with this idea: using mining is solving the
| problem "by side-effect."
|
| 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.
| adolph wrote:
| > The way economics is supposed to solve this sort of problem
|
| "The curious task of economics is to demonstrate to men how
| little they really know about what they imagine they can
| design." -- Hayek
| KennyBlanken wrote:
| Yup, just like the problem with plastics is "solved" by
| recycling, which only manages to handle a fraction of the
| plastic generated, doesn't address microplastic pollution,
| and the economic viability of recycling is incredibly poor,
| in part because the polymers break down quite a bit with
| use/age/reprocessing.
| trashtensor wrote:
| Plastics, climate change, we have a number of these
| problems that get worse over a long enough time scales that
| there is no incentive for the people in charge of our
| economy to fundamentally change their behavior. I find
| "economics will solve this" arguments really dubious.
| exe34 wrote:
| the market only really works when the perpetrators pay
| the cost.
| bryanlarsen wrote:
| Recycling works great for lots of resources: lead-acid
| batteries, steel, aluminum, etc. Just because it doesn't
| work well for one resource doesn't make it non-viable.
| resoluteteeth wrote:
| What OP is talking about is internalizing externalities. In
| the case of plastics this would presumably involve making
| companies that manufacture plastics bear the costs of
| disposing of them.
|
| 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.
| fshbbdssbbgdd wrote:
| In California you pay an extra deposit when you buy a
| plastic bottle. I don't know if that number is set to
| properly capture the externality, but it's enough to get
| people wandering the streets to pick up the bottles and
| turn them in (they even rifle through your trash can).
| Also, it doesn't apply to most forms of plastic packaging
| or goods.
| inglor_cz wrote:
| Liability can be quite a problem when the original entity
| collapses or thoroughly transforms itself. A possible
| development for both corporations and nation states.
| dredmorbius wrote:
| Yes, and ...
|
| 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.
| raincole wrote:
| > if orbital manufacturing finds it cheaper to collect space
| junk
|
| This is a giant "if" that generates enough gravity to pull all
| the space junk into a ball.
| PaulHoule wrote:
| It is not always cheap to change orbit around Earth, the old
| Heinlein quote: "If you can get your ship
| into orbit, you're halfway to anywhere."
|
| is mostly wrong. If you wanted to send up a satellite to pick
| up little bits of trash and bring them to one place for
| processing you would have to use fuel to maneuver from one to
| another: it is cheap to change the
|
| 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.
| aftbit wrote:
| I would like to see a website/app/program that can generate
| Delta-V charts like this one, but with different bodies and
| transfer orbits for scale.
|
| 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?"
| VyseofArcadia wrote:
| Semi-related, there is an excellent manga about Kessler syndrome
| called _Planetes_.
|
| I would avoid the anime adaptation.
| saagarjha wrote:
| What's wrong with the anime?
| VyseofArcadia wrote:
| Nothing wrong with it, exactly, but it's tonally very
| different, and I preferred the more serious tone of the
| manga. The anime has more comic relief, a more episodic story
| structure, and doesn't get into or take as seriously some of
| the themes that come up later in the manga.
| KennyBlanken wrote:
| I'm guessing they hate it because the main character shifts
| in the manga vs anime from a middle aged widower to an (at
| the start of the series) annoyingly idealistic teenage girl.
| Although as the anime progresses, it doesn't focus nearly as
| much on her, shifting to one of her coworkers...
|
| 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)
| VyseofArcadia wrote:
| Tanabe is also a big part of the manga, and seeing her grow
| as a character (along with the hothead Hachimaki) is one of
| the best parts.
|
| 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.
| wwalexander wrote:
| Also semi-related, the (multi -millenial) plot of Neal
| Stephenson's Seveneves is kicked off by Kessler sindrome caused
| by the Moon.
| VyseofArcadia wrote:
| I have a fun Seveneves story. One of the professors on my
| doctoral committee missed my preliminary orals because he was
| reading Seveneves and lost track of time.
| exe34 wrote:
| my favourite part of the book is climbing to orbit with a
| glider and a whip :-D
| everyone wrote:
| I saw one interesting plan to get rid of space junk. As far as I
| remember it involved using nuclear bombs to "puff up" the
| atmosphere, locally making the top of the atmosphere higher and
| thus inducing drag on the junk / satellites. I think NASA did a
| bit of work on it, but not much. I forget what it was called. But
| it was the only plausible plan I have seen.
| airstrike wrote:
| I love it. Surely nothing could go wrong with that plan!
| jandrese wrote:
| I'd like to see the math on that. It seems more practical to
| pump gigatons of CO2 into the atmosphere if you want to do
| that.
| dylan604 wrote:
| humans collectively are saying challenge accepted
| mncharity wrote:
| > using nuclear bombs to "puff up" the atmosphere [...]
| plausible plan
|
| 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
| rini17 wrote:
| Well then redirect icy asteroid/comet and evaporate it to
| make longer lived gas ring around Earth.
|
| In either case, it's likely to have unforeseen effects on
| atmosphere and thus climate.
| kryptiskt wrote:
| That sounds like a really bad idea, the EMP from such a blast
| would mess with electronics in a large area.
| nordsieck wrote:
| I think one thing that really causes people to worry about
| Kessler Syndrome unnecessarily are satellite visualizations.
|
| 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.
| RationPhantoms wrote:
| Genuinely asking, do you think that could be solved by having
| better orbital visualizations?
| lazide wrote:
| Not the poster, but the issue is one of scale.
|
| 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.
| WillAdams wrote:
| An accurate steel replica of earth the size of a ball-
| bearing would be the most precise ball bearing ever.
|
| Great book on this:
|
| https://goodreads.com/book/show/35068671-the-perfectionists
| coolspot wrote:
| Doubt it. Earth is not even a sphere.
| lazide wrote:
| Looks like you're right! Earth is within .3% of being a
| sphere, where ball bearings are within .01%.
|
| [https://en.m.wikipedia.org/wiki/Earth%27s_circumference]
| WillAdams wrote:
| Correct --- I should have said "smoothest".
| sandworm101 wrote:
| I've heard this a couple times and never believed it.
| Earth is perceptibly not round. Scott Manley did a quick
| video showing that in some satellite images the
| difference equates to more than a couple pixels. Some
| quick googling shows the earth being about 0.3% not-
| round, which would match a 1000-pixel image being not-
| round by a few pixels. But a 0.3% deviation is
| exponentially greater than is allowed by the standards
| for ball bearings.
|
| >> 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...
| lazide wrote:
| To do the last extra bit of math - that seems like the
| ball bearings would then be within .01%? Or am I missing
| a zero?
| QuercusMax wrote:
| Smoothness vs perfect roundness are two different things.
| The earth is very smooth, even if it's not perfectly
| round.
| aetherson wrote:
| I think you're talking about different things. It's true,
| the Earth is substantially non-spherical. But things like
| mountains are tiny irregularities on a smooth (not-
| perfectly-spherical) surface.
| samatman wrote:
| A better way to talk about this is something like: given
| a globe of Earth, say a 50cm diameter one, finished with
| plate Bristol paper, the texture of the surface would not
| be as smooth as a perfect model of Earth at that scale.
| lazide wrote:
| If I remember correctly, the term is 'rugosity'. Hah,
| yup! [https://en.m.wikipedia.org/wiki/Rugosity]
| jordanb wrote:
| No the dominant deformation on earth is that it is
| flattened at the poles and bulges at the equator. This is
| because of axial momentum and makes the earth an oblate
| spheroid.
|
| 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.
| BalinKing wrote:
| Only tangentially related, but GP's source was _The
| Perfectionists_ --I've had it on my list of "books to
| read one day" for a while now, but this makes me
| reconsider.... If the author didn't bother to verify a
| basic fact like this, what else might be wrong?
|
| 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?
| WillAdams wrote:
| My mis-representation wasn't from the book, and of
| course, what I meant was "smoothest" rather than
| "precise".
| aaronharnly wrote:
| I suppose you could generate an alternate view (maybe someone
| has?) that doesn't show the individual satellites, but
| instead only shows little green/yellow/red flashes whenever
| satellites cross within some radius of one another.
| cruffle_duffle wrote:
| That is a tricky problem to solve. The scales are so far
| apart from each other it's a bit like solving "how do you
| scale the distance between the sun and the planets in a way
| that keeps some detail of each while giving a sense of the
| true amount of nothing between them".
|
| 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.
| LeifCarrotson wrote:
| I don't. The human sensorium (whether actually looking at an
| image, or visualizing something based on some numbers) has
| limited dynamic range.
|
| 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.
| schiffern wrote:
| It's popular to point out how satellite visualizations
| exaggerate the size, but we never seem to notice how satellite
| visualizations _shrink the duration of time_. You only look at
| a visualization for maybe a minute, whereas these objects are
| actually out there whizzing around 24 /7 for decades or even
| millennia.
|
| 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
| bryanlarsen wrote:
| The third & fourth factor are whether the satellites are
| actively avoiding collisions and whether the satellites are
| in a self-clearing orbit.
|
| 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.
| nordsieck wrote:
| > Half of fragments are toward a lower orbit. The other
| half only boost apogee and either lower perigee or leave it
| unchanged.
|
| 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.
|
| ---
|
| 1. https://en.wikipedia.org/wiki/Hohmann_transfer_orbit
| bryanlarsen wrote:
| Even the FCC doesn't appear to understand this correctly.
| They denied a SpaceX application to put satellites into
| lower & safer orbits. https://spectrum.ieee.org/starlink-
| vleo-below-iss
| admax88qqq wrote:
| Absurd if you consider the utility to the average person
| of the ISS vs Starlink.
| bryanlarsen wrote:
| Putting Starlink satellites at an orbit below the ISS
| would be safer for the ISS than their current altitude
| above the ISS.
| tomrod wrote:
| How about MAXAR/Planet?
| jerf wrote:
| That more-or-less cancels; yes, the satellites are traveling
| through a 4D space and aren't just at one point in one time,
| but then that's still sparse in the full 4D space. If
| anything it makes it more sparse, not less. It's not like
| crossing paths, but separated by a year, matters at all, to
| the extent that such a thing can even be defined.
| denton-scratch wrote:
| > are traveling through a 4D space
|
| 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...
| denton-scratch wrote:
| Hey, vote me down to oblivion if you want; I don't care.
| But I think it's nice to say why.
|
| 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.
| dsabanin wrote:
| To me the main problem with "traveling through 4D" is the
| fact that "traveling" is happening in the 4-th dimension.
| merely-unlikely wrote:
| Isn't traveling happening in all 4 dimensions?
| Gravityloss wrote:
| This is a very informative video. Even if no more satellites
| were launched, the amount of objects would increase over time
| as collisions would occur. I think it could be submitted on
| its own. (Btw I checked and ERA-2 re-entered in February
| 2024. Great work ESA!)
| inglor_cz wrote:
| For some related ideas...
|
| 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.
| ninetyninenine wrote:
| A side note. There's a whole anime about this that's actually
| realistic. It's called planets.
| VyseofArcadia wrote:
| Spelling nitpick: Planetes
|
| It's Greek for "wanderers", and it's where we get the word
| planet.
| cletus wrote:
| Related [1] (framed in the context of the Fermi Paradox).
|
| 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...
|
| [5]: https://en.wikipedia.org/wiki/Graveyard_orbit
|
| [6]: https://en.wikipedia.org/wiki/Delta-v_budget
| FredFS456 wrote:
| > It still takes a delta-V of ~30m/s to hit the Sun.
|
| That number looks like it should be much much bigger to me.
| dabluecaboose wrote:
| Indeed, it's off by orders of magnitude (so probably a simple
| typo). The Earth orbits the Sun at between 29 and 30 km/s. It
| would take roughly that much dV to successfully create an
| orbit that intersects the sun.
| tialaramex wrote:
| The straight forward way is typically given as 30km/s so
| yeah, it's the wrong unit.
|
| 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".
| ninkendo wrote:
| Even without gravitational slingshots, the simple solution
| would be to just take advantage of the oberth effect and do
| many, many successive burns, retrograde at aphelion and
| prograde at perihelion, until your perihelion is low enough
| to intersect the sun. It wouldn't be crazily less delta-V
| but it would be appreciably lower.
|
| 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.wolfra
| malpha.com/input?i=hohmann+exit+delta+v%2C...
| pwndByDeath wrote:
| Did a simulation like the MIT one, instead of adding millions of
| tiny objects I tried making the thousands of current objects have
| a collision radius of 1-5km. Turns out space is big and I didn't
| have many more collisions. Mostly starlink bumping into each
| other gently
| klysm wrote:
| I'm curious what gently looks like at these speeds
| pwndByDeath wrote:
| Things in the same plane are moving at relative speeds of cm
| per second, so literally bumps. When things do intersect off
| plane its more energetic
| cubefox wrote:
| I read the article, but didn't come out much wiser. Apparently it
| is still not clear how big of a threat a potential future Kessler
| syndrome is.
| travisgriggs wrote:
| The article cites a number of western assets that do things like
| model and study this problem. The only credit India and Russia
| get is for contributing to the problem by shattering things in
| space. There is no mention of China at all.
|
| 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?
| XorNot wrote:
| India's ASAT test was a very well executed one if I recall:
| they launched a satellite dedicated to the task, and put it in
| an orbit where it would re-enter anyway and then hit it with
| the interceptor. As a result the debris was headed back to
| Earth and I believe was targeted to a known region as well.
|
| Basically a class act all round.
| dr_orpheus wrote:
| Yep, it was a dedicated satellite and it was an altitude of
| 283 km when they did the ASAT test. Everything from the test
| decayed within about 3 years [0].
|
| [0] https://en.wikipedia.org/wiki/Mission_Shakti#Space_debris
| jccooper wrote:
| Despite their intention of debris lasting a minimal amount of
| time ("weeks") some of the generated debris lasted for
| several years. While this was much better than the
| particularly reckless Russian destruction of K1408, orbital
| collisions are chaotic and energetic events, and there's no
| particular way to do it safely.
| pmayrgundter wrote:
| Does seem biased to not mention the prior US testing, which
| destroyed satellite Solwind P78-1 in 1985, leaving debris in
| orbit for 2 decades. (also suggestive of secret testing which
| may have left more)
|
| 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...
| dr_orpheus wrote:
| Also, the US Operation Burnt Frost which shot down a non-
| functioning NRO satellite in 2008. Luckily this one was in a
| low orbit and everything decayed within a couple years.
|
| https://en.wikipedia.org/wiki/Operation_Burnt_Frost
| dr_orpheus wrote:
| Certainly there is some bias, the other comments here have
| addressed some of the things we skim over. I don't know enough
| to speak to other countries specifically, but the US does now
| have the "de-orbited within five years" rule enforced by the
| FCC for any newly launched satellites. I believe Europe is also
| following this now as well, but I believe the ITU rules are
| less strict and still follow the older rule for de-orbit within
| 25 years.
| advisedwang wrote:
| I don't know the factual answer to your question, but just
| wanted to point out a potential motivation between such a
| discrepancy if it is real: western states have already achieved
| much of the benefit from space tech, and are ahead, giving the
| luxury of thinking about such things. Other states have not, so
| likely don't want to invest in research that would prevent them
| reaping the benefit others already got.
|
| 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.
| modeless wrote:
| IMO we need to stop putting satellites in orbits above ~800km
| altogether. No matter how careful you are there will always be
| accidents, and once a collision or explosion occurs in high orbit
| the debris is essentially a permanent fixture of the solar
| system, lasting far longer than a human lifetime. There is no
| feasible method to clean up such collision debris for the
| foreseeable future. Even assuming SpaceX Starship is wildly
| successful and launching a thousand times more mass to orbit for
| dirt cheap, collision debris cleanup is still infeasible. The
| _only_ realistic way of cleaning collision debris is the natural
| way, the atmosphere. But it only works on reasonable timeframes
| when you 're below a certain altitude.
|
| 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.
| bongodongobob wrote:
| Assuming a 10m wide satellite, that's like grains of sand in a
| 470 foot orbit. I'm not going to calculate the odds right now
| but the chances of collision (assuming they're even _capable_
| of colliding in their orbits) has to be infinitesimally small.
| Your assertion that "accidents always happen" is doing all the
| legwork for your argument and it's so unlikely it may as well
| be false.
| modeless wrote:
| No need to calculate odds, we have data. There have been
| hundreds of collision and explosion events creating debris in
| orbit. Many if not most of them have been unintentional
| accidents. https://en.wikipedia.org/wiki/List_of_space_debris
| _producing...
| bongodongobob wrote:
| In that list there's 1 intentional collision and 1
| accidental.
| modeless wrote:
| It's far from a comprehensive list. Many of the causes
| are listed as "unknown" as well. This page lists 9
| unintentional collision events:
| https://en.m.wikipedia.org/wiki/Satellite_collision and
| it's clearly not comprehensive either since it doesn't
| contain some from the other list. And collisions are not
| the only kind of accident creating debris clouds. The
| page cites 250 debris creation events as of 2015, there
| have been more since, and most of them were not
| intentional. Ultimately it doesn't matter what specific
| kind of unintentional accident created debris. All that
| matters is how long it will pollute orbit.
| marcosdumay wrote:
| Those are events that created debris, not events caused by
| debris.
| modeless wrote:
| That's right, illustrating my point that accidents
| creating debris are common and not realistically
| completely avoidable. Which is why we need to avoid
| putting satellites in orbits where any created debris
| will inevitably pollute space for millennia.
| TheDudeMan wrote:
| Frustrating that the charts do not show the elevation. I
| bet they are all LEO.
| AcerbicZero wrote:
| IMO your opinion is bad, and you should feel a little bad about
| it.
| jallmann wrote:
| Total layperson here, but here are some things I have been
| wondering that the article didn't really address.
|
| 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?
| Retric wrote:
| The vast majority of Starlink satellites experience fairly
| significant atmospheric drag with their current surface area to
| volume ratio. Blow them up and you get more drag so they
| deorbit much faster.
|
| 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.
| modeless wrote:
| Physically destroying one Starlink satellite is pointless as it
| wouldn't meaningfully disrupt service. Destroying enough
| Starlink satellites to disrupt service is infeasible. You would
| need to launch many hundreds if not thousands of interceptors.
| It would cost a fortune, probably a lot more than launching the
| constellation in the first place. It wouldn't deny access to
| space as you can simply launch through a debris cloud, spending
| only a few minutes in the danger zone which would give you a
| negligible collision risk compared to satellites that linger
| for years. You also couldn't intentionally create a debris
| cloud dense enough to disrupt communication or cause a chain
| reaction of collisions at Starlink's altitude. Space is too
| big.
| ianburrell wrote:
| There are rumors that the US and China have laser weapons for
| destroying satellites. Lasers are good for anti-satellites
| because they can sit on the ground with plentiful power. Then
| accurately target lots of satellites. Laser weapons possible
| whole constellation in short period of time depending on how
| fast they can fire.
|
| Lasers shouldn't produce lots of debris. If anything, they
| would be good at destroying debris.
| WhitneyLand wrote:
| Can't believe someone wrote that whole article without getting to
| some basic answers.
|
| 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?
| kidme5 wrote:
| Kessler Syndrome is the main problem with Elon's plan to build a
| nuclear defense shield in LEO
|
| according to Grok:
| https://www.reddit.com/r/ChatGPT/comments/1dgyujd/comment/l8...
| TheDudeMan wrote:
| FWIW, here is where satellites are distributed:
|
| 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).
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