[HN Gopher] Decluttering low-Earth orbit: It's time to tidy up s...
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Decluttering low-Earth orbit: It's time to tidy up space
Author : edward
Score : 147 points
Date : 2021-01-18 10:13 UTC (12 hours ago)
(HTM) web link (www.economist.com)
(TXT) w3m dump (www.economist.com)
| Symmetry wrote:
| One cool way of de-orbiting satellites is to brake against the
| Earth's magnetic field with a conducting wire. This is actually
| already a product.
|
| https://www.tethers.com/deorbit-systems/
| flipflipper wrote:
| There were couple demo sats launched a few months ago. One with
| the tether, one without. https://www.dragracersat.com/
| dukeofdoom wrote:
| Star Timelapse and long exposure night photographers get annoyed
| by all the current debris, they need to clean up their photos
| from the light streaks. On the other hand, I remember reading
| about this town in the mountains that wanted to build a giant
| mirror on top of a mountain, so that they could prolong daylight
| in their valley.
| josefresco wrote:
| For other space related content, check out The Orbital Index:
| https://orbitalindex.com
|
| A nice newsletter about space stuff (I have no affiliation, just
| a fan)
| konschubert wrote:
| We have a nice podcast episode on this topic. We go into a few
| scenarios on how this might end and how it could be fixed.
|
| (You can skip the first 30 seconds of intro)
|
| https://www.predictions-podcast.com/2020/03/14/space-debris-...
| napier wrote:
| What we need is a fleet of teleoperated VASIMIR-engined trawlers
| with electromagnetic fishing nets to clean up space garbage. What
| about funding? A levy on satellite launches and operators under
| the polluter pays principle. Perhaps this could be structured as
| an addition to insurance premiums, considering the purpose is
| perpetuation of access to Earth orbit and outer space for the
| sake of future generations and for all mankind.
| TheRealNGenius wrote:
| @dang, I thought paywalled articles weren't allowed.
| array wrote:
| Non-paywalled version: https://archive.is/GaWcS
| Noxmiles wrote:
| Meanwhile india: https://en.wikipedia.org/wiki/Mission_Shakti
|
| btw: The article is behind a paywall :(
| rocknor wrote:
| Meanwhile USA has 25x the debris (as of June 2019). Glass
| houses...
|
| https://orbitaldebris.jsc.nasa.gov/quarterly-news/pdfs/odqnv...
|
| https://www.businessinsider.in/us-russia-china-and-india-sta...
| Rebelgecko wrote:
| I think the concern is that despite increased activity in
| space, most countries have slowed down the amount of
| dangerous debris being created.
|
| Meanwhile, India created about as much space junk in a day as
| the US creates in 1-2 years. That's despite claiming that the
| the test was in an orbit that wouldn't leave any longterm
| debris.
| rocknor wrote:
| I think you should focus on the huge amount of garbage and
| carbon emissions produced everyday in the USA (biggest
| contributor to climate change), which is objectively a much
| bigger problem than this one-off event which media
| portrayed as some sort of catastrophe. It's "glass houses"
| all over again. Why should a nation of 350M people have
| ASAT capability in the interest of national security, but
| not a nation of 1.4B people? We're seeing what happens when
| power is concentrated in the hands of a few (Trump/Parler
| bans) and it cannot be allowed to happen at a geopolitical
| level, in the interest of world peace (it sounds crazy but
| it has worked post WW2).
| AniseAbyss wrote:
| Easy to criticize other countries when you've already had
| your space race.
|
| I do find it annoying that space is usually jingoistic
| bullshit involving flags and rousing speeches instead of
| actual science. I'm glad ESA never went that way.
| onethought wrote:
| Is this really a thing... orbit is a vastly bigger place than the
| earths surface... you'd have to try pretty hard to hit that junk
| wouldn't you?
| Cogito wrote:
| The issue is not in passing through the junk - that's like
| passing through the asteroid belt. We don't (or at least used
| to not) even plan a specific path through the asteroid belt, as
| the chance of hitting anything on the way through is so low.
|
| The problem is if you want to stay in an orbit alongside the
| junk.
|
| The dynamics of orbital mechanics are interesting, to say the
| least, but it in no way maps to the surface of some sphere.
|
| A somewhat useful analogy is to imagine two circular
| racetracks, that intersect with each other in two spots. Each
| racetrack is like an 'orbit', and racecars going around them
| are satellites.
|
| Make the racetracks really big, and put a car on each track.
| Have the cars drive around non-stop forever. The chance of them
| hitting each other on any lap is extremely small. However, if
| you let the cars go for a long time, and one of them completes
| a lap a little bit faster than the other, the times that they
| both cross the intersection will slowly get closer and closer
| together. Eventually, they will crash. If you put more cars on
| the track, the chance of two of them colliding increases. If
| everyone time they crash they create lots of baby cars, well
| you get Kessler Syndrome.
|
| This is only a problem for these racetracks because they touch.
| We protect against this in the orbital world by keeping
| satellites in different orbits, that don't cross. The problem
| is that the orbits can shift over time due to gravitaional
| inconsitencies, and solar flares causing the atmosphere to
| bleed off into space, and the moon, etc. With lots of long
| lived satellites in low earth orbit, the chance for a crash
| increases. But even if we do get lots of baby satellites the
| other orbits farther out will remain useable (like
| geostationary orbits), you just have to be a little careful
| when crossing the low earth orbits on the way out.
| nielsole wrote:
| on the other hand you move a lot faster than one usually does
| on earths surface
| Retric wrote:
| If everything on a given orbit it going in the same general
| direction then their relative velocity is what matters.
| Collisions are not an issue at geosynchronous orbit for
| example.
| Fradow wrote:
| From what you can read on the Internet, yes it appears to
| really be a thing. Read up on Kessler Syndrome to understand a
| bit more on the subject.
|
| The problem is not just about satellites, but random debris
| flying unpredictably on orbit. When there starts to be a
| critical number, the odds to hit something start to raise in
| the "very possible" territory.
|
| The Wikipedia page for Kessler Syndrome even state that,
| currently, one satellite is destroyed every year by junk.
| That's only going to increase if nothing is done.
| ehnto wrote:
| Check this site out, it's a catalogue of known stuff in space
| http://stuffin.space/
|
| The ISS has regular enough operations required to dodge debris
| detected approaching for a near miss in space that I think it's
| definitely a concern for future operations.
|
| Consider as well that stuff in orbit is going ~25,000km/h or
| more and at that speed even a small bolt would decimate a
| spacecraft on impact.
| onethought wrote:
| I always dislike those visualisations as it gives the
| impression it's crowded, because the dots aren't to scale.
|
| Are the orbits in opposing directions? If not, then the 25k
| number isn't meaningful right? Their relative velocity is
| what matters
|
| That's interesting about the ISS I hadn't heard of that as a
| regular thing.
| onethought wrote:
| Just to follow up on the ISS, they have made a total of 20
| avoidance maneuverers and they do it if they calculate the
| chance of hitting as greater than 1 in 10000.
|
| So it is a thing, but I wouldn't call < 1 per year regular
| 4ggr0 wrote:
| What on earth...I did not know that there are sooo many thing
| floating around near us. Absolutely crazy.
| Triv888 wrote:
| In this visualization, they probably look a lot larger then
| they are in reality...
| narag wrote:
| Why "deorbiting"? Considering the cost of putting it there,
| wouldn't it be better to group the debris in a junkyard? Tell the
| jawas, maybe they're interested in managing it.
| environment wrote:
| Kurzgesagt has made a video about space junk. End of Space -
| Creating a Prison for Humanity
| https://youtube.com/watch?v=yS1ibDImAYU
| tomhoward wrote:
| Fun fact: A hobby satellite my father helped build as a way to
| justify procrastinating during university in the late 60s is now
| low Earth orbit space junk. He says he's rather embarrassed to
| have learned, post launch, that it would likely remain in orbit
| for 100,000 years.
|
| https://en.wikipedia.org/wiki/Australis-OSCAR_5
|
| http://centralblue.williamsfoundation.org.au/oscar-5-the-fir...
|
| https://www.youtube.com/watch?v=hjhto6wUQYQ
| laurent92 wrote:
| > Launch date: 23 January 1970
|
| Phew, 23 days earlier your father would have had to code all
| timestamps in negative.
|
| Joke apart, which OS did such satellites run? Unix? Probably
| not, since timestamps only started in 1970. Just "C"? Even
| today, how do you register time on satellites? With Unix
| timestamps (a long since 1970-01-01)? Can they synchronize
| based on objective points (stars or Earth position to the sun)
| or are satellites always resynchronized from Earth signals?
| hnarn wrote:
| I have to say that the assumption of a hobbyist satellite in
| 1970 to be able to run UNIX is pretty amusing, considering
| (Wikipedia):
|
| > In a 1970 survey, The New York Times suggested a consensus
| definition of a minicomputer as a machine costing less than
| US$25,000 (equivalent to $165,000 in 2019), with an input-
| output device such as a teleprinter and at least four
| thousand words of memory, that is capable of running programs
| in a higher level language, such as Fortran or BASIC.
|
| I think it's safe to say that the biggest issue with
| launching computers running UNIX into space in 1970 probably
| was not the lack of a standardized time stamp :-)
| m4rtink wrote:
| Back then most satellites were likely just hardwired
| electronics, possibly with some limited remote command
| support. Sure, there were exceptions for high profile
| missions such as space probes and spy satellites.
|
| IIRC there have been some proposals to use Pulsar signals on
| satellites/probes not just for time synchronization but more
| importantly navigation. Not sure if it's actually in
| production use yet.
| eT8AZithxooKei6 wrote:
| > "Passive magnetic attitude stabilization was performed by
| carrying two bar magnets to align with the Earth's magnetic
| field in order to provide a favorable antenna footprint."
|
| Wow! I heard of this technique recently but I didn't realize it
| had already been deployed so long ago.
| tempest_ wrote:
| And here it is!
|
| http://stuffin.space/?intldes=1970-008B
| SilasX wrote:
| Wow, that's a cool site! I've never seen orbiting satellites
| visualized like that. (But of course, also haven't sought any
| out.)
| bluu00 wrote:
| what kind of black magic is that ?
| sandworm101 wrote:
| Your father's satellite is very high (1400km, 1000km above the
| ISS) at the edge of what is classified as low earth orbit. It
| will be up there for a long while but the chance of it ever
| hitting anything is infinitesimal.
| simonh wrote:
| Infinitesimal over 100,000 years? I'm not losing any sleep
| over it personally, but that's a long time.
| sandworm101 wrote:
| The surface area of the sphere at 1400km is far greater
| than the earth's surface area. And satellites at that
| altitude are traveling much slower. Put together, the
| probabilities would akin to a handful of birds flying on
| earth, at random altitudes/places/directions, and two of
| them colliding.
| bagels wrote:
| "much slower" is still >7000 m/s
| sandworm101 wrote:
| Yes but at that altitude their orbital period is about
| 1/2 that of low orbits, meaning that even if two orbits
| do cross paths, there would be fewer potential collisions
| in a given time. They are 'slower' in relation to size of
| the sphere they occupy.
| bagels wrote:
| 90 mins at 400km vs 110 mins at 1400km
| [deleted]
| dr_dshiv wrote:
| This! How likely would collisions be on a sphere the size
| of the earth? How do the probabilities change from low
| earth orbit to higher orbits?
| BurningFrog wrote:
| Yeah, that statement makes a lot of assumptions about the
| next 99,950 years.
| bgun wrote:
| That makes the very big assumption that the density of other
| things to hit doesn't massively increase.
| charlesju wrote:
| That makes a big assumption we can't remove the junk before
| the density is high enough
| btilly wrote:
| It is worthy of note that SpaceX is pitching Starship for
| active debris removal in space.
|
| It is worthy of note from https://spacenews.com/upper-
| stages-top-list-of-most-dangerou... that in a list of the
| 50 most concerning objects in orbit, 78% are rocket
| bodies, and 80% were launched before 2000 when various
| mitigation strategies for space junk began to be
| improved.
|
| There is therefore a Pareto principle at work here. We
| are tracking over 25,000 objects, but only a few of them
| contribute most of the risk, and we aren't adding as much
| to the risk as the number of launches would make you
| think.
| Zenst wrote:
| I wonder how the odds stack up against the odds of a human
| being hit by a meteorite? Those kind of odd's/statistics I
| can get my head around.
| titzer wrote:
| Suppose there are _just_ two satellites orbiting at the same
| altitude, a bit higher, let 's say 5 orbits a day (ISS orbits
| 18 times a day, roughly). The two satellites cross each
| other's path twice per orbit. Over the course of a year,
| that's 3650 potential collisions. Given the length of their
| orbit might be 50,000 km, then the average distance between
| these two crossings is 13 km. Over 10 years, that reduces
| down to 1.3 km. Over 100, 130m. Over 100000, it's 0.130m.
| They are gonna collide.
|
| Of course, I am assuming a few things, like their orbits
| don't decay, they aren't exactly synchronized (i.e. they
| drift, and will eventually cross every point on the other's),
| but also that the uneven gravity of Earth doesn't corral them
| into narrower orbital paths (which it absolutely will,
| increasing the chances of collision).
|
| That's for only _two_ satellites. There are literally
| thousands. And when they smash apart, they can each generate
| hundreds more killer-sized fragments.
|
| Kessler syndrome is a very real possibility on a long
| timescale.
|
| We should be more careful the junk we put in space.
| jimmaswell wrote:
| We'll figure out how to clean it up when or if it's ever a
| problem. He shouldn't worry about it.
| villgax wrote:
| Can a large magnetic pulse for a short duration get shards to at
| least come together & somehow be yeeted down towards earth?
| spockz wrote:
| I suppose a large blob of magnetic gel might be more useful,
| attached at the front of a rocket. Magnetic and gel like
| substance to trap any parts, dust, an debris from collisions.
| JulianMorrison wrote:
| Unlikely for several reasons. The volume of space is enormous,
| many shards aren't ferrous, and a magnetic field that intense
| would damage things on the ground.
| detritus wrote:
| Sounds like a great idea! Although I imagine the size of pulse
| required would probably be such that it would have some less
| than desired secondary effects on the upper atmosphere,
| technologies at ground level and the various early warning
| systems deployed by our nuclear-armed nations... .
| PaulDavisThe1st wrote:
| > The best idea, though, is to attack the problem at its roots.
| The littering of space is an example of the "tragedy of the
| commons", in which no charge is made for the use of a resource
| that is owned collectively.
|
| Garrett Hardin's article which created and promoted the "tragedy
| of the commons" doesn't describe historical "commons" at all,
| which were all managed over extended periods of time by complex
| rules and social norms. The "tragedies" happened primarily when
| capitalism emerged and demanded an end to the historical
| management of commons, allowing the interests of capital to
| destroy them.
|
| Space might actually be the first really good example of "the
| tragedy of the commons" inasmuch as it was a new, globally
| accessible (i.e. not geographically determined) resource which
| began to be used without any establishment of the usual norms and
| rules that accompanied historical commons. Something similar
| presumably happened with the oceans, but their physical nature
| (i.e. stuff sinks, and stuff moves) hasn't created an issue in
| the same way that is now happening in orbit.
| sampo wrote:
| There's a near-future hard science fiction manga and anime series
| Planetes, about these cleaning workers:
| https://en.wikipedia.org/wiki/Planetes
| copperwater69 wrote:
| Probably not a HN tier comment, but there's a great anime about
| space debris cleanup.
|
| https://en.wikipedia.org/wiki/Planetes
|
| https://www.youtube.com/watch?v=CZ-OyT4ivkM
| throwaway6734 wrote:
| Fantastic series!
| dgellow wrote:
| Also a great manga, some very nice editions are available
| teekert wrote:
| I also enjoyed that.
| m4rtink wrote:
| Adding couple space related yet quite plausible anime/manga
| series:
|
| https://en.m.wikipedia.org/wiki/Rocket_Girls - basically space
| flight marketing for highschoolers created in cooperation with
| JAXA - has a pretty good description of using a biosuit
|
| https://en.m.wikipedia.org/wiki/Space_Brothers_(manga) - a near
| future "so you want to be an astronaut, eh? " story - very
| realistic description of what you need to do before actually
| going to space (38 volumes/99 anime episodes)
|
| https://en.m.wikipedia.org/wiki/Starship_Operators - a space
| opera that has quite minimal super science and a lot of hard
| physics - lasers vs overheating, detection/stealth in space
| (and the lack thereof), signal propagation issues, how to turn
| big ships quickly enough to use thrusters/fire axial weapons,
| using neutrino detectors to spot enemy warships based on
| neutrinos from their nuclear reactors
|
| Various UC Gundam series - pretty accurate description of
| O'Neil Island 3 space colonies, mass drivers, orbital
| infrastructure in general - zero g only ships & stations
| Cogito wrote:
| This anime is brought up in a lot of threads on space debris,
| and as others attest is excellent. It's a fully fleshed out and
| plausible future, where people have jobs cleaning up space
| debris, and it explores many of the issues that may await that
| kind of work in the future.
|
| Your comment epitomises the golden rule of Hacker News, that
| you should post "anything that gratifies one's intellectual
| curiosity".
| AlanSE wrote:
| It was extremely good for its time. For instance, the
| creators asked scientists to estimate the efficiency of solar
| panels at the time, and computed the area needed for the
| space stations they drew. Truly incredible that they went to
| these lengths.
|
| Nonetheless, it is very dated. Fusion power looks a lot worse
| today than it did back in 2003. The fusion-powered space
| Jovian exploration ship would be right at home in today's
| sci-fi (just as much the future today as then), but He-3 as a
| reason to go into space as been eviscerated. People who still
| (unrealistically) hope for a fusion game-changer are more
| often touting proton-Boron, and He-3 doesn't even
| fundamentally change problems of ignition conditions and
| radiation, it just mitigates it.
|
| They also didn't do much to predict radical reduction in
| launch costs. In the PlanetES world, it still felt very
| expensive to get into space. They didn't go unless they had a
| corporate sponsor or were filthy rich. I don't even remember
| anything that hinted at booster re-usability, which is now
| (astonishingly) reality.
|
| There's also the obvious fact that sending people to do trash
| pickup was always more Hollywood than reality. They knew that
| then.
| m4rtink wrote:
| There was massive amount of in space infrastructure and
| lots of people. Even though they did space mining there is
| no way they would be able to put all that in place without
| RLVs. IIRC they even show them a couple times, basically
| big NASP like SSTO aerospaceplanes.
|
| They also have regular transcontinental flights going
| through space, even though its IIRC not clear if its sub
| orbital ballistic trajectories or FOBS like partial orbit
| ones.
|
| Still, many would-be hard SF films get this completely
| wrong - huge space stations and/or interplanetary
| spaceships yet they launch it all on rather dated looking
| expandable boosters!
|
| Already The Martian it's pushing is pushing it with using
| basically improved EELVs (launched by ULA, none the less!)
| yet having hundreds if not thousands of tons of equipment
| and propelant in place.
|
| Interstellar or Ad Astra is bad shit insane - dinky ELVs
| and multiple interplanetary colonization attempts and
| humongous space ship in the former and KFC & artillery
| fireballs on the Moon in the former. And Ad Astra even has
| booster stages being dropped when launching from Mars
| because hey, why not waste even more resources!
| immmmmm wrote:
| curious of the price of de-orbiting an m6 screw (say m = 4g, v =
| 8000m/s) given it has the same kinetic energy as a small car (m =
| 1000kg v = 16m/s).
| hoseja wrote:
| You don't need to get rid of all those 8km/s. Just enough to
| drop down into the atmosphere, the rest is a shooting star.
| f-word wrote:
| Suppose you put a largeish amount of polyurethane foam in orbit,
| possibly around some scaffold to take up even more space, had it
| inflate when up there and had it absorb any wandering garbage for
| a while. How long would it take for the giant garbage mound to
| deorbit and burn?
| [deleted]
| drfrank wrote:
| A spherical Whipple shield might be able to capture debris. A 1
| mm thick aluminum shell with a radius of 100 m would mass
| 810,000 kg. If SpaceX's Starship can achieve launch costs of
| 10/kg, that's $8 M per sphere.
|
| But passive objects are only as likely to provide value as the
| ratio of the number of the total volume of the sacrificial
| objects to the total volume of assets, so you'd want a bunch of
| them.
|
| Since the debris of interest is really just the material
| traveling in orbit, a cylinder might be more efficient, if some
| primitive attitude control could be included efficiently.
| MauranKilom wrote:
| I'm not exactly sure how you imagine the collisions to play
| out. If you think anything gets "stuck" in your foam, you're
| underestimating the speeds at which objects in orbit move. It's
| more like shooting a railgun at your impactor. I also recommend
| Netwon's impact depth approximation:
| https://en.wikipedia.org/wiki/Impact_depth
|
| For the purposes of deorbiting junk it may be sufficient to
| just impart _some_ delta-v, but you neither want that to be
| uncontrolled collisions sending stuff into even more erratic
| orbits, nor would you want to risk generating even _more_ tiny
| pieces.
| BurningFrog wrote:
| I don't have a good feel for the numbers either, but surely
| if you make the Space Sponge big enough, things _will_ get
| caught in it.
|
| There is almost certainly a better material to use as well,
| but I don't think either of these practical concerns
| invalidates the idea.
|
| Of course, big enough Space Sponges to make a practical
| difference would be very visible to the naked eye.
| MauranKilom wrote:
| Well, the reason why I brought up Newton's impact depth
| formula is that it quite clearly shows you have to have
| enough "braking" material up there. Distributing it over a
| greater area reduces the effectiveness proportionally.
|
| The problem in the end is launch costs. Yes, we're getting
| better, but that doesn't mean we can shoot up a "visible to
| the naked eye"-sized impactor. Not to mention what
| difficulties an object of that size would bring for non-
| garbage that also occupies those orbits.
|
| Lastly, I have no idea how much research there has been in
| containing the fragmentation of hypervelocity impacts. But
| presumably it would be an important part of the mission to
| not generate more garbage.
| BurningFrog wrote:
| OK, you've convinced me.
|
| Even if launching costs ever makes this feasible, any
| Space Sponge big enough to be efficient would be a big
| collision problem in itself.
| mdotshell wrote:
| Because of orbital mechanics, anything that would be traveling
| faster than the scaffold would be at a higher orbit and
| wouldn't be able to be caught.
|
| The exception to this would be if the object were in an
| elliptical orbit, which would allow for contact to be made with
| the scaffold at its perigee, which be impossibly rare.
| JshWright wrote:
| Faster orbits are lower, not higher.
| steerablesafe wrote:
| This is in fact correct, orbital velocity is sqrt(G*M/r)
| for circular orbits.
| Chris2048 wrote:
| what if that thing had an elliptical orbit?
| usrusr wrote:
| If you'd ever build an artificial "sponge moon" with the goal
| of assimilating as much spacejunk as possible you'd probably
| not want to circulate its orbit. But I doubt you'd ever face
| that decision, given the absurd materials requirements
| imposed by orbital collisions.
| f-word wrote:
| Wouldn't this be a matter of simply getting it to an useful
| starting position?
| JulianMorrison wrote:
| It might help to put it in a suborbital trajectory, so it would
| basically go up, squirt, expand to a huge size, and drop back
| down, being hit by the intended object as it falls. You'd need
| a lot of foam to knock significant delta-v off the junk, and it
| would be catastrophically smashed by the thing impacting, but
| most of it would drop straight back down, and the bits blasted
| into orbit would be small and light enough to deorbit
| themselves.
| gbrown wrote:
| In addition to the other objections, the polyurethane would
| likely disintegrate.
| jl6 wrote:
| There's a lot of junk but it's spread out over a _lot_ of
| space. You probably won't catch much by accident. Also, it may
| be going dramatically faster than your catcher, in which case
| it would be less like a mitten catching a ball and more like a
| mitten catching a bullet.
| f-word wrote:
| Sure, but there's also a lot of uh mitten in this case,
| getting progressively denser as more stuff gets trapped in
| it. I don't think there's that many ways to trap all the tons
| of hyperfast shrapnel we've up up there, unless we can get
| starlink to just sporadically throw small nets around in
| hopes of catching enough junk on any given throw?
| londons_explore wrote:
| I suspect if you did the analysis, you'd find rather than
| it getting denser over time, you'd find most bits of space
| debris (even tiny ones) would have enough energy to explode
| your catcher...
| jerf wrote:
| No, your "mitten" is getting blown apart, not getting
| progressively stronger. Your intuition is not tuned for
| space. Imagine trying to strengthen a structure by firing
| extremely high-powered bullets at it. "I have a tree near
| my house that is about to fall on us... how should I fire
| my high-powered rifle at it to reinforce it so it stays
| up?"
| f-word wrote:
| Right, so what's your solution then?
| jerf wrote:
| Who says I have a solution? Or that there even is one?
| sandworm101 wrote:
| What people forget is all the _natural_ junk up there. Space is
| not "clean". Something like 100 tons of rock, mostly dust, falls
| onto earth from space every day. That isn't stuff in orbit, but
| given the capture effects of our moon there is likely a
| significant amount that does achieve some sort of stability. That
| amount probably outweighs everything we have ever put up there.
|
| https://astronomy.com/magazine/ask-astro/2014/07/space-debri...
|
| The real problem isn't that space is getting full of our junk,
| but that our junk is in a very narrow band of orbits that we use
| for very specific missions: Sun synchronous polar orbits used by
| imaging satellites. Look at how these orbits all cross paths at
| the poles. That's the danger zone. While the military cares
| deeply about these orbits, civilian infrastructure in space
| (geosynchronous communications sats, GPS etc) are well beyond any
| real danger. Or, at least they are in orbits where danger from
| natural debris is vastly greater than from space junk.
| im3w1l wrote:
| > The real problem isn't that space is getting full of our
| junk, but that our junk is in a very narrow band of orbits that
| we use for very specific missions: Sun synchronous polar orbits
| used by imaging satellites.
|
| What's the significance of these orbits?
| sandworm101 wrote:
| A sun-synchronous orbit is a polar orbit where the satellite
| passes over each part of the earth at the same time every
| day. That is very useful if you want to photograph things at
| regular intervals using cameras (stable light, no nighttime)
| or if your satellite uses solar panels as these orbits can be
| such that the satellite never falls into the earth's shadow.
| bagels wrote:
| They still go in to shadow once per orbit typically.
| crazygringo wrote:
| But there's an enormous difference between cosmic dust, which
| generally doesn't pose any threat to satellites or spacecraft,
| and the man-made "junk" that are essentially destructive
| whizzing bullets, cannonballs, and worse. The total mass is
| essentially irrelevant, what matters is the mass of individual
| objects.
|
| > _Or, at least they are in orbits where danger from natural
| debris is vastly greater than from space junk._
|
| Are you sure? A quick online search reveals only two satellites
| appear to have been destroyed -- an Iridium satellite was
| destroyed in 2009 when it was hit by a junked Russian
| satellite, while in 1993 the European satellite Olympus was
| destroyed by a meteor.
|
| So it would seem that so far, natural debris and space junk are
| tied 1-1. Why do you think natural debris is that much more of
| a risk?
| sandworm101 wrote:
| >> natural debris and space junk are tied 1-1
|
| There are plenty of sats that have just stopped working, even
| broken apart, for unknown reasons. Telling the difference
| between a defect and a meteor impact is mostly impossible.
| Lots of spacecraft have just stopped working for unknown
| reasons. Until we start inspecting every failed satellite, as
| we do aircraft, we won't really know.
|
| And note where the 2009 collision happened: over the arctic.
| This was one polar orbit colliding with a near-polar orbit,
| right in the danger zone I mentioned above.
| dylan604 wrote:
| a rock the size of pebble or as small as a grain of sand will
| cause a very bad day when you realize that some of the
| objects have incredible amounts of kinetic energy due to the
| speeds involved (the speed of the rock or the speed of the
| thing to be damaged).
| giantrobot wrote:
| For many satellites the biggest cross sectional area are
| solar panels. So the _most_ likely part of a satellite
| impacts by debris will be there.
|
| In terms of probability with debris impacts on satellites
| the common effect is a slight drop in power output from the
| solar panels [0].
|
| Keep in mind stuff in orbit is pummeled by micrometeoroids
| pretty regularly. These are literally dust size grains of
| material in orbit. They face pretty constant abrasion yet
| remain fully functional.
|
| [0] https://www.space.com/20925-space-station-bullet-hole-
| photo....
| crazygringo wrote:
| But that's the entire point -- fragments of space junk can
| be the sizes of pebbles you're talking about.
|
| Cosmic dust, on the other hand, is just dust. It can be
| abrasive but satellites are designed to handle it, as is
| the ISS. It may have high velocity but the fact that its
| mass is miniscule means it can be shielded against.
| gchamonlive wrote:
| > In the long term, this accumulation of junk may lead to a chain
| reaction, known as Kessler syndrome, that would make some low-
| Earth orbits unusable.
|
| I read about it, and it seems a little counter-intuitive for me.
| I would expect that in a collision in space, some of the kinetic
| energy would be used in internal structural changes, and not all
| converted to the resulting motion.
|
| Am I wrong here? If not, does it still preserve enough kinetic
| energy after collision to promote this chain reaction? And how
| long until lower space ring is actually unusable?
| copperwater69 wrote:
| Imagine two objects hitting each other perpendicularly, as
| opposed to head on. Plenty of momentum could be conserved and
| thrown out in a median vector.
|
| Edit: Not only that, but even if 90% of momentum was lost - it
| only takes another satellite going in the opposite direction to
| supply all the energy. Here's what 2 ounces of plastic does at
| 15,000mph to a block of aluminium.
| https://imgur.com/gallery/8NwAhgK
| hiharryhere wrote:
| 1/2 an ounce (14 grams) according to that link. Even more
| nuts!
| gchamonlive wrote:
| It depends on the material. If they are flexible, and deform
| easily, a lot of energy would be converted into structural
| damage, I would presume.
|
| > it only takes another satellite going in the opposite
| direction to supply all the energy
|
| I see, indeed the next collision will supply a lot of
| external momentum.
| MauranKilom wrote:
| > It depends on the material. If they are flexible, and
| deform easily, a lot of energy would be converted into
| structural damage, I would presume.
|
| At those speeds, everything is "flexible" in the sense that
| even metal just flows in a fluid-like manner (see picture
| linked in the comment).
|
| Also, the material would have to somehow convert the energy
| of an entire car crashing into it at full speed. Except the
| car is only an inch wide.
| Tuna-Fish wrote:
| Material properties essentially become completely
| irrelevant when things hit into other things at speeds that
| greatly exceed the speed of sound in either material. At
| that point, you get best results if you just model both
| objects as fluids.
| gchamonlive wrote:
| interesting insight! thanks
| marsokod wrote:
| You are right that the collisions will dissipate some of the
| mechanical energy will be dissipated into heat and technically
| collisions will reduce the duration it takes for the mass of
| debris that are in orbit. I am not sure if that has a
| significant impact on top of the atmospheric drag though.
|
| However, the Kessler syndrome is not about the total mass of
| debris in orbit, but the number of individual debris. So while
| before the collision we had 2 nicely aggregated debris, after
| the collision you will have thousands of small ones.
|
| The small ones will tend to deorbit faster on average, because
| of the loss of energy mentioned above and also because their
| aggregated surface area increases, but you still have more
| debris. And when we are talking about multiple
| decades/centuries of lifetime, these debris will collide with
| other satellites, creating a positive feedback loop, increasing
| the numbers of debris exponentially, at least initially.
|
| Obviously this is just the beginning of the process, which will
| end up with a maximum number of debris and then a decrease
| towards zero, but that timeline is extremely long and therefore
| not really relevant to us.
| gchamonlive wrote:
| I see, thanks for taking the time to answer me =D
| losthobbies wrote:
| My first thought was the game Hardspace:Shipbreaker
|
| https://hardspace-shipbreaker.com/
| [deleted]
| yottalove wrote:
| Elon Musk's SpaceX Starlink: thousands of satellites that can be
| re-positioned en masse in time of need and meanwhile reserve a
| spot in the LEO surface.
|
| Useful in both communication and in denying the space to other
| classes of satellites.
| gruez wrote:
| >and in denying the space to other classes of satellites.
|
| Is this actually an issue? The earth has a surface area of 500M
| km^2 so if want 0.5km between each satellite you can fit 500M
| satellites at one orbit level. A few thousand spacex satellites
| is a drop in the bucket.
| tveita wrote:
| There are already near-misses happening from time to time.
|
| https://medium.com/@leolabs_space/the-iras-ggse-4-close-
| appr...
|
| https://spacenews.com/esa-spacecraft-dodges-potential-
| collis...
|
| Add in thousands of new satellites from various race-to-the-
| bottom move-fast-and-break-things companies and Kessler
| syndrome seems less hypothetical and more inevitable.
|
| "a bug in our on-call paging system prevented the Starlink
| operator from seeing the follow on correspondence on this
| probability increase"
|
| Imagine if the other satellite operator had been similarly
| negligent, or if the satellite had been defunct. It will be
| somewhat ironic if a Musk-led operation grounds humanity on
| Earth for a decade or more.
| Cogito wrote:
| Remember that, assuming circular orbits (which is fine for
| this discussion, I think), you have to fit _satellites on
| great circle paths_ next to each other. For a single great
| circle you can fit a significant number of satellites in a
| chain, but turns out you don 't want too many like that as
| all your satellites cover the same part of the earth.
|
| All great circles on a sphere will intersect in two places,
| which assures a collision if you have satellites in them both
| (without active avoidance). So you have to separate the great
| circles on to different sized spheres, or add a little
| eccentricity to make sure the rings don't touch.
|
| There is still a lot of space, but comparing to the size of
| the surface of the earth is not very informative when dealing
| with orbital dynamics.
| beerandt wrote:
| But you imply those mitigations must be made to correct the
| "natural," initial orbital state, when in reality, the
| orbits were never truly circular or co-spherical.
|
| It's not useful to make a simplifying assumption, if the
| solution to the problem is to reverse the resulting
| simplifications.
| williesleg wrote:
| Yeah it's a coordinated effort against elon musk again, but he'll
| win again. Can't wait for satellite internet.
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