Space junk removal is not going smoothly
scientificamerican.com
scientificamerican.com
>And the problem is now poised to get much worse because of the rise of satellite “mega constellations” requiring thousands of spacecraft, such as SpaceX’s Starlink, a broadband Internet network.
really could have used a LOT more qualification particularly since it's become a major recent talking point. There is one ultimate sure-fire way to reduce space junk: launch stuff to very low orbits. There is still some atmosphere (varying with heating and other factors) up a long ways in "space", and it's only above 600km or so that orbital drag becomes negligible enough that lifetimes really stretch out. The ISS for example requires regular reboosts or it would decay back into the atmosphere.
SpaceX focusing on economics has made it feasible to start planning constellations of comm sats that are low and very low earth orbit, with the understanding that inherently their lifetimes will be measured in single digit years. But that's ok since they can be replaced so cheaply. This is much better, not worse. Even if they go offline or got hit, the debris would have a very restricted lifetime. The media should do a better job of conveying how cheaper $/kg to LEO opens up a lot of new possibilities in what regulations are feasible and how we think about the basics of satellite design. A simple "Mega constellation bad!" is all wrong, and that's not necessarily going to be intuitive to everyone.
Edit: I think I now understand your comment. I mean sure it maybe adds less space junk than launching things into higher orbits, but it doesn't really reduce it, right?
That said, an impact at this level can still spew debris into higher orbits, as the chaos of the collision can impart enough energy to some collision ejecta to change their orbit significantly. So you still don't want things bumping into each other.
LEO sats will probably produce more space junk by mass but junk in LEO will be gone in a few years, no matter how much or little of it their is.
On the other hand Geostationary satellites produce much less junk in terms of mass, but once it's up there it's not coming down for centuries.
https://en.wikipedia.org/wiki/Orbital_decay#Atmospheric_drag
Is that a thing that can happen?
My intuition is it would be possible if a rocket currently boosting to a higher orbit were to collide with something on its way there, but two objects in the same orbit colliding couldn't get enough delta-v to actually get to a higher orbit. They could maybe get "higher", but not at orbital speeds and so would rapidly decay.
I know next to nothing about orbital mechanics, so maybe someone who does can provide some better insight here.
Apparently not as such. See sibling comment here:https://news.ycombinator.com/item?id=26809297
Basically, just based on impulse and energy conservation, and some assumptions on the size and number of fragments, a head-on collision of two satellites going opposite directions at the same orbit should send some pieces of debris into much higher orbit.
How likely this is to happen in reality, and thus how big a problem this could be is a subject of modeling and much more complex calculations.
See "can you throw a baseball from the ISS and hit the earth" (No, you can't.)
If it helps, start by imagining two satellite-like machines colliding in interstellar space (i.e. not in orbit), where they were initially moving at 1m/s in opposite directions. Even ignoring the possibility of an explosion (unspent fuel, pressurized areas, I dunno), it's still very easy for interactions to violently fling individual parts outward at speeds higher than 1m/s.
Of course, my guess is that the possible amounts of additional delta-v are pretty low, like 100 m/s, and as such the resulting orbit would not be much higher than the original orbit. But that's just wild conjecture.
Fragments that are launched down obviously hit the Earth. But an orbit is a closed ellipse, so the fragments that are launched up will _also_ hit the Earth -- they'll just go up steeply, turn around, and come down. The only fragments that won't initially hit the Earth are the ones that are ejected tangentially, parallel to the Earth's surface. Those will go into an elliptical orbit with a high apogee and perigee at the altitude of the collision. Which means they will _still _come down to that altitude and gradually lose energy.
However.
The grandparent post claimed that "Fragments that are ejected from the collision cannot have more than energy than they had originally, nor can they change direction very much", which I think is clearly what I addressed in my comment, and I stand by my correction of that, and your reply doesn't address this at all.
Also, with respect to "you _cannot_ launch them into a higher orbit", you just agreed that you can have a higher apogee than the collision. If the input satellites had perigees lower than the altitude of collision, you can also have a lower perigee. More velocity at this point on the orbit, higher apogee, higher perigee.... So how do you figure you cannot have a higher orbit?
But more generally, how does this justify your claim that "Fragments that are ejected from the collision cannot have more than energy than they had originally"? Or were you conceding that point and making a different point?
See also my more-detailed cousin of this comment.
Likewise, if the particle is slowed down, the highest point of the new orbit cannot be any lower than than the altitude of the collision.
An interesting feature of orbital mechanics is that a change in velocity at a given point in orbit will change the altitude of the orbit at every point except where the change took place.
Debris from an explosion/collision can have an unlimited apoapsis, but the periapsis is at most the altitude of the incident.
So if it started in low orbit, it will still drop down regularly, and drag will still remove it over time.
The orbits will be elliptical: exactly how elliptical depends on the directions of the two objects hitting each other and the dispersion of the fragments (how much the fragments have sped up or slowed down compared with original objects, and change of direction).
The fragments the stay in orbit the longest should be those that remain closest to a circular orbit?
Objects in low orbit don't stay there. They're slowed down by the atmosphere, and re-enter in a few months or a few years. Only if they're healthy enough to orient themselves, and have the fuel to do it, can they perform the re-boost maneuvers necessary to overcome atmospheric drag and stay up for longer.
So, a satellite which loses control, or gets smashed into bits which can't individually control themselves, just becomes fodder for the drag. It gets swept out of orbit by the wisps of atmosphere out there. Low orbit is very "clean" in terms of junk, because junk simply can't linger there. Just like there aren't a lot of ancient ruins on the beach.
The exact degree of drag is unpredictable because the exosphere is subject to a lot of variables, hence the "months to years" ambiguity. But they don't stay out there for decades or millennia, like junk in higher orbits.
That is a fantastic analogy.
Anything re-entering the atmosphere is subjected to temperatures around 8000 deg. Most things are just totally incinerated, unless they are well-enough insulated to withstand that temperature until they slow down from orbital velocity.
Sure, but that's not really the point. Using biodegradable plastic is much better than traditional plastic that stays in landfills forever. "Just don't generate trash" isn't an option.
Eg if it is $10m to LEO and $15m to HEO you will pay the extra to get to HEO and put a satellite designed for long life - but if it is $1m to LEO you can build a cheaper satellite and launch it 5 times over the following decades.
I like the idea of having internet on my sailboat as much as the next guy, but it takes some serious cognitive dissonance to convince oneself that 42,000 pieces of nearby junk is better than a handful of pieces of far away junk.
No. First, The whole reason they need to maintain a fleet, rather then just having it sit there for decades, is that they're so low. The vast majority of planned Starlink satellites from that number are from Phase 2, and are V-band VLEO sats with orbits around 340 km, which is really low. At that altitude, natural decay time is measured in weeks at best. To work they'll need both active thrusters providing regular boost and aerodynamic low drag design (and maintaining orientation for that will itself require fuel). Should they actually lose all control through malfunction or a collision, they and resulting debris will deorbit very rapidly (they'll both have no boost and be less aerodynamic).
And second, "through malfunction or collision", because it's not as if SpaceX (and other LEO satellite operators) doesn't have, and indeed are required to have, plans for controlled deorbit at EOL. Most of the satellites can be expected to get deorbited in a controlled way as planned. Making sure everything burns up has been one of the things slowing Starlink development, it took some work to ensure the optical links would properly go for example.
SpaceX is not interested in leaving them up there. I mean, FFS people, who would be hurt more than SpaceX by Kessler Syndrome!?
>I like the idea of having internet on my sailboat as much as the next guy, but it takes some serious cognitive dissonance to convince oneself that 42,000 pieces of nearby junk is better than a handful of pieces of far away junk.
Your dismissiveness towards hundreds of millions of underserved people and challenging use cases and ignorance of orbital dynamics does you no favors here.
This is pompous and elitist nonsense of the highest order. People have other more pressing concerns than fast internet. You know...like water, food and cheap power.
Also it's worth noting that communications networks is but one application for LEO satellite constellation technology.
With some gyroscopes, I think they only need electricity for it, not actual reaction mass.
Imagine thinking that a product that costs $500 up-front and $99/mo thereafter and uses ~100 W constantly is designed for "hundreds of millions of underserved people".
The biggest issue is by far the 600km to 2000km altitude band. It is popular for both LEO and SunSync sats and is high enough above the atmosphere that minimal propellant is needed for orbit boosting.
GEO is more or less safe because it's unstable (dead stuff drifts outwards), well kept (slots are limited by the resolution of customers' terminals) and typically doesn't have high relative velocities.
If the cloud of debris is gone in 5 years, that's a hurdle to some careers and a (hopefully) temporary shutdown for some businesses. Covid has taught us that the modern economy has traded a lot of robustness for profit and efficiency, and those would certainly be significant losses of billions or trillions of dollars, but it would be a small fraction of GDP, we would hopefully learn from the mistake, and we would still be a spacefaring species.
If Kessler syndrome occurred among geostationary satellites, that could potentially be a problem for millions of years. That's six orders of magnitude different and definitely needs qualification.
More stuff in orbit doesn't necessarily lead to higher risk of a catastrophic kessler syndrome event, if it's low-earth orbit. The risk is not the same as geosynchronous where it can stay there forever. The satellites themselves (and even the debris if there is a collision) will decay on a very short-term basis (single-digit number of years).
By making launch cost-per-kg cheaper, it is now plausible to put things in LEO instead of geo or other orbits. And doing that probably actually reduces the risk of a catastrophic event, even if there is more stuff.
Possibly higher risk of a smaller event, sure, but that is true of anything that puts more stuff in space. That's a generic argument that we shouldn't be doing anything in space at all, which I think is not compelling.
Seems like a pretty big consolation to me, no?
My intuition is that the velocities involved in being in orbit in the first place are so big (7 kilometers per second according to a quick search) that the orbit of the debris won't be substantially different, so it will still decay. Even if you give enormous kicks to the debris, most of it will end up with orbits intersecting the earth. The ones that don't will still intersect the original collision location, and so still experience decay during that part of their orbit.
Basically, to change your orbit you need to boost once to push the other side of the orbit out and then again at the other side to push the original side out. A collision can only give one of the boosts, and so is sort of inherently bad at moving the orbit.
But the danger is the debris that is ejected from a collision at a lower orbit would then collide with debris that is at a higher orbit. The debris from the 2nd collision would have its original periapsis, which may be high enough to stick around for decades.
Really? If there's a collision in LEO, doesn't debris spray in all directions, including some in the direction of higher, more stable orbits?
Think of exploding something 2 miles up the side of a mountain, what are the chances a piece goes another mile up the mountain. Like that but even harder.
Sibling comment ( https://news.ycombinator.com/item?id=26809297 ) is better at outlining that I was wrong: apparently a single impact cannot produce an entirely higher orbit, for debris sent in _any_ initial direction. At best, it produces elliptical orbits with a higher apogee, and the same drag at perigee.
So any ejecta from a single collision will still orbit through whatever altitude they started at, and in turn will be affected by atmospheric drag at that point regardless of how much farther out they get at the high point. In principle it's of course not impossible that they could collide with something else already in a higher stable orbit, but the odds of that get very, very low particularly in the short time frame they have before decay assuming they're starting in VLEO.
----
1: https://ocw.mit.edu/courses/aeronautics-and-astronautics/16-...
Is it the low point that is that same? I would have thought it was the current point (at time of delta-v addition), wherever that is, that must be part of the new orbit. Not that this is relevant for the topic at hand, just trying to check my understanding.
So if you're at point P in your orbit and suddenly kinetic energy was added, your velocity changes in some arbitrary way. While you aren't sure where you'll go and when you'll get there, as long as the new (position, velocity) pair still defines a closed orbit around the body, you can be damn sure you'll return to the exact point where you are now.
From this follows that the lowest point of your new orbit cannot be higher than where you are now, and the highest point of your orbit cannot be lower.
--
[0] - Ignoring gravitational effects of other bodies, residual drag, magnetic fields, solar pressure, etc. None of these matter on the scale of days to months.
Altitude Lifetime
200 km 1 day
300 km 1 month
400 km 1 year
500 km 10 years
700 km 100 years
900 km 1000 yearsAs soon as that shell burns through its going to break apart and each individual part will start burning up.
Medium and high orbits are a different story. Space junk is absolutely a real concern here.
edit: my concern is the long chain of the curve of low-orbit satellite companies as price continues to have downward pressure.
In order to go up, you have to bring something back.
Umm...this is utterly wrong, and has been since Gemini 10 in 1966, not to mention Skylab, Mir, ISS
There's a big difference between docking with a spacecraft that is designed to be docked with and capturing a satellite that was not designed to be captured.
People are making good progress on this - Northrup Grumman just had a successful life extension satellite mission very recently. But it's far from a mature technology.
Not to mention, if you're thinking of making LEO launches do this, then they'd either have to capture other LEO junk (makes little sense, most of it will deorbit itself), or you'd have to bolt on additional stage, which may very well introduce more junk itself (are people still using explosive bolts for upper stage separation?).
While this isn't entirely unreasonable, consider a few things. First, this is one case where even natural incentives line up pretty well. For the foreseeable future, no one is going to have more economic incentive to prevent the loss of usable LEO than companies that build themselves around usage of LEO. There are also virtuous spirals in the very technology that makes low cost possible, ie., the only way to reach SpaceX's targeted launch costs with Starship are to have a full reusability, and that itself cuts a ton of orbital debris (spent stages).
Second, much cheaper mass and higher cadence changes everything in space engineering, and that includes giving regulators significantly more leeway in what they can reasonably require. Things like more redundant controlled deorbit systems, requirements for lower orbits by default with higher orbits reserved, requirements for materials, and so on all ultimately boil down to how much it costs to get a kg to orbit and how regularly it can be done. More leeway there makes a lot of things easier without destroying utility, which in turn raises the chances we can make solid systematic changes.
Not saying there isn't plenty of room for error overall, or that regulators shouldn't be thinking about it too. But I do think the "mega constellation commercial" focus is mostly misguided. If anything the biggest risks seem to be from government actors, in terms of things like a-sat weapons and Old Space big companies not feeling the need to care.
I guess my concern would be who actually has regulatory authority over space and how can they ensure all actors play fairly. I would have to imagine this is a situation that is similar to the tragedy of the commons type scenario.
To be clear - I really don't fall into one side of the camp or the other but I can see how a lot of the waste management side of things can fall by the wayside given our track record on waste cleanup (mines, municipal solid waste, nuclear)
This line of reasoning never seems to work out the way you are suggesting. It's more likely to wind up in a giant Mexican standoff once there a multiple entities who all have the individual ability to ruin it for everyone.
Almost all upper stages for LEO missions get deorbited (or at least they're meant to be deorbited). It's typically only the high energy missions like GEO/GTO where upper stages get left in a "graveyard orbit".
How big of a problem this can be is something to model and calculate, it's not something one figures out just from the general principles.
This seems wrong, from what I understand of orbital mechanics.
There are thus two takeaways:
1. By definition, this means that part of the orbit will always be at low altitude, regardless of the collision dynamics. So this means that it will continue to decay over time, albeit perhaps at a slower rate (decay being proportional to the time spent at lower altitude).
2. While that eccentric orbit will intersect with a higher circular orbital plane, it does so in a predictable fashion that can be routed around. The higher orbits are also much sparser, so the chance of this intersecting with a satellite that is already present is very, very small.
I guess if a collision is messy enough, there would be secondary collisions between debris pieces, and it sounds like these in principle can push some junk into higher orbits. But I think the probability is really low; this should not be a concern.
How so? According to my understanding of orbital mechanics, if an object begins its orbit at a certain altitude, it will return to that altitude exactly one orbit later. While a collision can change the shape of the object's orbit, it can't change the spot of collision - which it will return to every cycle of its orbit.
Oh cool, let's shoot even more soon-to-obsolete pollution into the atmosphere. That's working so well on Earth. /s
Atmospheric pollution from earth based sources is different because it’s something that is being done in the scale of billions of people, not 1000s, and CO2 doesn’t naturally disappear from the atmosphere over time and is growing decade after decade.
Over one hundred metric tons of space dust falls on the earth daily. Do you really think SpaceX de-orbiting a 200 Kg satellite once a day or so is going to change that significantly?
The problem is, of course, the atmosphere. That thick soup of gas that's at its densest near the surface, and has the annoying tendency of engulfing hypersonic projectiles in a thick ball of screaming-hot plasma.
Earth's atmosphere is around 5 x 10^18 kg. All the satellites put together are not going to increase the amount of toxic material enough to matter whatsoever.
With each launch emitting roughly as much as a single commercial flight and typically around 100 launches happening globally per year, even a tiny change in the tens of millions of commercial flights per year has a far larger impact on emissions than launches will for the foreseeable future.
It's one of those "connective" facts that puts so many distinct things into perspective. When I first learned it a few years ago, I became simultaneously very relieved that a rocket launch doesn't really have that big of a carbon footprint, and horrified by how much emissions a single passenger plane can make. It's a lesson about how visuals can be misleading: a plane looks tiny and doesn't really seem to be doing anything, while a rocket is big and rises to heavens on a pillar of flame, propelled by the anger of hell itself - and yet it turns out they're roughly the same, emissions-wise.
https://twitter.com/rocketrundown/status/956079854511972352
https://twitter.com/erdayastronaut/status/123959552711483801...
To make the calculation more difficult, like the 80% of the volume of a Boeing 747 is room for humans, and like 50% of the volume of a Falcon 9 is room for Oxygen and thrusters.
Though, the Delta III and Ariane 5 boosters do contain ammonium perchlorate, which is worse for the environment than jet fuel.
And at the same time fuck up our planet in a major way. There is a lot of life dependent on the plant on that dust. Everything from micro organisms in the sea, the Amazon gets its phosphorus from it, etc (it is a long list of things).
https://www.reddit.com/r/space/comments/ld4vlq/gabbard_diagr...
Let's not do that again.
I suspect the diagonal line between the colors represents the duration of a stable orbit at that altitude. Anything with a more elliptical orbit will drag when it's in the closer phase and decay. Anything with a lower orbit is already slowing to a tighter orbit (and more drag on the denser atmosphere).
While it does look like 500km is about where things fall out quickly, it also looks like there's a sweet spot of altitude to orbital period ratio where stuff just stays there. Outside of that sweet spot stuff still falls out fairly quickly.
Edit: I think I now understand what you mean, but I suspect you're not realizing that every satellite appears twice on the chart: once in blue, for its periapsis (perigee, i.e. low point of its orbit), and once in red, for its apoapsis (apogee, i.e. high point of its orbit). You're probably noticing that some of the red dots, at high altitude, are decaying quickly, but that's because the corresponding blue dots are at low altitude.
Note also that orbital period is a monotonic function of altitude. More precisely, the square of orbital period goes with the cube of the semi-major axis (the long axis of the orbital ellipse).
This would increase the "drag" and deorbit debris in higher orbit much faster. My physics intuition says it would affect smaller things much more than bigger, which is what you'd want.
If it can ever be practical, I don't know, but conceptually that works, right?
That approach can help, but the problem persists. Lower orbits are much smaller than higher orbits. Focusing megaconstellations into a narrow 100-110km band is asking for trouble. The kessler syndrome could occur in a very narrow band, quickly rendering even short-lived satellites uneconomical. The narrower the band of orbits, the more likely and more aggressive kessler becomes. It is one thing to loose a few sats every year, very much another to have your entire constellation wiped out every year.
Not "much".
A 1200 km circular orbit is ~10% longer than a 550 km one, so a max of ~20% more "room" in the larger orbital shell.
The quicker de-orbiting of debris from the lower shell more than makes up for this IMHO.
Strictly the low orbits of StarLink actually make it a sort of non-issue: there's PLENTY of atmospheric friction at the orbits used so re-entry is only a matter of time.
The bigger issue is higher orbits where orbital decay has far small perturbations to rely on. Those can be 10,000 year orbits which makes for a real problem.
It might be better to keep everything up there. Assuming the junk is re-usable in some way: If one day, we do manage to build some kind of industry in orbit, it will need to consume raw materials, and having all this scrap in orbit already means you saved most of the energy cost it would have taken to get all that mass up there.
The heating approach is one way, but I believe something that could use the kinetic energy of ablative laser pulses would work for smaller objects. To get the correct retrograde velocity, however, I believe you would need an orbital platform and some ridiculous laser technology (which, when combined, tend to create political drag)
I also wonder about sending focused packets of ionized gas to collide with an object and reduce its kinetic energy. If you were operating in an opposite orbit you'd have a ~35km/sec closing velocity. Then spit out small targeted puffs of krypton/xenon at 50km/s, it wouldn't take a lot to knock real energy off of the target. (Stubby pencil work says 80 femtojoules per molecule or roughly 30 micrograms of gas to reduce the velocity of a 20g bolt by 1000m/s. I think.)
I was thinking something similar but instead launching equivalent mass of water in the exact same orbit in the opposite direction. Right before the collision, release the water. The water would spread enough that the entire spacecraft would basically slam into a wall. The net momentum post collision should be 0. Most spacecraft debris would fall straight down to earth.
>How would you prevent the puff of gas from diffusing into nothing?
My thinking about this is that at low concentrations the gas would maintain a largely ballistic trajectory and not be subject to typical diffusion properties. Would require a purpose-built accelerator to condition for 'beam' coherency. Not sure how well that scales.
> Where did you get ~35km/sec? ISS orbital speed is 7.66 km/s and it only gets slower the higher you go up.
Major brain-o.
Ultimately I think we're on the same page of 'kinetic deorbit', just a function of what is actually feasible.
I have no idea what I'm talking about really, but its a sort of interesting concept...
Me neither, fortunately we don't have the burden of actually having to solve this problem xD. The big bubble o' gas idea is honestly where I started and I think there's real merit to the idea...it's relatively harmless to operational satellites yet operates rather indiscriminately on debris and isn't as finicky as the directed energy options. Basically a fly trap for space.
Most of the SpaceX commentators use it too.
It's always cool to me when something meant as a toy gets used for real. Like city planners practicing in SimCity or more recently CitySkylines.
Recycling what's up there might eventually be viable but for the start we'll be shipping up raw stocks. Recycling is probably about as difficult as refining from metal rich asteroids once you consider all the coatings and paints that are added to things and having to sort all the different metals, plastics, and what have you out.
Lets say you are in a really, really close orbit to your target and you only need to spend delta-v of 100m/sec to intercept . If you only use 90% of the fuel you'd need to perfectly match orbits then you are still going to impact your target at 10m/sec. Thats 36 km/h, which is a very violent collision. You aren't going to just grab your target on the way past.
Also 36 km/h isn't /that/ fast you could have a capture mechanism that absorbs that impact or where it doesn't matter like a net.
I mean, if they are at a standstill relative to each other then their orbits would be identical??
As others have noted, putting satellites in lower orbits, below 500km or so, definitely helps with keeping things tidy.
Beyond that, robust regulation about ensuring that very little or no additional non-useful stuff is placed into orbit is also good. That is, require everything that isn't useful to deorbit right away or relatively quickly, and have the ability to deorbit at EOL.
What's beyond all that is the set of all things in orbits that aren't useful and that will naturally stay up there for a long time, in addition to any NEW stuff that's added, either by error or by accident. For example, a satellite in a 1000km orbit that has everything it needs to deorbit at the ends of its life, but fails to do so for whatever reason.
As others have noted, matching orbits is a lot harder than most people realize. Specifically, it's quite energy intensive.
At this point, basic physics tells us what we must do. In order to get long-lived, useless stuff out of orbit, we need to be able to send up specifically designed stuff, and a lot of it.
In summary: the most fundamental solution to this problem is to vastly decrease the price per kg to orbit. Regulation helps, but does nothing to clean up what's already there, and to resolve the unintended addition of new junk.
Summary to the summary: the newest crop of launch providers are aggressively working on this problem by aggressively pursuing reusability.
I know the article touches on these points, I am mostly just commenting on the strange headline.
Or manga, it's originally a manga series before the 26-episode anime adaptation.
The anime actually diverges from the manga in the latter section, because it was started before the series had ended (the manga finished serialisation in January 2004, the anime finished airing in February of the same year… and it was a 26ep full-season thing), so viewing both can be interesting in more ways than the usual watching of filler and interest in cross-media adaptation:
> While the manga deals more with existential themes, and humanity's relationship with space, the anime further expands the political elements of the story.
The 'weapon' would reflect sunlight and 'shave' against cross-sections of the edge of earth's orbital spheres. Solar sail like light pressure would slowly nudge objects to either slower, or more erratic orbits where they'd drag and get lower.
Warning, link autoplays with sound: https://www.imdb.com/video/vi1534902553?playlistId=tt1283876...
You have to be in the right place at the right time (4), but if you have the wrong velocity (+3) you just end up causing the very problem you're trying to prevent.
For some context of the amount of 'stuff' in space..
This does include debris also. It's a serious amount.
There is an incredible amount of Iridium from the mentioned collision :
I always look in articles about space junk for any inkling of addressing the fundamental physics issues we identified back in the 1980s and I've yet to ever see those mentioned. It's always some shallowly thought-out, gee-whiz ideas by someone who's never actually worked in the field. Elon Musk-style.
It is indeed unusable now, but it is a lot of highly refined matter that is already high in the earth's gravity well.
The question is whether whether enough of it exists that it could become useful, or even profitable, to reuse/recycle it.
Once you've gotten a herding satellite to rendezvous and dock/grab the junk, how much extra energy is needed to park it in a useful common orbital location for later reuse/recycling, vs making it new on the ground and lifting it out of the gravity well again?
Seems it could be a profitably exploitable resource, if the scale is right?
The vast majority of space junk (by number) is small pieces of metal, bolts, specks of paint, that sort of thing.
The few bigger things are rocket stages, decommissioned satellites, and larger collision fragments.
The problem is that the most dangerous debris (e.g. debris that doesn't deorbit on its own anytime soon) orbits between 2000km and GEO at varying inclinations.
These orbits are difficult to get to and the debris is worth nothing compared to the energy you'd have to spend to catch it.
The value of the debris itself is comparable to the value of junk here on Earth.
Unless space faring nations are paying for removal, I cannot see any scenario in which the ~8,000 metric tons of space debris [0] can be collected and recycled at a profit. It's just too difficult and costly to do.
[0] https://trumpwhitehouse.archives.gov/wp-content/uploads/2021...
1. When that busy ~500km orbit has a collision, some pieces might be kicked up to higher orbits where they pose a risk to other satellites. There's also important things in lower orbits, like ISS.
2. Every satellite that falls back to earth from any orbital altitude has to pass through very low earth orbit.
Between 1 and 2, the debris is never going to be confined to low orbits where everything decays quickly.
..It takes an Iridium-Cosmos-type collision to get everyone’s attention. That’s what it boils down to.... And we’re overdue for something like that to happen."
Perhaps the former is gentler, more statistical an alternative to the latter. Everybody be so cataclysmic these days.
The reason debris in LEO is dangerous is because it's going really, really fast and continually orbiting for years so if there's enough of it eventually you'll run into something.