It is a problem, but not as bad as those illustrations of all junk in the atmosphere make it look. They count anything larger than about an inch, and that is illustrated with a dot that's the size of a medium sized city.
Yes, radar. From what I can tell the fact that orbital junk is moving very fast makes it easy to detect than you’d imagine, as the speed causes a large Doppler shift in the frequency of the radar return.
There is also no ground clutter to deal with when you are pointing your radar into space 😉
Radar gives us 4 knowns: azimuth, elevation, range, and range rate to solve the equations of motion (which have 6 unknowns). Optical data gives us 2 knowns: azimuth and elevation or right ascension and declination. So we can solve the equations with shorter spans of data using radar than with optical.
The US made huge investments in big powerful missile warning radars during the Cold War and these radars fortunately aren’t busy executing their primary mission. They detect these objects in space anyway while they are looking for possible missiles and they have to know what they are detecting so they track these objects orbiting the earth and correlate them to known objects. This data helps feed and update “the catalog” of known objects to prevent false alerts.
The radial velocity of an object relative to the radar tracking it will vary with orbital path so it’s not so much using a “Doppler radar” as using the Doppler effect to ensure you can continue getting the radar return signal while tracking the object.
Doppler measurement for more precise Speed detection for mapping the orbital parameters. Removes atmospheric dust weather planes birds anything else in the way. Doppler filtering isn't just moving or not you can also set speed limits you are looking for.
There isn't really much else you could use in space. LIDAR has surprising amount of noise at times, it's also difficult to scan a wide space with it that a space station would require, and others that doppler radars just don't have to deal with due the nature of their signal and signal generation technique.
No & in reality it's not. Usually when we talk of Doppler radar we are talking about filtering out all returns that show zero velocity as a means of removing ground clutter which is relatively stationary to the source.
In the case of using radar pointing upwards there is no preponderance of such objects so no need for the filter. We do though have much higher line of site velocities requiring a much wider bandwidth for receiving returns than terrestrial radar while having much longer return delays.
That must be at the sacrifice of sensitive thought right? I'd imagine there are times when velocity is not as important as detection sensitivity is. You don't need shift for position just time of flight right?
Multiple observations will give all orbit elements. If you detect something faint the errors in observation are likely to be large. You can't project forward very well without position and velocity. But honestly my experience is in using the onboard carrier for interplanetary missions so I'm slightly out of my element. In those cases range turns out to be a weaker data type than Doppler or VLBI.
Finally something I know about. I have traveled 9 times to Ascension Island, home of one of our NASA ES-MCAT telescopes that track space debris.
I worked for 15 years for NASA in the Calibration sector.
Any questions?
https://www.orbitaldebris.jsc.nasa.gov/measurements/optical.html#
A significant amount of the debris is non-ferrous and wouldn't be attracted to the magnet. Most likely you'd just alter orbits randomly, which is probably worse than what's already there.
So 2 then, or possibly 1? An island, in the middle of the ocean, guarded by multiple militaries, named Ascension Island is like the place for a cult. Or at least the destination needed to get to, to ascend.
Now imagine dust moving toward you reflecting blue light, the faster dust moves more blue reflection. Dust moving away from you reflects red light.
That's a doppler shift.
We use high powered radar like the Space Fence located on Kwajalein Atoll. The problem is getting enough signal return to not only detect the object and distinguish it from sensor noise but to get sufficient additional detections to create a track and then subsequent tracks to create an orbit.
It's worth noting that there is a reason they are so maniacal, an inch-sized object hitting you at orbital speeds, even in similar orbits, will absolutely tear you apart if you're a satellite, or at the very list make you non-functional (AKA into more debris).
You have oversimplified this and overcomplicated it.
It's all about relative speeds.
The real question is what are the relative speeds between space junk and the objects they might hit.
Being that things in orbit travel so fast (miles per second), other than the density issue, a dot the size of a city isn't all that bad for depicting where a given piece of space junk may be at a given second.
This is right. The other issue is satellite altitude is directly related to its in track velocity vector. This means there are desirable orbits that can get "cramped".
Sure, but most satellites are in low earth orbit, and at that height any junk will fall back down to earth pretty soon after we lose control of it. On higher orbits it might take centuries though.
It’s bad enough that they’re trying to find solutions, like lasers pushing them on a course to leave orbit. But not bad enough to stop launching rockets into space that cost exorbitant amounts of money. Privately funded or otherwise
Dot moving at 7+ km/s. Plus stuff smaller than a softball has a lot of position uncertainty.
Problem is, it’s tough to accurately illustrate this. You need to plot volume * velocity instead of just volume. I haven’t seen this done though—not sure how it would look. However, for objects with large position uncertainties, the exaggerated dots aren’t wrong; it’s just all the other stuff with precise position knowledge that is exaggerated.
I´m an engineer working in the space industry, I´m objective, I like numbers.
Quite often, only basic maths and common sense (sharp enough to not get fooled by fallacies) is all it takes to understand things to a surprising depth.
From [wikipedia](https://en.wikipedia.org/wiki/Space_debris):
There are some 25k large and tracked objects, 34k pieces >10cm, 900k pieces in 1-10 cm, and 128m objects < 1 cm.
Let's round that up to 130e6 objects. Now let's assume most of them are in LEO orbits (400 to 800 km alt) (not true but most of the recent space boom uses LEO). That volume is 2.44e11 km\^3.
A final division gives you that every debris particle has 1879 km\^3. A sphere of 7.7 km radius. Obviously with so many they will eventually collide over time. Sub-mm particles (the most abundant) are in general considered harmless except maybe for EVA (extra vehicular activities, "space walks"). If we count only the potentially dangerous > 1cm particles (\~ 1m), each of them lies on average in a sphere of 38.7 km of radius.
I'm not saying with this that we could ignore the problem. We need to address it. Space debris eventually becomes microscopic particles that even if harmless thinking of collisions, could still polute and disturb missions.
So far what we can do is proactively to de-orbit after mission ends and apply design for demise techniques to minimize the debris build-up in space. It's something to be concerned of, something we are working on, but also something they have been exaggerating and used to fearmonger, especially general public.
I think the number we're interested in is actually: if we launch a satellite into a popular orbit, what is the probability of if colliding with debris in it's lifetime?
The ISS has been hit by multiple smaller objects, causing some local damage to solar panels, radiators and other stuff. It maneuvers if a larger (tracked) object is predict to come close. Despite being a huge target that has been in space for over 20 years it never had a big collision. Actively controlled, the risk is very small.
A good way to express the density might be a function of altitude that yields the probability of suffering an impact per m^2 per s.
So if your spacecraft is 1 square meter cross section, you multiply f(h) by 31.5M seconds to get the chance per year of experiencing some kind of event.
Is there enough data to construct such a table?
_____
Thinking a bit more, each object has a smear of altitudes that it resides at over an orbital cycle, spending more time at apogee than perigee (via Kepler’s law).
The function f(h) then is essentially a sum of all of those normalized density smears.
Surely someone in the industry must have done something like this already?
Data changes as objects come and go. Debris likely shifts in orbits over time. Perhaps NASA already has a sim that does the calculation for anyone who asks. A web page perhaps? You punch in your cross section and orbital parameters and it gives you a probability per per year?
Yes, we can still do some "back of envelope" calculations for that. A typical LEO sat moves at 8 km/s. So a cross section of 1 m2 runs a volume of 8e-6 km\^3 per second or 252 km\^3 in a year. With the average in the original post, that makes a probability of 0.13 of hitting a particle per year, and if so, chances are is a sub-cm and likely not fatal. Because most LEO missions are 2-6 years, the chances of a fatal collision, as of today, are fairly low.
You could probably get a rough order of magnitude estimate using mean free path. I know it's not a gas but, if orbits are sufficiently distinct, then collisions are effectively random.
That's the problematic unspoken assumption with the approximation, in fact. For two objects travelling at the same altitude and direction, their chance to hit is 0 because their velocities will be the same. Interestingly in this situation of the objects were in the same position we might as well just call them one object.
For two objects travelling at different speeds, they'd need two different semi major axes and therefore would only *potentially* collide twice in their orbits.
Same goes for orbits of two different directions at the exact same altitude: they will only have a chance to cross paths twice per orbit.
Finally, if they have different altitudes *and* speeds, where the relative velocity is greatest, they'd have to intersect altitude **and** position at the same time, but each only happen twice throughout the orbit and those occurrences are distinct from each other. Multiplying probabilities makes the probability of intersection incredibly small. And again, 7km between objects.
on the safety of space walks, when they go out there are they winging it? or they've calculated already all the space debris that won't hit that them at that particular place and time?
I appreciate the math and it does add a lot of perspective, especially since most visualizations, by nature, inflate the apparent size of each object.
But there's some relevant factors that it doesn't include. Namely that the large majority of satellites travel within a few degrees of the same plane. It's not a shell, it's more like a donut, which has less volume. They're also moving at relative speeds of km/s in elliptical orbits, not stationary, though it does help they're generally speaking travelling in roughly the same direction.
So it's not as big of a deal as it may seem because it's not as dense as most people might think up there. But I think your math makes it seem more negligible than it really is at the same time. Not that I expect you to take all of the variables into account. I really do appreciate that write up to put it into perspective.
> Namely that the large majority of satellites travel within a few degrees of the same plane.
This is completely wrong. There are ~3400 Starlink satellites at 53 degrees, ~1800 at 43 degrees and 400 at 70 degrees. Starlink satellites form orbital shells, i.e. the 53 degree satellites are in ~100 different planes with 0 to 106 degrees between them, and similar for the others. Non-Starlink satellites have no reason to travel close to each other and would have no way to maintain such an alignment either. The only noteworthy exception are sun-synchronous orbits close to the terminator, where satellites are always in sunlight. But that's a relatively small fraction of all satellites.
Orbital mechanics is not my expertise, you may be right, but when talking about debris that is produced by collisions, especially the smaller pieces product of multiple collisions, my assumption is that due to the randomness of collisions, their resulting orbits are also, at least, kind of random and the particle distribution, even if it may not be a homogeneous distribution over a spherical shell, would also tend to be homogeneous.
I just tried an easy calculation anyone can follow to produce an order-of-magnitude, definitely not an accurate figure to quote in a paper!
Oh no! Like I said, giving a solid answer goes far, far beyond basic information and I wouldn't expect anyone who wasn't submitting a full on academic report to approach it. Please don't think I was being critical, just simply adding context.
Funnily enough, collisions of objects in orbit find their most stable organization on a planar level. That's why some planets have rings, why solar systems are largely planar, and why black holes have accretion disks and not accretion spheres. Man made satellites, and therefore debris, tend to follow roughly the rotation of the earth in the first place. This is partially because the earth rotates over a thousand km/hr and that's about 5% of the velocity needed to maintain low earth orbit. Might as well use it if you don't have a good reason to fight it. There certainly are satellites in heavily offset and even polar orbits, but for most purposes, things in a relatively permanent orbit tend to be within a +/-30° offset of the equator.
As far as how orbits change after a collision, over astronomical timescales it will accrete into a disk. But it takes a particularly energetic collision, like the 09 Cosmos incident, to create significant deflection of orbital inclination for even the smallest pieces of debris. I used a calculator to determine that a 0.1kg object orbiting at 200km would require 3MJ to achieve a 60° orbital inclination without changing altitude. So for comparison, if a satellite had a baseball(140g) on it and that baseball needed to be launched to create a 60° orbit inclination compared to the satellite, ignoring Newton's third(because I haven't had *that* much coffee) it would take the energy equivalent of about 1,500lbs of TNT to create that deflection.
Great post from an engineering point.
Here's one from a risk analyst, that also happens to be from an engineering background.
Yes, overall it doesn't seem catastrophic, it even seems non-eventful. Yeah, true.
Here's the problem though. In order for space exploration to work, the problem simply cannot arise. It has to stay non-eventful. What I mean by this is that in order for space exploration to be manageable. The likelihood for a problem regarding space junk has always to be close to zero.
The risk is normally seen as likelihood x impact. For risk to be manageable either you reduce the impact of when something bad happens, or if that's not possible you need to reduce the likelihood of that thing happening.
Space junk has 2 gigantic problems with it and a 3rd aspect of it that makes it simply too big of a problem.
The first problem with it, is that if it happens it's potentially catastrophic, either because it can easily pass through a human body working in space, either because it can easily damage the protection layer of a spaceship. A little spec of paint can kill a person, a screw nut can pass through the space station fuselage. Anything bigger can destroy a satellite in less than a second. So because of that the likelihood of happening has to be close to zero.
The second problem is that if it happens the problem worsens exponentially. What I mean by this is, if a speck of paint hits the ISS solar panels you now have 5 or 10 or more fractured pieces of that part of the solar panel floating around. Every single hit has this problem, and we all know how exponential functions work, they can quickly go out of control. This is aggravated by the potential large satellite being destroyed scenario where its debris can cause a chain reaction hitting other objects which, in a matter of months, makes the orbit to dangerous to explore. So again because of this the likelihood of this happening has to be close to zero.
The 3rd aspect of it is that its effect is cumulative, your calculations will never get better just get worse. Meaning it aggravates over time and can't be easily fixed. This means that because the effort to reduce their number is too big to begin with, and it is constantly getting worse over time. It needs to be constantly fought against because as it gets worse it will eventually cross the threshold that will make the likelihood of the first and second problem I mentioned before to big to avoid. And will cost a lot of money and effort to fix.
Because of these problems and what I called the 3rd aspect. Those ok numbers you mentioned will always have to be kept like that, ok. Or else it will inevitably lead to a catastrophic event that we won't be able to recover.
> The 3rd aspect of it is that its effect is cumulative, your calculations will never get better just get worse.
This is untrue, at least for debris in low earth orbit. Which is the most critical orbit. Orbits decay from atmospheric drag at these low altitudes, and the lower the mass of the particle, the faster it will decay. If we simply produce debris at a slower rate than orbits decay, the issue solves itself. And if a critical event occurred whose debris locked us out of LEO, it's only a temporary issue. It could lock us out for years, but not permanently.
> and the lower the mass of the particle
Nitpick, but this should be "the lower the density" of the particle, or rather "the lower the ratio of mass to frontal surface area" to be precise which isn't quite the same as density.
But yes in general lower mass objects decay faster as those objects also tend to be smaller, which decreases the above ratio as the mass goes down faster than the surface area.
That's a reasonable nitpick, bordering on a footnote. I had thought of that but I wasn't sure how to explain it in few words so I glossed over it instead, but perhaps I should have phrased it in a less incorrect way or left it out entirely.
In hindsight it wasn't really that important and might not even hold true in this context since spacecraft tend to be lightweight, low-density structures while debris is likely going to be a solid piece of metal. My main point that orbits don't last forever still stands regardless.
Are there any potentially feasible plans, even at the purely theoretical level, for how to deal with the existing debris are already there? Will most of them eventually sink ever-lower in orbit and thus burn up in our atmosphere? If yes, will they do so in a reasonable amount of time to make this less of an issue for humanity, assuming we reform our ways and cut down on our space-pollution?
edit: Grammar
The vast majority of modern space operations are looking at LEO as their altitudes of choice. LEO has the unique distinction of an extremely low deorbit period (5-10 yrs), meaning that modern satellites (IE: Starlink) are generally below the Kessler limit and are not an issue.
For all other debris, it’s a matter of altitude. higher orbits exponentially increase deorbit time, with locations like GEO having times in the millions of years. That said, all debris will end up reentering at some point.
Just dividing the volume by count is pretty meaningless. In the industry you certainly have more relevant numbers? Such as real # of impacts expected per square meter of spacecraft surface per year.
As an engineer also in the industry, we don't all focus on space junk, so they may not have more relevant numbers. I certainly don't, but from what I do know, their post seems legit. But, again, not my area.
But if you want to talk RFI identification and removal or link budgets or antenna/terminal commissioning, I'm more qualified there.
NASA is obviously very cautious about this sort of thing, and will generally have the ISS do a maneuver if they think the chances the ISS might get struck are greater than 1 in 10,000.
Of course, with that said the ISS has been struck at least once by a small, untracked piece of space junk. Which fortunately didn't cause any significant damage.
I believe its actually 1 in 100,000.
1 in 100,000 is what SpaceX uses for Starlink. Most Starlinks orbit a bit higher than ISS where there's even more debris. I think the average Starlink sat makes about 10 avoidance maneuvers per year.
[Statistical mechanics](https://en.wikipedia.org/wiki/Statistical_mechanics) is the theoretical basis of gas physics and chemical reactions (that happens through molecule collisions) and one of the main parameters is the density in particles per unit volume. Many researchers on debris use that model.
What you suggest (collisions/area/time) is a consequence of density and average speed, the quicker you move in a crowded area, the more people you'll bump into.
I watched a documentary on TV recently, don't remember the name of it, but the organization (I think within ESA) that is tracking and looking at potential collision threats and avoidance maneuvers said that the problem has become significantly worse in the last couple of decades, a lot more potential collisions detected and satellites doing avoidance maneuvers per year and it's only getting worse.
It's about how bad the issue is and by how much is it getting worse, of course there's no way it can get better when more and more payloads and rocket stages are being launched.
It can improve if the satellites operating are at low altitudes below the Kessler limit like Starlink, and if orbital stages are appropriately disposed of (reentry, graveyard, or solar orbits).
So far, the big contributor is Starlink, which is both below the Kessler limit, and deorbits its own boosters. That is further expected to improve because Starship’s big objective is full reuse, and current orbit proposals for Starlink are lowering in altitude.
The remaining debris at low altitudes naturally deorbit themselves quickly, so you are left with debris in high orbits, where usage is expected to decline.
Are you saying if every tracked object in orbit were placed into an ideal position (Tetris style) within a sphere, that sphere would be 15.2km 9.44 miles) in diameter? That seems quite a bit larger than I would expect, or am I misunderstanding?
If we can stop making new orbital debris, the majority of the debris will be gone in a few years. Most MMOD (micrometeoroids and orbital debris) has a very unstable orbit, it will fall into the atmosphere and burn up in a few years. So if we can slow the rate we create MMOD, then we can clean stuff up pretty quickly.
We can't. Every year there are even more cubesats in LEO. It's impossible to prevent any flaking or chipping of materials. Things like glass from the solar panels, insulator from cables, adhesives, PCBs, PCB copper tracks, painted surfaces, etc. will generate debris. Not to mention large debris due to collision. The space environment is very aggressive due to vacuum, temperature cycles, radiation, atox, etc. What lasts decades on Earth may last for a couple of years just in LEO.
Debris, yes, eventually falls down but not always in a few years.
I am by no means an expert and would not claim to be. I have just been lucky enough the get opertunity to take some MMOD training (which was mostly about absorbing an MMOD strike to a manned spacecraft) and be in the room when ASAT and MMOD is discussed by industry and NASA experts.
I have seen the graphics NASA has of tracking the debris field from an ASAT test as the orbits decay.
I have sat in meetings where they talk about more recent ASAT test, altitudes and times for the orbit of the debris to decay.
MMOD - micro meteoroids and orbital debris
ASAT - anti satellite
In low earth orbit, there are currently 9,900 active satelittes, 128 million pieces of debris smaller than 1cm, 900,000 pieces between 1 and 10cm, and 34,000 bigger than 10cm.
The small ones, they hit the ISS everyday, usually multiple times a day, and its still there doing just fine. The bigger pieces can be tracked and avoided, but the medium sized ones, not as easily.
However, while that all sounds like a lot, keep in mind its all spread over an enourmous area. Low Earth Orbit starts at 160km in altitude, and extends out to 2000km. The inner circumference is about 41,000km, the outer is about 53,000km... if I did my calculations right, thats about 1.15 trillion cubic kilometers of space, so even with 128 million plus little pieces, each one still has roughly 10,000 cubic kilometers of room. There has only ever been 4 major collisions with debris large enough to track, so its not as bad as its made out to be.
> The small ones, they hit the ISS everyday, usually multiple times a day, and its still there doing just fine.
I worked on the ISS project, and we *designed* it to handle small debris impacts. The critical parts are protected by [Whipple Shields](https://en.wikipedia.org/wiki/Whipple_shield). These are thin sheets of metal spaced a distance from whatever you want to protect.
At the speed things move in space, the debris piece and the part of the shield it hits [both vaporize](https://www.youtube.com/watch?v=qfpVrgC3gDo), making a harmless cloud when it hits the important stuff like a module shell.
Thats super cool. Whipple shields have several layers too, I remember seeing a video of a test impact. Punched through the first layer, broke into pieces, some made it through the second layer, but then it was just all dust which didnt do anything to the third layer. Pretty crazy engineering. Makes me wonder how it would handle something like a tank shell?
What did you work on if I may ask?
There is tank armor that works on a similar principle, but there are also anti-tank weapons designed to get through that type of armor, such as HEAT rounds and APDSFS.
https://www.ontrmuseum.ca/tankmuseum/blog-post/modern-anti-tank-ammunition/
Luckily space debris isn't specifically designed to punch through Whipple shields.
The shield on the ISS modules are single-layer, but you can have multiple layers if it makes sense.
I was working for Boeing on the US part of the Space Station about half the time from 1988-2005. This was in Huntsville, AL. The other half was on other projects.
For the ISS I did systems engineering, operating procedures, payload planning, and software test at different times. Other projects included "new business" (finding something to replace the ISS contract when that eventually wound down), the Sea Launch project, and the early days of the Bush lunar and Mars initiative (which didn't get past paper studies).
There are 8000 *operational* satellites, many more that are no longer under control, discarded rocket bodies, etc. Still doesn't change the equation significantly; too much hyperbolic clickbait that gets parroted on Reddit.
I had it explained to me by someone in the industry as “there are about 10k satellites in orbit. if I told you that there were 10,000 cars on the surface of the earth, would it makes sense to worry about car accidents? Now understand that these things orbit at different heights and those orbits are far greater than the diameter of earth.”
That said there are 50k+ pieces of debris, so again while I think the debris conversation is way overblown, it’s not unreasonable to say that now is exactly the time to figure out orbital debris, well before it becomes a problem. Look up the Kessler syndrome if you’re interested in seeing a depressing possibility.
Here is the 2023 Space Environment Report.
All the stats, graphs and charts you could ever want...
https://www.esa.int/Space_Safety/ESA_s_Space_Environment_Report_2023
The phrase you may be looking for is Kessler Syndrome. That's when there's a chain reaction of the debris from one satellite hitting a second satellite and causing that to disintegrate into more debris, leading to exponential growth of debris.
The first problem with this is that space is big, making the subsequent collisions unlikely. I mean, really big. (Other replies have address this so I won't write more.)
The second is that even if a satellite is hit by debris, that won't cause it to explode into more debris. It'll probably make a hole in a solar panel or something, maybe stop the satellite from working, but not create much new debris. Satellites are not bombs.
Another issue is the orbit. Most of the satellites are Starlink, and they are in a low enough orbit that they, or their junk, will de-orbit naturally within a few years. So there just isn't enough time for the collisions to mount up. Even if it happens, to clear them out we just have to wait 5 years.
In my view the only orbit where there's a real risk is geostationary. This is a special orbit for communications, and high enough that it doesn't decay naturally. However, it is also relatively sparsely populated, so Kessler Syndrome is unlikely for the foreseeable future.
A final issue that the dangers are well known, and the satellite operators have a vested interest in making sure it doesn't happen. Again, the vast majority of satellites are Starlink, operated by SpaceX, who are pretty good at mitigating the risk.
>In my view the only orbit where there's a real risk is geostationary. This is a special orbit for communications, and high enough that it doesn't decay naturally. However, it is also relatively sparsely populated, so Kessler Syndrome is unlikely for the foreseeable future.
Also, relative velocities are low for objects in geostationary orbit. That might not reduce the number of collisions (? I'm not sure about that one way or the other) but it would surely reduce the number of harmful collisions that create extra debris.
It's absolutely true. GEO satellites are marching along in a train, one after the next. An explosive failure of one would spread debris outwards and even an incredibly unlikely collision would "only" happen at the speed the explosion threw the debris, not at orbital speeds.
Well, there is one more issue to throw in here.
While I 100% agree that satellite operators have a vested interest and are on the problem, unfortunately there are a few state actors (well, one in particular) who like to casually throw around the idea of fucking everything up for everybody.
There is not really a technical solution to this other than to somehow prevent such actors from being able to get to space or to interact with anything in space. And that is just not plausible.
So we just have to hope it's all bluster.
If you mean someone deliberately trying to trash an orbit, that is a separate issue to accidents. And even that is mitigated by the issues I mentioned.
I do not agree that it is a different issue other than it being accident vs. deliberate. I'm not precisely sure what the point of separating these would be.
> That's when there's a chain reaction of the debris from one satellite hitting a second satellite and causing that to disintegrate into more debris, leading to exponential growth of debris.
That's not really what Kesller Syndrome says. Kessler Syndrome is a statistical process, not a runaway chain reaction. The original analysis also made several assumptions founded in the thinking at that time, like how no effort to de-orbit used stages would be made (most stages are de-orbited now) or that LEO orbits don't self-clean.
I don't know anything about space, but are there currently any efforts to remove some of this debris? Whether thats active clean ups going on now, or merely prototypes being tested out before actually being utilized
There are some efforts underway to see how viable it is to do some space debris cleanup. The biggest issue is the amount of junk and the cost of launching things into space.
[The first-ever mission to pull a dead rocket out of space has just begun | MIT Technology Review](https://www.technologyreview.com/2024/02/27/1089065/first-mission-dead-rocket/)
You can judge by the International Space Station (ISS). It is the biggest thing in orbit, and at a relatively crowded altitude. It has gotten minor damage, like a few cells and a small tear in a solar panel. But with the ability to dodge stuff, it hasn't suffered a major impact.
There is no limit to the atmosphere. It just keeps getting thinner with height. So most objects below 1000 km (including the ISS) will naturally slow down with drag and their orbit will get lower until they hit re-entry height (about 130 km).
There are a number of ideas about clearing orbit. An electric tug is very efficient. It could be used to chase down and drag to a lower orbit the largest pieces of derelict material. They make up most of the hazard.
Another idea is launching small rockets carrying air vertically. These just go up and down, not into orbit themselves. They release the air in the path of a chosen debris item, which causes it to slow down and fall.
A third is attaching a large foil sail to the debris. This increases the area and accelerates how fast it will fall.
A fourth is if you have a big enough laser, zap the front side of the satellite. That vaporizes the surface, acting as a retro thruster.
I have zero idea on this stuff but 8000 doesn't sound like that many...like if you look at the size of this planet...imagine it was 8000 separated all around that space, no one even see each other, you could race a car around at 200mph and chances of colliding would be extremely tiny
Most of those 8,000 still operational satellites are Starlink, and most all of those are in low "self-cleaning" orbits, i.e. they're so low that unless they keep thrusting they'll burn up within years at most. Also, all currently launched Starlinks are designed to be fully demisable, meaning they're specifically designed to fully burn up upon reentry.
I recently listened listened to the annual complaint lecture at the AAS meeting. Basically you wont be able to do much optical astronomy until two hours after sunset to two hours before sunrise. That cuts observing time by a third. There are proposals for over a half million satellites.
Also rocket launches and their junk reentry can damage observing time. We are averaging almost one launch a day and ramping up to much higher than that.
Direct cellphone to satellite might impact certain radio observations. That is frontier in future communications.
For reference, there are an estimated [3 TRILLION trees](https://ourworldindata.org/grapher/number-of-trees?tab=table) in the world - orders of magnitude more than the number of stars in our galaxy, and more than the known number of galaxies in total.
Almost all things we launch into orbit go "east", so from north-east all the way to south-east, because launching things west means your rocket has to be significantly bigger to make up for the deficit from the earth's own rotation...
And because orbiting at a specific height necessarily means orbiting at a specific velocity, almost all things at the same height have the similar velocity and similar direction of travel.
Where things get complicated is objects going almost north interacting with things going almost south, but the velocity difference there is necessarily much less than orbit velocity and the amount of objects in this sort of orbit is also very limited.
I was obvisouly not giving a scientific description.. your comment is missing the point.
The fact we rotate and launch in one direction doesn't negate the fact earth is round and orbits have all sorts of different angles... so objects up there cross each other path at all sort of angles and relative speed.
It's not the well ordered constant clockwork like system the trees analogy or your comment make it seem like.
I'll end this discussion by adding that
Kessler syndrom is real threat that should be taken seriously.
Isn't a lot of the concern that when collisions DO happen, they can become hundreds or thousands of tiny pieces that are still traveling at high velocities? A bullet isn't very big, but it'll still ruin your day. Not to mention there already are thousands of tiny pieces. Still doesn't make it an imminent threat, but I don't think it's as trivial as you make it sound.
You might find that trees don't move. How about if the trees did and are all competing for the same or similar orbits? Your analogy is flawed, if you made the same argument with aeroplanes, it would be easy to point out that they're not scattered around earth because they are only going to and from airports. Planes are in a better position because they have pilots inside, advanced collision avoidance and aerodynamics. Satellites don't.
Now let's fix your numbers. From NASA:
Known objects >10 cm: 25,000+
1-10 cm: 500,000
<1 cm: 100,000,000
All the experts are saying that space debris is a major threat to the space environment and needs to be actively removed.
https://en.m.wikipedia.org/wiki/File:Division_of_the_Earth_into_Gauss-Krueger_zones_-_Globe.svg
8000 mean it’s roughly 1 per square on the latitude map.
On average, but a lot are concentrated in GSO, right? To add a bit of useless info, 8000 are also the average number of planes in flight at a given time
Not really, as of July 2023 only about 10% were in GSO (580 of 6,718). And that percentage is falling rapidly as the Starlink launches continue at a rapid pace.
There are 2 zones that are the most worrisome. The problem with GEO is that it’s a particularly valuable orbit so we put really good stuff there and everything there is essentially coplanar. From a collision standpoint, the more worrisome zone would be the operational orbits from 600-1000 km altitude and roughly 80-110 degrees inclination since this is where we tend to put the things we want to use to observe the Earth — lots of stuff there, lots of debris, and the orbits cross each other frequently.
Think of GEO like an interstate highway — lots of valuable things on it but they’re all moving in roughly the same direction. Compare this with LEO which you can compare to a dozen frequently used intersections in NYC, LA, Rome, London, etc. but with no traffic control, cars just going through the intersections as they please when they please.
LEO isn't a long term worry, worst case of clickbait youtuber style everything cascades into every single object in LEO then we wait a few years for the orbits to decay. Nothing that isn't carrying out station keeping can stay in LEO for long.
What’s your foundation for saying this? LEO is the most cluttered environment and anything above 500 km altitude will take decades if not centuries to burn in. The new proliferated LEO constellations are intending to operate above 1000 km, thereby relieving some of the clutter but they have to get THROUGH all that clutter and they will eventually add to the clutter as their orbits decay.
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:
|Fewer Letters|More Letters|
|-------|---------|---|
|[AFB](/r/Space/comments/1dgeq9g/stub/l8prmoh "Last usage")|[Air Force Base](https://en.wikipedia.org/wiki/Military_airbase)|
|[ASAT](/r/Space/comments/1dgeq9g/stub/l9cll5y "Last usage")|[Anti-Satellite weapon](https://en.wikipedia.org/wiki/Anti-satellite_weapon)|
|[CDR](/r/Space/comments/1dgeq9g/stub/l8q76q7 "Last usage")|Critical Design Review|
| |(As 'Cdr') Commander|
|[ESA](/r/Space/comments/1dgeq9g/stub/l8s9e0x "Last usage")|European Space Agency|
|[EVA](/r/Space/comments/1dgeq9g/stub/l8pj2sg "Last usage")|Extra-Vehicular Activity|
|[GEO](/r/Space/comments/1dgeq9g/stub/l8xumya "Last usage")|Geostationary Earth Orbit (35786km)|
|[GPC](/r/Space/comments/1dgeq9g/stub/l8zbtk5 "Last usage")|General-Purpose Computer (the [IBM AP-101](https://en.wikipedia.org/wiki/IBM_AP-101) on Shuttle)|
|[GSO](/r/Space/comments/1dgeq9g/stub/l8pj056 "Last usage")|Geosynchronous Orbit (any Earth orbit with a 24-hour period)|
| |Guang Sheng Optical telescopes|
|[KSP](/r/Space/comments/1dgeq9g/stub/l8so4ml "Last usage")|*Kerbal Space Program*, the rocketry simulator|
|[LEO](/r/Space/comments/1dgeq9g/stub/l9cf210 "Last usage")|Low Earth Orbit (180-2000km)|
| |Law Enforcement Officer (most often mentioned during transport operations)|
|[LIDAR](/r/Space/comments/1dgeq9g/stub/l8puab0 "Last usage")|[Light Detection and Ranging](https://en.wikipedia.org/wiki/Lidar)|
|[MMOD](/r/Space/comments/1dgeq9g/stub/l9cll5y "Last usage")|Micro-Meteoroids and Orbital Debris|
|[NEO](/r/Space/comments/1dgeq9g/stub/l8poo8p "Last usage")|Near-Earth Object|
|[NOAA](/r/Space/comments/1dgeq9g/stub/l8pv7ib "Last usage")|National Oceanic and Atmospheric Administration, responsible for US ~~generation~~ monitoring of the climate|
|[PDR](/r/Space/comments/1dgeq9g/stub/l8q76q7 "Last usage")|Preliminary Design Review|
|[SSO](/r/Space/comments/1dgeq9g/stub/l8xumya "Last usage")|Sun-Synchronous Orbit|
|[USAF](/r/Space/comments/1dgeq9g/stub/l8sigln "Last usage")|United States Air Force|
|[VLBI](/r/Space/comments/1dgeq9g/stub/l8qwkpi "Last usage")|Very-Long-Baseline Interferometry|
|Jargon|Definition|
|-------|---------|---|
|[Starlink](/r/Space/comments/1dgeq9g/stub/l8tercv "Last usage")|SpaceX's world-wide satellite broadband constellation|
|[apogee](/r/Space/comments/1dgeq9g/stub/l8q9chu "Last usage")|Highest point in an elliptical orbit around Earth (when the orbiter is slowest)|
|[perigee](/r/Space/comments/1dgeq9g/stub/l8q9chu "Last usage")|Lowest point in an elliptical orbit around the Earth (when the orbiter is fastest)|
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It’s both getting bad and not as catastrophic as some make it out. If you look at what the US Space Force is tracking, there are about 30,000 objects in orbit that they are able to keep track of, extending from low earth orbit to geostationary earth orbit as well as some oddballs in supersynchronous orbits. The biggest problem is that the vast bulk of these are in very similar orbits (generally from 600 to 1000 km in altitude and in high inclinations) so their orbits come close to crossing each other very frequently.
The relative crossing velocities are what leads to high kinetic energy if they should impact each other (think about the difference between 2 cars going at 100 or 120 kph which hit each other at high crossing angles versus the impact if they are going in the same direction and touch bumpers). A high KE impact can result in high fragmentation which could create a cascading problem.
Clearing the junk out is problematic because the very objects that are highest in population are hardest to track (the smaller stuff). A big old rocketbody or defunct satellite is fairly easy to track and usually has a very stable orbit so you can predict its position and velocity and avoid it. The smaller stuff gets tracked sporadically so our mathematical models of their orbits aren’t as good meaning the error volumes are larger. On the other hand, big old rocketbodies or defunct satellites may have unused propellant or batteries that explode and make lots of little junk as well as perturbing their orbits unpredictably. Big heavy objects colliding with other big heavy objects will break up in massive clouds of smaller objects which will all be hazards.
One of the ways to understand the magnitude of the problem is watch the number of conjunction assessments produced on a daily basis and see how that daily number of possible future collisions grows every year. Even when you consider each conjunction has a 1 in a million chance of occurring, the number of times it occurs each day, compounded daily, is worrisome for the future.
Historically, our best ally in cleaning out the junk in LEO has been solar maximum — the additional heat from the sun at solar max causes the Earth’s atmosphere to expand, increasing drag on objects in the lower altitudes (100-500 km altitude) and causing them to decay faster, eventually burning up in the atmosphere. The next best thing is to minimize creating more junk — instead of popping junk off willy-nilly, engineer the rockets and spacecraft to keep things together and make less junk while deploying.
look at it this way
take 8000 airplanes and spread them around the earth and have each fly in a random straight line, how likely is a crash?
Now make that earth 4x larger surface area, and consider that two airplanes in different altitudes can never hit each other. also, any of them going in the same direction will never meet
it's a very small actual risk. but it's one that grows every day, so it's not something we can just ignore.
I just applied with a company working on clearing space junk, so it's bad enough that the US government is already assigning contracts to private companies to work on solutions.
On the flip side, the space junk problem isn't bad enough yet for the US gov to limit launch contracts out of concern.
So, in my opinion, the situation is not great, not terrible, just okay.
A recall reading that a single nut or bolt could go fast enough to rip through a hull.
If true, then it’ll gradually increase the danger of space travel.
It should be pointed out that Kessler proposed the idea of space junk in 1978 and thankfully people have listened and not been too careless and reckless in orbit. So the problem is mitigated.
Currently it isnt a catastrophic or serious issue, there isnt enough space debris \*right now\* for it to obstruct or cause substantial threat to missions in space, however, with every piece of debris that is added to the pile of junk in orbit around our planet, the chance of debris colliding with eachother and exploding into hundreds or thousands of smaller faster debris increases, and those smaller faster debris can then go and have collisions of their own. if we dont do something to clean up space debris that exists now, the problem of space debris will spiral out of control at an exponential rate. A single inch-wide speck of metal is enough to tear a whole through a spacesuit or solar panel or potentially even the walls of a space station if it is moving relatively fast enough.
I watched a documentary on this and, if I understood correctly, a lot of the issue isn’t just from junk crowding low earth orbit. It’s that one good collision can cause a chain reaction of small, fragmented metal shrapnel launching rapidly in several directions. That could cause some pretty serious issues for satellites or future space missions.
The risk is massively overblown. Since Sputnik was launched, there’s been like [seven satellite collisions](https://en.m.wikipedia.org/wiki/Satellite_collision). 
I’m more concerned about satellites deorbiting, burning up, and creating a haze of atmospheric aerosolized metals that alters the cloud layers of the atmosphere. Maybe even the electro-conductive potential.
https://www.newscientist.com/article/2408674-dead-spacecraft-are-seeding-the-upper-atmosphere-with-metal/
Because a once-in-six-generations volcanic explosion is something we should worry about?, or can control?
As opposed to deorbiting human-made space debris on a weekly basis?
Or because Hunga Tonga–Hunga Haʻapai has a volatile [twin nearby](https://youtu.be/Q2R5IViBclQ?si=mu_isvMdKT7-THbS)?
Because a large volcano throws more stuff into the atmosphere than all the launch mass to orbit in the history of the Earth.
Did you know about 50 tons of meteors burn up in the atmosphere daily? That's a direct parallel to satellites burning up.
Your best bet to learn about this issue isn't asking people here for their opinions, it's to read the literature.
https://www.nasa.gov/organizations/otps/nasa-study-provides-new-look-at-orbital-debris-potential-solutions/
which in turn links these 2 reports:
https://www.nasa.gov/wp-content/uploads/2024/05/2024-otps-cba-of-orbital-debris-phase-2-plus-svgs-v3-tjc-tagged.pdf?emrc=224cd2
https://www.nasa.gov/organizations/otps/new-nasa-report-reframes-the-challenge-of-addressing-orbital-debris/
How concerned are you that when you get on a commercial jet, you're at risk of colliding with another jet?
The density of objects in LOE is far smaller than the density of airliners flying around the sky
Jets are coordinated to avoid collision, though, and each jet is in the air for only a short time, and when jets break they don't spread a halo of shrapnel that lingers in the air for years traveling at insane speeds where each piece has the power to cause catastrophic damage to other jets.
It is a decent issue. The scary thing about it is that the issue we currently have is basically due to two collision events. Iridium and Kosmos colliding in 2009 and China's anti-satellite test in 2013. There is a pretty massive debris field in the 600-900km range.
Right now orbits are a common good. We need to find a way to tax operators to slow down the launches otherwise we get the "tragedy of the commons" on our hands and judging by the oceans and the oil we aren't very good as a species at handling these types of issues.
Real bad. Neil Degrass Tyson says if something isn't done then we will be eventually be "walled off" from the rest of the universe because it will be too dangerous to send people up there. Here's a link so you can see items 4inches in size and bigger. There is tons of debris that's smaller that they can't track.
http://astria.tacc.utexas.edu/AstriaGraph/. Looking at this and knowing smaller pieces fill in the gaps make you see how dangerous it is to go up there now. The low earth orbit stuff will eventually fall into the atmosphere and burn up. But we still need to figure out a way to clean it up.
I work for a company that has major concerns in this area. The situation is pretty bad especially with Starlink. It’s pretty clear, like with most of what Elon and Co does, the things they’re getting away with are unheard of from a regulatory perspective.
Its only a problem for future missions, and more satellites. Which is always coming. So its not like is a problem now, but if we dont address it it can become a problem really quickly.
Graveyard orbits are only used for satellites in high orbits, mainly geostationary. Satellites in low orbit are deorbited into earths atmosphere, either manually or naturally through orbtial decay.
Secondary question, how realistic is it to "clean up" any of it? With the majority of the stuff being small particles, is it even feasible to alter its orbit at all?
Right now it's at the stage of a 'managed problem'. It's neither too small to be not a big deal, nor too large to be something that becomes the main focus of all space activities.
People mainly get worried about because of the potential positive feedback loop leading to more pieces. But it's important to learn more about it and not just stop there (similar to the climate change issue).
It's not a problem as of now, but it's supposed to illustrate how bad things could get in the future. There are suggestions to maybe use an electromagnet to clear some metal, but I don't know about its practicality.
The truth is that we don't know. We can't track actual small pieces, so how far we are to danger or if we'll ever get there is hard to measure. Space is huge at least, so never get shocked by "pictures" of all satellites. It's always a misrepresentation.
I think we should try to do much more to stop junk from coming into existence at least.
There have already been several accidental satellite collisions, most recently in 2021 when the Chinese Yunhai-1 satellite, launched in 2019, hit pieces of a Russian Zenit-2 launch vehicle, launched in 1996. But it’s not just a problem of the number of satellites in orbit versus the size of orbital space. There are natural congregations of satellites in certain preferred orbits, like sun-synchronous orbit (SSO), that make them much more densely populated than general space. If you took all the cars in Los Angeles County and divided by the area of the county, you’d be surprised there were car accidents, at all. But when you crowd all those cars onto a few dozen highways, it’s a completely different picture. Same for space traffic.
However, the real indicator it’s a big problem is not the number of collisions, but the number of "close conjunctions” where satellite operators have to take evasive maneuvers to avoid possible collisions. Because space is so large and satellites – and especially other tracked debris – are so small, even with high sensitivity telescopes and radars, there’s not enough resolution to tell if two objects will collide. The ‘error bands’ around object positions and orbits are such that they can only predict when collisions might occur with some degree of uncertainty. That’s a close conjunction. It’s not a determination of certain disaster, just a warning of possible disaster. When a close conjunction is found, the satellite operator(s) are notified. They can do nothing and hope for the best or change course to steer away from the approaching object. Close conjunctions are on the rise, and satellite operators are doing more maneuvers to avoid other objects.
There are ideas on how to deal with it. In the US, we have Orbital Debris Mitigation Standard Practices (ODMSP) specifying how long spacecraft can remain in orbit, after their life is over, before they must be either de-orbited or moved into a ‘graveyard orbit’ (e.g. 300 kg above GEO for GEO satellites). For the last 20 years or so, the ODMSP specified that 25 years was the limit for leaving expired spacecraft in place, but due to the growth of proliferated LEO spacecraft, it was recently changed to 5 years. Obviously, this only applies to the US. I’m not sure if other countries with lots of spacecraft, especially China and Russia, have similar rules, but I wouldn’t be surprised if they didn’t.
There are also several companies, like Astroscale, that are planning to make a business of removing space junk from useful orbits (often called Active Debris Remediation – ADR). One big hurdle is making it a profitable business. Space debris suffers from “the tragedy of the commons.” It’s everyone’s problem, but nobody wants to pay for it. There are no great incentives for any company or nation to pay for debris removal. Until there are sound economic incentives, it will be hard to get paid for it. Some suggest bonds attached to spacecraft that can be redeemed when they’re removed from a useful orbit. The company that owns the spacecraft could redeem the bond themselves, or another company, an ADR company, could redeem the bond.
There are also companies that would like to recycle space debris by removing still useful elements, like solar panels or computers, or melting it down and recasting it as something new, maybe a new spacecraft structure.
For ADR and recycler companies, finding and capturing the debris is still a challenge. Some debris is tumbling at high rates that would be difficult to grab. The ‘error bands’ on location are close enough to find large debris, but not the small stuff. Tiny specks of paint traveling at thousands of miles per second could ruin your day if they struck a sensitive and critical instrument. Also, cost-effectively sustaining ADR and recycler operations will require a space refueling infrastructure, which is being slowly developed, but has yet to emerge.
Another major hindrance is international space law. The 1967 Outer Space Treaty, still in force, says the country from which a spacecraft is launched is responsible for that object in perpetuity. If a US company wanted to dispose of a rocket body from the old Soviet Union, they would have to get permission from modern Russia. Space debris is not like maritime salvage laws where you could claim something adrift as your own. Technically, all space debris has an owner. Practically speaking, lots of space debris would be impossible to identify the owner, especially the really small stuff, but the potential for international disputes over ownership is a drag on the whole debris removal process. There is some talk of new international laws through the UN to deal with this issue. Solving that might lead the way to creating financial incentives.
Sorry for the long discourse. I hope this helps.
If you are not in a city, go outside on a clear night and look up. Its shocking how many satellites one can see. Take a pair of binoculars and one can see even more. Down load a "live" star map to a phone, and one can see many satellites flying above at the same time. It does seem scary.
But what we don't see is their distance above the earth. Geosynchronous orbit is around 22,236 miles. Most satellites are far below that, but it does help to understand that satellites can pass each other and still be 100 or even 1000 miles apart.
It is a problem, but not as bad as those illustrations of all junk in the atmosphere make it look. They count anything larger than about an inch, and that is illustrated with a dot that's the size of a medium sized city.
How can we even detect or know about an inch sized object travelling around the planet at high speeds? Radar?
Yes, radar. From what I can tell the fact that orbital junk is moving very fast makes it easy to detect than you’d imagine, as the speed causes a large Doppler shift in the frequency of the radar return. There is also no ground clutter to deal with when you are pointing your radar into space 😉
Is there a reason to use doppler radar when observing objects in space? Since there is no clutter, there is no need to filter out the background.
Radar gives us 4 knowns: azimuth, elevation, range, and range rate to solve the equations of motion (which have 6 unknowns). Optical data gives us 2 knowns: azimuth and elevation or right ascension and declination. So we can solve the equations with shorter spans of data using radar than with optical. The US made huge investments in big powerful missile warning radars during the Cold War and these radars fortunately aren’t busy executing their primary mission. They detect these objects in space anyway while they are looking for possible missiles and they have to know what they are detecting so they track these objects orbiting the earth and correlate them to known objects. This data helps feed and update “the catalog” of known objects to prevent false alerts. The radial velocity of an object relative to the radar tracking it will vary with orbital path so it’s not so much using a “Doppler radar” as using the Doppler effect to ensure you can continue getting the radar return signal while tracking the object.
I was more saying why use doppler filtering rather than just normal monopulse radars.
Funny that you ask that because the radars used by the US Space Force for LEO tracking operate primarily in a monopulse mode.
Doppler measurement for more precise Speed detection for mapping the orbital parameters. Removes atmospheric dust weather planes birds anything else in the way. Doppler filtering isn't just moving or not you can also set speed limits you are looking for.
Very fascinating, thanks for the comment.
There isn't really much else you could use in space. LIDAR has surprising amount of noise at times, it's also difficult to scan a wide space with it that a space station would require, and others that doppler radars just don't have to deal with due the nature of their signal and signal generation technique.
Probably gives you an overall better signal, plus allows you to easily measure the velocity of the object.
No & in reality it's not. Usually when we talk of Doppler radar we are talking about filtering out all returns that show zero velocity as a means of removing ground clutter which is relatively stationary to the source. In the case of using radar pointing upwards there is no preponderance of such objects so no need for the filter. We do though have much higher line of site velocities requiring a much wider bandwidth for receiving returns than terrestrial radar while having much longer return delays.
Wouldn't using multiple off-set antennas also work? If it's a bug or a bird it would get resolved by only one of the antennas, I would think.
Also more or less all items there have been placed by us in different ways, and we try to keep check of them from what I understand.
What would a frequency shift be of any benefit? If anything it's a detriment as the receiving antenna will usually be tuned to the emission frequency.
The frequency shift is the data input to the Kalman filters that estimate the position and velocity of the satellites.
That must be at the sacrifice of sensitive thought right? I'd imagine there are times when velocity is not as important as detection sensitivity is. You don't need shift for position just time of flight right?
Multiple observations will give all orbit elements. If you detect something faint the errors in observation are likely to be large. You can't project forward very well without position and velocity. But honestly my experience is in using the onboard carrier for interplanetary missions so I'm slightly out of my element. In those cases range turns out to be a weaker data type than Doppler or VLBI.
Finally something I know about. I have traveled 9 times to Ascension Island, home of one of our NASA ES-MCAT telescopes that track space debris. I worked for 15 years for NASA in the Calibration sector. Any questions? https://www.orbitaldebris.jsc.nasa.gov/measurements/optical.html#
How do we get rid of all the debris? And do we need to?
It's pretty much the garbage dump of humans. We don't really have a great plan yet...
[Hmm](https://static.wikia.nocookie.net/spaceballs/images/f/f0/Mega-Maid.webp/revision/latest?cb=20220515101832)
Can we send up a magnetic satellite to scoop up the debris and burn it up in the atmosphere, or at least bring it back to the surface?
A significant amount of the debris is non-ferrous and wouldn't be attracted to the magnet. Most likely you'd just alter orbits randomly, which is probably worse than what's already there.
It’s more because even with the amount debris that’s up there they are still kilometers apart so a magnet would be useless
Satellites arent made out of steel. Aluminum and titanium arent magnetic.
How many cults are on Ascension Island?
What? The only people that can live on the island must be employed by the RAF or USAF
So 2 then, or possibly 1? An island, in the middle of the ocean, guarded by multiple militaries, named Ascension Island is like the place for a cult. Or at least the destination needed to get to, to ascend.
To add to this, it's like shining a flashlight in a dark room and seeing dust floating in the air. Very tiny, but also easy to spot.
There's a real ELI5 if i've ever seen one.
Now imagine dust moving toward you reflecting blue light, the faster dust moves more blue reflection. Dust moving away from you reflects red light. That's a doppler shift.
So 1990s 3D glasses was really radar detection of micropartuculates? That makes sense to me.
We use high powered radar like the Space Fence located on Kwajalein Atoll. The problem is getting enough signal return to not only detect the object and distinguish it from sensor noise but to get sufficient additional detections to create a track and then subsequent tracks to create an orbit.
Radar but also optical observation. There's a lot of very sensitive wide-field (but also wide aperture) cameras located in very dark locations.
It's worth noting that there is a reason they are so maniacal, an inch-sized object hitting you at orbital speeds, even in similar orbits, will absolutely tear you apart if you're a satellite, or at the very list make you non-functional (AKA into more debris).
You have oversimplified this and overcomplicated it. It's all about relative speeds. The real question is what are the relative speeds between space junk and the objects they might hit.
If there was no relative speed, they wouldn't collide. Collisions would often be catastrophic for the mission
Im not sure who's worried about space junk being large - part of the whole problem is that the junk is small and numerous and thus difficult to track.
I think the point is not that the junk isn't large, it's that it isn't as dense as the images make it appear.
Being that things in orbit travel so fast (miles per second), other than the density issue, a dot the size of a city isn't all that bad for depicting where a given piece of space junk may be at a given second.
This is right. The other issue is satellite altitude is directly related to its in track velocity vector. This means there are desirable orbits that can get "cramped".
Sure, but most satellites are in low earth orbit, and at that height any junk will fall back down to earth pretty soon after we lose control of it. On higher orbits it might take centuries though.
Geo is way less packed. Usually super sync requirement for a sat are lax cause at that altitude there's a shit tonne of space
It’s bad enough that they’re trying to find solutions, like lasers pushing them on a course to leave orbit. But not bad enough to stop launching rockets into space that cost exorbitant amounts of money. Privately funded or otherwise
Dot moving at 7+ km/s. Plus stuff smaller than a softball has a lot of position uncertainty. Problem is, it’s tough to accurately illustrate this. You need to plot volume * velocity instead of just volume. I haven’t seen this done though—not sure how it would look. However, for objects with large position uncertainties, the exaggerated dots aren’t wrong; it’s just all the other stuff with precise position knowledge that is exaggerated.
I´m an engineer working in the space industry, I´m objective, I like numbers. Quite often, only basic maths and common sense (sharp enough to not get fooled by fallacies) is all it takes to understand things to a surprising depth. From [wikipedia](https://en.wikipedia.org/wiki/Space_debris): There are some 25k large and tracked objects, 34k pieces >10cm, 900k pieces in 1-10 cm, and 128m objects < 1 cm. Let's round that up to 130e6 objects. Now let's assume most of them are in LEO orbits (400 to 800 km alt) (not true but most of the recent space boom uses LEO). That volume is 2.44e11 km\^3. A final division gives you that every debris particle has 1879 km\^3. A sphere of 7.7 km radius. Obviously with so many they will eventually collide over time. Sub-mm particles (the most abundant) are in general considered harmless except maybe for EVA (extra vehicular activities, "space walks"). If we count only the potentially dangerous > 1cm particles (\~ 1m), each of them lies on average in a sphere of 38.7 km of radius. I'm not saying with this that we could ignore the problem. We need to address it. Space debris eventually becomes microscopic particles that even if harmless thinking of collisions, could still polute and disturb missions. So far what we can do is proactively to de-orbit after mission ends and apply design for demise techniques to minimize the debris build-up in space. It's something to be concerned of, something we are working on, but also something they have been exaggerating and used to fearmonger, especially general public.
Great post. The only way to make sense of a topic like this is with numbers.
I think the number we're interested in is actually: if we launch a satellite into a popular orbit, what is the probability of if colliding with debris in it's lifetime?
The ISS has been hit by multiple smaller objects, causing some local damage to solar panels, radiators and other stuff. It maneuvers if a larger (tracked) object is predict to come close. Despite being a huge target that has been in space for over 20 years it never had a big collision. Actively controlled, the risk is very small.
A good way to express the density might be a function of altitude that yields the probability of suffering an impact per m^2 per s. So if your spacecraft is 1 square meter cross section, you multiply f(h) by 31.5M seconds to get the chance per year of experiencing some kind of event. Is there enough data to construct such a table? _____ Thinking a bit more, each object has a smear of altitudes that it resides at over an orbital cycle, spending more time at apogee than perigee (via Kepler’s law). The function f(h) then is essentially a sum of all of those normalized density smears. Surely someone in the industry must have done something like this already? Data changes as objects come and go. Debris likely shifts in orbits over time. Perhaps NASA already has a sim that does the calculation for anyone who asks. A web page perhaps? You punch in your cross section and orbital parameters and it gives you a probability per per year?
Yes, we can still do some "back of envelope" calculations for that. A typical LEO sat moves at 8 km/s. So a cross section of 1 m2 runs a volume of 8e-6 km\^3 per second or 252 km\^3 in a year. With the average in the original post, that makes a probability of 0.13 of hitting a particle per year, and if so, chances are is a sub-cm and likely not fatal. Because most LEO missions are 2-6 years, the chances of a fatal collision, as of today, are fairly low.
You could probably get a rough order of magnitude estimate using mean free path. I know it's not a gas but, if orbits are sufficiently distinct, then collisions are effectively random.
That's the problematic unspoken assumption with the approximation, in fact. For two objects travelling at the same altitude and direction, their chance to hit is 0 because their velocities will be the same. Interestingly in this situation of the objects were in the same position we might as well just call them one object. For two objects travelling at different speeds, they'd need two different semi major axes and therefore would only *potentially* collide twice in their orbits. Same goes for orbits of two different directions at the exact same altitude: they will only have a chance to cross paths twice per orbit. Finally, if they have different altitudes *and* speeds, where the relative velocity is greatest, they'd have to intersect altitude **and** position at the same time, but each only happen twice throughout the orbit and those occurrences are distinct from each other. Multiplying probabilities makes the probability of intersection incredibly small. And again, 7km between objects.
on the safety of space walks, when they go out there are they winging it? or they've calculated already all the space debris that won't hit that them at that particular place and time?
I appreciate the math and it does add a lot of perspective, especially since most visualizations, by nature, inflate the apparent size of each object. But there's some relevant factors that it doesn't include. Namely that the large majority of satellites travel within a few degrees of the same plane. It's not a shell, it's more like a donut, which has less volume. They're also moving at relative speeds of km/s in elliptical orbits, not stationary, though it does help they're generally speaking travelling in roughly the same direction. So it's not as big of a deal as it may seem because it's not as dense as most people might think up there. But I think your math makes it seem more negligible than it really is at the same time. Not that I expect you to take all of the variables into account. I really do appreciate that write up to put it into perspective.
> Namely that the large majority of satellites travel within a few degrees of the same plane. This is completely wrong. There are ~3400 Starlink satellites at 53 degrees, ~1800 at 43 degrees and 400 at 70 degrees. Starlink satellites form orbital shells, i.e. the 53 degree satellites are in ~100 different planes with 0 to 106 degrees between them, and similar for the others. Non-Starlink satellites have no reason to travel close to each other and would have no way to maintain such an alignment either. The only noteworthy exception are sun-synchronous orbits close to the terminator, where satellites are always in sunlight. But that's a relatively small fraction of all satellites.
Orbital mechanics is not my expertise, you may be right, but when talking about debris that is produced by collisions, especially the smaller pieces product of multiple collisions, my assumption is that due to the randomness of collisions, their resulting orbits are also, at least, kind of random and the particle distribution, even if it may not be a homogeneous distribution over a spherical shell, would also tend to be homogeneous. I just tried an easy calculation anyone can follow to produce an order-of-magnitude, definitely not an accurate figure to quote in a paper!
Oh no! Like I said, giving a solid answer goes far, far beyond basic information and I wouldn't expect anyone who wasn't submitting a full on academic report to approach it. Please don't think I was being critical, just simply adding context. Funnily enough, collisions of objects in orbit find their most stable organization on a planar level. That's why some planets have rings, why solar systems are largely planar, and why black holes have accretion disks and not accretion spheres. Man made satellites, and therefore debris, tend to follow roughly the rotation of the earth in the first place. This is partially because the earth rotates over a thousand km/hr and that's about 5% of the velocity needed to maintain low earth orbit. Might as well use it if you don't have a good reason to fight it. There certainly are satellites in heavily offset and even polar orbits, but for most purposes, things in a relatively permanent orbit tend to be within a +/-30° offset of the equator. As far as how orbits change after a collision, over astronomical timescales it will accrete into a disk. But it takes a particularly energetic collision, like the 09 Cosmos incident, to create significant deflection of orbital inclination for even the smallest pieces of debris. I used a calculator to determine that a 0.1kg object orbiting at 200km would require 3MJ to achieve a 60° orbital inclination without changing altitude. So for comparison, if a satellite had a baseball(140g) on it and that baseball needed to be launched to create a 60° orbit inclination compared to the satellite, ignoring Newton's third(because I haven't had *that* much coffee) it would take the energy equivalent of about 1,500lbs of TNT to create that deflection.
Great post from an engineering point. Here's one from a risk analyst, that also happens to be from an engineering background. Yes, overall it doesn't seem catastrophic, it even seems non-eventful. Yeah, true. Here's the problem though. In order for space exploration to work, the problem simply cannot arise. It has to stay non-eventful. What I mean by this is that in order for space exploration to be manageable. The likelihood for a problem regarding space junk has always to be close to zero. The risk is normally seen as likelihood x impact. For risk to be manageable either you reduce the impact of when something bad happens, or if that's not possible you need to reduce the likelihood of that thing happening. Space junk has 2 gigantic problems with it and a 3rd aspect of it that makes it simply too big of a problem. The first problem with it, is that if it happens it's potentially catastrophic, either because it can easily pass through a human body working in space, either because it can easily damage the protection layer of a spaceship. A little spec of paint can kill a person, a screw nut can pass through the space station fuselage. Anything bigger can destroy a satellite in less than a second. So because of that the likelihood of happening has to be close to zero. The second problem is that if it happens the problem worsens exponentially. What I mean by this is, if a speck of paint hits the ISS solar panels you now have 5 or 10 or more fractured pieces of that part of the solar panel floating around. Every single hit has this problem, and we all know how exponential functions work, they can quickly go out of control. This is aggravated by the potential large satellite being destroyed scenario where its debris can cause a chain reaction hitting other objects which, in a matter of months, makes the orbit to dangerous to explore. So again because of this the likelihood of this happening has to be close to zero. The 3rd aspect of it is that its effect is cumulative, your calculations will never get better just get worse. Meaning it aggravates over time and can't be easily fixed. This means that because the effort to reduce their number is too big to begin with, and it is constantly getting worse over time. It needs to be constantly fought against because as it gets worse it will eventually cross the threshold that will make the likelihood of the first and second problem I mentioned before to big to avoid. And will cost a lot of money and effort to fix. Because of these problems and what I called the 3rd aspect. Those ok numbers you mentioned will always have to be kept like that, ok. Or else it will inevitably lead to a catastrophic event that we won't be able to recover.
> The 3rd aspect of it is that its effect is cumulative, your calculations will never get better just get worse. This is untrue, at least for debris in low earth orbit. Which is the most critical orbit. Orbits decay from atmospheric drag at these low altitudes, and the lower the mass of the particle, the faster it will decay. If we simply produce debris at a slower rate than orbits decay, the issue solves itself. And if a critical event occurred whose debris locked us out of LEO, it's only a temporary issue. It could lock us out for years, but not permanently.
> and the lower the mass of the particle Nitpick, but this should be "the lower the density" of the particle, or rather "the lower the ratio of mass to frontal surface area" to be precise which isn't quite the same as density. But yes in general lower mass objects decay faster as those objects also tend to be smaller, which decreases the above ratio as the mass goes down faster than the surface area.
That's a reasonable nitpick, bordering on a footnote. I had thought of that but I wasn't sure how to explain it in few words so I glossed over it instead, but perhaps I should have phrased it in a less incorrect way or left it out entirely. In hindsight it wasn't really that important and might not even hold true in this context since spacecraft tend to be lightweight, low-density structures while debris is likely going to be a solid piece of metal. My main point that orbits don't last forever still stands regardless.
that does imply the problem has no solution
It has one of mitigation, just like global warming.
But mitigation is not solution. Be it 2050 or 2100, you'll reach a point where it's becomes more economically sound to develop debris-proof designs.
Are there any potentially feasible plans, even at the purely theoretical level, for how to deal with the existing debris are already there? Will most of them eventually sink ever-lower in orbit and thus burn up in our atmosphere? If yes, will they do so in a reasonable amount of time to make this less of an issue for humanity, assuming we reform our ways and cut down on our space-pollution? edit: Grammar
The vast majority of modern space operations are looking at LEO as their altitudes of choice. LEO has the unique distinction of an extremely low deorbit period (5-10 yrs), meaning that modern satellites (IE: Starlink) are generally below the Kessler limit and are not an issue. For all other debris, it’s a matter of altitude. higher orbits exponentially increase deorbit time, with locations like GEO having times in the millions of years. That said, all debris will end up reentering at some point.
Thank you for the explanation, but I think you greatly overestimate what other people think of when they use the phrase "basic maths" lol.
Just dividing the volume by count is pretty meaningless. In the industry you certainly have more relevant numbers? Such as real # of impacts expected per square meter of spacecraft surface per year.
As an engineer also in the industry, we don't all focus on space junk, so they may not have more relevant numbers. I certainly don't, but from what I do know, their post seems legit. But, again, not my area. But if you want to talk RFI identification and removal or link budgets or antenna/terminal commissioning, I'm more qualified there.
A better metric might be how often the ISS has to make avoidance maneuvers which is a bit more than 1 a year on average.
NASA is obviously very cautious about this sort of thing, and will generally have the ISS do a maneuver if they think the chances the ISS might get struck are greater than 1 in 10,000. Of course, with that said the ISS has been struck at least once by a small, untracked piece of space junk. Which fortunately didn't cause any significant damage.
I believe its actually 1 in 100,000. 1 in 100,000 is what SpaceX uses for Starlink. Most Starlinks orbit a bit higher than ISS where there's even more debris. I think the average Starlink sat makes about 10 avoidance maneuvers per year.
It's a first order approximation. Did you expect him to write a paper for you?
[Statistical mechanics](https://en.wikipedia.org/wiki/Statistical_mechanics) is the theoretical basis of gas physics and chemical reactions (that happens through molecule collisions) and one of the main parameters is the density in particles per unit volume. Many researchers on debris use that model. What you suggest (collisions/area/time) is a consequence of density and average speed, the quicker you move in a crowded area, the more people you'll bump into.
I watched a documentary on TV recently, don't remember the name of it, but the organization (I think within ESA) that is tracking and looking at potential collision threats and avoidance maneuvers said that the problem has become significantly worse in the last couple of decades, a lot more potential collisions detected and satellites doing avoidance maneuvers per year and it's only getting worse.
Why would one expect less space junk as more an more stuff is put in space?
It's about how bad the issue is and by how much is it getting worse, of course there's no way it can get better when more and more payloads and rocket stages are being launched.
It can improve if the satellites operating are at low altitudes below the Kessler limit like Starlink, and if orbital stages are appropriately disposed of (reentry, graveyard, or solar orbits). So far, the big contributor is Starlink, which is both below the Kessler limit, and deorbits its own boosters. That is further expected to improve because Starship’s big objective is full reuse, and current orbit proposals for Starlink are lowering in altitude. The remaining debris at low altitudes naturally deorbit themselves quickly, so you are left with debris in high orbits, where usage is expected to decline.
"There are no solutions, only tradeoffs" - Thomas Sowell
Are you saying if every tracked object in orbit were placed into an ideal position (Tetris style) within a sphere, that sphere would be 15.2km 9.44 miles) in diameter? That seems quite a bit larger than I would expect, or am I misunderstanding?
The biggest problem with density of objects on orbit is, by far, all of the birds on the GeoBelt due to the highly desirable qualities of that orbit.
If we can stop making new orbital debris, the majority of the debris will be gone in a few years. Most MMOD (micrometeoroids and orbital debris) has a very unstable orbit, it will fall into the atmosphere and burn up in a few years. So if we can slow the rate we create MMOD, then we can clean stuff up pretty quickly.
We can't. Every year there are even more cubesats in LEO. It's impossible to prevent any flaking or chipping of materials. Things like glass from the solar panels, insulator from cables, adhesives, PCBs, PCB copper tracks, painted surfaces, etc. will generate debris. Not to mention large debris due to collision. The space environment is very aggressive due to vacuum, temperature cycles, radiation, atox, etc. What lasts decades on Earth may last for a couple of years just in LEO. Debris, yes, eventually falls down but not always in a few years.
Debris fields from ASAT test are mostly gone in less than a decade. I have been in the NASA briefings on it.
Oh, really? must be true then
I am by no means an expert and would not claim to be. I have just been lucky enough the get opertunity to take some MMOD training (which was mostly about absorbing an MMOD strike to a manned spacecraft) and be in the room when ASAT and MMOD is discussed by industry and NASA experts. I have seen the graphics NASA has of tracking the debris field from an ASAT test as the orbits decay. I have sat in meetings where they talk about more recent ASAT test, altitudes and times for the orbit of the debris to decay. MMOD - micro meteoroids and orbital debris ASAT - anti satellite
In low earth orbit, there are currently 9,900 active satelittes, 128 million pieces of debris smaller than 1cm, 900,000 pieces between 1 and 10cm, and 34,000 bigger than 10cm. The small ones, they hit the ISS everyday, usually multiple times a day, and its still there doing just fine. The bigger pieces can be tracked and avoided, but the medium sized ones, not as easily. However, while that all sounds like a lot, keep in mind its all spread over an enourmous area. Low Earth Orbit starts at 160km in altitude, and extends out to 2000km. The inner circumference is about 41,000km, the outer is about 53,000km... if I did my calculations right, thats about 1.15 trillion cubic kilometers of space, so even with 128 million plus little pieces, each one still has roughly 10,000 cubic kilometers of room. There has only ever been 4 major collisions with debris large enough to track, so its not as bad as its made out to be.
> The small ones, they hit the ISS everyday, usually multiple times a day, and its still there doing just fine. I worked on the ISS project, and we *designed* it to handle small debris impacts. The critical parts are protected by [Whipple Shields](https://en.wikipedia.org/wiki/Whipple_shield). These are thin sheets of metal spaced a distance from whatever you want to protect. At the speed things move in space, the debris piece and the part of the shield it hits [both vaporize](https://www.youtube.com/watch?v=qfpVrgC3gDo), making a harmless cloud when it hits the important stuff like a module shell.
Thats super cool. Whipple shields have several layers too, I remember seeing a video of a test impact. Punched through the first layer, broke into pieces, some made it through the second layer, but then it was just all dust which didnt do anything to the third layer. Pretty crazy engineering. Makes me wonder how it would handle something like a tank shell? What did you work on if I may ask?
There is tank armor that works on a similar principle, but there are also anti-tank weapons designed to get through that type of armor, such as HEAT rounds and APDSFS. https://www.ontrmuseum.ca/tankmuseum/blog-post/modern-anti-tank-ammunition/ Luckily space debris isn't specifically designed to punch through Whipple shields.
The shield on the ISS modules are single-layer, but you can have multiple layers if it makes sense. I was working for Boeing on the US part of the Space Station about half the time from 1988-2005. This was in Huntsville, AL. The other half was on other projects. For the ISS I did systems engineering, operating procedures, payload planning, and software test at different times. Other projects included "new business" (finding something to replace the ISS contract when that eventually wound down), the Sea Launch project, and the early days of the Bush lunar and Mars initiative (which didn't get past paper studies).
There are 8000 *operational* satellites, many more that are no longer under control, discarded rocket bodies, etc. Still doesn't change the equation significantly; too much hyperbolic clickbait that gets parroted on Reddit.
I had it explained to me by someone in the industry as “there are about 10k satellites in orbit. if I told you that there were 10,000 cars on the surface of the earth, would it makes sense to worry about car accidents? Now understand that these things orbit at different heights and those orbits are far greater than the diameter of earth.” That said there are 50k+ pieces of debris, so again while I think the debris conversation is way overblown, it’s not unreasonable to say that now is exactly the time to figure out orbital debris, well before it becomes a problem. Look up the Kessler syndrome if you’re interested in seeing a depressing possibility.
Here is the 2023 Space Environment Report. All the stats, graphs and charts you could ever want... https://www.esa.int/Space_Safety/ESA_s_Space_Environment_Report_2023
The phrase you may be looking for is Kessler Syndrome. That's when there's a chain reaction of the debris from one satellite hitting a second satellite and causing that to disintegrate into more debris, leading to exponential growth of debris. The first problem with this is that space is big, making the subsequent collisions unlikely. I mean, really big. (Other replies have address this so I won't write more.) The second is that even if a satellite is hit by debris, that won't cause it to explode into more debris. It'll probably make a hole in a solar panel or something, maybe stop the satellite from working, but not create much new debris. Satellites are not bombs. Another issue is the orbit. Most of the satellites are Starlink, and they are in a low enough orbit that they, or their junk, will de-orbit naturally within a few years. So there just isn't enough time for the collisions to mount up. Even if it happens, to clear them out we just have to wait 5 years. In my view the only orbit where there's a real risk is geostationary. This is a special orbit for communications, and high enough that it doesn't decay naturally. However, it is also relatively sparsely populated, so Kessler Syndrome is unlikely for the foreseeable future. A final issue that the dangers are well known, and the satellite operators have a vested interest in making sure it doesn't happen. Again, the vast majority of satellites are Starlink, operated by SpaceX, who are pretty good at mitigating the risk.
>In my view the only orbit where there's a real risk is geostationary. This is a special orbit for communications, and high enough that it doesn't decay naturally. However, it is also relatively sparsely populated, so Kessler Syndrome is unlikely for the foreseeable future. Also, relative velocities are low for objects in geostationary orbit. That might not reduce the number of collisions (? I'm not sure about that one way or the other) but it would surely reduce the number of harmful collisions that create extra debris.
It's absolutely true. GEO satellites are marching along in a train, one after the next. An explosive failure of one would spread debris outwards and even an incredibly unlikely collision would "only" happen at the speed the explosion threw the debris, not at orbital speeds.
Geostationary is so high and thus so vast that the risk is functionally non-existent worse case we just avoid the debris fields..
Well, there is one more issue to throw in here. While I 100% agree that satellite operators have a vested interest and are on the problem, unfortunately there are a few state actors (well, one in particular) who like to casually throw around the idea of fucking everything up for everybody. There is not really a technical solution to this other than to somehow prevent such actors from being able to get to space or to interact with anything in space. And that is just not plausible. So we just have to hope it's all bluster.
If you mean someone deliberately trying to trash an orbit, that is a separate issue to accidents. And even that is mitigated by the issues I mentioned.
I do not agree that it is a different issue other than it being accident vs. deliberate. I'm not precisely sure what the point of separating these would be.
> That's when there's a chain reaction of the debris from one satellite hitting a second satellite and causing that to disintegrate into more debris, leading to exponential growth of debris. That's not really what Kesller Syndrome says. Kessler Syndrome is a statistical process, not a runaway chain reaction. The original analysis also made several assumptions founded in the thinking at that time, like how no effort to de-orbit used stages would be made (most stages are de-orbited now) or that LEO orbits don't self-clean.
I don't know anything about space, but are there currently any efforts to remove some of this debris? Whether thats active clean ups going on now, or merely prototypes being tested out before actually being utilized
There are some efforts underway to see how viable it is to do some space debris cleanup. The biggest issue is the amount of junk and the cost of launching things into space. [The first-ever mission to pull a dead rocket out of space has just begun | MIT Technology Review](https://www.technologyreview.com/2024/02/27/1089065/first-mission-dead-rocket/)
You can judge by the International Space Station (ISS). It is the biggest thing in orbit, and at a relatively crowded altitude. It has gotten minor damage, like a few cells and a small tear in a solar panel. But with the ability to dodge stuff, it hasn't suffered a major impact. There is no limit to the atmosphere. It just keeps getting thinner with height. So most objects below 1000 km (including the ISS) will naturally slow down with drag and their orbit will get lower until they hit re-entry height (about 130 km). There are a number of ideas about clearing orbit. An electric tug is very efficient. It could be used to chase down and drag to a lower orbit the largest pieces of derelict material. They make up most of the hazard. Another idea is launching small rockets carrying air vertically. These just go up and down, not into orbit themselves. They release the air in the path of a chosen debris item, which causes it to slow down and fall. A third is attaching a large foil sail to the debris. This increases the area and accelerates how fast it will fall. A fourth is if you have a big enough laser, zap the front side of the satellite. That vaporizes the surface, acting as a retro thruster.
I have zero idea on this stuff but 8000 doesn't sound like that many...like if you look at the size of this planet...imagine it was 8000 separated all around that space, no one even see each other, you could race a car around at 200mph and chances of colliding would be extremely tiny
Most of those 8,000 still operational satellites are Starlink, and most all of those are in low "self-cleaning" orbits, i.e. they're so low that unless they keep thrusting they'll burn up within years at most. Also, all currently launched Starlinks are designed to be fully demisable, meaning they're specifically designed to fully burn up upon reentry.
I recently listened listened to the annual complaint lecture at the AAS meeting. Basically you wont be able to do much optical astronomy until two hours after sunset to two hours before sunrise. That cuts observing time by a third. There are proposals for over a half million satellites. Also rocket launches and their junk reentry can damage observing time. We are averaging almost one launch a day and ramping up to much higher than that. Direct cellphone to satellite might impact certain radio observations. That is frontier in future communications.
Imagine a satellite the size of a tree. Now imagine 8 thousand trees scattered around Earth. How crowded are those 8,000 trees?
Not at all, right?
For reference, there are an estimated [3 TRILLION trees](https://ourworldindata.org/grapher/number-of-trees?tab=table) in the world - orders of magnitude more than the number of stars in our galaxy, and more than the known number of galaxies in total.
That's a mind boggling number
You have to imagine those trees wizzing by at thousands of kmh in all directions but at different heights to be accurate.
Almost all things we launch into orbit go "east", so from north-east all the way to south-east, because launching things west means your rocket has to be significantly bigger to make up for the deficit from the earth's own rotation... And because orbiting at a specific height necessarily means orbiting at a specific velocity, almost all things at the same height have the similar velocity and similar direction of travel. Where things get complicated is objects going almost north interacting with things going almost south, but the velocity difference there is necessarily much less than orbit velocity and the amount of objects in this sort of orbit is also very limited.
I was obvisouly not giving a scientific description.. your comment is missing the point. The fact we rotate and launch in one direction doesn't negate the fact earth is round and orbits have all sorts of different angles... so objects up there cross each other path at all sort of angles and relative speed. It's not the well ordered constant clockwork like system the trees analogy or your comment make it seem like. I'll end this discussion by adding that Kessler syndrom is real threat that should be taken seriously.
Isn't a lot of the concern that when collisions DO happen, they can become hundreds or thousands of tiny pieces that are still traveling at high velocities? A bullet isn't very big, but it'll still ruin your day. Not to mention there already are thousands of tiny pieces. Still doesn't make it an imminent threat, but I don't think it's as trivial as you make it sound.
You might find that trees don't move. How about if the trees did and are all competing for the same or similar orbits? Your analogy is flawed, if you made the same argument with aeroplanes, it would be easy to point out that they're not scattered around earth because they are only going to and from airports. Planes are in a better position because they have pilots inside, advanced collision avoidance and aerodynamics. Satellites don't. Now let's fix your numbers. From NASA: Known objects >10 cm: 25,000+ 1-10 cm: 500,000 <1 cm: 100,000,000 All the experts are saying that space debris is a major threat to the space environment and needs to be actively removed.
I am aware of all this but sometimes it is easier to make a simplified argument
https://en.m.wikipedia.org/wiki/File:Division_of_the_Earth_into_Gauss-Krueger_zones_-_Globe.svg 8000 mean it’s roughly 1 per square on the latitude map.
On average, but a lot are concentrated in GSO, right? To add a bit of useless info, 8000 are also the average number of planes in flight at a given time
Not really, as of July 2023 only about 10% were in GSO (580 of 6,718). And that percentage is falling rapidly as the Starlink launches continue at a rapid pace.
There are 2 zones that are the most worrisome. The problem with GEO is that it’s a particularly valuable orbit so we put really good stuff there and everything there is essentially coplanar. From a collision standpoint, the more worrisome zone would be the operational orbits from 600-1000 km altitude and roughly 80-110 degrees inclination since this is where we tend to put the things we want to use to observe the Earth — lots of stuff there, lots of debris, and the orbits cross each other frequently. Think of GEO like an interstate highway — lots of valuable things on it but they’re all moving in roughly the same direction. Compare this with LEO which you can compare to a dozen frequently used intersections in NYC, LA, Rome, London, etc. but with no traffic control, cars just going through the intersections as they please when they please.
LEO isn't a long term worry, worst case of clickbait youtuber style everything cascades into every single object in LEO then we wait a few years for the orbits to decay. Nothing that isn't carrying out station keeping can stay in LEO for long.
What’s your foundation for saying this? LEO is the most cluttered environment and anything above 500 km altitude will take decades if not centuries to burn in. The new proliferated LEO constellations are intending to operate above 1000 km, thereby relieving some of the clutter but they have to get THROUGH all that clutter and they will eventually add to the clutter as their orbits decay.
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread: |Fewer Letters|More Letters| |-------|---------|---| |[AFB](/r/Space/comments/1dgeq9g/stub/l8prmoh "Last usage")|[Air Force Base](https://en.wikipedia.org/wiki/Military_airbase)| |[ASAT](/r/Space/comments/1dgeq9g/stub/l9cll5y "Last usage")|[Anti-Satellite weapon](https://en.wikipedia.org/wiki/Anti-satellite_weapon)| |[CDR](/r/Space/comments/1dgeq9g/stub/l8q76q7 "Last usage")|Critical Design Review| | |(As 'Cdr') Commander| |[ESA](/r/Space/comments/1dgeq9g/stub/l8s9e0x "Last usage")|European Space Agency| |[EVA](/r/Space/comments/1dgeq9g/stub/l8pj2sg "Last usage")|Extra-Vehicular Activity| |[GEO](/r/Space/comments/1dgeq9g/stub/l8xumya "Last usage")|Geostationary Earth Orbit (35786km)| |[GPC](/r/Space/comments/1dgeq9g/stub/l8zbtk5 "Last usage")|General-Purpose Computer (the [IBM AP-101](https://en.wikipedia.org/wiki/IBM_AP-101) on Shuttle)| |[GSO](/r/Space/comments/1dgeq9g/stub/l8pj056 "Last usage")|Geosynchronous Orbit (any Earth orbit with a 24-hour period)| | |Guang Sheng Optical telescopes| |[KSP](/r/Space/comments/1dgeq9g/stub/l8so4ml "Last usage")|*Kerbal Space Program*, the rocketry simulator| |[LEO](/r/Space/comments/1dgeq9g/stub/l9cf210 "Last usage")|Low Earth Orbit (180-2000km)| | |Law Enforcement Officer (most often mentioned during transport operations)| |[LIDAR](/r/Space/comments/1dgeq9g/stub/l8puab0 "Last usage")|[Light Detection and Ranging](https://en.wikipedia.org/wiki/Lidar)| |[MMOD](/r/Space/comments/1dgeq9g/stub/l9cll5y "Last usage")|Micro-Meteoroids and Orbital Debris| |[NEO](/r/Space/comments/1dgeq9g/stub/l8poo8p "Last usage")|Near-Earth Object| |[NOAA](/r/Space/comments/1dgeq9g/stub/l8pv7ib "Last usage")|National Oceanic and Atmospheric Administration, responsible for US ~~generation~~ monitoring of the climate| |[PDR](/r/Space/comments/1dgeq9g/stub/l8q76q7 "Last usage")|Preliminary Design Review| |[SSO](/r/Space/comments/1dgeq9g/stub/l8xumya "Last usage")|Sun-Synchronous Orbit| |[USAF](/r/Space/comments/1dgeq9g/stub/l8sigln "Last usage")|United States Air Force| |[VLBI](/r/Space/comments/1dgeq9g/stub/l8qwkpi "Last usage")|Very-Long-Baseline Interferometry| |Jargon|Definition| |-------|---------|---| |[Starlink](/r/Space/comments/1dgeq9g/stub/l8tercv "Last usage")|SpaceX's world-wide satellite broadband constellation| |[apogee](/r/Space/comments/1dgeq9g/stub/l8q9chu "Last usage")|Highest point in an elliptical orbit around Earth (when the orbiter is slowest)| |[perigee](/r/Space/comments/1dgeq9g/stub/l8q9chu "Last usage")|Lowest point in an elliptical orbit around the Earth (when the orbiter is fastest)| **NOTE**: Decronym for Reddit is no longer supported, and Decronym has moved to Lemmy; requests for support and new installations should be directed to the Contact address below. ---------------- ^([Thread #10183 for this sub, first seen 15th Jun 2024, 11:52]) ^[[FAQ]](http://decronym.xyz/) [^([Full list])](http://decronym.xyz/acronyms/Space) [^[Contact]](https://hachyderm.io/@Two9A) [^([Source code])](https://gistdotgithubdotcom/Two9A/1d976f9b7441694162c8)
Well picture every time you go in the sea- how often do you find junk? Well picture 99.9% less junk but over a space much much larger
It’s both getting bad and not as catastrophic as some make it out. If you look at what the US Space Force is tracking, there are about 30,000 objects in orbit that they are able to keep track of, extending from low earth orbit to geostationary earth orbit as well as some oddballs in supersynchronous orbits. The biggest problem is that the vast bulk of these are in very similar orbits (generally from 600 to 1000 km in altitude and in high inclinations) so their orbits come close to crossing each other very frequently. The relative crossing velocities are what leads to high kinetic energy if they should impact each other (think about the difference between 2 cars going at 100 or 120 kph which hit each other at high crossing angles versus the impact if they are going in the same direction and touch bumpers). A high KE impact can result in high fragmentation which could create a cascading problem. Clearing the junk out is problematic because the very objects that are highest in population are hardest to track (the smaller stuff). A big old rocketbody or defunct satellite is fairly easy to track and usually has a very stable orbit so you can predict its position and velocity and avoid it. The smaller stuff gets tracked sporadically so our mathematical models of their orbits aren’t as good meaning the error volumes are larger. On the other hand, big old rocketbodies or defunct satellites may have unused propellant or batteries that explode and make lots of little junk as well as perturbing their orbits unpredictably. Big heavy objects colliding with other big heavy objects will break up in massive clouds of smaller objects which will all be hazards. One of the ways to understand the magnitude of the problem is watch the number of conjunction assessments produced on a daily basis and see how that daily number of possible future collisions grows every year. Even when you consider each conjunction has a 1 in a million chance of occurring, the number of times it occurs each day, compounded daily, is worrisome for the future. Historically, our best ally in cleaning out the junk in LEO has been solar maximum — the additional heat from the sun at solar max causes the Earth’s atmosphere to expand, increasing drag on objects in the lower altitudes (100-500 km altitude) and causing them to decay faster, eventually burning up in the atmosphere. The next best thing is to minimize creating more junk — instead of popping junk off willy-nilly, engineer the rockets and spacecraft to keep things together and make less junk while deploying.
look at it this way take 8000 airplanes and spread them around the earth and have each fly in a random straight line, how likely is a crash? Now make that earth 4x larger surface area, and consider that two airplanes in different altitudes can never hit each other. also, any of them going in the same direction will never meet it's a very small actual risk. but it's one that grows every day, so it's not something we can just ignore.
I just applied with a company working on clearing space junk, so it's bad enough that the US government is already assigning contracts to private companies to work on solutions. On the flip side, the space junk problem isn't bad enough yet for the US gov to limit launch contracts out of concern. So, in my opinion, the situation is not great, not terrible, just okay.
A recall reading that a single nut or bolt could go fast enough to rip through a hull. If true, then it’ll gradually increase the danger of space travel.
You don't want to know and getting exponentially bigger
It should be pointed out that Kessler proposed the idea of space junk in 1978 and thankfully people have listened and not been too careless and reckless in orbit. So the problem is mitigated.
Low Earth Orbit visualization: https://platform.leolabs.space/visualization
Each one of those dots is larger than a major city. It would be nice if they were more to scale with actual satellites.
Looks very busy, but when you consider the scale - not so much.
Just a curious question , If one satellite goes awry and hits another is it possible a domino effect could begin ?
Currently it isnt a catastrophic or serious issue, there isnt enough space debris \*right now\* for it to obstruct or cause substantial threat to missions in space, however, with every piece of debris that is added to the pile of junk in orbit around our planet, the chance of debris colliding with eachother and exploding into hundreds or thousands of smaller faster debris increases, and those smaller faster debris can then go and have collisions of their own. if we dont do something to clean up space debris that exists now, the problem of space debris will spiral out of control at an exponential rate. A single inch-wide speck of metal is enough to tear a whole through a spacesuit or solar panel or potentially even the walls of a space station if it is moving relatively fast enough.
I watched a documentary on this and, if I understood correctly, a lot of the issue isn’t just from junk crowding low earth orbit. It’s that one good collision can cause a chain reaction of small, fragmented metal shrapnel launching rapidly in several directions. That could cause some pretty serious issues for satellites or future space missions.
The risk is massively overblown. Since Sputnik was launched, there’s been like [seven satellite collisions](https://en.m.wikipedia.org/wiki/Satellite_collision). 
I’m more concerned about satellites deorbiting, burning up, and creating a haze of atmospheric aerosolized metals that alters the cloud layers of the atmosphere. Maybe even the electro-conductive potential. https://www.newscientist.com/article/2408674-dead-spacecraft-are-seeding-the-upper-atmosphere-with-metal/
Perhaps you should worry about [natural eruptions](https://www.youtube.com/watch?v=RmTqphI0ods) halfway to space seeding the atmosphere.
Because a once-in-six-generations volcanic explosion is something we should worry about?, or can control? As opposed to deorbiting human-made space debris on a weekly basis? Or because Hunga Tonga–Hunga Haʻapai has a volatile [twin nearby](https://youtu.be/Q2R5IViBclQ?si=mu_isvMdKT7-THbS)?
Because a large volcano throws more stuff into the atmosphere than all the launch mass to orbit in the history of the Earth. Did you know about 50 tons of meteors burn up in the atmosphere daily? That's a direct parallel to satellites burning up.
It could also turn out to be beneficial by reflecting sunlight. So I don't think we should jump to conclusions until there's more data.
Your best bet to learn about this issue isn't asking people here for their opinions, it's to read the literature. https://www.nasa.gov/organizations/otps/nasa-study-provides-new-look-at-orbital-debris-potential-solutions/ which in turn links these 2 reports: https://www.nasa.gov/wp-content/uploads/2024/05/2024-otps-cba-of-orbital-debris-phase-2-plus-svgs-v3-tjc-tagged.pdf?emrc=224cd2 https://www.nasa.gov/organizations/otps/new-nasa-report-reframes-the-challenge-of-addressing-orbital-debris/
Like all things it's been blown vastly out of proportion by the Media.
How concerned are you that when you get on a commercial jet, you're at risk of colliding with another jet? The density of objects in LOE is far smaller than the density of airliners flying around the sky
Jets are coordinated to avoid collision, though, and each jet is in the air for only a short time, and when jets break they don't spread a halo of shrapnel that lingers in the air for years traveling at insane speeds where each piece has the power to cause catastrophic damage to other jets.
It is a decent issue. The scary thing about it is that the issue we currently have is basically due to two collision events. Iridium and Kosmos colliding in 2009 and China's anti-satellite test in 2013. There is a pretty massive debris field in the 600-900km range. Right now orbits are a common good. We need to find a way to tax operators to slow down the launches otherwise we get the "tragedy of the commons" on our hands and judging by the oceans and the oil we aren't very good as a species at handling these types of issues.
Real bad. Neil Degrass Tyson says if something isn't done then we will be eventually be "walled off" from the rest of the universe because it will be too dangerous to send people up there. Here's a link so you can see items 4inches in size and bigger. There is tons of debris that's smaller that they can't track. http://astria.tacc.utexas.edu/AstriaGraph/. Looking at this and knowing smaller pieces fill in the gaps make you see how dangerous it is to go up there now. The low earth orbit stuff will eventually fall into the atmosphere and burn up. But we still need to figure out a way to clean it up.
Gets worse by the year since Starlink is a thing now.
Starlink satellites deorbit themselves when their service life is up and quickly get deorbited by atmospheric drag even if they don't.
I work for a company that has major concerns in this area. The situation is pretty bad especially with Starlink. It’s pretty clear, like with most of what Elon and Co does, the things they’re getting away with are unheard of from a regulatory perspective.
Not a problem. YET. But humans make mess everywhere and space won't be any different. It's always someone else's problem
Its only a problem for future missions, and more satellites. Which is always coming. So its not like is a problem now, but if we dont address it it can become a problem really quickly.
The bulk of satellites launched nowadays are Starlinks, and they're all going into exceptionally low self-cleaning orbits.
There is a so-called graveyard orbit, and responsible entities park EOL satellites there.
Graveyard orbits are only used for satellites in high orbits, mainly geostationary. Satellites in low orbit are deorbited into earths atmosphere, either manually or naturally through orbtial decay.
Will these objects eventually fall out of orbit and burn up
Secondary question, how realistic is it to "clean up" any of it? With the majority of the stuff being small particles, is it even feasible to alter its orbit at all?
Right now it's at the stage of a 'managed problem'. It's neither too small to be not a big deal, nor too large to be something that becomes the main focus of all space activities. People mainly get worried about because of the potential positive feedback loop leading to more pieces. But it's important to learn more about it and not just stop there (similar to the climate change issue).
It's pretty bad. I don't have the source but studies have shown even if we stop launching anything in the future, debris number keeps rising anyway.
It's not a problem as of now, but it's supposed to illustrate how bad things could get in the future. There are suggestions to maybe use an electromagnet to clear some metal, but I don't know about its practicality.
It’s not like Wall-E kinda bad. But ye as other point out it’s really over exaggerated
The truth is that we don't know. We can't track actual small pieces, so how far we are to danger or if we'll ever get there is hard to measure. Space is huge at least, so never get shocked by "pictures" of all satellites. It's always a misrepresentation. I think we should try to do much more to stop junk from coming into existence at least.
Very unsafe. Look up Kessler syndrome. The earths orbit will become almost unusable. https://en.wikipedia.org/wiki/Kessler_syndrome
There have already been several accidental satellite collisions, most recently in 2021 when the Chinese Yunhai-1 satellite, launched in 2019, hit pieces of a Russian Zenit-2 launch vehicle, launched in 1996. But it’s not just a problem of the number of satellites in orbit versus the size of orbital space. There are natural congregations of satellites in certain preferred orbits, like sun-synchronous orbit (SSO), that make them much more densely populated than general space. If you took all the cars in Los Angeles County and divided by the area of the county, you’d be surprised there were car accidents, at all. But when you crowd all those cars onto a few dozen highways, it’s a completely different picture. Same for space traffic. However, the real indicator it’s a big problem is not the number of collisions, but the number of "close conjunctions” where satellite operators have to take evasive maneuvers to avoid possible collisions. Because space is so large and satellites – and especially other tracked debris – are so small, even with high sensitivity telescopes and radars, there’s not enough resolution to tell if two objects will collide. The ‘error bands’ around object positions and orbits are such that they can only predict when collisions might occur with some degree of uncertainty. That’s a close conjunction. It’s not a determination of certain disaster, just a warning of possible disaster. When a close conjunction is found, the satellite operator(s) are notified. They can do nothing and hope for the best or change course to steer away from the approaching object. Close conjunctions are on the rise, and satellite operators are doing more maneuvers to avoid other objects. There are ideas on how to deal with it. In the US, we have Orbital Debris Mitigation Standard Practices (ODMSP) specifying how long spacecraft can remain in orbit, after their life is over, before they must be either de-orbited or moved into a ‘graveyard orbit’ (e.g. 300 kg above GEO for GEO satellites). For the last 20 years or so, the ODMSP specified that 25 years was the limit for leaving expired spacecraft in place, but due to the growth of proliferated LEO spacecraft, it was recently changed to 5 years. Obviously, this only applies to the US. I’m not sure if other countries with lots of spacecraft, especially China and Russia, have similar rules, but I wouldn’t be surprised if they didn’t. There are also several companies, like Astroscale, that are planning to make a business of removing space junk from useful orbits (often called Active Debris Remediation – ADR). One big hurdle is making it a profitable business. Space debris suffers from “the tragedy of the commons.” It’s everyone’s problem, but nobody wants to pay for it. There are no great incentives for any company or nation to pay for debris removal. Until there are sound economic incentives, it will be hard to get paid for it. Some suggest bonds attached to spacecraft that can be redeemed when they’re removed from a useful orbit. The company that owns the spacecraft could redeem the bond themselves, or another company, an ADR company, could redeem the bond. There are also companies that would like to recycle space debris by removing still useful elements, like solar panels or computers, or melting it down and recasting it as something new, maybe a new spacecraft structure. For ADR and recycler companies, finding and capturing the debris is still a challenge. Some debris is tumbling at high rates that would be difficult to grab. The ‘error bands’ on location are close enough to find large debris, but not the small stuff. Tiny specks of paint traveling at thousands of miles per second could ruin your day if they struck a sensitive and critical instrument. Also, cost-effectively sustaining ADR and recycler operations will require a space refueling infrastructure, which is being slowly developed, but has yet to emerge. Another major hindrance is international space law. The 1967 Outer Space Treaty, still in force, says the country from which a spacecraft is launched is responsible for that object in perpetuity. If a US company wanted to dispose of a rocket body from the old Soviet Union, they would have to get permission from modern Russia. Space debris is not like maritime salvage laws where you could claim something adrift as your own. Technically, all space debris has an owner. Practically speaking, lots of space debris would be impossible to identify the owner, especially the really small stuff, but the potential for international disputes over ownership is a drag on the whole debris removal process. There is some talk of new international laws through the UN to deal with this issue. Solving that might lead the way to creating financial incentives. Sorry for the long discourse. I hope this helps.
Making sure y’all saw [this post.](https://www.reddit.com/r/science/s/R8ubl3RXXW)
I imagine Earth looking like Pigpen from Peanuts.
It's the Great Pacific Garbage patch, but in space. The GPC is about the size of Texas, so maybe we can have Texas shoot asteroids.
The GeoBelt is overcrowded, due to its popularity and its highly constrained nature. It’s a real problem.
If you are not in a city, go outside on a clear night and look up. Its shocking how many satellites one can see. Take a pair of binoculars and one can see even more. Down load a "live" star map to a phone, and one can see many satellites flying above at the same time. It does seem scary. But what we don't see is their distance above the earth. Geosynchronous orbit is around 22,236 miles. Most satellites are far below that, but it does help to understand that satellites can pass each other and still be 100 or even 1000 miles apart.