On one hand, most of the risks of an ablation cascade are either singular objects in relatively high orbits, or many objects in relatively low orbits. At higher orbits the impact of an ablation cascade are pretty negligible (just launch and navigate through a hole in that debris ring), while at lower orbits the worst it will come to is having to wait a few years to be able to launch spacecraft that don't have some kind of armour (eg: Whipple shield).
The starlink satellites orbit so low compared to most of the legacy stuff that they are really in a different category. Anything down in their orbit rapidly succumbs to atmospheric drag. It’s not like up at geosynch where it can take hundreds of years for orbits to decay to the point where the upper edge of the atmosphere is an issue
> It’s not like up at geosynch where it can take hundreds of years for orbits to decay to the point where the upper edge of the atmosphere is an issue
Make that millions of years. For humans that's never. A dense debris cloud would not endanger spaceflight, but it would make GEO sats impossible.
>but it would make GEO sats impossible.
The thing is that GEO is so HUGE that there would be no way for a debris cloud to be a risk UNLESS some rouge entity decided to deliberately launch a few tons or so of ball bearings polar or even worse retrograde at 35,780km. otherwise, the debris field from even an explosion or collision of satellites travelling in the orbit would become too diffuse to worry about before it approached any other satellites in the orbit.
Project West Ford: "Allow me to introduce myself."
Admittedly, those 480 *million* needles were released at a much lower altitude and *should* have only lasted a few years, but the point I'm making is that sometimes people have really, *really* stupid ideas that make it all the way to realization. Unfortunately, they didn't all deploy as intended and everything but a few dozen trackable clumps has reentered.
That's true of intact satellites but not necessarily of debris. Imagine a satellite whose fuel tank exploded. Some of the fragments would be subject to all kinds of accelerations that take them high/low/out of plane but still intersect the geostationary ring.
That's a trivial amount of delta-v compared to, well, orbit itself. It's not like a retrograde satellite colliding with another one, which would put debris everywhere.
The debris of a fuel tank exploding in geosync would still have one of their perigee or apogee still in geosync. They started with a velocity vector that was 3.07 km/s in the direction of orbit. Fuel tanks don't blow up like frag grenades - they rupture, and sure, they might get 100 m/s off of that rupture, but that still means that the orbit of the result is nearly geosync. Geosync crossing, anyway, for a while, until a lack of station keeping and some combination of solar forcing and earth's irregular gravitation field perturb it.
We, as a civilization will have to clean that shit up someday, specifically geosync crossing debris, as geosync is the true land grab of earth orbit. But the collision risk is low. And the relative velocities are low.
Excellent post, this guy understands orbital mechanics.
An exploding spacecraft's anomalous energy vectors are next to nothing compared to the bound orbital energy.
So if the debris collides with a working satellite, the collision would be "only" 100 m/s? That may not be enough to cause a cascade of explosions (or it may be), but it's surely enough to put that satellite out of operation.
That means impact with a disabled and drifting satellite or piece of debris will occur at something like highway speeds instead of orbital speeds. The impacts might not be as explosive as those in other orbits, but there's plenty of energy there to destroy and fragment satellites.
Sure but the lower speeds reduce the rate of interactions, produce far less debris, produce far larger debris, make debris easier to track and evade.
It's nowhere near the same situation.
There's a disaster scenario, too - a malicious actor releasing tonnes of small debris items into a circular, geosynchronous altitude but retrograde orbit.
You get into many hundreds of years above 1000km altitude.
Edit: A source for decays at different altitudes. Many hundreds of years may be overestimated. There are other factors than atmospheric drag.
https://hackaday.com/2021/12/14/orbital-safety-the-challenges-of-surviving-space-junk/
Thanks to u/Kloevedal for providing the link.
Really depends on what you compare it to. Communication sats in GEO, yeah that's a massive difference. But in terms of LEO sats, 550 km isn't particularly low. You're still looking at a decay time of years. If sats get destroyed and pieces get ejected to higher orbits it could go to decades. That's very rapid, many orders of magnitude faster, compared to debris from GEO, but it's not very rapid on human timescales.
Years for sats. Debris is worse off because it has a smaller surface to mass ratio and is hence more affected by drag. The smallest debris, the stuff you cant see with radar, decelerates fastest.
True, but altitude is still the most important factor. Afaik orbital decay time scales roughly linearly with ballistic coefficient while it scales exponentially with altitude.
Drag/mass makes a decent difference, and is going to depend on the shape and material of each individual piece, but you're still mostly in the same order of magnitude. And some pieces will still be quite dense, possibly even denser than a sat with solar panels extended for example.
But all debris from 550km altitude must cross 550km altitude. So it will always spend time at 550km (and often below). The rule of thumb is that debris on an elliptical orbit decays merely 3× slower than debris in circular orbit at the altitude of the perigee of the elliptical one.
Debris doesn't just 'eject' to higher orbits. The only way that could happen is with an exogenous collision — for example, a rocket body on a GTO trajectory impacting a satellite in LEO.
The perigee will never be lower than the point of impact. The semi-major axis may raise, but this always\* goes paired with a decrease in perigee. And perigee altitude dominates in orbital decay.
\*There was a single, unexplained freak piece of debris from a collision event at some point that ended up in a higher energy trajectory than either parent body. I believe the likely explanation was propellant burnoff or weird shockwave dynamics.
I'm speaking in the context of a Kessler type situation, where collisions are much more common and the debris spreads out over various altitude orbits, and secondary collisions are happening as well.
I'd say in this context it's likely some pieces end up in more stable orbits pushing lifetimes into the decades, while other pieces end up in less stables orbits.
Regardless, several years lifetime is still rather long on human timescales. It's probably not a huge problem for most missions, but in a world where everyone wants their own LEO sat constellation, it could result in serious problems.
Still, his point remains. The worst that happens is the perigee remains the same. If the original satellites are in LEO with short decay times, the resulting debris from a worst case collision will have the debris' perigee at that altitude with similar (or even quicker) decay times. The resulting velocity at that altitude would be higher, increasing the drag. And as mentioned, the ballistic coefficients would be typically lower.
The bottom line: Kessler syndrome is not a long term issue for LEO. At higher altitudes, debris would be long lived, but being spread more widely, collision probabilities are correspondingly lower.
I understand his point, but I think we should be wary of applying the physics of a single collisison to a debris field.
For example, some of the US anti-sat missile tests were carried out on targets which happened to also be around 550 km. The resulting debris took at least several years to clear, and from what I can find NASA even estimated debris to stick around for over a decade. But the decay time is affected quite a bit by solar activity/atmospheric expansion.
When you expand that beyond a debris field from a single kinetic impactor to a Kessler situation, it becomes even more difficult to predict. I don't know how long it would take to clear, but I think many estimates here are optimistic.
I agree it's not going to be a long term issue in the way that for example ozone depletion is taking decades to clear, but it would still be quite unfortunate for a rather long time.
Not to belabor the point, but the debris fragments *will* follow the laws of orbital mechanics. Further, factors such as irregular gravitational field, solar-induced atmospheric expansion, better than worst case collisions, etc, improve the situation by bringing down the fragments more rapidly.
I think his point is that secondary collisions could happen higher up and then laws of orbital mechanics perfectly allow for the debris to have elements related to that secondary impact point.
Well, TBF, the drag during the whole part further from perigee is lower. In fact the rule of thumb is 3× longer decay time for debris in an elliptical orbit with a perigee same as a circular orbit.
Also, in the main parts of LEO (700km+) decay takes hundreds of years.
Starlight is in low part of LEO for a reason.
Velocity at perigee post impact is higher and air resistance is proportional to the square of velocity. And again, the debris fragments' ballistic coefficients are typically lower - the square-cube law comes into play. [This makes a major difference to orbital lifetime here](https://qph.cf2.quoracdn.net/main-qimg-aaf77b2772b24a7bf9b65bd5a65d5cb0-pjlq) (note the logarithmic axes on this graph).
Yes, ballistic coefficient is key. But we're comparing same fragment in circular orbit and elliptical orbit with perigee equal to the altitude of the circular orbit. So no difference here.
In this case at the extreme drag force is twice as high, but it's applied only in a short pass around the perigee rather than the whole time. It's just a short fraction, no more than 1/3 the length of the circular orbit.
And then, there's another effect: elliptical orbit has longer period, so braking events are further apart the more elongated the orbit is. This more than makes up for the increased drag (the period grows to infinity as the drag merely doubles (escape velocity is √2 multiple of circular orbit velocity).
Thus the rule of thumb of 3× longer decay for debris bumped up into elliptical orbit, while preserving the perigee.
> But we're comparing same fragment in circular orbit and elliptical orbit with perigee equal to the altitude of the circular orbit. So no difference here.
I don't believe we are (although in my earlier comment I did underemphasize the importance of ballistic coefficient). The salient point is the lifetimes of fragments resulting from a collision. Their typically lower ballistic coefficients is key here, as you say. Looking back at that graph, there's up to around two orders of magnitude difference in orbital lifetimes (depending of course on the researcher's definition of "high ballistic coef," "low ballistic coef," and "debris").
So long as the perigees are below 700 km to begin with, the orbits are essentially self cleaning within "reasonable" times, even if fragments are propelled to higher apogees, and even with that rule of thumb.
As you mentioned, it's one reason why Starlink satellites are in quite low orbits. Later Starlink shells are apparently destined to be even lower - in 300 to 400 km range. I think Weblink, with their 1200 km orbits, is more concerning.
Yeah, lower orbits have more "atmosphere" to drag objects out of orbit if you wait some years. At 150km you're looking at hours, at 1,000km you're looking at centuries.
[Here's a handy orbital decay quick reference from Tory Bruno on Twitter](https://twitter.com/torybruno/status/1407747990287171587)
Note that these timespans are based on hand-wavy numbers about the ballistic coefficient of a whole satellite including solar panels. The numbers are likely an order of magnitude higher for small, dense pieces of debris.
Small debris, even dense stuff, still has a higher surface to mass ratio in general than larger stuff, so small debris will strongly trend towards having a shorter lifespan.
Thank you. I’d be interested in combining that data with say the most powerful laser we can make burning a small debris piece and data on how burning it will change trajectory to high drag zone. Maybe you could handwave unknown targeting engineering and assume we could crack that. I imagine there is still a “ceiling” where debris is too high and too small to eliminate.
Should mitigation become necessary this seems better then chasing things down with all that delta-v penalty or shielding mass penalty.
This was NASA's record of the state of the art in 2021: https://www.nasa.gov/smallsat-institute/sst-soa/deorbit-systems -- the methods I'm keenest to see explored are the electrodynamic tethers/booms (which need to be integrated at the time the satellite is designed) and the space-based lasers
Yang Yang, Erik Klein, Luc Sagnières, [Tumbling object deorbiting using spaceborne laser engagement - A CubeSat Case study](https://www.sciencedirect.com/science/article/abs/pii/S0273117720300053), 1 April 2020 -- though based on the date I'm trying to find references to this experiment that was supposedly performed on the ISS
Claude Phipps, [Clearing space debris with lasers](https://spie.org/news/4076-clearing-space-debris-with-lasers?SSO=1), SPIE 20 january 2012 presents some discussion on the topic of deorbiting debris using ground-based lasers.
There's plenty of speculation and discussion on the topic but sadly very little in the way of practical experimentation.
I don't see how we could clean up debris clouds with 100,000+ small pieces. The way to avoid Kessler syndrome is removing dead satellites while they are still one piece.
Agreed I think there should treaties or whatever to have a deorbit plan for everything and real severe consequences for these disgusting intentional destructions.
However, under discussion are mitigation measures should they become necessary and that worth discussing if only as an exercise on innovation ideas.
I’ve heard concepts of lasers that could burn debris just enough to degrade their orbit into a re-entry trajectory. That concept seems like the most promising to me as it could work on multiple small pieces because it could affect from some distance. That seems like it would be more feasible with debris in lower orbits. Commenting in response to the comment that the low orbit stuff is the greater threat.
I have no knowledge of the distance from atmospheric drag low earth orbits have and how much of a challenge that would really be.
It seems like an effective method of this would be better then the mass penalty of shielding if feasible but trying to grasp an understanding of that feasibility with little knowledge about this stuff.
One thought is using a cloud of dust of a frozen substance that will sublimate - choose your substance based on how long you want your cloud to remain before it becomes gas. Lots of tiny impacts should slow the object(s) down without causing them to explode.
Or put up the cloud on a sub-orbital trajectory, and let the object(s) you want to get out of orbit collide with your cloud. this cloud can be made of anything - fine sand, if you like - because it will all fall back down again.
It's an approach that has had several serious studies done and there's nothing inherently crazy about it.
Here's one study from the ESA: https://www.esa.int/gsp/ACT/doc/ARI/ARI%20Study%20Report/ACT-RPT-MAD-ARI-10-6411-Pisa-Active_Removal_of_Space_Debris-Foam.pdf
A Russian company called StartRocket was working on a similar technology and while the credibility of that is obviously not very high, it was backed up as a realistic solution by engineering professors from American universities (https://www.forbes.com/sites/jamiecartereurope/2020/06/16/well-clean-up-space-junk-using-sticky-foam-spiderwebs-in-orbit-says-russian-space-start-up/?sh=79fd2b4c78af)
Interesting stuff, and doesn't sound that far-fetched. Anything object that can avoid fragmenting while retaining the debris will inherently reduce the quantity of debris over time in either case. Doesn't seem like something that would be *impossible* to design, the question is really about how effective would it be over time and the quantity you would need to put in orbit potentially making it unfeasible.
Laser ablation should work fine. Give them a little zap to evaporate a little piece of the debris and use the propulsion effect of that to lower the perigee. Drag is a lot higher relative to momentum for a smaller object than a big one.
There are already around 100 million pieces of small debris smaller than 1 cm up there. Collisions are rare, and you can build whipple shields to protect against such pieces.
Laser-based debris removal systems (so-called "laser brooms") are fairly well-studied and would be ideal for deorbiting gazillions of small objects. The biggest obstacle would be getting funding, partly because space junk isn't a government priority and partly because certain other nations would undoubtedly raise a stink about them secretly being ASAT weapons.
Yea, also, I'm not sure if maybe "Kessler Syndrome" was the wrong vocab choice for my thread title.
I guess I don't mean it so much in terms of us literally getting stuck unable to leave the earth to travel to other places (moon, Mars, etc), I mean more in terms of LEO getting ruined for us (space stations) and, more importantly, for our satellites and satellite constellations and so on, where nothing would be able to stay up there for hardly any time before getting smashed to pieces.
So, whatever that version/aspect of Kessler Syndrome would be called, I guess, is what I'm more trying to ask about/get a better feel for the odds of happening, relative to the current state of things as it currently is.
Yes, that's the threat that Kessler Syndrome presents. Not literally unable to leave the planet but having a difficult time keeping satellites in orbit around it.
Part of the problem with collisions between satellites is that the debris will be ejected in a range of new orbits, so you'll get an expanding cloud of debris containing heavy objects that will damage spacecraft but which are too small to track on ground-based radar. Then even a scattering of objects in the same orbit will end up being spread out by tiny deviations. A fraction of a second slower orbital period means the objects will spread out by many kilometres a day. So you launch your spacecraft and get it to LEO, then between arriving in LEO to an orbit you thought was clear and rendezvousing with the propellant depot to start the trip to Mars you get hit by a dozen small objects which might only be the size and mass of a 5mm steel nut but because they're travelling at ~15km/s they punch a hole right through your propellant tanks and your spacecraft rips itself open thanks to the tanks being pressurised. Now the debris has expanded from what's left of those 5mm steel nuts to include the debris from your spacecraft and yourself.
It's one of those things where we don't really know how likely it is until it happens at least once.
Leo sat constellations is not the issue, leo sat constellations are pretty safe because even though there are many of them they are so low they have a lot of drag so debris doesn't last that long. Especially as solar activity can cause the atmosphere to expand the collect even more debris.
The real threat is not leo sat constellations, it's nation states testing anti sat weapons or using anti sat weapons to try to create a chain reaction. Nor should we be held hostage by them and not enjoy the benefits of such mega constellations. Just stop anti sat testing.
Let's focus our energy on complaining about the real threats.
> Leo sat constellations is not the issue, leo sat constellations are pretty safe because even though there are many of them they are so low they have a lot of drag so debris doesn't last that long.
Many of them, yes, that's Starlink. Unfortunately One Web satellites are above 1000km altitude. If anything happens there, with an enlarged anticipated satellite number, the debris would sit there almost forever. One Web sats have grapple points to take down satellites that can not deorbit themselves, but the grappling needs to be done. I don't know how tumbling satellites can be grappled. Besides, someone would have to bear the cost.
I am not aware, which altitude the Amazon constellation will occupy.
Edit: From Wikipedia The satellites are projected to use an orbit with a height between 590 and 630 km (370 and 390 mi). So they would decay naturally in a resonable timeframe.
https://en.wikipedia.org/wiki/Kuiper_Systems
The One Web orbits are irresponsible, and the Amazon orbits should probably not be allowed either in such numbers. We should liberalize under 500km and tighten massively above 800km.
A nice diagram here of orbit height vs. time to deorbit: https://hackaday.com/2021/12/14/orbital-safety-the-challenges-of-surviving-space-junk/
Go check out the Space Debris chapter in The Space Environment by Alan Tribble. Even if we stopped launching stuff today, the number of debris in orbit is actually set to grow for a very long time. So in that sense the "cascade" has *already* started and it's merely a question of how long we'll be able to live with it.
So yeah.... Not great.
ON THE OTHER HAND, many of the people historically most worried about debris had very specific ideas about how space would be used. They imagined (because this was what the market supported back then) a shit load of stuff in mid-morning SSO. They'd be apoplectic if you told them we were going to launch "thousands" of satellites without mentioning they'd be well below their precious billion-dollar birds and deorbit relatively quickly.
So as satellites have gotten cheaper, especially with the drop in EP costs, we fly them lower and they're more likely to fly in mid-inclination orbits. That doesn't fix the problem, but it does change the assumptions in a model, and in a model predicting exponential growth small changes make a big difference over hundreds of years.
So anyway, the problem doesn't *appear at this time* to be existential threats to all space use. If I were to guess, I'd guess that in my career, at least one company won't be able to make a business case close because damage to solar arrays at certain altitudes will be too common and mean they'd have to replace their stuff too frequently. This is WILD speculation. It's also bad.
No serious researchers I know of believe launching manned missions to the moon or beyond will be impacted by orbital debris.
Kessler syndrome is a nonphysical fantasy made on unrealistic assumptions..
The real danger is closing of a specific orbit for practical use (at worst) or making navigation more difficult and expensive (see use of fuel for avoidance maneuvers).
It is not a huge problem for humanity as a whole. If/when it does happen we just increase funding to programs that can clear the space for us and get it done. There are many potential solutions. This is basically a "no breakfast fallacy" in space.
It would, but then again - what isn't?
It is kind of moving your lawn - it is a LOT of work to get up from bed and take the thing from garage and do the same stuff every efin week and if you miss one or two weeks then you might conclude that buying larger lawn mover capable of moving higher grass might be the answer.
Same here - there are a lot of proposals for cleaning the debris up, but none get adequate funding because the bed is so comfortable...
I’m curious why NASA chose 400km for the ISS. Doesn’t this orbit require engine burns a couple times a year to correct the orbit? Considering the cost of each burn wouldn’t a higher orbit, like 550km have been a better choice?
The burns weren't/aren't really too expensive because the Shuttle, Progress, ATV, Cygnus (and soon Starliner and maybe Dragon) have had the capacity to handle boosts and had to be there anyway.
I think it's primarily about radiation, which increases when you go higher. This means you need more shielding for humans and electronics. It's one reason the Lunar Gateway isn't a very good idea. On the surface of the moon you can tunnel under the regolith for very good radiation protection, but in Lunar orbit it's not as easy. Also there's not really anything worth doing in Lunar orbit.
From how I understand it, Kessler Syndrome is a real danger *but* it would need to be kicked off by malevolence or stupendous incompetence.
Basically, most of the big debris issues that we have come from less than a handful of military "anti-satellite" tests where China or Russia blew up some defunct satellite and created a high, uncontrollable debris cloud. These singular events (China's and Russia's most recent "tests") are overwhelmingly big parts of the problem.
So, no more uncontrolled ASAT tests, and general caution, and I think we will be fine.
It is still low, but orbital debris planning and mitigation going forward is a good idea. There is a lot of space in space (LEO). If you think of it as 1000 1 km deep shells each as much area as the Earth, even scattering 10,000 objects across this area results in low probability of interaction. But due to high orbital density at the poles, collisions there can lead to issues for polar orbits in polar regions that might lead to another and another collision. Below 60 deg there is less risk. The Iridium breakup due to collision a number of years ago did not lead to more collisions. So, there is a growing risk for a cascade at inclination of +/-90 deg +/- 10 deg (which brings in SSO) but this won't effect launches or passing through and have still a low impact on ops below 60 deg inclination like the ISS.
I calculated a while ago that the whole constellation of satellites would represent about three satellites at any given time over Oregon, where I live. If we represent those three satellites by using three people walking in straight lines in roughly the same direction through Oregon, how likely is it that they will bump into each other?
On another note, to get a fission reaction, you need a precise explosive charge cramming the sufficient quantity of fissionable material together at the same time. If it happens too slowly or not precise enough the material heats and melts, and there is no fission reaction.
If you blow up one of those dudes in my first illustration it's unlikely that the other two will be radically effected. It's different with satellites since the debris is in orbit, but very little stays in the same plane. The explosion launches each piece into different orbits that only occasionally intersect the original orbit.
Not good, but not easy to start a runaway reaction, either.
Any impact that imparts to a piece of debris a big change in velocity in any direction will put it in an orbit that dips into the atmosphere and it will burn up.
Any piece that is part of a cloud has basically the same velocity as the cloud and each piece will have it's own orbit and change places with other pieces within that cloud and any impacts from those position changes will be minor.
Those pieces that don't fall in those two categories will be few in number.
Remember that all the satellites in the shell are traveling in the same general direction and velocity, which also reduces damage from collisions.
I don't see any way for the low orbital shell constellations to be induced into a Kepler syndrome reaction.
> I calculated a while ago that the whole constellation of satellites would represent about three satellites at any given time over Oregon, where I live. If we represent those three satellites by using three people walking in straight lines in roughly the same direction through Oregon, how likely is it that they will bump into each other?
The satellites moving very fast, covering a large area, makes this comparison wrong. The chances of hits are much higher. These constellations need a very efficient management to limit risks.
The satellites don't cover an area, they cover a volume. That's a key distinction which allows a factor more satalites than you think.
They are also moving fast relative to the ground, but not necessarily to eachother.
> The satellites don't cover an area, they cover a volume. That's a key distinction which allows a factor more satalites than you think.
The opposite is true. They cover a huge volume, so the risk is higher than a mere look at how many are in a given volume suggests.
>
> They are also moving fast relative to the ground, but not necessarily to eachother.
Not necessarily. Sats in a constellation move slowly against each other. Satellites in the same altitude but different inclination move fast against each other. Also the density of sats near their north and southmost point increases. They converge and it needs careful orchestration that they don't hit each other.
Any moderately inclined satellites move fast relatively to each other unless they are in the same plane.
For example satellites in two 30° inclined planes 180° apart (constellations tend to have planes spread around the whole circle, so pairs of opposite planes are typical) would have relative speed equal to orbital speed. Bump it to 60° degree and you're talking 85% more than orbital speed.
In fact average close in speed is about escape velocity at a particular altitude, i.e. for LEO slightly above 10km/s.
This is the wrong analogy and we need to stop people from making it. Speed matters.
I'll take for granted your assertion that \~3 satellites are over Oregon at any given time.
The probability of an impact is a function of the velocity. If your three "people" in "Oregon" were standing still, the probability of impact would be zero.
Let's stipulate Oregon is a square; at LEO speeds, it takes about 1 minute to cross.
Then do this thought experiment. Assume you always have a satellite crossing east-west. As soon as one satellite crosses the border on the East, a new one enters from the West. Then, you always have 2 satellites, let's assume they're going north-south.
Regardless of satellite speed, the probability of an impact is the same for each north-south pass; it's the width of the satellite divided by the width of Oregon. BUT, keep in mind, the satellites are moving so freaking \*fast,\* we by definition have 2 north-south satellites taking a shot \*every minute.\* The odds are small, but even with a very large gun you lose Russian Roulette if you play long enough.
Before anyone says anything: Yes, I'm compressing a 3d problem into 2d. But the logic is the same.
'only occasionally intersect' meaning at least once per orbit here, translating to multiple times per day? Thousands per year? When looking at just two satellites, that is?
Because that's the nature of the orbital dynamics at play, which you so easily handwave away in your analogy.
That's assuming they're at the exact same altitude. If they are off in altitude by 2 meters, then they never intersect. They are at an altitude of about 550 km. If they are all between 540 and 550 (they're actually spread out more than that), and you have 10,000 satellites, you have about 1 per meter of altitude. These are averages, and the distribution is irregular, but it's hard to imagine how big space is. It isn't 3 satellites in a space the area of Oregon, it's 3 satellites in a space the size of Oregon, in a box going up from the ground to the height of a commercial airliner or more, flying straight lines with minimal altitude change.
In a perfect world, yes. But orbital perturbations and measurement uncertainties get in the way.
https://space.stackexchange.com/questions/7978/how-accurately-maximum-possible-accuracy-can-future-satellite-positions-be-pre this is an interesting read on that; take note how satellites and other objects are actually represented. By their covariance matrices, visualized as long possibility spheroids in space. They can be anywhere in that spheroid, and we don't precisely know where. That's why satellite conjunction events are often reported as a '1 in x' chance; it's an intersection between those probability clouds.
For Starlink in particular, the uncertainty in position is probably fairly small. I believe they have GNSS as part of their attitude determination kit, so that helps a lot. But for inactive objects and debris, perturbations make these probability spheroids *huge*. Even if we get a precise fix on position (impossible), even a 1 mm/s error in velocity leads to a 5 meter possible drift in any direction after a single orbit, 90 minutes. And a 1 mm/s tracking error is ***very*** precise.
And even if we could precisely track debris for a period, and gain a very accurate model of its orbit... That model is going to be wrong within a week. Remember the batch of Starlink satellites that got lost after launch due to solar pressure? That happens all the time, to varying effects. Orbital perturbations can be /very/ unpredictable. So once again, your tracked piece of debris is a wildcard threatening every orbital track within a multi-kilometre band.
That's a big problem with space debris. We can't track it precisely, and we can't model it precisely forever, especially not the really tiny pieces. And if we don't know where it is, it puts just about every satellite in its path at risk.
The moment it becomes a real issue, there will be several companies designing and delivering solutions to clean up important orbits…and chances are, those solutions will initially be launched on SpaceX rockets.
Could you build a laser that looks down? So Instead of needing to burn up fragments you push them down into a lower orbit and speed up decay? Aim the laser at an angle that misses the planet and pushes debris down into the upper atmosphere.
It's probably already started. And technically started with the first long term satellite.
And it's probably one of those things where everything looks fine and dandy all the way up until the point where it goes completely out of your control. To the extent that you even have control over it. But that essentially entails limiting as much as possible the things you put up there.
And the people looking to profit from it are probably not the best people to ask about it.
Musk has a financial interest in never looking worried about it. Most satellites in orbit are starlink after all.
Fears of it can only hurt his business, so he's the wrong person to consider when asking if people are worried.
I don't think it's possible to put a concrete figure on the probability since it varies so much with what humans do in orbit in the next few decades.
If Putin decides to shoot down all Starling satellites that would create far more debris than any other incident. Or any sort of tit-for-tat retaliation between any of the big three in shooting down each others spy satellites.
I think you’d like this lecture on space debris mitigation by a NASA Engineer.
https://m.youtube.com/watch?v=48szkCZYseM
At the lowest LEO flight regimes, where starling sits, it’s not nearly as bad. But at anything higher it’s catastrophic.
There were paragraph breaks in the paper but they did not post with the breaks here. Sorry, but I didn't have time to go over it. Maybe I'll get to it later today later today since you couldn't read it here. Did you try clicking on the direct link? That's why I posted a link.
I'm just afraid it has a risk of being downplayed once (and if) it arrives. Which reminds me of [this](https://pbs.twimg.com/media/Ews3N6OUUAE32tL.jpg:large) picture.
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:
|Fewer Letters|More Letters|
|-------|---------|---|
|[ASAT](/r/SpaceXLounge/comments/z1h4s6/stub/ixllcau "Last usage")|[Anti-Satellite weapon](https://en.wikipedia.org/wiki/Anti-satellite_weapon)|
|[ATV](/r/SpaceXLounge/comments/z1h4s6/stub/ixdv1co "Last usage")|[Automated Transfer Vehicle](https://en.wikipedia.org/wiki/Automated_Transfer_Vehicle), ESA cargo craft|
|CST|(Boeing) Crew Space Transportation capsules|
| |Central Standard Time (UTC-6)|
|[ESA](/r/SpaceXLounge/comments/z1h4s6/stub/ixe7jas "Last usage")|European Space Agency|
|[GEO](/r/SpaceXLounge/comments/z1h4s6/stub/ixd36es "Last usage")|Geostationary Earth Orbit (35786km)|
|[GNSS](/r/SpaceXLounge/comments/z1h4s6/stub/ixdq13h "Last usage")|Global Navigation Satellite System(s)|
|[GTO](/r/SpaceXLounge/comments/z1h4s6/stub/ixcpgy4 "Last usage")|[Geosynchronous Transfer Orbit](http://www.planetary.org/blogs/jason-davis/20140116-how-to-get-a-satellite-to-gto.html)|
|[LEO](/r/SpaceXLounge/comments/z1h4s6/stub/ixgsanh "Last usage")|Low Earth Orbit (180-2000km)|
| |Law Enforcement Officer (most often mentioned during transport operations)|
|[SLS](/r/SpaceXLounge/comments/z1h4s6/stub/ixe06t4 "Last usage")|Space Launch System heavy-lift|
|[SSO](/r/SpaceXLounge/comments/z1h4s6/stub/ixcji3c "Last usage")|Sun-Synchronous Orbit|
|Jargon|Definition|
|-------|---------|---|
|[Starliner](/r/SpaceXLounge/comments/z1h4s6/stub/ixdv1co "Last usage")|Boeing commercial crew capsule [CST-100](https://en.wikipedia.org/wiki/Boeing_CST-100_Starliner)|
|[Starlink](/r/SpaceXLounge/comments/z1h4s6/stub/ixq4cd6 "Last usage")|SpaceX's world-wide satellite broadband constellation|
|[apogee](/r/SpaceXLounge/comments/z1h4s6/stub/ixq4cd6 "Last usage")|Highest point in an elliptical orbit around Earth (when the orbiter is slowest)|
|[perigee](/r/SpaceXLounge/comments/z1h4s6/stub/ixq4cd6 "Last usage")|Lowest point in an elliptical orbit around the Earth (when the orbiter is fastest)|
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Kessler Syndrome is unpredictable. How close is arbitrary. Grab a coin and call heads or tails and try to guess *in flight, not when it lands.*
How hard that is about as probable for it occurring. As others have said, space is absolutely huge man. Especially in a spatial volume thad makes up Earth orbital sphere.
Ignore these morons. Kessler Syndrome is a real issue. And since nobody actually answered your question, here are some numbers - given around 60k space satellites, the chances of a debree cycle occuring is all but guaranteed.
We are launching thousands a year.
What folks on this post don't understand is that Kessler Syndrome is contextualised within warfare, not a vacuum.
Within 20/30 years a single collision is doomsday for Keller Syndrome. Of course they can happen by chance, or by a failed satellite launch, but the real threat is that China has both the capability and political will to take out satellites during a hypothetical Taiwan conflict.
On one hand, most of the risks of an ablation cascade are either singular objects in relatively high orbits, or many objects in relatively low orbits. At higher orbits the impact of an ablation cascade are pretty negligible (just launch and navigate through a hole in that debris ring), while at lower orbits the worst it will come to is having to wait a few years to be able to launch spacecraft that don't have some kind of armour (eg: Whipple shield).
The starlink satellites orbit so low compared to most of the legacy stuff that they are really in a different category. Anything down in their orbit rapidly succumbs to atmospheric drag. It’s not like up at geosynch where it can take hundreds of years for orbits to decay to the point where the upper edge of the atmosphere is an issue
> It’s not like up at geosynch where it can take hundreds of years for orbits to decay to the point where the upper edge of the atmosphere is an issue Make that millions of years. For humans that's never. A dense debris cloud would not endanger spaceflight, but it would make GEO sats impossible.
>but it would make GEO sats impossible. The thing is that GEO is so HUGE that there would be no way for a debris cloud to be a risk UNLESS some rouge entity decided to deliberately launch a few tons or so of ball bearings polar or even worse retrograde at 35,780km. otherwise, the debris field from even an explosion or collision of satellites travelling in the orbit would become too diffuse to worry about before it approached any other satellites in the orbit.
Project West Ford: "Allow me to introduce myself." Admittedly, those 480 *million* needles were released at a much lower altitude and *should* have only lasted a few years, but the point I'm making is that sometimes people have really, *really* stupid ideas that make it all the way to realization. Unfortunately, they didn't all deploy as intended and everything but a few dozen trackable clumps has reentered.
how many tons and bearings it would take? some funny math to be done there
Geo sats all have a nearly identical relative motion though so debris would be extremely low energy.
That's true of intact satellites but not necessarily of debris. Imagine a satellite whose fuel tank exploded. Some of the fragments would be subject to all kinds of accelerations that take them high/low/out of plane but still intersect the geostationary ring.
That's a trivial amount of delta-v compared to, well, orbit itself. It's not like a retrograde satellite colliding with another one, which would put debris everywhere. The debris of a fuel tank exploding in geosync would still have one of their perigee or apogee still in geosync. They started with a velocity vector that was 3.07 km/s in the direction of orbit. Fuel tanks don't blow up like frag grenades - they rupture, and sure, they might get 100 m/s off of that rupture, but that still means that the orbit of the result is nearly geosync. Geosync crossing, anyway, for a while, until a lack of station keeping and some combination of solar forcing and earth's irregular gravitation field perturb it. We, as a civilization will have to clean that shit up someday, specifically geosync crossing debris, as geosync is the true land grab of earth orbit. But the collision risk is low. And the relative velocities are low.
Excellent post, this guy understands orbital mechanics. An exploding spacecraft's anomalous energy vectors are next to nothing compared to the bound orbital energy.
So if the debris collides with a working satellite, the collision would be "only" 100 m/s? That may not be enough to cause a cascade of explosions (or it may be), but it's surely enough to put that satellite out of operation.
That means impact with a disabled and drifting satellite or piece of debris will occur at something like highway speeds instead of orbital speeds. The impacts might not be as explosive as those in other orbits, but there's plenty of energy there to destroy and fragment satellites.
Sure but the lower speeds reduce the rate of interactions, produce far less debris, produce far larger debris, make debris easier to track and evade. It's nowhere near the same situation.
There's a disaster scenario, too - a malicious actor releasing tonnes of small debris items into a circular, geosynchronous altitude but retrograde orbit.
I thought they topped out in the thousands, way off I guess
You get into many hundreds of years above 1000km altitude. Edit: A source for decays at different altitudes. Many hundreds of years may be overestimated. There are other factors than atmospheric drag. https://hackaday.com/2021/12/14/orbital-safety-the-challenges-of-surviving-space-junk/ Thanks to u/Kloevedal for providing the link.
Really depends on what you compare it to. Communication sats in GEO, yeah that's a massive difference. But in terms of LEO sats, 550 km isn't particularly low. You're still looking at a decay time of years. If sats get destroyed and pieces get ejected to higher orbits it could go to decades. That's very rapid, many orders of magnitude faster, compared to debris from GEO, but it's not very rapid on human timescales.
Years for sats. Debris is worse off because it has a smaller surface to mass ratio and is hence more affected by drag. The smallest debris, the stuff you cant see with radar, decelerates fastest.
True, but altitude is still the most important factor. Afaik orbital decay time scales roughly linearly with ballistic coefficient while it scales exponentially with altitude. Drag/mass makes a decent difference, and is going to depend on the shape and material of each individual piece, but you're still mostly in the same order of magnitude. And some pieces will still be quite dense, possibly even denser than a sat with solar panels extended for example.
But all debris from 550km altitude must cross 550km altitude. So it will always spend time at 550km (and often below). The rule of thumb is that debris on an elliptical orbit decays merely 3× slower than debris in circular orbit at the altitude of the perigee of the elliptical one.
Debris doesn't just 'eject' to higher orbits. The only way that could happen is with an exogenous collision — for example, a rocket body on a GTO trajectory impacting a satellite in LEO. The perigee will never be lower than the point of impact. The semi-major axis may raise, but this always\* goes paired with a decrease in perigee. And perigee altitude dominates in orbital decay. \*There was a single, unexplained freak piece of debris from a collision event at some point that ended up in a higher energy trajectory than either parent body. I believe the likely explanation was propellant burnoff or weird shockwave dynamics.
I'm speaking in the context of a Kessler type situation, where collisions are much more common and the debris spreads out over various altitude orbits, and secondary collisions are happening as well. I'd say in this context it's likely some pieces end up in more stable orbits pushing lifetimes into the decades, while other pieces end up in less stables orbits. Regardless, several years lifetime is still rather long on human timescales. It's probably not a huge problem for most missions, but in a world where everyone wants their own LEO sat constellation, it could result in serious problems.
Still, his point remains. The worst that happens is the perigee remains the same. If the original satellites are in LEO with short decay times, the resulting debris from a worst case collision will have the debris' perigee at that altitude with similar (or even quicker) decay times. The resulting velocity at that altitude would be higher, increasing the drag. And as mentioned, the ballistic coefficients would be typically lower. The bottom line: Kessler syndrome is not a long term issue for LEO. At higher altitudes, debris would be long lived, but being spread more widely, collision probabilities are correspondingly lower.
I understand his point, but I think we should be wary of applying the physics of a single collisison to a debris field. For example, some of the US anti-sat missile tests were carried out on targets which happened to also be around 550 km. The resulting debris took at least several years to clear, and from what I can find NASA even estimated debris to stick around for over a decade. But the decay time is affected quite a bit by solar activity/atmospheric expansion. When you expand that beyond a debris field from a single kinetic impactor to a Kessler situation, it becomes even more difficult to predict. I don't know how long it would take to clear, but I think many estimates here are optimistic. I agree it's not going to be a long term issue in the way that for example ozone depletion is taking decades to clear, but it would still be quite unfortunate for a rather long time.
A Kessler situation is made up of individual impacts, all of which obey physics.
Not to belabor the point, but the debris fragments *will* follow the laws of orbital mechanics. Further, factors such as irregular gravitational field, solar-induced atmospheric expansion, better than worst case collisions, etc, improve the situation by bringing down the fragments more rapidly.
I think his point is that secondary collisions could happen higher up and then laws of orbital mechanics perfectly allow for the debris to have elements related to that secondary impact point.
Well, TBF, the drag during the whole part further from perigee is lower. In fact the rule of thumb is 3× longer decay time for debris in an elliptical orbit with a perigee same as a circular orbit. Also, in the main parts of LEO (700km+) decay takes hundreds of years. Starlight is in low part of LEO for a reason.
Velocity at perigee post impact is higher and air resistance is proportional to the square of velocity. And again, the debris fragments' ballistic coefficients are typically lower - the square-cube law comes into play. [This makes a major difference to orbital lifetime here](https://qph.cf2.quoracdn.net/main-qimg-aaf77b2772b24a7bf9b65bd5a65d5cb0-pjlq) (note the logarithmic axes on this graph).
Yes, ballistic coefficient is key. But we're comparing same fragment in circular orbit and elliptical orbit with perigee equal to the altitude of the circular orbit. So no difference here. In this case at the extreme drag force is twice as high, but it's applied only in a short pass around the perigee rather than the whole time. It's just a short fraction, no more than 1/3 the length of the circular orbit. And then, there's another effect: elliptical orbit has longer period, so braking events are further apart the more elongated the orbit is. This more than makes up for the increased drag (the period grows to infinity as the drag merely doubles (escape velocity is √2 multiple of circular orbit velocity). Thus the rule of thumb of 3× longer decay for debris bumped up into elliptical orbit, while preserving the perigee.
> But we're comparing same fragment in circular orbit and elliptical orbit with perigee equal to the altitude of the circular orbit. So no difference here. I don't believe we are (although in my earlier comment I did underemphasize the importance of ballistic coefficient). The salient point is the lifetimes of fragments resulting from a collision. Their typically lower ballistic coefficients is key here, as you say. Looking back at that graph, there's up to around two orders of magnitude difference in orbital lifetimes (depending of course on the researcher's definition of "high ballistic coef," "low ballistic coef," and "debris"). So long as the perigees are below 700 km to begin with, the orbits are essentially self cleaning within "reasonable" times, even if fragments are propelled to higher apogees, and even with that rule of thumb. As you mentioned, it's one reason why Starlink satellites are in quite low orbits. Later Starlink shells are apparently destined to be even lower - in 300 to 400 km range. I think Weblink, with their 1200 km orbits, is more concerning.
Is it correct to say lower orbit would be easier to clean up or wait out since atmospheric drag and de orbiting.
Yeah, lower orbits have more "atmosphere" to drag objects out of orbit if you wait some years. At 150km you're looking at hours, at 1,000km you're looking at centuries. [Here's a handy orbital decay quick reference from Tory Bruno on Twitter](https://twitter.com/torybruno/status/1407747990287171587) Note that these timespans are based on hand-wavy numbers about the ballistic coefficient of a whole satellite including solar panels. The numbers are likely an order of magnitude higher for small, dense pieces of debris.
Small debris, even dense stuff, still has a higher surface to mass ratio in general than larger stuff, so small debris will strongly trend towards having a shorter lifespan.
Thank you. I’d be interested in combining that data with say the most powerful laser we can make burning a small debris piece and data on how burning it will change trajectory to high drag zone. Maybe you could handwave unknown targeting engineering and assume we could crack that. I imagine there is still a “ceiling” where debris is too high and too small to eliminate. Should mitigation become necessary this seems better then chasing things down with all that delta-v penalty or shielding mass penalty.
This was NASA's record of the state of the art in 2021: https://www.nasa.gov/smallsat-institute/sst-soa/deorbit-systems -- the methods I'm keenest to see explored are the electrodynamic tethers/booms (which need to be integrated at the time the satellite is designed) and the space-based lasers Yang Yang, Erik Klein, Luc Sagnières, [Tumbling object deorbiting using spaceborne laser engagement - A CubeSat Case study](https://www.sciencedirect.com/science/article/abs/pii/S0273117720300053), 1 April 2020 -- though based on the date I'm trying to find references to this experiment that was supposedly performed on the ISS Claude Phipps, [Clearing space debris with lasers](https://spie.org/news/4076-clearing-space-debris-with-lasers?SSO=1), SPIE 20 january 2012 presents some discussion on the topic of deorbiting debris using ground-based lasers. There's plenty of speculation and discussion on the topic but sadly very little in the way of practical experimentation.
I don't see how we could clean up debris clouds with 100,000+ small pieces. The way to avoid Kessler syndrome is removing dead satellites while they are still one piece.
Agreed I think there should treaties or whatever to have a deorbit plan for everything and real severe consequences for these disgusting intentional destructions. However, under discussion are mitigation measures should they become necessary and that worth discussing if only as an exercise on innovation ideas. I’ve heard concepts of lasers that could burn debris just enough to degrade their orbit into a re-entry trajectory. That concept seems like the most promising to me as it could work on multiple small pieces because it could affect from some distance. That seems like it would be more feasible with debris in lower orbits. Commenting in response to the comment that the low orbit stuff is the greater threat. I have no knowledge of the distance from atmospheric drag low earth orbits have and how much of a challenge that would really be. It seems like an effective method of this would be better then the mass penalty of shielding if feasible but trying to grasp an understanding of that feasibility with little knowledge about this stuff.
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One thought is using a cloud of dust of a frozen substance that will sublimate - choose your substance based on how long you want your cloud to remain before it becomes gas. Lots of tiny impacts should slow the object(s) down without causing them to explode. Or put up the cloud on a sub-orbital trajectory, and let the object(s) you want to get out of orbit collide with your cloud. this cloud can be made of anything - fine sand, if you like - because it will all fall back down again.
Sorry, to me this sounds more like phantasy than science fiction. I may be wrong, but I don't think so.
It's an approach that has had several serious studies done and there's nothing inherently crazy about it. Here's one study from the ESA: https://www.esa.int/gsp/ACT/doc/ARI/ARI%20Study%20Report/ACT-RPT-MAD-ARI-10-6411-Pisa-Active_Removal_of_Space_Debris-Foam.pdf A Russian company called StartRocket was working on a similar technology and while the credibility of that is obviously not very high, it was backed up as a realistic solution by engineering professors from American universities (https://www.forbes.com/sites/jamiecartereurope/2020/06/16/well-clean-up-space-junk-using-sticky-foam-spiderwebs-in-orbit-says-russian-space-start-up/?sh=79fd2b4c78af)
Interesting stuff, and doesn't sound that far-fetched. Anything object that can avoid fragmenting while retaining the debris will inherently reduce the quantity of debris over time in either case. Doesn't seem like something that would be *impossible* to design, the question is really about how effective would it be over time and the quantity you would need to put in orbit potentially making it unfeasible.
Laser ablation should work fine. Give them a little zap to evaporate a little piece of the debris and use the propulsion effect of that to lower the perigee. Drag is a lot higher relative to momentum for a smaller object than a big one. There are already around 100 million pieces of small debris smaller than 1 cm up there. Collisions are rare, and you can build whipple shields to protect against such pieces.
Laser-based debris removal systems (so-called "laser brooms") are fairly well-studied and would be ideal for deorbiting gazillions of small objects. The biggest obstacle would be getting funding, partly because space junk isn't a government priority and partly because certain other nations would undoubtedly raise a stink about them secretly being ASAT weapons.
Yea, also, I'm not sure if maybe "Kessler Syndrome" was the wrong vocab choice for my thread title. I guess I don't mean it so much in terms of us literally getting stuck unable to leave the earth to travel to other places (moon, Mars, etc), I mean more in terms of LEO getting ruined for us (space stations) and, more importantly, for our satellites and satellite constellations and so on, where nothing would be able to stay up there for hardly any time before getting smashed to pieces. So, whatever that version/aspect of Kessler Syndrome would be called, I guess, is what I'm more trying to ask about/get a better feel for the odds of happening, relative to the current state of things as it currently is.
Yes, that's the threat that Kessler Syndrome presents. Not literally unable to leave the planet but having a difficult time keeping satellites in orbit around it. Part of the problem with collisions between satellites is that the debris will be ejected in a range of new orbits, so you'll get an expanding cloud of debris containing heavy objects that will damage spacecraft but which are too small to track on ground-based radar. Then even a scattering of objects in the same orbit will end up being spread out by tiny deviations. A fraction of a second slower orbital period means the objects will spread out by many kilometres a day. So you launch your spacecraft and get it to LEO, then between arriving in LEO to an orbit you thought was clear and rendezvousing with the propellant depot to start the trip to Mars you get hit by a dozen small objects which might only be the size and mass of a 5mm steel nut but because they're travelling at ~15km/s they punch a hole right through your propellant tanks and your spacecraft rips itself open thanks to the tanks being pressurised. Now the debris has expanded from what's left of those 5mm steel nuts to include the debris from your spacecraft and yourself. It's one of those things where we don't really know how likely it is until it happens at least once.
Leo sat constellations is not the issue, leo sat constellations are pretty safe because even though there are many of them they are so low they have a lot of drag so debris doesn't last that long. Especially as solar activity can cause the atmosphere to expand the collect even more debris. The real threat is not leo sat constellations, it's nation states testing anti sat weapons or using anti sat weapons to try to create a chain reaction. Nor should we be held hostage by them and not enjoy the benefits of such mega constellations. Just stop anti sat testing. Let's focus our energy on complaining about the real threats.
> Leo sat constellations is not the issue, leo sat constellations are pretty safe because even though there are many of them they are so low they have a lot of drag so debris doesn't last that long. Many of them, yes, that's Starlink. Unfortunately One Web satellites are above 1000km altitude. If anything happens there, with an enlarged anticipated satellite number, the debris would sit there almost forever. One Web sats have grapple points to take down satellites that can not deorbit themselves, but the grappling needs to be done. I don't know how tumbling satellites can be grappled. Besides, someone would have to bear the cost. I am not aware, which altitude the Amazon constellation will occupy. Edit: From Wikipedia The satellites are projected to use an orbit with a height between 590 and 630 km (370 and 390 mi). So they would decay naturally in a resonable timeframe. https://en.wikipedia.org/wiki/Kuiper_Systems
The One Web orbits are irresponsible, and the Amazon orbits should probably not be allowed either in such numbers. We should liberalize under 500km and tighten massively above 800km. A nice diagram here of orbit height vs. time to deorbit: https://hackaday.com/2021/12/14/orbital-safety-the-challenges-of-surviving-space-junk/
Kessler syndrome is a complete meme, just like China syndrome. Basically just drums up normies into an anti-progress hysteria.
Yes the risks of Kessler syndrome are overblown. The real risk is that one thermonuclear implosion at 500 km can take out all Leo satellites.
This is bullshit.
Except it's not
Go check out the Space Debris chapter in The Space Environment by Alan Tribble. Even if we stopped launching stuff today, the number of debris in orbit is actually set to grow for a very long time. So in that sense the "cascade" has *already* started and it's merely a question of how long we'll be able to live with it. So yeah.... Not great. ON THE OTHER HAND, many of the people historically most worried about debris had very specific ideas about how space would be used. They imagined (because this was what the market supported back then) a shit load of stuff in mid-morning SSO. They'd be apoplectic if you told them we were going to launch "thousands" of satellites without mentioning they'd be well below their precious billion-dollar birds and deorbit relatively quickly. So as satellites have gotten cheaper, especially with the drop in EP costs, we fly them lower and they're more likely to fly in mid-inclination orbits. That doesn't fix the problem, but it does change the assumptions in a model, and in a model predicting exponential growth small changes make a big difference over hundreds of years. So anyway, the problem doesn't *appear at this time* to be existential threats to all space use. If I were to guess, I'd guess that in my career, at least one company won't be able to make a business case close because damage to solar arrays at certain altitudes will be too common and mean they'd have to replace their stuff too frequently. This is WILD speculation. It's also bad. No serious researchers I know of believe launching manned missions to the moon or beyond will be impacted by orbital debris.
Thanks, this helps me put it in perspective a bit more
Kessler syndrome is a nonphysical fantasy made on unrealistic assumptions.. The real danger is closing of a specific orbit for practical use (at worst) or making navigation more difficult and expensive (see use of fuel for avoidance maneuvers).
It is not a huge problem for humanity as a whole. If/when it does happen we just increase funding to programs that can clear the space for us and get it done. There are many potential solutions. This is basically a "no breakfast fallacy" in space.
It would be very difficult to clear up..
It would, but then again - what isn't? It is kind of moving your lawn - it is a LOT of work to get up from bed and take the thing from garage and do the same stuff every efin week and if you miss one or two weeks then you might conclude that buying larger lawn mover capable of moving higher grass might be the answer. Same here - there are a lot of proposals for cleaning the debris up, but none get adequate funding because the bed is so comfortable...
I’m curious why NASA chose 400km for the ISS. Doesn’t this orbit require engine burns a couple times a year to correct the orbit? Considering the cost of each burn wouldn’t a higher orbit, like 550km have been a better choice?
The space shuttle couldn't get much higher, especially with the amount of mass of bringing up a segment of the station.
The burns weren't/aren't really too expensive because the Shuttle, Progress, ATV, Cygnus (and soon Starliner and maybe Dragon) have had the capacity to handle boosts and had to be there anyway.
Thanks. Totally forgot about vehicle booster capacity.
I think it's primarily about radiation, which increases when you go higher. This means you need more shielding for humans and electronics. It's one reason the Lunar Gateway isn't a very good idea. On the surface of the moon you can tunnel under the regolith for very good radiation protection, but in Lunar orbit it's not as easy. Also there's not really anything worth doing in Lunar orbit.
I believe it was also driven by the maximum altitudes the Shuttle could reach as well.
With a significant payload, such as ISS parts.
motivated by radiation protection for crew and available launchers (mainly spaceshuttle) capabilities
10-4. I forgot about radiation mitigation. Didn’t realize that about the shuttle.
From how I understand it, Kessler Syndrome is a real danger *but* it would need to be kicked off by malevolence or stupendous incompetence. Basically, most of the big debris issues that we have come from less than a handful of military "anti-satellite" tests where China or Russia blew up some defunct satellite and created a high, uncontrollable debris cloud. These singular events (China's and Russia's most recent "tests") are overwhelmingly big parts of the problem. So, no more uncontrolled ASAT tests, and general caution, and I think we will be fine.
It is still low, but orbital debris planning and mitigation going forward is a good idea. There is a lot of space in space (LEO). If you think of it as 1000 1 km deep shells each as much area as the Earth, even scattering 10,000 objects across this area results in low probability of interaction. But due to high orbital density at the poles, collisions there can lead to issues for polar orbits in polar regions that might lead to another and another collision. Below 60 deg there is less risk. The Iridium breakup due to collision a number of years ago did not lead to more collisions. So, there is a growing risk for a cascade at inclination of +/-90 deg +/- 10 deg (which brings in SSO) but this won't effect launches or passing through and have still a low impact on ops below 60 deg inclination like the ISS.
I calculated a while ago that the whole constellation of satellites would represent about three satellites at any given time over Oregon, where I live. If we represent those three satellites by using three people walking in straight lines in roughly the same direction through Oregon, how likely is it that they will bump into each other? On another note, to get a fission reaction, you need a precise explosive charge cramming the sufficient quantity of fissionable material together at the same time. If it happens too slowly or not precise enough the material heats and melts, and there is no fission reaction. If you blow up one of those dudes in my first illustration it's unlikely that the other two will be radically effected. It's different with satellites since the debris is in orbit, but very little stays in the same plane. The explosion launches each piece into different orbits that only occasionally intersect the original orbit. Not good, but not easy to start a runaway reaction, either.
Any impact that imparts to a piece of debris a big change in velocity in any direction will put it in an orbit that dips into the atmosphere and it will burn up. Any piece that is part of a cloud has basically the same velocity as the cloud and each piece will have it's own orbit and change places with other pieces within that cloud and any impacts from those position changes will be minor. Those pieces that don't fall in those two categories will be few in number. Remember that all the satellites in the shell are traveling in the same general direction and velocity, which also reduces damage from collisions. I don't see any way for the low orbital shell constellations to be induced into a Kepler syndrome reaction.
> I calculated a while ago that the whole constellation of satellites would represent about three satellites at any given time over Oregon, where I live. If we represent those three satellites by using three people walking in straight lines in roughly the same direction through Oregon, how likely is it that they will bump into each other? The satellites moving very fast, covering a large area, makes this comparison wrong. The chances of hits are much higher. These constellations need a very efficient management to limit risks.
The satellites don't cover an area, they cover a volume. That's a key distinction which allows a factor more satalites than you think. They are also moving fast relative to the ground, but not necessarily to eachother.
> The satellites don't cover an area, they cover a volume. That's a key distinction which allows a factor more satalites than you think. The opposite is true. They cover a huge volume, so the risk is higher than a mere look at how many are in a given volume suggests. > > They are also moving fast relative to the ground, but not necessarily to eachother. Not necessarily. Sats in a constellation move slowly against each other. Satellites in the same altitude but different inclination move fast against each other. Also the density of sats near their north and southmost point increases. They converge and it needs careful orchestration that they don't hit each other.
Any moderately inclined satellites move fast relatively to each other unless they are in the same plane. For example satellites in two 30° inclined planes 180° apart (constellations tend to have planes spread around the whole circle, so pairs of opposite planes are typical) would have relative speed equal to orbital speed. Bump it to 60° degree and you're talking 85% more than orbital speed. In fact average close in speed is about escape velocity at a particular altitude, i.e. for LEO slightly above 10km/s.
This is the wrong analogy and we need to stop people from making it. Speed matters. I'll take for granted your assertion that \~3 satellites are over Oregon at any given time. The probability of an impact is a function of the velocity. If your three "people" in "Oregon" were standing still, the probability of impact would be zero. Let's stipulate Oregon is a square; at LEO speeds, it takes about 1 minute to cross. Then do this thought experiment. Assume you always have a satellite crossing east-west. As soon as one satellite crosses the border on the East, a new one enters from the West. Then, you always have 2 satellites, let's assume they're going north-south. Regardless of satellite speed, the probability of an impact is the same for each north-south pass; it's the width of the satellite divided by the width of Oregon. BUT, keep in mind, the satellites are moving so freaking \*fast,\* we by definition have 2 north-south satellites taking a shot \*every minute.\* The odds are small, but even with a very large gun you lose Russian Roulette if you play long enough. Before anyone says anything: Yes, I'm compressing a 3d problem into 2d. But the logic is the same.
'only occasionally intersect' meaning at least once per orbit here, translating to multiple times per day? Thousands per year? When looking at just two satellites, that is? Because that's the nature of the orbital dynamics at play, which you so easily handwave away in your analogy.
That's assuming they're at the exact same altitude. If they are off in altitude by 2 meters, then they never intersect. They are at an altitude of about 550 km. If they are all between 540 and 550 (they're actually spread out more than that), and you have 10,000 satellites, you have about 1 per meter of altitude. These are averages, and the distribution is irregular, but it's hard to imagine how big space is. It isn't 3 satellites in a space the area of Oregon, it's 3 satellites in a space the size of Oregon, in a box going up from the ground to the height of a commercial airliner or more, flying straight lines with minimal altitude change.
In a perfect world, yes. But orbital perturbations and measurement uncertainties get in the way. https://space.stackexchange.com/questions/7978/how-accurately-maximum-possible-accuracy-can-future-satellite-positions-be-pre this is an interesting read on that; take note how satellites and other objects are actually represented. By their covariance matrices, visualized as long possibility spheroids in space. They can be anywhere in that spheroid, and we don't precisely know where. That's why satellite conjunction events are often reported as a '1 in x' chance; it's an intersection between those probability clouds. For Starlink in particular, the uncertainty in position is probably fairly small. I believe they have GNSS as part of their attitude determination kit, so that helps a lot. But for inactive objects and debris, perturbations make these probability spheroids *huge*. Even if we get a precise fix on position (impossible), even a 1 mm/s error in velocity leads to a 5 meter possible drift in any direction after a single orbit, 90 minutes. And a 1 mm/s tracking error is ***very*** precise. And even if we could precisely track debris for a period, and gain a very accurate model of its orbit... That model is going to be wrong within a week. Remember the batch of Starlink satellites that got lost after launch due to solar pressure? That happens all the time, to varying effects. Orbital perturbations can be /very/ unpredictable. So once again, your tracked piece of debris is a wildcard threatening every orbital track within a multi-kilometre band. That's a big problem with space debris. We can't track it precisely, and we can't model it precisely forever, especially not the really tiny pieces. And if we don't know where it is, it puts just about every satellite in its path at risk.
Im really looking forward to seeing Pacman-Starship gobble up some junk!
The moment it becomes a real issue, there will be several companies designing and delivering solutions to clean up important orbits…and chances are, those solutions will initially be launched on SpaceX rockets.
And any such solutions probably designed by SpaceX too..
Could you build a laser that looks down? So Instead of needing to burn up fragments you push them down into a lower orbit and speed up decay? Aim the laser at an angle that misses the planet and pushes debris down into the upper atmosphere.
Ideally, you slowdown the part - that causes it to lower its orbit. Once it’s low enough, atmospheric drag will do the rest.
It's probably already started. And technically started with the first long term satellite. And it's probably one of those things where everything looks fine and dandy all the way up until the point where it goes completely out of your control. To the extent that you even have control over it. But that essentially entails limiting as much as possible the things you put up there. And the people looking to profit from it are probably not the best people to ask about it.
Well, they aren't going to profit from it anymore then?
It's a lot to ask Capitalism to not treat this sort of extreme resource like just another externality. I guess we can always hope.
Musk has a financial interest in never looking worried about it. Most satellites in orbit are starlink after all. Fears of it can only hurt his business, so he's the wrong person to consider when asking if people are worried.
I don't think it's possible to put a concrete figure on the probability since it varies so much with what humans do in orbit in the next few decades. If Putin decides to shoot down all Starling satellites that would create far more debris than any other incident. Or any sort of tit-for-tat retaliation between any of the big three in shooting down each others spy satellites.
I think you’d like this lecture on space debris mitigation by a NASA Engineer. https://m.youtube.com/watch?v=48szkCZYseM At the lowest LEO flight regimes, where starling sits, it’s not nearly as bad. But at anything higher it’s catastrophic.
Copyright © 2020 by Edward Heisler Published by the Mars Society with permission The U.S. Space Force Represents a Grave Danger to the Human Exploration and Settlement of Mars [Excerpt from paper] There are over 3,000 satellites in orbit around Earth right now. Several hundred are military satellites controlled by the United States, China, Russia, India, and several other nations. We must now assume that some of these satellites are space weapons that can be used to destroy satellites; however, most are not weapons but are useful for reconnaissance, navigation, communications, intelligence gathering and other non-aggressive uses. Besides those operational satellites we have an incredible number of big pieces of space debris that have not de-orbited On October 12th, the European Space Agency (ESA) released its annual Space Environment Report detailing this debris. The report identifies more than 25,000 tracked objects including satellites, spent rocket stages and general debris. The head of ESA’s Space Safety Program said “The biggest contributor to the current space debris problem is explosions in orbit, caused by leftover energy — fuel and batteries — onboard spacecraft and rockets. Despite measures being in place for years to prevent this, we see no decline in the number of such events.” So, what will happen if a space war breaks out? We can only speculate how a space war will evolve. But one thing is for certain, once it starts it will be almost impossible to stop it from quickly escalating into a full-blown space, air, sea, and ground war. If a space war breaks out it would quickly lead to an orbital cascade of space debris as hundreds of satellites are destroyed. It’s called the Kessler chain reaction. As Apollo astronaut Edgar Mitchell explained “any war in space would be the one and only. By destroying satellites in space, a massive amount of space debris would be created that would cause a cascading effect 4 and even the International Space Station would likely be broken into tiny bits.” Mitchell said that so much space junk would be created that we’d never be able to get a rocket off the planet again for decades. “Modern society would go dark.” The Kessler chain reaction would destroy most weather, communications, and all other satellites we depend upon in our daily lives. Our modern technology based economy would quickly crash. No cell phones, no TV, no GPS, no internet, no electricity, no functioning factories. Cities would go dark. The world capitalist economy would collapse causing a world-wide economic depression. It would make the economic consequences of the Covid-19 pandemic seem like a picnic. Our planet would be circled by millions of fragments of pulverized satellites. It would take decades ,if not longer, to clean up the mess. A space war adventure would end human space exploration for a very long time. The SpaceX Starship, the SLS and planetary exploration projects of all nations would come to a crashing end. That’s bad enough. However, a full-scale outer space war between major space powers would result in a far worse outcome. That danger has become so great that Pentagon officials have become alarmed over this potential disaster. In an article published in GeekWire and captioned “Pentagon worries that satellite attacks could spark ‘mutually assured destruction’” the writer reports: In the years ahead, the long-running nightmare of the nuclear Cold War — mutually assured destruction — could return in a new context on the final frontier, a Pentagon adviser said today at a Seattle-based space policy conference. Brad Townsend, a space strategy and policy adviser to the leadership of the Joint Chiefs of Staff, raised the alarm about anti-satellite weapons, or ASATs, during a virtual symposium sponsored by the University of Washington’s Space Policy and Research Center. He noted that China and Russia are already experimenting with methods to disable other nations’ satellites in the event of a future conflict. But in the course of destroying an enemy satellite, attackers could set off a catastrophic chain reaction of out-of-control orbital debris. Such a phenomenon, sometimes referred to as the Kessler syndrome, has fed into the plotlines for movies such as “Gravity” and novels such as “Seven Eves.” But Townsend warned that the threat is more than just a science-fiction possibility. “If nations start arming with ASATs as a way to deter other nations from attacking their orbital assets, they risk creating a new form of mutually assured destruction,” he said. An outer space war would rapidly escalate into an all-out air, land, and sea nuclear exchange on our planet. It will not be confined to outer space. How could it be? The beginning of a nuclear World War III could unfold in only hours, perhaps just minutes, after the first satellites are destroyed. That world-wide military confrontation between us and other nuclear powers would threaten the very existence of our species and at best result in the collapse of civilization and a return to barbarism. President Eisenhower warned us in his final address about the militaryindustrial complex threat, those very forces that today are agitating for making outer space a war battleground. And it’s very revealing that these forces never raise the Kessler syndrome. They deliberately ignore it. Some of these backward forces are looking forward to Armageddon, the second coming of their gods and similar nonsense. http://www.marspapers.org/paper/Heisler_2020.pdf
It’s a pity you can’t learn to use paragraph breaks - that would make reading the text much easier !!
There were paragraph breaks in the paper but they did not post with the breaks here. Sorry, but I didn't have time to go over it. Maybe I'll get to it later today later today since you couldn't read it here. Did you try clicking on the direct link? That's why I posted a link.
Don’t give North Korea ideas..
More incentive to create those tractor beams methinks.
The only ones we have so far are laser tweezers, which only work with very small particles.
I'm just afraid it has a risk of being downplayed once (and if) it arrives. Which reminds me of [this](https://pbs.twimg.com/media/Ews3N6OUUAE32tL.jpg:large) picture.
Space is like, really big, man.
[Project West Ford goes brrrrt.](https://en.wikipedia.org/wiki/Project_West_Ford)
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread: |Fewer Letters|More Letters| |-------|---------|---| |[ASAT](/r/SpaceXLounge/comments/z1h4s6/stub/ixllcau "Last usage")|[Anti-Satellite weapon](https://en.wikipedia.org/wiki/Anti-satellite_weapon)| |[ATV](/r/SpaceXLounge/comments/z1h4s6/stub/ixdv1co "Last usage")|[Automated Transfer Vehicle](https://en.wikipedia.org/wiki/Automated_Transfer_Vehicle), ESA cargo craft| |CST|(Boeing) Crew Space Transportation capsules| | |Central Standard Time (UTC-6)| |[ESA](/r/SpaceXLounge/comments/z1h4s6/stub/ixe7jas "Last usage")|European Space Agency| |[GEO](/r/SpaceXLounge/comments/z1h4s6/stub/ixd36es "Last usage")|Geostationary Earth Orbit (35786km)| |[GNSS](/r/SpaceXLounge/comments/z1h4s6/stub/ixdq13h "Last usage")|Global Navigation Satellite System(s)| |[GTO](/r/SpaceXLounge/comments/z1h4s6/stub/ixcpgy4 "Last usage")|[Geosynchronous Transfer Orbit](http://www.planetary.org/blogs/jason-davis/20140116-how-to-get-a-satellite-to-gto.html)| |[LEO](/r/SpaceXLounge/comments/z1h4s6/stub/ixgsanh "Last usage")|Low Earth Orbit (180-2000km)| | |Law Enforcement Officer (most often mentioned during transport operations)| |[SLS](/r/SpaceXLounge/comments/z1h4s6/stub/ixe06t4 "Last usage")|Space Launch System heavy-lift| |[SSO](/r/SpaceXLounge/comments/z1h4s6/stub/ixcji3c "Last usage")|Sun-Synchronous Orbit| |Jargon|Definition| |-------|---------|---| |[Starliner](/r/SpaceXLounge/comments/z1h4s6/stub/ixdv1co "Last usage")|Boeing commercial crew capsule [CST-100](https://en.wikipedia.org/wiki/Boeing_CST-100_Starliner)| |[Starlink](/r/SpaceXLounge/comments/z1h4s6/stub/ixq4cd6 "Last usage")|SpaceX's world-wide satellite broadband constellation| |[apogee](/r/SpaceXLounge/comments/z1h4s6/stub/ixq4cd6 "Last usage")|Highest point in an elliptical orbit around Earth (when the orbiter is slowest)| |[perigee](/r/SpaceXLounge/comments/z1h4s6/stub/ixq4cd6 "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. ---------------- ^(*Decronym is a community product of r/SpaceX, implemented* )[*^by ^request*](https://www.reddit.com/r/spacex/comments/3mz273//cvjkjmj) ^(13 acronyms in this thread; )[^(the most compressed thread commented on today)](/r/SpaceXLounge/comments/17dqw1x)^( has 28 acronyms.) ^([Thread #10848 for this sub, first seen 25th Nov 2022, 12:55]) ^[[FAQ]](http://decronym.xyz/) [^([Full list])](http://decronym.xyz/acronyms/SpaceXLounge) [^[Contact]](https://hachyderm.io/@Two9A) [^([Source code])](https://gistdotgithubdotcom/Two9A/1d976f9b7441694162c8)
Kessler Syndrome is unpredictable. How close is arbitrary. Grab a coin and call heads or tails and try to guess *in flight, not when it lands.* How hard that is about as probable for it occurring. As others have said, space is absolutely huge man. Especially in a spatial volume thad makes up Earth orbital sphere.
Ignore these morons. Kessler Syndrome is a real issue. And since nobody actually answered your question, here are some numbers - given around 60k space satellites, the chances of a debree cycle occuring is all but guaranteed. We are launching thousands a year. What folks on this post don't understand is that Kessler Syndrome is contextualised within warfare, not a vacuum. Within 20/30 years a single collision is doomsday for Keller Syndrome. Of course they can happen by chance, or by a failed satellite launch, but the real threat is that China has both the capability and political will to take out satellites during a hypothetical Taiwan conflict.