Space junk removal is not going smoothly(scientificamerican.com)
scientificamerican.com
Space junk removal is not going smoothly
https://www.scientificamerican.com/article/space-junk-removal-is-not-going-smoothly/
233 comments
Sigh.
Strictly the low orbits of StarLink actually make it a sort of non-issue: there's PLENTY of atmospheric friction at the orbits used so re-entry is only a matter of time.
The bigger issue is higher orbits where orbital decay has far small perturbations to rely on. Those can be 10,000 year orbits which makes for a real problem.
Strictly the low orbits of StarLink actually make it a sort of non-issue: there's PLENTY of atmospheric friction at the orbits used so re-entry is only a matter of time.
The bigger issue is higher orbits where orbital decay has far small perturbations to rely on. Those can be 10,000 year orbits which makes for a real problem.
Wait, how does launching stuff to low orbits reduce space junk?
Edit: I think I now understand your comment. I mean sure it maybe adds less space junk than launching things into higher orbits, but it doesn't really reduce it, right?
Edit: I think I now understand your comment. I mean sure it maybe adds less space junk than launching things into higher orbits, but it doesn't really reduce it, right?
There's atmosphere up there, so it creates drag which slows the stuff down and causes it to re-enter and burn up or crash onto the planet in only a few years. Compare that to higher orbit, where there's much less drag and space junk could last centuries or more before it deorbits.
Low Earth orbit satellites drag in the fringes of the upper atmosphere a lot more, so their lifetime in space, unboosted, is typically only a few years. If your satellite dies, it's "self-cleaning."
That said, an impact at this level can still spew debris into higher orbits, as the chaos of the collision can impart enough energy to some collision ejecta to change their orbit significantly. So you still don't want things bumping into each other.
That said, an impact at this level can still spew debris into higher orbits, as the chaos of the collision can impart enough energy to some collision ejecta to change their orbit significantly. So you still don't want things bumping into each other.
[deleted]
It’s subject to drag from the whispy atmosphere and relatively quickly de orbits and burns up (thus no junk is left behind)
It's not a matter of 'more' or 'less' rather than 'easier to deal with'.
LEO sats will probably produce more space junk by mass but junk in LEO will be gone in a few years, no matter how much or little of it their is.
On the other hand Geostationary satellites produce much less junk in terms of mass, but once it's up there it's not coming down for centuries.
LEO sats will probably produce more space junk by mass but junk in LEO will be gone in a few years, no matter how much or little of it their is.
On the other hand Geostationary satellites produce much less junk in terms of mass, but once it's up there it's not coming down for centuries.
Atmospheric drag causes a relatively speedy deorbit if not actively resisted. The starlink satellites use Hall effect thrusters to maintain their orbit. If a unit fails, it should deorbit in under 5 years. If the thrusters work, they could also force it to deorbit much faster. The risk comes from debris from a possible collision being ejected into a higher orbit.
https://en.wikipedia.org/wiki/Orbital_decay#Atmospheric_drag
https://en.wikipedia.org/wiki/Starlink#Space_debris
https://en.wikipedia.org/wiki/Orbital_decay#Atmospheric_drag
https://en.wikipedia.org/wiki/Starlink#Space_debris
> The risk comes from debris from a possible collision being ejected into a higher orbit.
Is that a thing that can happen?
My intuition is it would be possible if a rocket currently boosting to a higher orbit were to collide with something on its way there, but two objects in the same orbit colliding couldn't get enough delta-v to actually get to a higher orbit. They could maybe get "higher", but not at orbital speeds and so would rapidly decay.
I know next to nothing about orbital mechanics, so maybe someone who does can provide some better insight here.
Is that a thing that can happen?
My intuition is it would be possible if a rocket currently boosting to a higher orbit were to collide with something on its way there, but two objects in the same orbit colliding couldn't get enough delta-v to actually get to a higher orbit. They could maybe get "higher", but not at orbital speeds and so would rapidly decay.
I know next to nothing about orbital mechanics, so maybe someone who does can provide some better insight here.
The way to think about orbits is not one height but two: apoapsis and periapsis.
Debris from an explosion/collision can have an unlimited apoapsis, but the periapsis is at most the altitude of the incident.
So if it started in low orbit, it will still drop down regularly, and drag will still remove it over time.
Debris from an explosion/collision can have an unlimited apoapsis, but the periapsis is at most the altitude of the incident.
So if it started in low orbit, it will still drop down regularly, and drag will still remove it over time.
The intuition is: all the debris from a collision now has an orbit passing through the point of collision (at that point of time). Collision at 300km means all the debris must have an orbit that passes through 300km at that moment.
The orbits will be elliptical: exactly how elliptical depends on the directions of the two objects hitting each other and the dispersion of the fragments (how much the fragments have sped up or slowed down compared with original objects, and change of direction).
The fragments the stay in orbit the longest should be those that remain closest to a circular orbit?
The orbits will be elliptical: exactly how elliptical depends on the directions of the two objects hitting each other and the dispersion of the fragments (how much the fragments have sped up or slowed down compared with original objects, and change of direction).
The fragments the stay in orbit the longest should be those that remain closest to a circular orbit?
Set a baseball on top of a basket ball and drop them both from waist high, the baseball will shoot really high into the air by stealing energy from the basketball. The same principle can occur when you start breaking pieces off of spacecraft with collisions. Also the two colliding objects might not be in "the same orbit" one could be in a polar orbit and one could be in a more equitorial orbit. One could be circular and the other highly eliptical, etc. This could boost parts of one of them into a higher orbit (though honestly it would be just as likely to slow things down).
> Ejected into a higher orbit. Is that a thing that can happen?
Apparently not as such. See sibling comment here:https://news.ycombinator.com/item?id=26809297
Apparently not as such. See sibling comment here:https://news.ycombinator.com/item?id=26809297
I am no expert either, but a paper-napkin calculation tells me yes, this can happen.
Basically, just based on impulse and energy conservation, and some assumptions on the size and number of fragments, a head-on collision of two satellites going opposite directions at the same orbit should send some pieces of debris into much higher orbit.
How likely this is to happen in reality, and thus how big a problem this could be is a subject of modeling and much more complex calculations.
Basically, just based on impulse and energy conservation, and some assumptions on the size and number of fragments, a head-on collision of two satellites going opposite directions at the same orbit should send some pieces of debris into much higher orbit.
How likely this is to happen in reality, and thus how big a problem this could be is a subject of modeling and much more complex calculations.
It turns out that intuitive reasoning for orbital mechanics is not easy. Two satellites having a head on collision become space junk because now you have many fragments that themselves can't control their altitude or deorbit. Fragments that are ejected from the collision cannot have more than energy than they had originally, nor can they change direction very much. If pieces are ejected vertically, they are always going to have less lateral velocity than they had going into the collision, therefore will end up in an elliptic orbit with a high probability of colliding with the atmosphere at perigree.
See "can you throw a baseball from the ISS and hit the earth" (No, you can't.)
See "can you throw a baseball from the ISS and hit the earth" (No, you can't.)
The key insight there doesn't have that much to do with orbital mechanics, it's more that in a collision, small fragments can come out with vastly more momentum than they went in with, which in orbits translates to a higher apogee. If you have ever bounced a small ball off a large one, you know the effect. See this video for an intuitive example https://youtu.be/2UHS883_P60
Yes, it translates into a higher apogee, but not a higher perigee. So they will still come down to the altitudes with higher drag.
Strictly speaking this is only true if you start with a perfectly circular orbit, right?
Nope, any orbit. Think of it this way: an orbiting particle (or piece of debris) with no independent control/thrust will stay along whatever orbital path it's following, round and round (modulo any further orbital decay). After a collision, the particle is on a new elliptical trajectory, but the new trajectory still passes through the location of the collision. So the lowest point of the new orbit cannot be any higher than the altitude of the collision.
Likewise, if the particle is slowed down, the highest point of the new orbit cannot be any lower than than the altitude of the collision.
An interesting feature of orbital mechanics is that a change in velocity at a given point in orbit will change the altitude of the orbit at every point except where the change took place.
Likewise, if the particle is slowed down, the highest point of the new orbit cannot be any lower than than the altitude of the collision.
An interesting feature of orbital mechanics is that a change in velocity at a given point in orbit will change the altitude of the orbit at every point except where the change took place.
I think you're claiming that it is impossible for two colliding objects to release fragments that have more energy than either of the original objects. That's wrong.
If it helps, start by imagining two satellite-like machines colliding in interstellar space (i.e. not in orbit), where they were initially moving at 1m/s in opposite directions. Even ignoring the possibility of an explosion (unspent fuel, pressurized areas, I dunno), it's still very easy for interactions to violently fling individual parts outward at speeds higher than 1m/s.
Of course, my guess is that the possible amounts of additional delta-v are pretty low, like 100 m/s, and as such the resulting orbit would not be much higher than the original orbit. But that's just wild conjecture.
If it helps, start by imagining two satellite-like machines colliding in interstellar space (i.e. not in orbit), where they were initially moving at 1m/s in opposite directions. Even ignoring the possibility of an explosion (unspent fuel, pressurized areas, I dunno), it's still very easy for interactions to violently fling individual parts outward at speeds higher than 1m/s.
Of course, my guess is that the possible amounts of additional delta-v are pretty low, like 100 m/s, and as such the resulting orbit would not be much higher than the original orbit. But that's just wild conjecture.
If you were to collide two LEO satellites and turn them into fragments, even if you give those fragments much higher velocity than the initial satellites, you _cannot_ launch them into a higher orbit.
Fragments that are launched down obviously hit the Earth. But an orbit is a closed ellipse, so the fragments that are launched up will _also_ hit the Earth -- they'll just go up steeply, turn around, and come down. The only fragments that won't initially hit the Earth are the ones that are ejected tangentially, parallel to the Earth's surface. Those will go into an elliptical orbit with a high apogee and perigee at the altitude of the collision. Which means they will _still _come down to that altitude and gradually lose energy.
Fragments that are launched down obviously hit the Earth. But an orbit is a closed ellipse, so the fragments that are launched up will _also_ hit the Earth -- they'll just go up steeply, turn around, and come down. The only fragments that won't initially hit the Earth are the ones that are ejected tangentially, parallel to the Earth's surface. Those will go into an elliptical orbit with a high apogee and perigee at the altitude of the collision. Which means they will _still _come down to that altitude and gradually lose energy.
I agree that the best case (uh, best for people who like Kessler cascades?) is that the new fragment has a perigee equal to the location of the collision, and a higher apogee. That means, yes, that it will suffer whatever degree of drag was present at the altitude of the collision.
However.
The grandparent post claimed that "Fragments that are ejected from the collision cannot have more than energy than they had originally, nor can they change direction very much", which I think is clearly what I addressed in my comment, and I stand by my correction of that, and your reply doesn't address this at all.
Also, with respect to "you _cannot_ launch them into a higher orbit", you just agreed that you can have a higher apogee than the collision. If the input satellites had perigees lower than the altitude of collision, you can also have a lower perigee. More velocity at this point on the orbit, higher apogee, higher perigee.... So how do you figure you cannot have a higher orbit?
However.
The grandparent post claimed that "Fragments that are ejected from the collision cannot have more than energy than they had originally, nor can they change direction very much", which I think is clearly what I addressed in my comment, and I stand by my correction of that, and your reply doesn't address this at all.
Also, with respect to "you _cannot_ launch them into a higher orbit", you just agreed that you can have a higher apogee than the collision. If the input satellites had perigees lower than the altitude of collision, you can also have a lower perigee. More velocity at this point on the orbit, higher apogee, higher perigee.... So how do you figure you cannot have a higher orbit?
Parts could be squeezed between high pressure zones and get shot out of the collision, but even those parts won't gain a higher orbit because the perigee will be below the original orbit.
First of all, no, the perigee need not be "below the original orbit", where did you get that? The correct thing to say is that the new orbit's perigee cannot be any lower than the location of the collision.
But more generally, how does this justify your claim that "Fragments that are ejected from the collision cannot have more than energy than they had originally"? Or were you conceding that point and making a different point?
See also my more-detailed cousin of this comment.
But more generally, how does this justify your claim that "Fragments that are ejected from the collision cannot have more than energy than they had originally"? Or were you conceding that point and making a different point?
See also my more-detailed cousin of this comment.
It's like building a structure in the middle of the plains where it'll sit untouched for decades, versus building a structure on the beach where the incessant waves will grind it to bits in short order.
Objects in low orbit don't stay there. They're slowed down by the atmosphere, and re-enter in a few months or a few years. Only if they're healthy enough to orient themselves, and have the fuel to do it, can they perform the re-boost maneuvers necessary to overcome atmospheric drag and stay up for longer.
So, a satellite which loses control, or gets smashed into bits which can't individually control themselves, just becomes fodder for the drag. It gets swept out of orbit by the wisps of atmosphere out there. Low orbit is very "clean" in terms of junk, because junk simply can't linger there. Just like there aren't a lot of ancient ruins on the beach.
The exact degree of drag is unpredictable because the exosphere is subject to a lot of variables, hence the "months to years" ambiguity. But they don't stay out there for decades or millennia, like junk in higher orbits.
Objects in low orbit don't stay there. They're slowed down by the atmosphere, and re-enter in a few months or a few years. Only if they're healthy enough to orient themselves, and have the fuel to do it, can they perform the re-boost maneuvers necessary to overcome atmospheric drag and stay up for longer.
So, a satellite which loses control, or gets smashed into bits which can't individually control themselves, just becomes fodder for the drag. It gets swept out of orbit by the wisps of atmosphere out there. Low orbit is very "clean" in terms of junk, because junk simply can't linger there. Just like there aren't a lot of ancient ruins on the beach.
The exact degree of drag is unpredictable because the exosphere is subject to a lot of variables, hence the "months to years" ambiguity. But they don't stay out there for decades or millennia, like junk in higher orbits.
Does that mean the material can still fully burn when falling down from under 2000km altitude? Or would we see pollution for example from battery materials?
The original altitude is not relevant to how the item burns up. Its not the vertical velocity when it hits the atmosphere, its the horizontal velocity.
Anything re-entering the atmosphere is subjected to temperatures around 8000 deg. Most things are just totally incinerated, unless they are well-enough insulated to withstand that temperature until they slow down from orbital velocity.
Anything re-entering the atmosphere is subjected to temperatures around 8000 deg. Most things are just totally incinerated, unless they are well-enough insulated to withstand that temperature until they slow down from orbital velocity.
> It's like building a structure in the middle of the plains where it'll sit untouched for decades, versus building a structure on the beach where the incessant waves will grind it to bits in short order.
That is a fantastic analogy.
That is a fantastic analogy.
> I mean sure it maybe adds less space junk than launching things into higher orbits, but it doesn't really reduce it, right?
Sure, but that's not really the point. Using biodegradable plastic is much better than traditional plastic that stays in landfills forever. "Just don't generate trash" isn't an option.
Sure, but that's not really the point. Using biodegradable plastic is much better than traditional plastic that stays in landfills forever. "Just don't generate trash" isn't an option.
There is literally no problem with plastics that stay in landfills forever. Landfills are underground, like the oil that the plastic is derived from.
Landfills are generally very close to the surface, filling holes created by activities like strip mining, so they do occupy surface area. Unless you're wiling to dig down under existing landfill to dig out voids to pack with more landfill.
If the cost to LEO is a fraction of the cost to HEO or geostationary, it becomes economical to send cheap satellites to LEO and let them burn up in a few years than to send expensive satellites to HEO or geostationary and let them become multi-decade space junk.
Eg if it is $10m to LEO and $15m to HEO you will pay the extra to get to HEO and put a satellite designed for long life - but if it is $1m to LEO you can build a cheaper satellite and launch it 5 times over the following decades.
Eg if it is $10m to LEO and $15m to HEO you will pay the extra to get to HEO and put a satellite designed for long life - but if it is $1m to LEO you can build a cheaper satellite and launch it 5 times over the following decades.
This is only true if the cost of the launch dominates the total mission price. That just isn't true any more. Engineering labor is the dominant cost until you have very high volumes. Even then, component costs are still far higher than launch costs.
But they aren’t building 1 satellite and launching it 5 times over the next decade. They’re maintaining a constant fleet of 42000 satellites, which means putting up new junk to replace the old junk while its still flying junk and not de-orbited junk.
I like the idea of having internet on my sailboat as much as the next guy, but it takes some serious cognitive dissonance to convince oneself that 42,000 pieces of nearby junk is better than a handful of pieces of far away junk.
I like the idea of having internet on my sailboat as much as the next guy, but it takes some serious cognitive dissonance to convince oneself that 42,000 pieces of nearby junk is better than a handful of pieces of far away junk.
>They’re maintaining a constant fleet of 42000 satellites, which means putting up new junk to replace the old junk while its still flying junk and not de-orbited junk.
No. First, The whole reason they need to maintain a fleet, rather then just having it sit there for decades, is that they're so low. The vast majority of planned Starlink satellites from that number are from Phase 2, and are V-band VLEO sats with orbits around 340 km, which is really low. At that altitude, natural decay time is measured in weeks at best. To work they'll need both active thrusters providing regular boost and aerodynamic low drag design (and maintaining orientation for that will itself require fuel). Should they actually lose all control through malfunction or a collision, they and resulting debris will deorbit very rapidly (they'll both have no boost and be less aerodynamic).
And second, "through malfunction or collision", because it's not as if SpaceX (and other LEO satellite operators) doesn't have, and indeed are required to have, plans for controlled deorbit at EOL. Most of the satellites can be expected to get deorbited in a controlled way as planned. Making sure everything burns up has been one of the things slowing Starlink development, it took some work to ensure the optical links would properly go for example.
SpaceX is not interested in leaving them up there. I mean, FFS people, who would be hurt more than SpaceX by Kessler Syndrome!?
>I like the idea of having internet on my sailboat as much as the next guy, but it takes some serious cognitive dissonance to convince oneself that 42,000 pieces of nearby junk is better than a handful of pieces of far away junk.
Your dismissiveness towards hundreds of millions of underserved people and challenging use cases and ignorance of orbital dynamics does you no favors here.
No. First, The whole reason they need to maintain a fleet, rather then just having it sit there for decades, is that they're so low. The vast majority of planned Starlink satellites from that number are from Phase 2, and are V-band VLEO sats with orbits around 340 km, which is really low. At that altitude, natural decay time is measured in weeks at best. To work they'll need both active thrusters providing regular boost and aerodynamic low drag design (and maintaining orientation for that will itself require fuel). Should they actually lose all control through malfunction or a collision, they and resulting debris will deorbit very rapidly (they'll both have no boost and be less aerodynamic).
And second, "through malfunction or collision", because it's not as if SpaceX (and other LEO satellite operators) doesn't have, and indeed are required to have, plans for controlled deorbit at EOL. Most of the satellites can be expected to get deorbited in a controlled way as planned. Making sure everything burns up has been one of the things slowing Starlink development, it took some work to ensure the optical links would properly go for example.
SpaceX is not interested in leaving them up there. I mean, FFS people, who would be hurt more than SpaceX by Kessler Syndrome!?
>I like the idea of having internet on my sailboat as much as the next guy, but it takes some serious cognitive dissonance to convince oneself that 42,000 pieces of nearby junk is better than a handful of pieces of far away junk.
Your dismissiveness towards hundreds of millions of underserved people and challenging use cases and ignorance of orbital dynamics does you no favors here.
> Your dismissiveness towards hundreds of millions of underserved people and challenging use cases
This is pompous and elitist nonsense of the highest order. People have other more pressing concerns than fast internet. You know...like water, food and cheap power.
This is pompous and elitist nonsense of the highest order. People have other more pressing concerns than fast internet. You know...like water, food and cheap power.
Communications infrastructure is essential for any developing/developed nation. It's easy to take for granted while living in an urban center of a 1st world nation just how game-changing communications is. A truly global, easily accessible network has the potential to lift millions out of poverty through facilitating economic growth of remote, unconnected areas. Dismissing satellite constellation networks as merely "faster internet" misses the bigger picture.
Also it's worth noting that communications networks is but one application for LEO satellite constellation technology.
Also it's worth noting that communications networks is but one application for LEO satellite constellation technology.
> and maintaining orientation for that will itself require fuel
With some gyroscopes, I think they only need electricity for it, not actual reaction mass.
With some gyroscopes, I think they only need electricity for it, not actual reaction mass.
> Your dismissiveness towards hundreds of millions of underserved people and challenging use cases and ignorance of orbital dynamics does you no favors here.
Imagine thinking that a product that costs $500 up-front and $99/mo thereafter and uses ~100 W constantly is designed for "hundreds of millions of underserved people".
Imagine thinking that a product that costs $500 up-front and $99/mo thereafter and uses ~100 W constantly is designed for "hundreds of millions of underserved people".
It's not less so much as zero. Space junk isn't really a problem to worry about below a certain point.
[deleted]
Can you give a rough estimate of what fraction of space waste is due to differing orbits of satelites? Like very low vs low vs geostationary? I don't know the gradations between those either.
Wikipedia to the rescue (note the log-log scale)
https://en.wikipedia.org/wiki/File:Spacedebris_small.png
The biggest issue is by far the 600km to 2000km altitude band. It is popular for both LEO and SunSync sats and is high enough above the atmosphere that minimal propellant is needed for orbit boosting.
The biggest issue is by far the 600km to 2000km altitude band. It is popular for both LEO and SunSync sats and is high enough above the atmosphere that minimal propellant is needed for orbit boosting.
The actual amount/distribution of stuff can be misleading. What really matters is the risk of collision, which is the highest for Sun-synchronous orbits. The fact that lower SSOs are also the most convenient for remote sensing work doesn't help.
GEO is more or less safe because it's unstable (dead stuff drifts outwards), well kept (slots are limited by the resolution of customers' terminals) and typically doesn't have high relative velocities.
GEO is more or less safe because it's unstable (dead stuff drifts outwards), well kept (slots are limited by the resolution of customers' terminals) and typically doesn't have high relative velocities.
SpaceX is planning to launch up to 42 000 satellites (there are about 3000 now). Cheaper $/kg leads to more space junk and higher risk of Kessler syndrome, that doesn't need any qualifications, I think. If something goes wrong the fact that the cloud of debris will be there for 10 years and not 100 years is not a huge consolation
How does the cloud of debris stick around? For context, I've played Kerbal so I know a bit about orbits but not much.
My intuition is that the velocities involved in being in orbit in the first place are so big (7 kilometers per second according to a quick search) that the orbit of the debris won't be substantially different, so it will still decay. Even if you give enormous kicks to the debris, most of it will end up with orbits intersecting the earth. The ones that don't will still intersect the original collision location, and so still experience decay during that part of their orbit.
Basically, to change your orbit you need to boost once to push the other side of the orbit out and then again at the other side to push the original side out. A collision can only give one of the boosts, and so is sort of inherently bad at moving the orbit.
My intuition is that the velocities involved in being in orbit in the first place are so big (7 kilometers per second according to a quick search) that the orbit of the debris won't be substantially different, so it will still decay. Even if you give enormous kicks to the debris, most of it will end up with orbits intersecting the earth. The ones that don't will still intersect the original collision location, and so still experience decay during that part of their orbit.
Basically, to change your orbit you need to boost once to push the other side of the orbit out and then again at the other side to push the original side out. A collision can only give one of the boosts, and so is sort of inherently bad at moving the orbit.
You are totally correct (and yay KSP!)
But the danger is the debris that is ejected from a collision at a lower orbit would then collide with debris that is at a higher orbit. The debris from the 2nd collision would have its original periapsis, which may be high enough to stick around for decades.
But the danger is the debris that is ejected from a collision at a lower orbit would then collide with debris that is at a higher orbit. The debris from the 2nd collision would have its original periapsis, which may be high enough to stick around for decades.
Timing is absolutely a huge qualification to Kessler syndrome.
If the cloud of debris is gone in 5 years, that's a hurdle to some careers and a (hopefully) temporary shutdown for some businesses. Covid has taught us that the modern economy has traded a lot of robustness for profit and efficiency, and those would certainly be significant losses of billions or trillions of dollars, but it would be a small fraction of GDP, we would hopefully learn from the mistake, and we would still be a spacefaring species.
If Kessler syndrome occurred among geostationary satellites, that could potentially be a problem for millions of years. That's six orders of magnitude different and definitely needs qualification.
If the cloud of debris is gone in 5 years, that's a hurdle to some careers and a (hopefully) temporary shutdown for some businesses. Covid has taught us that the modern economy has traded a lot of robustness for profit and efficiency, and those would certainly be significant losses of billions or trillions of dollars, but it would be a small fraction of GDP, we would hopefully learn from the mistake, and we would still be a spacefaring species.
If Kessler syndrome occurred among geostationary satellites, that could potentially be a problem for millions of years. That's six orders of magnitude different and definitely needs qualification.
But there is a lot more space in geostationary orbits and lot less stuff so the risk of chain of collisions is lower
There is far less space in geostationary orbit, because the locus of GEO is a one-dimensional ring above the equator.
It's true that there is less GEO real estate in this sense. But to kick off Kessler syndrome, you need two objects in different orbital planes so that they collide at very high speed. It wouldn't be possible for two defunct GEO satellites to collide, because two nearby GEO satellites are moving in the same direction at the same speed.
but aren't the satellites in GEO stationary relative to one another? And if by chance they all get destroyed in collision the debris would mostly also stay in that ring so we could still launch rockets and have satellites in other orbits that don't cross it.
And this is exactly the sort of comment that grandparent addressed with their post.
More stuff in orbit doesn't necessarily lead to higher risk of a catastrophic kessler syndrome event, if it's low-earth orbit. The risk is not the same as geosynchronous where it can stay there forever. The satellites themselves (and even the debris if there is a collision) will decay on a very short-term basis (single-digit number of years).
By making launch cost-per-kg cheaper, it is now plausible to put things in LEO instead of geo or other orbits. And doing that probably actually reduces the risk of a catastrophic event, even if there is more stuff.
Possibly higher risk of a smaller event, sure, but that is true of anything that puts more stuff in space. That's a generic argument that we shouldn't be doing anything in space at all, which I think is not compelling.
More stuff in orbit doesn't necessarily lead to higher risk of a catastrophic kessler syndrome event, if it's low-earth orbit. The risk is not the same as geosynchronous where it can stay there forever. The satellites themselves (and even the debris if there is a collision) will decay on a very short-term basis (single-digit number of years).
By making launch cost-per-kg cheaper, it is now plausible to put things in LEO instead of geo or other orbits. And doing that probably actually reduces the risk of a catastrophic event, even if there is more stuff.
Possibly higher risk of a smaller event, sure, but that is true of anything that puts more stuff in space. That's a generic argument that we shouldn't be doing anything in space at all, which I think is not compelling.
> If something goes wrong the fact that the cloud of debris will be there for 10 years and not 100 years is not a huge consolation
Seems like a pretty big consolation to me, no?
Seems like a pretty big consolation to me, no?
No kidding. Order of magnitude
> There is one ultimate sure-fire way to reduce space junk: launch stuff to very low orbits
Really? If there's a collision in LEO, doesn't debris spray in all directions, including some in the direction of higher, more stable orbits?
Really? If there's a collision in LEO, doesn't debris spray in all directions, including some in the direction of higher, more stable orbits?
Not a physicist, but I doubt the debris would have the energy to reach geostationary orbits.
Not relevant? There are many orbits that are below geostationary and are also high enough to avoid atmospheric drag for a long time.
In the direction, yes, but it would still cross the original orbit. You need a second collision to actually get stuff into higher orbits.
With my limited knowledge of orbital mechanics I believe this wouldn't be a problem. It takes a lot of energy to move to a higher orbit. I would think the probability of enough energy to fling something to a higher orbit where it would be stable for a noticeably longer time would be very low.
Think of exploding something 2 miles up the side of a mountain, what are the chances a piece goes another mile up the mountain. Like that but even harder.
Think of exploding something 2 miles up the side of a mountain, what are the chances a piece goes another mile up the mountain. Like that but even harder.
This would just create an oblong orbit, which would still cause re-entry into thicker atmosphere for a portion of the orbit.
I thought the debris that gets lifted upward tends to go into elliptical orbits. Apogee would still create a significant amount of drag, wouldn't it?
Yes, I'm aware that orbital mechanics is not that simple, that's why I specifically didn't talk about "upward" as a higher orbit isn't necessarily caused by a push in that direction.
Sibling comment ( https://news.ycombinator.com/item?id=26809297 ) is better at outlining that I was wrong: apparently a single impact cannot produce an entirely higher orbit, for debris sent in _any_ initial direction. At best, it produces elliptical orbits with a higher apogee, and the same drag at perigee.
Sibling comment ( https://news.ycombinator.com/item?id=26809297 ) is better at outlining that I was wrong: apparently a single impact cannot produce an entirely higher orbit, for debris sent in _any_ initial direction. At best, it produces elliptical orbits with a higher apogee, and the same drag at perigee.
Just to add to sibling comments who already answered this, that isn't how orbital mechanics work (or else a lot of things would be much easier!). A good place to start reading is on Hohmann transfer orbits [1, 2]. They're commonly covered in the context of interplanetary travel, but the exact same principle applies to changing orbits around a single gravity well. The key take home as applied to here is that a single instantaneous addition of energy (delta-v) to an object in stable circular orbit just changes it to an elliptical orbit where the high point is determined by the added delta-v but the low point is the same as where it started. It takes a properly timed second instantaneous application of energy to stabilize at a different orbit.
So any ejecta from a single collision will still orbit through whatever altitude they started at, and in turn will be affected by atmospheric drag at that point regardless of how much farther out they get at the high point. In principle it's of course not impossible that they could collide with something else already in a higher stable orbit, but the odds of that get very, very low particularly in the short time frame they have before decay assuming they're starting in VLEO.
----
1: https://ocw.mit.edu/courses/aeronautics-and-astronautics/16-...
2: https://solarsystem.nasa.gov/basics/chapter4-1/
So any ejecta from a single collision will still orbit through whatever altitude they started at, and in turn will be affected by atmospheric drag at that point regardless of how much farther out they get at the high point. In principle it's of course not impossible that they could collide with something else already in a higher stable orbit, but the odds of that get very, very low particularly in the short time frame they have before decay assuming they're starting in VLEO.
----
1: https://ocw.mit.edu/courses/aeronautics-and-astronautics/16-...
2: https://solarsystem.nasa.gov/basics/chapter4-1/
That's a comprehensive answer, thank you. TIL.
> high point is determined by the added delta-v but the low point is the same as where it started
Is it the low point that is that same? I would have thought it was the current point (at time of delta-v addition), wherever that is, that must be part of the new orbit. Not that this is relevant for the topic at hand, just trying to check my understanding.
Is it the low point that is that same? I would have thought it was the current point (at time of delta-v addition), wherever that is, that must be part of the new orbit. Not that this is relevant for the topic at hand, just trying to check my understanding.
This is correct. The simplification being made is that the original orbit was circular, so if you increase the debris' velocity, the current point is now the low point of the new orbit.
Even for circular orbits, is that the case? The new low point would be lower if impulse is not parallel to the velocity.
Correct, so basically the lowest point(periapsis) of the new orbit cannot be any higher than the point where the collision happened.
Another way to think about it is, an orbit around a single body is entirely defined[0] by your current position and your instantaneous velocity. Six numbers. Where you are, which direction you're going, and how fast. Such orbits are closed, which means wherever you are right now, you'll return to that exact point later.
So if you're at point P in your orbit and suddenly kinetic energy was added, your velocity changes in some arbitrary way. While you aren't sure where you'll go and when you'll get there, as long as the new (position, velocity) pair still defines a closed orbit around the body, you can be damn sure you'll return to the exact point where you are now.
From this follows that the lowest point of your new orbit cannot be higher than where you are now, and the highest point of your orbit cannot be lower.
--
[0] - Ignoring gravitational effects of other bodies, residual drag, magnetic fields, solar pressure, etc. None of these matter on the scale of days to months.
So if you're at point P in your orbit and suddenly kinetic energy was added, your velocity changes in some arbitrary way. While you aren't sure where you'll go and when you'll get there, as long as the new (position, velocity) pair still defines a closed orbit around the body, you can be damn sure you'll return to the exact point where you are now.
From this follows that the lowest point of your new orbit cannot be higher than where you are now, and the highest point of your orbit cannot be lower.
--
[0] - Ignoring gravitational effects of other bodies, residual drag, magnetic fields, solar pressure, etc. None of these matter on the scale of days to months.
Yes, if you start from roughly circular orbit, and the impulse is in the opposite direction to the direction of travel, it will slow you down and then the location of impulse is now the new highest point on orbit, and the lowest point after the impulse is even lower than before it.
Thank you, this is really informative.
Altitude Lifetime
200 km 1 day
300 km 1 month
400 km 1 year
500 km 10 years
700 km 100 years
900 km 1000 yearsHa - and the altitude of the space station is 408 km so most of the junk should clear out in a year? That sounds too easy.
The space station has to add energy almost weekly to overcome drag. If it didn't it would likely come down within a couple years. When they want to throw trash away, they literally just drop it off the side and it burns up eventually: https://gizmodo.com/iss-ditches-2-9-ton-pallet-of-batteries-...
Would that stuff cause a huge fireball in the night sky? 2.9 tons is a hell of a lot of mass... amazing to think it will just burn up in the atmosphere.
I'd say it would burn up pretty nicely. Its not gonna be one homogenous lump of stuff that holds together on re-entry, its a bunch of smaller "things" (battery cells) bundled up and held together with an external shell.
As soon as that shell burns through its going to break apart and each individual part will start burning up.
As soon as that shell burns through its going to break apart and each individual part will start burning up.
Yeah probably most of the mass is aluminium sheet which melts quite easily hence Starship and the MiG-25 switching to steel, and also can burn quite well - it was the fuel in the shuttle's boosters.
I don't think it is to worry about, 1 cubic meter of iron weighs 7.8 tons for example... it is not a huge mass in the end.
Because it is really that easy. Space-junk in low-earth orbit is not really a concern, and alarmist articles about space-junk in connection with projects like Starlink are just click-bait that rely on the general public's ignorance of orbital mechanics and space.
Medium and high orbits are a different story. Space junk is absolutely a real concern here.
Medium and high orbits are a different story. Space junk is absolutely a real concern here.
Also, take out SpaceX from the name and add all the competitors (potentially lower quality) that are starting or about to get into the space and you can understand the concern.
edit: my concern is the long chain of the curve of low-orbit satellite companies as price continues to have downward pressure.
edit: my concern is the long chain of the curve of low-orbit satellite companies as price continues to have downward pressure.
Why not incentivize these companies with grant such that they will get the grant if their TO orbit launches _include_ the retrieval of space junk as well on the RETURN back to earth.
In order to go up, you have to bring something back.
In order to go up, you have to bring something back.
Makes no sense. Satellite retrieval is something that you definitely want to run a separate mission for - you don't want to bolt a visit to a completely separate orbit (and then transfer back to reentry) on top of a regular mission. The amount of fuel you need to launch something grows exponentially with the amount of fuel you need at the final stage.
Not to mention, if you're thinking of making LEO launches do this, then they'd either have to capture other LEO junk (makes little sense, most of it will deorbit itself), or you'd have to bolt on additional stage, which may very well introduce more junk itself (are people still using explosive bolts for upper stage separation?).
Not to mention, if you're thinking of making LEO launches do this, then they'd either have to capture other LEO junk (makes little sense, most of it will deorbit itself), or you'd have to bolt on additional stage, which may very well introduce more junk itself (are people still using explosive bolts for upper stage separation?).
So make 'em separate missions, of course. You have to run the retrieval mission and have it succeed before you're granted a launch license for the original mission of putting something up.
Mission-for-mission makes no sense, who decides what mass or orbit of junk counts for your mission? You really have to wait years and set up a whole different mission architecture before you can launch your own project? It's bananas. However a cleanup tax on satellite launches used to fund recovery efforts might work.
The whole article is about how no one knows a good way to do that yet.
Rendezvousing with, capturing and then manoeuvring with a captured object is an extremely hard and as yet unsolved problem, although there are some experiment. Also it is only feasible to rendezvous with a target on an almost identical orbit, otherwise the fuel and thrust requirements to reach it very quickly balloon to hugely prohibitive proportions.
> Rendezvoing with, capturing and then manoeuvring with another object is an extremely hard and as yet unsolved problem, although there are some experiment
Umm...this is utterly wrong, and has been since Gemini 10 in 1966, not to mention Skylab, Mir, ISS
Umm...this is utterly wrong, and has been since Gemini 10 in 1966, not to mention Skylab, Mir, ISS
> Umm...this is utterly wrong, and has been since Gemini 10 in 1966, not to mention Skylab, Mir, ISS
There's a big difference between docking with a spacecraft that is designed to be docked with and capturing a satellite that was not designed to be captured.
People are making good progress on this - Northrup Grumman just had a successful life extension satellite mission very recently. But it's far from a mature technology.
There's a big difference between docking with a spacecraft that is designed to be docked with and capturing a satellite that was not designed to be captured.
People are making good progress on this - Northrup Grumman just had a successful life extension satellite mission very recently. But it's far from a mature technology.
>edit: my concern is the long chain of the curve of low-orbit satellite companies as price continues to have downward pressure.
While this isn't entirely unreasonable, consider a few things. First, this is one case where even natural incentives line up pretty well. For the foreseeable future, no one is going to have more economic incentive to prevent the loss of usable LEO than companies that build themselves around usage of LEO. There are also virtuous spirals in the very technology that makes low cost possible, ie., the only way to reach SpaceX's targeted launch costs with Starship are to have a full reusability, and that itself cuts a ton of orbital debris (spent stages).
Second, much cheaper mass and higher cadence changes everything in space engineering, and that includes giving regulators significantly more leeway in what they can reasonably require. Things like more redundant controlled deorbit systems, requirements for lower orbits by default with higher orbits reserved, requirements for materials, and so on all ultimately boil down to how much it costs to get a kg to orbit and how regularly it can be done. More leeway there makes a lot of things easier without destroying utility, which in turn raises the chances we can make solid systematic changes.
Not saying there isn't plenty of room for error overall, or that regulators shouldn't be thinking about it too. But I do think the "mega constellation commercial" focus is mostly misguided. If anything the biggest risks seem to be from government actors, in terms of things like a-sat weapons and Old Space big companies not feeling the need to care.
While this isn't entirely unreasonable, consider a few things. First, this is one case where even natural incentives line up pretty well. For the foreseeable future, no one is going to have more economic incentive to prevent the loss of usable LEO than companies that build themselves around usage of LEO. There are also virtuous spirals in the very technology that makes low cost possible, ie., the only way to reach SpaceX's targeted launch costs with Starship are to have a full reusability, and that itself cuts a ton of orbital debris (spent stages).
Second, much cheaper mass and higher cadence changes everything in space engineering, and that includes giving regulators significantly more leeway in what they can reasonably require. Things like more redundant controlled deorbit systems, requirements for lower orbits by default with higher orbits reserved, requirements for materials, and so on all ultimately boil down to how much it costs to get a kg to orbit and how regularly it can be done. More leeway there makes a lot of things easier without destroying utility, which in turn raises the chances we can make solid systematic changes.
Not saying there isn't plenty of room for error overall, or that regulators shouldn't be thinking about it too. But I do think the "mega constellation commercial" focus is mostly misguided. If anything the biggest risks seem to be from government actors, in terms of things like a-sat weapons and Old Space big companies not feeling the need to care.
Full reusability makes sense and limits space junk - though the counter to that is they are launching more satellites into space - so probably negate each other to a certain point.
I guess my concern would be who actually has regulatory authority over space and how can they ensure all actors play fairly. I would have to imagine this is a situation that is similar to the tragedy of the commons type scenario.
To be clear - I really don't fall into one side of the camp or the other but I can see how a lot of the waste management side of things can fall by the wayside given our track record on waste cleanup (mines, municipal solid waste, nuclear)
I guess my concern would be who actually has regulatory authority over space and how can they ensure all actors play fairly. I would have to imagine this is a situation that is similar to the tragedy of the commons type scenario.
To be clear - I really don't fall into one side of the camp or the other but I can see how a lot of the waste management side of things can fall by the wayside given our track record on waste cleanup (mines, municipal solid waste, nuclear)
> For the foreseeable future, no one is going to have more economic incentive to prevent the loss of usable LEO than companies that build themselves around usage of LEO.
This line of reasoning never seems to work out the way you are suggesting. It's more likely to wind up in a giant Mexican standoff once there a multiple entities who all have the individual ability to ruin it for everyone.
This line of reasoning never seems to work out the way you are suggesting. It's more likely to wind up in a giant Mexican standoff once there a multiple entities who all have the individual ability to ruin it for everyone.
Which is when it's time to sit down and institute a system of property rights for what has now become a scarce resource.
> and that itself cuts a ton of orbital debris (spent stages).
Almost all upper stages for LEO missions get deorbited (or at least they're meant to be deorbited). It's typically only the high energy missions like GEO/GTO where upper stages get left in a "graveyard orbit".
Almost all upper stages for LEO missions get deorbited (or at least they're meant to be deorbited). It's typically only the high energy missions like GEO/GTO where upper stages get left in a "graveyard orbit".
This is important correction. But a high-speed collision at a very low orbit can trow debris to not-so-low orbit.
How big of a problem this can be is something to model and calculate, it's not something one figures out just from the general principles.
How big of a problem this can be is something to model and calculate, it's not something one figures out just from the general principles.
I don't see how that's a major issue, It'd take a pretty odd angle for a high speed collision to push something into a higher orbit. That seems like a pretty rare event.
Not really. High speed collisions are high entropy events, so debris fills state space, and you get SOME debris at high altitudes (usually in highly eccentric orbits). That being said, low altitude is much safer since you don’t get as many long lived dead satellites
From super-low Earth orbits, more of the orbits that go really high also impact Earth or its atmosphere on the other side, so they only are up there once, rather than over and over and over.
Yep!
> But a high-speed collision at a very low orbit can trow debris to not-so-low orbit.
This seems wrong, from what I understand of orbital mechanics.
This seems wrong, from what I understand of orbital mechanics.
Yeah, the terminology is wrong. It's not a high orbit, it's a high ballistic trajectory, which then is terminated on the low side. But if that object improbably happens to collide with a high-orbit object then you could get a spreading of the consequences to higher orbit.
Curious how big of an issue this actually ends up being since they can't be put in a stable higher orbit without a second burn/collision to circularize. Without a change to the orbit perigee it would still decay, just more slowly?
[deleted]
A high speed collision in low orbit can change a circular low orbit into an elliptical eccentric orbit that intersects a higher circular orbit, but unless there is an additional accelerating event at that higher altitude, it cannot recircularize its orbit at that higher altitude.
There are thus two takeaways:
1. By definition, this means that part of the orbit will always be at low altitude, regardless of the collision dynamics. So this means that it will continue to decay over time, albeit perhaps at a slower rate (decay being proportional to the time spent at lower altitude).
2. While that eccentric orbit will intersect with a higher circular orbital plane, it does so in a predictable fashion that can be routed around. The higher orbits are also much sparser, so the chance of this intersecting with a satellite that is already present is very, very small.
There are thus two takeaways:
1. By definition, this means that part of the orbit will always be at low altitude, regardless of the collision dynamics. So this means that it will continue to decay over time, albeit perhaps at a slower rate (decay being proportional to the time spent at lower altitude).
2. While that eccentric orbit will intersect with a higher circular orbital plane, it does so in a predictable fashion that can be routed around. The higher orbits are also much sparser, so the chance of this intersecting with a satellite that is already present is very, very small.
Thank you, others pointed this out too.
Proves that "celestial mechanics" is trickier than I thought.
I guess if a collision is messy enough, there would be secondary collisions between debris pieces, and it sounds like these in principle can push some junk into higher orbits. But I think the probability is really low; this should not be a concern.
I guess if a collision is messy enough, there would be secondary collisions between debris pieces, and it sounds like these in principle can push some junk into higher orbits. But I think the probability is really low; this should not be a concern.
> a high-speed collision at a very low orbit can trow debris to not-so-low orbit
How so? According to my understanding of orbital mechanics, if an object begins its orbit at a certain altitude, it will return to that altitude exactly one orbit later. While a collision can change the shape of the object's orbit, it can't change the spot of collision - which it will return to every cycle of its orbit.
How so? According to my understanding of orbital mechanics, if an object begins its orbit at a certain altitude, it will return to that altitude exactly one orbit later. While a collision can change the shape of the object's orbit, it can't change the spot of collision - which it will return to every cycle of its orbit.
Some of the debris will be thrown into eccentric orbits reaching significantly higher altitudes as part of the orbit. If these fragments hit objects in these higher orbits, that will create further debris clouds in more stable high orbits, etc, etc. That way you can get a runaway chain reaction that could escalate to arbitrarily high orbits and debris cloud lifetimes.
> inherently their lifetimes will be measured in single digit years. But that's ok since they can be replaced so cheaply
Oh cool, let's shoot even more soon-to-obsolete pollution into the atmosphere. That's working so well on Earth. /s
Oh cool, let's shoot even more soon-to-obsolete pollution into the atmosphere. That's working so well on Earth. /s
1000s of satellites are irrelevant to atmospheric pollution. The numbers are so small compared to the vast size of the atmosphere it isn’t really a concern to worry about.
Atmospheric pollution from earth based sources is different because it’s something that is being done in the scale of billions of people, not 1000s, and CO2 doesn’t naturally disappear from the atmosphere over time and is growing decade after decade.
Atmospheric pollution from earth based sources is different because it’s something that is being done in the scale of billions of people, not 1000s, and CO2 doesn’t naturally disappear from the atmosphere over time and is growing decade after decade.
You're so confident. How adorably naive.
Do you math?
Over one hundred metric tons of space dust falls on the earth daily. Do you really think SpaceX de-orbiting a 200 Kg satellite once a day or so is going to change that significantly?
Over one hundred metric tons of space dust falls on the earth daily. Do you really think SpaceX de-orbiting a 200 Kg satellite once a day or so is going to change that significantly?
Comments like this aren't constructive.
Aren't their lifetimes so short because they will fall out of orbit? That's not really polluting orbit.
You seem to know a lot about this subject! Years ago, an acquaintance of mine told me of their idea to use railguns to remove space junk. Is this a remotely feasible solution?
From space, maybe. A railgun on the surface of Earth that was trying to slow down a piece of space junk would, by necessity, be aimed at a low angle. Getting a projectile a couple hundred kilometers up while launching at such angle would make this railgun be something between a window-shattering nuisance and a weapon of mass destruction, depending on muzzle velocity and the size of the projectile.
The problem is, of course, the atmosphere. That thick soup of gas that's at its densest near the surface, and has the annoying tendency of engulfing hypersonic projectiles in a thick ball of screaming-hot plasma.
The problem is, of course, the atmosphere. That thick soup of gas that's at its densest near the surface, and has the annoying tendency of engulfing hypersonic projectiles in a thick ball of screaming-hot plasma.
When these satellites burn up in the atmosphere, what happens to all the particles? Do we have lots of likely toxic material just constantly being burned and circulating around?
We estimate that the amount of dust and meteorites entering earth's atmosphere is about 100 metric tons per day. Combine that with emissions from volcanoes, many of which are highly toxic, and vaporised satellites are really insignificant.
The proportions remind me of another somewhat common space-related misconception, which is that rocket launches are big polluters.
With each launch emitting roughly as much as a single commercial flight and typically around 100 launches happening globally per year, even a tiny change in the tens of millions of commercial flights per year has a far larger impact on emissions than launches will for the foreseeable future.
With each launch emitting roughly as much as a single commercial flight and typically around 100 launches happening globally per year, even a tiny change in the tens of millions of commercial flights per year has a far larger impact on emissions than launches will for the foreseeable future.
> With each launch emitting roughly as much as a single commercial flight
It's one of those "connective" facts that puts so many distinct things into perspective. When I first learned it a few years ago, I became simultaneously very relieved that a rocket launch doesn't really have that big of a carbon footprint, and horrified by how much emissions a single passenger plane can make. It's a lesson about how visuals can be misleading: a plane looks tiny and doesn't really seem to be doing anything, while a rocket is big and rises to heavens on a pillar of flame, propelled by the anger of hell itself - and yet it turns out they're roughly the same, emissions-wise.
It's one of those "connective" facts that puts so many distinct things into perspective. When I first learned it a few years ago, I became simultaneously very relieved that a rocket launch doesn't really have that big of a carbon footprint, and horrified by how much emissions a single passenger plane can make. It's a lesson about how visuals can be misleading: a plane looks tiny and doesn't really seem to be doing anything, while a rocket is big and rises to heavens on a pillar of flame, propelled by the anger of hell itself - and yet it turns out they're roughly the same, emissions-wise.
An easy way to compare the amount of CO2 they release is looking at the size. They only can burn the fuel they carry, and the density of the fuel is similar. The best images I got are
https://twitter.com/rocketrundown/status/956079854511972352
https://twitter.com/erdayastronaut/status/123959552711483801...
To make the calculation more difficult, like the 80% of the volume of a Boeing 747 is room for humans, and like 50% of the volume of a Falcon 9 is room for Oxygen and thrusters.
https://twitter.com/rocketrundown/status/956079854511972352
https://twitter.com/erdayastronaut/status/123959552711483801...
To make the calculation more difficult, like the 80% of the volume of a Boeing 747 is room for humans, and like 50% of the volume of a Falcon 9 is room for Oxygen and thrusters.
Some rockets use toxic fuel though, so it's not entirely apples to apples.
Some of the propellants (especially the hypergolics) are pretty toxic. However, Soyuz, Long March 5 (and later), Falcon 9, and Delta III (first stage) all use high-grade kerosene (RP-1 or its Russian equivalent) and liquid oxygen. Jet-A isn't too far from high-grade kerosene. Ariane 5 uses liquid hydrogen and liquid oxygen in its first stage. Many of the smaller players use RP-1/LOX, and some of the next-generation rockets will use methane/LOX propellants.
Though, the Delta III and Ariane 5 boosters do contain ammonium perchlorate, which is worse for the environment than jet fuel.
Though, the Delta III and Ariane 5 boosters do contain ammonium perchlorate, which is worse for the environment than jet fuel.
No, we have very small amounts of likely toxic material circulating around.
Earth's atmosphere is around 5 x 10^18 kg. All the satellites put together are not going to increase the amount of toxic material enough to matter whatsoever.
Earth's atmosphere is around 5 x 10^18 kg. All the satellites put together are not going to increase the amount of toxic material enough to matter whatsoever.
If you are concerned about metal oxide dust, then you would want to shut down every blast furnace in the world, and also pave over the Sahara, since it throws millions of tons of iron oxide dust into the air every year: https://en.wikipedia.org/wiki/Saharan_dust
> Also pave over the Sahara, since it throws millions of tons of iron oxide dust into the air every year
And at the same time fuck up our planet in a major way. There is a lot of life dependent on the plant on that dust. Everything from micro organisms in the sea, the Amazon gets its phosphorus from it, etc (it is a long list of things).
And at the same time fuck up our planet in a major way. There is a lot of life dependent on the plant on that dust. Everything from micro organisms in the sea, the Amazon gets its phosphorus from it, etc (it is a long list of things).
[deleted]
Here's an awesome diagram of all tracked space debris from 1959 to 2021 showing the constant cleaning by drag happening at lower orbits. It's the higher ones we really need to care about.
https://www.reddit.com/r/space/comments/ld4vlq/gabbard_diagr...
https://www.reddit.com/r/space/comments/ld4vlq/gabbard_diagr...
So... this means we could theoretically handle the outer orbit space junk problem by putting more gas in those orbits!
This would increase the "drag" and deorbit debris in higher orbit much faster. My physics intuition says it would affect smaller things much more than bigger, which is what you'd want.
If it can ever be practical, I don't know, but conceptually that works, right?
This would increase the "drag" and deorbit debris in higher orbit much faster. My physics intuition says it would affect smaller things much more than bigger, which is what you'd want.
If it can ever be practical, I don't know, but conceptually that works, right?
That's an amazing visual. Really helps to inform the debate. (Watch on full screen).
Was waiting for that time in the '00s when China conducted an anti-satellite missile test. Did not disappoint.
Let's not do that again.
Let's not do that again.
Can someone explain the reason for the mirror across the diagonal? Is there some altitude/velocity ratio that causes debris to spiral outward vs inward?
The mirror line would be a circular orbit, this plots each tracked orbiting debris with two dots, the blue dot being the lowest altitude of the orbit and red the highest.
I'm not an expert BUT...
I suspect the diagonal line between the colors represents the duration of a stable orbit at that altitude. Anything with a more elliptical orbit will drag when it's in the closer phase and decay. Anything with a lower orbit is already slowing to a tighter orbit (and more drag on the denser atmosphere).
I suspect the diagonal line between the colors represents the duration of a stable orbit at that altitude. Anything with a more elliptical orbit will drag when it's in the closer phase and decay. Anything with a lower orbit is already slowing to a tighter orbit (and more drag on the denser atmosphere).
Thank you for showing me the coolest graph I have ever seen.
Wow. Am I interpreting that correctly? Lower orbit stuff falls out of orbit pretty fast while the higher orbit stuff just kind of stays there.
Basically, yes. The atmosphere is a gradient, and the nearer you are, the higher the drag, and the faster you slow down.
I think you're interpreting it a little wrong.
While it does look like 500km is about where things fall out quickly, it also looks like there's a sweet spot of altitude to orbital period ratio where stuff just stays there. Outside of that sweet spot stuff still falls out fairly quickly.
While it does look like 500km is about where things fall out quickly, it also looks like there's a sweet spot of altitude to orbital period ratio where stuff just stays there. Outside of that sweet spot stuff still falls out fairly quickly.
I'm not 100% sure I'm interpreting your comment correctly, but higher orbits will always decay more slowly, all other things being equal. There's just far less atmosphere to bleed off the energy.
Edit: I think I now understand what you mean, but I suspect you're not realizing that every satellite appears twice on the chart: once in blue, for its periapsis (perigee, i.e. low point of its orbit), and once in red, for its apoapsis (apogee, i.e. high point of its orbit). You're probably noticing that some of the red dots, at high altitude, are decaying quickly, but that's because the corresponding blue dots are at low altitude.
Note also that orbital period is a monotonic function of altitude. More precisely, the square of orbital period goes with the cube of the semi-major axis (the long axis of the orbital ellipse).
Edit: I think I now understand what you mean, but I suspect you're not realizing that every satellite appears twice on the chart: once in blue, for its periapsis (perigee, i.e. low point of its orbit), and once in red, for its apoapsis (apogee, i.e. high point of its orbit). You're probably noticing that some of the red dots, at high altitude, are decaying quickly, but that's because the corresponding blue dots are at low altitude.
Note also that orbital period is a monotonic function of altitude. More precisely, the square of orbital period goes with the cube of the semi-major axis (the long axis of the orbital ellipse).
I see what you're saying, and you're right, I am mistaken. Thanks!
>> launch stuff to very low orbits.
>>Even if they go offline or got hit, the debris would have a very restricted lifetime.
That approach can help, but the problem persists. Lower orbits are much smaller than higher orbits. Focusing megaconstellations into a narrow 100-110km band is asking for trouble. The kessler syndrome could occur in a very narrow band, quickly rendering even short-lived satellites uneconomical. The narrower the band of orbits, the more likely and more aggressive kessler becomes. It is one thing to loose a few sats every year, very much another to have your entire constellation wiped out every year.
That approach can help, but the problem persists. Lower orbits are much smaller than higher orbits. Focusing megaconstellations into a narrow 100-110km band is asking for trouble. The kessler syndrome could occur in a very narrow band, quickly rendering even short-lived satellites uneconomical. The narrower the band of orbits, the more likely and more aggressive kessler becomes. It is one thing to loose a few sats every year, very much another to have your entire constellation wiped out every year.
You can't have a stable orbit at 110km. The atmosphere is much too thick. You'll need at least twice that, and likely more to maintain vehicle attitude unless you have a very smooth drag profile, which is uncommon in orbital craft.
If you are low enough, Kessler is simply not possible because square-cube scaling means that the fragments deorbit in less than a single orbit.
> Lower orbits are much smaller than higher orbits.
Not "much".
A 1200 km circular orbit is ~10% longer than a 550 km one, so a max of ~20% more "room" in the larger orbital shell.
The quicker de-orbiting of debris from the lower shell more than makes up for this IMHO.
Not "much".
A 1200 km circular orbit is ~10% longer than a 550 km one, so a max of ~20% more "room" in the larger orbital shell.
The quicker de-orbiting of debris from the lower shell more than makes up for this IMHO.
Not longer, three dimensions. Low orbits range from about 110 to 200km. The next range, from 200 to a few thousand km is vastly larger in three dimensions.
[deleted]
All I had to do is play a little Kerbal Space Program to understand how difficult it would be to clean up space junk in orbit. Orbit isn't like some 3D grid where you stick a roomba up there, and have it go back and forth until you get everything. Even if you have the technology that lets you grab anything you encounter, you first have to reach something. And then burn some fuel to match its orbit. And then burn some fuel to get to the next thing. And then burn some fuel to match that thing's orbit (more than before because you are now carrying more mass around).
It might be better to keep everything up there. Assuming the junk is re-usable in some way: If one day, we do manage to build some kind of industry in orbit, it will need to consume raw materials, and having all this scrap in orbit already means you saved most of the energy cost it would have taken to get all that mass up there.
It might be better to keep everything up there. Assuming the junk is re-usable in some way: If one day, we do manage to build some kind of industry in orbit, it will need to consume raw materials, and having all this scrap in orbit already means you saved most of the energy cost it would have taken to get all that mass up there.
In theory you could do it without completely matching orbits to save a lot of fuel. Just getting a close slow encounter, grabbing it and letting your orbit just be whatever the new average of your velocities is. It'd require a stronger capture system perhaps depending on the mass of your capture vehicle, but it would save a lot of fuel.
Recycling what's up there might eventually be viable but for the start we'll be shipping up raw stocks. Recycling is probably about as difficult as refining from metal rich asteroids once you consider all the coatings and paints that are added to things and having to sort all the different metals, plastics, and what have you out.
Recycling what's up there might eventually be viable but for the start we'll be shipping up raw stocks. Recycling is probably about as difficult as refining from metal rich asteroids once you consider all the coatings and paints that are added to things and having to sort all the different metals, plastics, and what have you out.
Sorry, not practical. Intercepting debris requires FAR more delta-v than you may expect. Changing the plane of your orbit is so expensive you just don't do it. Its cheaper to just launch a new satellite in a different plane. For example, to intercept hubble from the ISS (or vice-versa) you are looking at a velocity change of a bit over 3000m/sec. Compare that to delta-v of just over 9000 m/sec to reach the ISS from the surface of earth.
Lets say you are in a really, really close orbit to your target and you only need to spend delta-v of 100m/sec to intercept . If you only use 90% of the fuel you'd need to perfectly match orbits then you are still going to impact your target at 10m/sec. Thats 36 km/h, which is a very violent collision. You aren't going to just grab your target on the way past.
Lets say you are in a really, really close orbit to your target and you only need to spend delta-v of 100m/sec to intercept . If you only use 90% of the fuel you'd need to perfectly match orbits then you are still going to impact your target at 10m/sec. Thats 36 km/h, which is a very violent collision. You aren't going to just grab your target on the way past.
I know plane changes are a real problem but you can get nearly velocity intercepts without matching orbits. The timing is brief but to objects on dissimilar orbits can come to a relative standstill for brief periods when their orbits are setup properly.
Also 36 km/h isn't /that/ fast you could have a capture mechanism that absorbs that impact or where it doesn't matter like a net.
Also 36 km/h isn't /that/ fast you could have a capture mechanism that absorbs that impact or where it doesn't matter like a net.
Sorry, I have no idea what you are talking about. I can't see how two objects on dissimilar orbits could possibly be at a standstill relative to each other.
I mean, if they are at a standstill relative to each other then their orbits would be identical??
I mean, if they are at a standstill relative to each other then their orbits would be identical??
I think the much more likely method would be a laser that heats one side of an object, causing a net propulsive effect leading to eventual deorbit.
https://en.wikipedia.org/wiki/Laser_broom
https://en.wikipedia.org/wiki/Laser_broom
Directed energy approaches are the only thing that will scale IMHO.
The heating approach is one way, but I believe something that could use the kinetic energy of ablative laser pulses would work for smaller objects. To get the correct retrograde velocity, however, I believe you would need an orbital platform and some ridiculous laser technology (which, when combined, tend to create political drag)
I also wonder about sending focused packets of ionized gas to collide with an object and reduce its kinetic energy. If you were operating in an opposite orbit you'd have a ~35km/sec closing velocity. Then spit out small targeted puffs of krypton/xenon at 50km/s, it wouldn't take a lot to knock real energy off of the target. (Stubby pencil work says 80 femtojoules per molecule or roughly 30 micrograms of gas to reduce the velocity of a 20g bolt by 1000m/s. I think.)
The heating approach is one way, but I believe something that could use the kinetic energy of ablative laser pulses would work for smaller objects. To get the correct retrograde velocity, however, I believe you would need an orbital platform and some ridiculous laser technology (which, when combined, tend to create political drag)
I also wonder about sending focused packets of ionized gas to collide with an object and reduce its kinetic energy. If you were operating in an opposite orbit you'd have a ~35km/sec closing velocity. Then spit out small targeted puffs of krypton/xenon at 50km/s, it wouldn't take a lot to knock real energy off of the target. (Stubby pencil work says 80 femtojoules per molecule or roughly 30 micrograms of gas to reduce the velocity of a 20g bolt by 1000m/s. I think.)
The gas idea is interesting, and gave me another idea. Assuming that you could track an object, I wonder how much much you could slow down/redirect debris using air resistance. The idea would be to fill a balloon with air, and then release the air at exactly the right moment just as the debris is passing. The air shoots out into the vacuum right into the path of the oncoming debris. If you got the timing and positioning just right, you could probably both slow down and redirect the debris earthward. These things could use their pressurized air for maneuvering themselves, and given that they just use air itself, you could probably devise an efficient means of refueling them via some kind of weather balloon thing where you'd refill at high atmosphere without having to go all the way back to earth.
I have no idea what I'm talking about really, but its a sort of interesting concept...
I have no idea what I'm talking about really, but its a sort of interesting concept...
>I have no idea what I'm talking about really, but its a sort of interesting concept...
Me neither, fortunately we don't have the burden of actually having to solve this problem xD. The big bubble o' gas idea is honestly where I started and I think there's real merit to the idea...it's relatively harmless to operational satellites yet operates rather indiscriminately on debris and isn't as finicky as the directed energy options. Basically a fly trap for space.
Me neither, fortunately we don't have the burden of actually having to solve this problem xD. The big bubble o' gas idea is honestly where I started and I think there's real merit to the idea...it's relatively harmless to operational satellites yet operates rather indiscriminately on debris and isn't as finicky as the directed energy options. Basically a fly trap for space.
How would you prevent the puff of gas from diffusing into nothing?
Where did you get ~35km/sec? ISS orbital speed is 7.66 km/s and it only gets slower the higher you go up.
I was thinking something similar but instead launching equivalent mass of water in the exact same orbit in the opposite direction. Right before the collision, release the water. The water would spread enough that the entire spacecraft would basically slam into a wall. The net momentum post collision should be 0. Most spacecraft debris would fall straight down to earth.
I was thinking something similar but instead launching equivalent mass of water in the exact same orbit in the opposite direction. Right before the collision, release the water. The water would spread enough that the entire spacecraft would basically slam into a wall. The net momentum post collision should be 0. Most spacecraft debris would fall straight down to earth.
Quick caveat, I'm extremely shallow in my knowledge of any of this:
>How would you prevent the puff of gas from diffusing into nothing?
My thinking about this is that at low concentrations the gas would maintain a largely ballistic trajectory and not be subject to typical diffusion properties. Would require a purpose-built accelerator to condition for 'beam' coherency. Not sure how well that scales.
> Where did you get ~35km/sec? ISS orbital speed is 7.66 km/s and it only gets slower the higher you go up.
Major brain-o.
Ultimately I think we're on the same page of 'kinetic deorbit', just a function of what is actually feasible.
>How would you prevent the puff of gas from diffusing into nothing?
My thinking about this is that at low concentrations the gas would maintain a largely ballistic trajectory and not be subject to typical diffusion properties. Would require a purpose-built accelerator to condition for 'beam' coherency. Not sure how well that scales.
> Where did you get ~35km/sec? ISS orbital speed is 7.66 km/s and it only gets slower the higher you go up.
Major brain-o.
Ultimately I think we're on the same page of 'kinetic deorbit', just a function of what is actually feasible.
I assume you are proposing to launch these packets from some other sattelite? Then by conservation of momentum, you will be boosting your own orbit by the same amount you are diminishing the target, right? Not sure this would be a very sustainable model.
Yes it would require equal/opposite correction and lots of mass on board to send.
There's another game that I think really goes to show orbital mechanics in how a little for longer is better (in controlibility) than faster for shorter. It's one of those low action games, so if you're into FPS, probably not your cup of tea. There are a couple of levels specifically for the oribiting examples.
https://apps.apple.com/us/app/osmos-for-ipad/id379323382
https://apps.apple.com/us/app/osmos-for-ipad/id379323382
I believe I saw a Scott Manley video recently where he mentioned that he does consulting work for people, and one of his customers apparently doesn't know about KSP because he built their simulation in something like a day and they were astonished that he was done already.
Most of the SpaceX commentators use it too.
It's always cool to me when something meant as a toy gets used for real. Like city planners practicing in SimCity or more recently CitySkylines.
Most of the SpaceX commentators use it too.
It's always cool to me when something meant as a toy gets used for real. Like city planners practicing in SimCity or more recently CitySkylines.
It should be noted that Kerbal Space Program's orbital mechanics are not all that realistic, especially when you introduce the three-body problem. The world of KSP is also scaled down to about 1/10 of real life unless you use mods. A game like Orbiter really reinforces how much harder the problems are at real-life scale.
It always struck me as weird that you have to mod KSP just to make gravity assists work accurately or Lagrange points work at all.
The default physics model in KSP was chosen for its computational simplicity, which allows for the extensive maneuver planning tools without requiring high-end hardware to continually re-run n-body simulations at several orders of magnitude faster than realtime.
You don't need high-end hardware to do an approximate simulation of a handful of gravitational sources. Also it wouldn't be terrible if maneuver nodes took a tenth of a second to update, and they weren't even in the game for a significant while.
Worth noting that the game came out in 2011, and they wanted people to be able to play it on laptops. They were aiming for really minimal computation.
I mean it's the actual craft physics that are hard to calculate and bog down computers, and you'll never be doing those and orbit fast-forwarding at the same time.
For those that haven't seen the video, he consulted on the Netflix film 'Stowaway' (that comes out later this month). He whipped up a design for the proposed spacecraft in a few minutes to help the directors visualize it better.
Video: https://www.youtube.com/watch?v=WCwXJMVVdck
Video: https://www.youtube.com/watch?v=WCwXJMVVdck
The following is based on the assumption that more and more stuff is going into earth orbit over time.
As others have noted, putting satellites in lower orbits, below 500km or so, definitely helps with keeping things tidy.
Beyond that, robust regulation about ensuring that very little or no additional non-useful stuff is placed into orbit is also good. That is, require everything that isn't useful to deorbit right away or relatively quickly, and have the ability to deorbit at EOL.
What's beyond all that is the set of all things in orbits that aren't useful and that will naturally stay up there for a long time, in addition to any NEW stuff that's added, either by error or by accident. For example, a satellite in a 1000km orbit that has everything it needs to deorbit at the ends of its life, but fails to do so for whatever reason.
As others have noted, matching orbits is a lot harder than most people realize. Specifically, it's quite energy intensive.
At this point, basic physics tells us what we must do. In order to get long-lived, useless stuff out of orbit, we need to be able to send up specifically designed stuff, and a lot of it.
In summary: the most fundamental solution to this problem is to vastly decrease the price per kg to orbit. Regulation helps, but does nothing to clean up what's already there, and to resolve the unintended addition of new junk.
Summary to the summary: the newest crop of launch providers are aggressively working on this problem by aggressively pursuing reusability.
As others have noted, putting satellites in lower orbits, below 500km or so, definitely helps with keeping things tidy.
Beyond that, robust regulation about ensuring that very little or no additional non-useful stuff is placed into orbit is also good. That is, require everything that isn't useful to deorbit right away or relatively quickly, and have the ability to deorbit at EOL.
What's beyond all that is the set of all things in orbits that aren't useful and that will naturally stay up there for a long time, in addition to any NEW stuff that's added, either by error or by accident. For example, a satellite in a 1000km orbit that has everything it needs to deorbit at the ends of its life, but fails to do so for whatever reason.
As others have noted, matching orbits is a lot harder than most people realize. Specifically, it's quite energy intensive.
At this point, basic physics tells us what we must do. In order to get long-lived, useless stuff out of orbit, we need to be able to send up specifically designed stuff, and a lot of it.
In summary: the most fundamental solution to this problem is to vastly decrease the price per kg to orbit. Regulation helps, but does nothing to clean up what's already there, and to resolve the unintended addition of new junk.
Summary to the summary: the newest crop of launch providers are aggressively working on this problem by aggressively pursuing reusability.
"Not going smoothly" is weird phrasing - it's not "going" at all. It's still in the technology development phase, and meanwhile there is still insufficient consensus that more dramatic action needs to be taken.
I know the article touches on these points, I am mostly just commenting on the strange headline.
I know the article touches on these points, I am mostly just commenting on the strange headline.
This is the premise of _Planetes_ if anyone is an anime fan here.
> if anyone is an anime fan here.
Or manga, it's originally a manga series before the 26-episode anime adaptation.
The anime actually diverges from the manga in the latter section, because it was started before the series had ended (the manga finished serialisation in January 2004, the anime finished airing in February of the same year… and it was a 26ep full-season thing), so viewing both can be interesting in more ways than the usual watching of filler and interest in cross-media adaptation:
> While the manga deals more with existential themes, and humanity's relationship with space, the anime further expands the political elements of the story.
Or manga, it's originally a manga series before the 26-episode anime adaptation.
The anime actually diverges from the manga in the latter section, because it was started before the series had ended (the manga finished serialisation in January 2004, the anime finished airing in February of the same year… and it was a 26ep full-season thing), so viewing both can be interesting in more ways than the usual watching of filler and interest in cross-media adaptation:
> While the manga deals more with existential themes, and humanity's relationship with space, the anime further expands the political elements of the story.
The manga feels much more personal, by which I mean the author likes to put in moralistic side stories, but he's not very good at it and I couldn't figure out what the moral was supposed to be. Sometimes he also stops the story so everyone can stand around discussing Kenji Miyazawa novels.
bomb ass opening theme song, for real.
It might be silly that it wasn't until watching this anime (and the whole premise for WHY space junk removal was/is so dangerous as shown by the show) that I fully "understood" the problem with space junk. It was good show on it's own as well but it really made the "space junk" click for me.
Love Planetes, I always tell my friends its Gravity done right.
Man I love Planetes, such a good series! They put some effort into keeping it realistic too: https://en.wikipedia.org/wiki/Planetes#Realism
Also Anime; the much looser Gundam anime (particularly Gundam 00) and James Bond films (was it at least two now?) made me think of using super solar collection weapons.
The 'weapon' would reflect sunlight and 'shave' against cross-sections of the edge of earth's orbital spheres. Solar sail like light pressure would slowly nudge objects to either slower, or more erratic orbits where they'd drag and get lower.
The 'weapon' would reflect sunlight and 'shave' against cross-sections of the edge of earth's orbital spheres. Solar sail like light pressure would slowly nudge objects to either slower, or more erratic orbits where they'd drag and get lower.
ＹＥＳ
I love the vibe of that show so so much.
Netflix has the South Korean SF flick "Space Sweeper". Do read the serious article first. The film is for entertainment. Crossing Belter and cyberpunk aesthetics, mixing up human languages as you'd expect from the future, it's fun.
Warning, link autoplays with sound: https://www.imdb.com/video/vi1534902553?playlistId=tt1283876...
Warning, link autoplays with sound: https://www.imdb.com/video/vi1534902553?playlistId=tt1283876...
'Catching' a piece of space debris is really a 7-dimensional problem, isn't it?
You have to be in the right place at the right time (4), but if you have the wrong velocity (+3) you just end up causing the very problem you're trying to prevent.
You have to be in the right place at the right time (4), but if you have the wrong velocity (+3) you just end up causing the very problem you're trying to prevent.
I think there has to be a way around this, at least for the small stuff. You ought to be able to catch flecks of paint and the like with a Whipple shield backed by a plate of steel. Or maybe the same kind of aerogel setup they use for collecting comet tails.
I think we have done some experiments with that already but I can’t recall what the outcomes were.
http://stuffin.space/
For some context of the amount of 'stuff' in space..
This does include debris also. It's a serious amount.
There is an incredible amount of Iridium from the mentioned collision :
http://stuffin.space/?search=1999-037
For some context of the amount of 'stuff' in space..
This does include debris also. It's a serious amount.
There is an incredible amount of Iridium from the mentioned collision :
http://stuffin.space/?search=1999-037
Space Junk has been an issue for "rocket scientists" since the 1980s. The consensus even back than was that it's really not doable simply due to physics and the volume of "space" in orbit. The only viable strategy identified was to design launched objects to re-enter and burn up. But that was only started with DOD and NASA - nothing could be assured that the USSR/Russia or China would ever do the same. And the military always kept the option to put national defense ahead of this as well.
I always look in articles about space junk for any inkling of addressing the fundamental physics issues we identified back in the 1980s and I've yet to ever see those mentioned. It's always some shallowly thought-out, gee-whiz ideas by someone who's never actually worked in the field. Elon Musk-style.
I always look in articles about space junk for any inkling of addressing the fundamental physics issues we identified back in the 1980s and I've yet to ever see those mentioned. It's always some shallowly thought-out, gee-whiz ideas by someone who's never actually worked in the field. Elon Musk-style.
I want to know the collective mass of this 'space junk'.
It is indeed unusable now, but it is a lot of highly refined matter that is already high in the earth's gravity well.
The question is whether whether enough of it exists that it could become useful, or even profitable, to reuse/recycle it.
Once you've gotten a herding satellite to rendezvous and dock/grab the junk, how much extra energy is needed to park it in a useful common orbital location for later reuse/recycling, vs making it new on the ground and lifting it out of the gravity well again?
Seems it could be a profitably exploitable resource, if the scale is right?
It is indeed unusable now, but it is a lot of highly refined matter that is already high in the earth's gravity well.
The question is whether whether enough of it exists that it could become useful, or even profitable, to reuse/recycle it.
Once you've gotten a herding satellite to rendezvous and dock/grab the junk, how much extra energy is needed to park it in a useful common orbital location for later reuse/recycling, vs making it new on the ground and lifting it out of the gravity well again?
Seems it could be a profitably exploitable resource, if the scale is right?
It's not much and it's definitely not profitable.
The vast majority of space junk (by number) is small pieces of metal, bolts, specks of paint, that sort of thing.
The few bigger things are rocket stages, decommissioned satellites, and larger collision fragments.
The problem is that the most dangerous debris (e.g. debris that doesn't deorbit on its own anytime soon) orbits between 2000km and GEO at varying inclinations.
These orbits are difficult to get to and the debris is worth nothing compared to the energy you'd have to spend to catch it.
The value of the debris itself is comparable to the value of junk here on Earth.
Unless space faring nations are paying for removal, I cannot see any scenario in which the ~8,000 metric tons of space debris [0] can be collected and recycled at a profit. It's just too difficult and costly to do.
[0] https://trumpwhitehouse.archives.gov/wp-content/uploads/2021...
The vast majority of space junk (by number) is small pieces of metal, bolts, specks of paint, that sort of thing.
The few bigger things are rocket stages, decommissioned satellites, and larger collision fragments.
The problem is that the most dangerous debris (e.g. debris that doesn't deorbit on its own anytime soon) orbits between 2000km and GEO at varying inclinations.
These orbits are difficult to get to and the debris is worth nothing compared to the energy you'd have to spend to catch it.
The value of the debris itself is comparable to the value of junk here on Earth.
Unless space faring nations are paying for removal, I cannot see any scenario in which the ~8,000 metric tons of space debris [0] can be collected and recycled at a profit. It's just too difficult and costly to do.
[0] https://trumpwhitehouse.archives.gov/wp-content/uploads/2021...
For all the people saying that there's no issue with thing in very low orbits, I'm going to suggest considering the following issues.
1. When that busy ~500km orbit has a collision, some pieces might be kicked up to higher orbits where they pose a risk to other satellites. There's also important things in lower orbits, like ISS.
2. Every satellite that falls back to earth from any orbital altitude has to pass through very low earth orbit.
Between 1 and 2, the debris is never going to be confined to low orbits where everything decays quickly.
1. When that busy ~500km orbit has a collision, some pieces might be kicked up to higher orbits where they pose a risk to other satellites. There's also important things in lower orbits, like ISS.
2. Every satellite that falls back to earth from any orbital altitude has to pass through very low earth orbit.
Between 1 and 2, the debris is never going to be confined to low orbits where everything decays quickly.
"And the problem is now poised to get much worse because of the rise of satellite “mega constellations” requiring thousands of spacecraft, such as SpaceX’s Starlink..
..It takes an Iridium-Cosmos-type collision to get everyone’s attention. That’s what it boils down to.... And we’re overdue for something like that to happen."
Perhaps the former is gentler, more statistical an alternative to the latter. Everybody be so cataclysmic these days.
..It takes an Iridium-Cosmos-type collision to get everyone’s attention. That’s what it boils down to.... And we’re overdue for something like that to happen."
Perhaps the former is gentler, more statistical an alternative to the latter. Everybody be so cataclysmic these days.
I'm confused by the photo. Newtonian impact depth says an impactor of equal density to the target will only penetrate to its own length. How come the aluminum ball clearly went way deeper than that?
That first picture: wouldn't that sphere deform as well?
I would guess so (like a bullet). I suspect they placed a second ball for illustration.
I think you are correct. The original ball is what appears like a paint splatter inside the deformed area.
I assume they put another sphere in the hole for the purposes of the picture.
It's probably not the aluminum sphere that was used in the impact but included for reference to allow readers to visualize the effect of impact versus the size of the debris.
[deleted]
[deleted]
As other have said it's likely a second sphere there for illustration purposes. Also, I wonder if the original sphere would outright vaporize or melt into the block.
As other comments point out, the sphere would have immediately vaporized. Similar reason behind most impact craters being circular. Scott Manley has a nice explainer: https://www.youtube.com/watch?v=BCGWGJOUjHY
I predict we will be just as successful in looking after space as we have been with the planet. So no worries.
Anyone who knows stuff about this, could LEO debris become dangerous for commercial airplanes?
No. At the height airplanes fly, any debris would just be falling almost straight down, if it even makes it that far (I think most would just burn up in the atmosphere anyway).
The reason debris in LEO is dangerous is because it's going really, really fast and continually orbiting for years so if there's enough of it eventually you'll run into something.
The reason debris in LEO is dangerous is because it's going really, really fast and continually orbiting for years so if there's enough of it eventually you'll run into something.
Yeah that's what I'm wondering: if there's enough debris in LEO is there any danger that small/not fully burned pieces going down at high speed would pierce airplanes?
I have no idea what kind of volume/probability we're talking about...
And after all those warnings. https://www.youtube.com/watch?v=1REkejAMnNo
This is amazing too
mesofile(3)
Who would have thought...
>And the problem is now poised to get much worse because of the rise of satellite “mega constellations” requiring thousands of spacecraft, such as SpaceX’s Starlink, a broadband Internet network.
really could have used a LOT more qualification particularly since it's become a major recent talking point. There is one ultimate sure-fire way to reduce space junk: launch stuff to very low orbits. There is still some atmosphere (varying with heating and other factors) up a long ways in "space", and it's only above 600km or so that orbital drag becomes negligible enough that lifetimes really stretch out. The ISS for example requires regular reboosts or it would decay back into the atmosphere.
SpaceX focusing on economics has made it feasible to start planning constellations of comm sats that are low and very low earth orbit, with the understanding that inherently their lifetimes will be measured in single digit years. But that's ok since they can be replaced so cheaply. This is much better, not worse. Even if they go offline or got hit, the debris would have a very restricted lifetime. The media should do a better job of conveying how cheaper $/kg to LEO opens up a lot of new possibilities in what regulations are feasible and how we think about the basics of satellite design. A simple "Mega constellation bad!" is all wrong, and that's not necessarily going to be intuitive to everyone.