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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 lau

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?

aftbit 6y ago
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.
ericbarrett 6y ago
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.
- deleted 6y ago
  [deleted]
gumby 6y ago
It’s subject to drag from the whispy atmosphere and relatively quickly de orbits and burns up (thus no junk is left behind)
jkilpatr 6y ago
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.
ortusdux 6y ago
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/Orbital_decay#Atmospheric_drag https://en.wikipedia.org/wiki/Starlink#Space_debris https://en.wikipedia.org/wiki/Starlink#Space_debris
- gregmac 6y ago
  > 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.
  - pilom 6y ago
    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).
  - SideburnsOfDoom 6y ago
    > 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 https://news.ycombinator.com/item?id=26809297
  - 6y ago
myself248 6y ago
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.
- cptskippy 6y ago
  > 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.
- aledalgrande 6y ago
  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?
  - KiwiJohnno 6y ago
    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.
dahfizz 6y ago
> 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.
- ouid 6y ago
  There is literally no problem with plastics that stay in landfills forever. Landfills are underground, like the oil that the plastic is derived from.
  - simonh 6y ago
    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.
    - ouid 6y ago
      Landfills are covered when they are full, effectively isolating them from surface ecosystems.
      - simonh 6y ago
        The point is you can't use that area for getting rid of landfill anymore. From that perspective that area is 'used up'.
        deleted 6y ago
        [deleted]
bombcar 6y ago
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.
- jakear 6y ago
  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.
  - xoa 6y ago
    >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.
ravi-delia 6y ago
It's not less so much as zero. Space junk isn't really a problem to worry about below a certain point.

aftbit 6y ago

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.

ericbarrett 6y ago

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.

deleted 6y ago
[deleted]

gumby 6y ago

It’s subject to drag from the whispy atmosphere and relatively quickly de orbits and burns up (thus no junk is left behind)

jkilpatr 6y ago

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.

ortusdux 6y ago

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/Orbital_decay#Atmospheric_drag https://en.wikipedia.org/wiki/Starlink#Space_debris https://en.wikipedia.org/wiki/Starlink#Space_debris

gregmac 6y ago
> 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.
- pilom 6y ago
  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).
- SideburnsOfDoom 6y ago
  > 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 https://news.ycombinator.com/item?id=26809297
- 6y ago

myself248 6y ago

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.

cptskippy 6y ago
> 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.
aledalgrande 6y ago
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?
- KiwiJohnno 6y ago
  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.

dahfizz 6y ago

> 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.

ouid 6y ago
There is literally no problem with plastics that stay in landfills forever. Landfills are underground, like the oil that the plastic is derived from.
- simonh 6y ago
  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.
  - ouid 6y ago
    Landfills are covered when they are full, effectively isolating them from surface ecosystems.
    - simonh 6y ago
      The point is you can't use that area for getting rid of landfill anymore. From that perspective that area is 'used up'.
      - deleted 6y ago
        [deleted]

bombcar 6y ago

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.

jakear 6y ago
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.
- xoa 6y ago
  >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.

ravi-delia 6y ago

It's not less so much as zero. Space junk isn't really a problem to worry about below a certain point.