5 ms·

If a satellite is in a very low orbit then any debris fall to earth quickly. Almost all cubesats have a orbital life of six to five years. The space station, in

If a satellite is in a very low orbit then any debris fall to earth quickly. Almost all cubesats have a orbital life of six to five years. The space station, in a normal low earth orbit, would hit the earth in around three years without reboosts. The higher you go, the more absolute volume there is, the slower the satellites there travel and the fewer satellites there are. So that leaves a band of mid-upper LEO satellites to consider for Kessler Syndrome. When you have a collision between satellites, the velocity on average of each fragment is less than it was before, making the fragments decay faster. The fragments after each collision are smaller than they were before as well, thus having more air and solar resistance, which also makes them decay faster. The Chinese FY-1C satellite that was blown up was the absolute worst case for a satellite explosion. It was located on the high side of LEO with a decay time measured in human generations, and it was in a super crowded sun-following orbit altitude, sharing space with lots of weather and earth observation satellites. The explosion generated 150,000 debris fragments. In the ten years since, most of those fragments have reentered. We now have 2,000 golfball sized or bigger fragments being tracked, and over the past ten years, the only casualty has been a small, ten pound reflector satellite. Small debris pieces fall, and big pieces can be tracked and avoided. If every satellite we have put into space magically exploded, and the debris was magically moved to a high LEO altitude and evenly distributed to avoid any holes, then we could still launch through this orbit of death to higher altitudes with only a 1 in 1000 probability of impact. Space regulation has gotten much tougher since the bad old days. Satellites are now required to have deorbit or safeing plans, and the median satellites size has gone down by a couple orders of magnitude. Kessler syndrome isn't something that keeps me up at night.

ogre_magi 8y ago
I see so many people around the Internet who smugly explain to their comments section of choice what Kessler Syndrome is, and link the Wikipedia page for it, and almost none of them actually know what they're talking about. Whenever I bring up the density of debris in a given orbit, or the drag characteristics of the debris, they get mad. Everyone should read your comment and realize that it's possible to know a lot more about this than the Wikipedia article tells you, and accept that they are not a special enlightened environmentalist. Kessler Syndrome is not a serious risk for Earth. It would be expensive and difficult to cause a long-lasting debris field that made space launches impossible on purpose. And we're trying to avoid it. Every organization with access to space is taking steps to mitigate space junk, including CNSA.
- Diederich 8y ago
  https://en.wikipedia.org/wiki/Gravity_(2013_film) https://en.wikipedia.org/wiki/Gravity_(2013_film) doesn't help matters, though I did enjoy watching it overall.
- stcredzero 8y ago
  Whenever I bring up the density of debris in a given orbit, or the drag characteristics of the debris, they get mad. That's kind of nuts. You'd think they'd feel relieved, like I just did when I read the top comment. It's like they want environmental disasters to be bad, like they have an ulterior motive.
CompelTechnic 8y ago
I wonder how well the best designed intentional "Kessler weapon" could perform. Some sort of large rocket that would fly to the right orbit height, and orient itself in a manner to ensure it's shaped charge explosives would send maximal debris (ball bearings of the right size) in directions azimuthal to the planet. How many satellites could you knock out if you really tried? Quite an optimization problem for the secret skunkworks folks.
- ogre_magi 8y ago
  >How many satellites could you knock out if you really tried? With a single launch scattering a lot of debris? You could reliably take out ONE satellite. The clouds of debris creating a cascade of destruction as depicted in the movie Gravity are entirely fictional.
  - stcredzero 8y ago
    How about a hundred BFR sized launchers? (Just scaling it up to nation-state/Bond villain levels, out of curiosity.)
    - ogre_magi 8y ago
      That's enough debris to choke off LEO, but it wont stay up there for very long. You'd need to refresh the debris cloud every few decades. Edit to add: The easier and cheaper villainous way to deny spaceflight to someone is just to shoot missiles at their spacecraft.
      - stcredzero 8y ago
        The easier and cheaper villainous way to deny spaceflight to someone is just to shoot missiles at their spacecraft. Missiles can be pretty expensive, and if you go far downscale on cost and capabilities, you'll need to recruit fanatics who are willing to get caught every time a missile is fired at a spacecraft. On the other hand, if the fleet of BFRs grows in numbers, then 100 flights of a BFR might be pretty inexpensive for a military operation that affects all strategic theaters at once. The chief advantage of missiles, would be the ability to not shoot down your own rockets.
tfha 8y ago
You make 1 in 1000 sound peachy. Imagine if you had a 1 in 1000 chance of collision every time your 747 crossed the ocean. In 50 years I hope we are doing 50 space launches a day. At that volume, every single debris item is risk and headache. 10 years later and we've got a full 2,000 golf balls left in orbit? That's a lot. There have actually been casualties to blowing up the FY-1C? That's also significant. These things get worse as we put more in space. If each explosion takes out on average 1 victim satellite per 5,000 satellites, and generates 1/100th the debris of the original explosion, we've got a cascade at just 500,000 total objects in orbit. That may seem like a lot compared to the 5,000 we have today, but already we are discovering materials and technologies that are useful which can only be manufactured in free-fall. If orbital manufacturing ever takes off, 500,000 objects in orbit will be nothing.
- danielvf 8y ago
  The space shuttle had 135 flights, of which 2 were TPK’s. So a 1 in 68 chance of failure. And that’s on a man-rated launch system. The Russians have been having 1 in 10 to 1 in 20 non-human rated rockets failing. So even compared to our non-Kessler Syndrome world, a 1 in 1000 risk is almost insignificant. However, what I’m really comparing it to is the popular perception - that Kessler means hundreds of years of humanity trapped on earth - In which case 999 non-issues in 1000 is fantastic. And that’s with a magical worst case.
- ogre_magi 8y ago
  Dude, actually read. He said: >If every satellite we have put into space magically exploded, and the debris was magically moved to a high LEO altitude and evenly distributed to avoid any holes, then we could still launch through this orbit of death to higher altitudes with only a 1 in 1000 probability of impact. Sorry, but this is a pet peeve of mine. If you don't know anything about orbital mechanics or the fine details of spaceflight, don't smug about Kessler Syndrome. It's really vapid.
nwah1 8y ago
Kessler syndrome isn't an issue now, but as more projects like SpaceX's starlink program go online, it could become one. Starlink's goal is to deploy many thousands of satelites.
- ogre_magi 8y ago
  You have no idea what you're talking about. Those thousands of satellites will be in very low orbits, they will be well-tracked, and will not cause any issues for space access.
  - zbentley 8y ago
    > You have no idea what you're talking about. That's not necessary.
    - ogre_magi 8y ago
      Sorry -- people having very badly informed opinions about spaceflight are a pet peeve. Apologies if I'm being rude. I'll stop commenting.
      - tomhoward 8y ago
        Don't stop making good comments! Just keep within the guidelines (avoid making personal swipes). https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html
- danielvf 8y ago
  Yeah, starlink is planning on putting 8,000 satellites in low LEO, and 4000 in high LEO. The low ones don’t matter but the high ones are certainly worth thinking about.
js2 8y ago
IOW, "Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." (Sorry, I know this isn't a substantive reply but it's all I could think of reading your comment.)
stcredzero 8y ago
If a satellite is in a very low orbit then any debris fall to earth quickly. Almost all cubesats have a orbital life of six to five years. So then it should be possible to shift the world's global satellite infrastructure to low orbits, even if the unlikely worst case would happen. You wouldn't have geosynchronous satellites anymore, but we could work around that. If every satellite we have put into space magically exploded, and the debris was magically moved to a high LEO altitude and evenly distributed to avoid any holes, then we could still launch through this orbit of death to higher altitudes with only a 1 in 1000 probability of impact. Much better odds than flying the Space Shuttle. Much worse odds than flying on an airline. That would still curtail civilization's expansion into space, though it wouldn't stop it.

ogre_magi 8y ago

I see so many people around the Internet who smugly explain to their comments section of choice what Kessler Syndrome is, and link the Wikipedia page for it, and almost none of them actually know what they're talking about. Whenever I bring up the density of debris in a given orbit, or the drag characteristics of the debris, they get mad. Everyone should read your comment and realize that it's possible to know a lot more about this than the Wikipedia article tells you, and accept that they are not a special enlightened environmentalist. Kessler Syndrome is not a serious risk for Earth. It would be expensive and difficult to cause a long-lasting debris field that made space launches impossible on purpose. And we're trying to avoid it. Every organization with access to space is taking steps to mitigate space junk, including CNSA.

Diederich 8y ago
https://en.wikipedia.org/wiki/Gravity_(2013_film) https://en.wikipedia.org/wiki/Gravity_(2013_film) doesn't help matters, though I did enjoy watching it overall.
stcredzero 8y ago
Whenever I bring up the density of debris in a given orbit, or the drag characteristics of the debris, they get mad. That's kind of nuts. You'd think they'd feel relieved, like I just did when I read the top comment. It's like they want environmental disasters to be bad, like they have an ulterior motive.

CompelTechnic 8y ago

I wonder how well the best designed intentional "Kessler weapon" could perform. Some sort of large rocket that would fly to the right orbit height, and orient itself in a manner to ensure it's shaped charge explosives would send maximal debris (ball bearings of the right size) in directions azimuthal to the planet. How many satellites could you knock out if you really tried? Quite an optimization problem for the secret skunkworks folks.

ogre_magi 8y ago
>How many satellites could you knock out if you really tried? With a single launch scattering a lot of debris? You could reliably take out ONE satellite. The clouds of debris creating a cascade of destruction as depicted in the movie Gravity are entirely fictional.
- stcredzero 8y ago
  How about a hundred BFR sized launchers? (Just scaling it up to nation-state/Bond villain levels, out of curiosity.)
  - ogre_magi 8y ago
    That's enough debris to choke off LEO, but it wont stay up there for very long. You'd need to refresh the debris cloud every few decades. Edit to add: The easier and cheaper villainous way to deny spaceflight to someone is just to shoot missiles at their spacecraft.
    - stcredzero 8y ago
      The easier and cheaper villainous way to deny spaceflight to someone is just to shoot missiles at their spacecraft. Missiles can be pretty expensive, and if you go far downscale on cost and capabilities, you'll need to recruit fanatics who are willing to get caught every time a missile is fired at a spacecraft. On the other hand, if the fleet of BFRs grows in numbers, then 100 flights of a BFR might be pretty inexpensive for a military operation that affects all strategic theaters at once. The chief advantage of missiles, would be the ability to not shoot down your own rockets.

tfha 8y ago

You make 1 in 1000 sound peachy. Imagine if you had a 1 in 1000 chance of collision every time your 747 crossed the ocean. In 50 years I hope we are doing 50 space launches a day. At that volume, every single debris item is risk and headache. 10 years later and we've got a full 2,000 golf balls left in orbit? That's a lot. There have actually been casualties to blowing up the FY-1C? That's also significant. These things get worse as we put more in space. If each explosion takes out on average 1 victim satellite per 5,000 satellites, and generates 1/100th the debris of the original explosion, we've got a cascade at just 500,000 total objects in orbit. That may seem like a lot compared to the 5,000 we have today, but already we are discovering materials and technologies that are useful which can only be manufactured in free-fall. If orbital manufacturing ever takes off, 500,000 objects in orbit will be nothing.

danielvf 8y ago
The space shuttle had 135 flights, of which 2 were TPK’s. So a 1 in 68 chance of failure. And that’s on a man-rated launch system. The Russians have been having 1 in 10 to 1 in 20 non-human rated rockets failing. So even compared to our non-Kessler Syndrome world, a 1 in 1000 risk is almost insignificant. However, what I’m really comparing it to is the popular perception - that Kessler means hundreds of years of humanity trapped on earth - In which case 999 non-issues in 1000 is fantastic. And that’s with a magical worst case.
ogre_magi 8y ago
Dude, actually read. He said: >If every satellite we have put into space magically exploded, and the debris was magically moved to a high LEO altitude and evenly distributed to avoid any holes, then we could still launch through this orbit of death to higher altitudes with only a 1 in 1000 probability of impact. Sorry, but this is a pet peeve of mine. If you don't know anything about orbital mechanics or the fine details of spaceflight, don't smug about Kessler Syndrome. It's really vapid.

nwah1 8y ago

Kessler syndrome isn't an issue now, but as more projects like SpaceX's starlink program go online, it could become one. Starlink's goal is to deploy many thousands of satelites.

ogre_magi 8y ago
You have no idea what you're talking about. Those thousands of satellites will be in very low orbits, they will be well-tracked, and will not cause any issues for space access.
- zbentley 8y ago
  > You have no idea what you're talking about. That's not necessary.
  - ogre_magi 8y ago
    Sorry -- people having very badly informed opinions about spaceflight are a pet peeve. Apologies if I'm being rude. I'll stop commenting.
    - tomhoward 8y ago
      Don't stop making good comments! Just keep within the guidelines (avoid making personal swipes). https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html
danielvf 8y ago
Yeah, starlink is planning on putting 8,000 satellites in low LEO, and 4000 in high LEO. The low ones don’t matter but the high ones are certainly worth thinking about.

js2 8y ago

IOW, "Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." (Sorry, I know this isn't a substantive reply but it's all I could think of reading your comment.)

stcredzero 8y ago

If a satellite is in a very low orbit then any debris fall to earth quickly. Almost all cubesats have a orbital life of six to five years. So then it should be possible to shift the world's global satellite infrastructure to low orbits, even if the unlikely worst case would happen. You wouldn't have geosynchronous satellites anymore, but we could work around that. If every satellite we have put into space magically exploded, and the debris was magically moved to a high LEO altitude and evenly distributed to avoid any holes, then we could still launch through this orbit of death to higher altitudes with only a 1 in 1000 probability of impact. Much better odds than flying the Space Shuttle. Much worse odds than flying on an airline. That would still curtail civilization's expansion into space, though it wouldn't stop it.