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> the Starlink sats are so low that they dont really turn very meaningful debris ever. Is that right? Scientific American seemed to think it could be a problem

> the Starlink sats are so low that they dont really turn very meaningful debris ever. Is that right? Scientific American seemed to think it could be a problem in 2019[1]. Space.com says Starlink satellites orbit at an altitude of about 342 miles (550 kilometers)[2]. And the Wikipedia article on Kessler Syndrome[3] (which is a chain reaction of satellite debris) mentions an incident at 555km that was problematic: "In 1985, the first anti-satellite (ASAT) missile was used in the destruction of a satellite. The American 1985 ASM-135 ASAT test was carried out, in which the Solwind P78-1 satellite flying at an altitude of 555 kilometres was struck by the 14-kilogram payload at a velocity of 24,000 kilometres per hour (15,000 mph; 6.7 km/s). When NASA learned of U.S. Air Force plans for the Solwind ASAT test, they modeled the effects of the test and determined that debris produced by the collision would still be in orbit late into the 1990s. It would force NASA to enhance debris shielding for its planned space station." [1] https://www.scientificamerican.com/article/spacexs-starlink-could-cause-cascades-of-space-junk/ https://www.scientificamerican.com/article/spacexs-starlink-... [2] https://www.space.com/spacex-starlink-satellites.html https://www.space.com/spacex-starlink-satellites.html [3] https://en.wikipedia.org/wiki/Kessler_syndrome https://en.wikipedia.org/wiki/Kessler_syndrome

nordsieck 3y ago
Space junk at that altitude does turn into debris, but it tends to deorbit on its own in around 5-10 years. The real danger is space junk that's at much higher altitudes. OneWeb and Telesat Lightspeed (in planning) operate at 1000+ km, where space junk will take 1000+ years to deorbit on its own. And OneWeb has already had a satellite failure where it can't deorbit the satellite.
montagg 3y ago
I don’t have references for this, but my understanding is that you have more to worry about space debris that is higher/faster than lower/slower. The atmospheric drag is such that any out of control craft at [some threshold] or under will deorbit themselves fairly quickly, and the debris will burn up entirely. I believe that threshold is around 450-500km, but it’s also probably not a literal height, more of a gradient of risk. Higher/faster, they will be up there for longer (years? decades?) and it’s harder to predict where any broken pieces will go over time.
- ninjanomnom 3y ago
  Higher orbits are slower, not faster. Very low orbits as you say though are less an issue due to atmospheric drag deorbiting debris. A bit higher and debris will stay up much longer, even higher up though and there's so much room we can't possibly put out enough material to fill the orbits yet. The mid point of that scale is the dangerous region.
  - quailfarmer 3y ago
    Higher altitude orbits are slower in angular velocity, but faster in linear velocity, assuming a circular orbit. Faster debris ends up in higher orbit.
    - d_tr 3y ago
      Higher altitude circular orbits are slower in linear velocity too. Look it up or work it out by equating the centripetal force with the gravitational attraction, which is the condition for a circular orbit.
panick21_ 3y ago
The decay where the waste majority of it is gone in 10 years is just not long enough to meaningfully have a Kessler syndrom. The reality humanity wouldn't even have the launch capacity to put enough into orbit in that time period for it to matter. The real concern for meaningful space debris issues is in the regions where decay requires 100+ of years. The articles mentions the ASAT because that's what they used to study orbital behavior and decay. Also generally, Space.com is universally agree to be the single worst 'space news' page known. I would never use it as a source for anything.
- jcims 3y ago
  just because I appreciate it when people do it for me waste -> vast https://www.merriam-webster.com/dictionary/vast https://www.merriam-webster.com/dictionary/vast
  - s3p 3y ago
    Thank you for this. Is 'waste' used in a specific vernacular? I've never heard of someone saying waste instead of vast before.
    - deleted 3y ago
      [deleted]
    - RheingoldRiver 3y ago
      No, it was almost certainly a typo. There is no condition under which "waste majority" makes sense, but the poster was talking about waste, and the two words share 3 letters in common, so an easy mistake to make when typing quickly. But for anyone who's not 100% comfortable with English, "the vast majority" is not simply a case of a descriptive adjective modifying the noun "majority," but it's actually a common phrase. People don't say "the big majority" or "the large majority," it's specifically "the vast majority." If you wanted to use a different adjective, you could say "a large majority," and that would mean something like "most but not all and the 'but not all' is kind of significant" where as "the vast majority" means "nearly all of them, and the 'not all' is insignificant."
samus 3y ago
Most satellites are deorbited in a planned fashion and thus generate very little if any space debris. If the orbit is low enough, the orbit will decay by themselves by aerodynamic braking after a few years. Compared to that, anti-satellite missile bust a satellite into pieces and carry indeed the danger of creating a Kessler syndrome. In case these would be used on a large scale, WW III would be imminent anyways. Apart from that, missiles are too expensive to knock out Starlink satellites, and the latter are comparatively easy to replace.

nordsieck 3y ago

Space junk at that altitude does turn into debris, but it tends to deorbit on its own in around 5-10 years. The real danger is space junk that's at much higher altitudes. OneWeb and Telesat Lightspeed (in planning) operate at 1000+ km, where space junk will take 1000+ years to deorbit on its own. And OneWeb has already had a satellite failure where it can't deorbit the satellite.

montagg 3y ago

I don’t have references for this, but my understanding is that you have more to worry about space debris that is higher/faster than lower/slower. The atmospheric drag is such that any out of control craft at [some threshold] or under will deorbit themselves fairly quickly, and the debris will burn up entirely. I believe that threshold is around 450-500km, but it’s also probably not a literal height, more of a gradient of risk. Higher/faster, they will be up there for longer (years? decades?) and it’s harder to predict where any broken pieces will go over time.

ninjanomnom 3y ago
Higher orbits are slower, not faster. Very low orbits as you say though are less an issue due to atmospheric drag deorbiting debris. A bit higher and debris will stay up much longer, even higher up though and there's so much room we can't possibly put out enough material to fill the orbits yet. The mid point of that scale is the dangerous region.
- quailfarmer 3y ago
  Higher altitude orbits are slower in angular velocity, but faster in linear velocity, assuming a circular orbit. Faster debris ends up in higher orbit.
  - d_tr 3y ago
    Higher altitude circular orbits are slower in linear velocity too. Look it up or work it out by equating the centripetal force with the gravitational attraction, which is the condition for a circular orbit.

panick21_ 3y ago

The decay where the waste majority of it is gone in 10 years is just not long enough to meaningfully have a Kessler syndrom. The reality humanity wouldn't even have the launch capacity to put enough into orbit in that time period for it to matter. The real concern for meaningful space debris issues is in the regions where decay requires 100+ of years. The articles mentions the ASAT because that's what they used to study orbital behavior and decay. Also generally, Space.com is universally agree to be the single worst 'space news' page known. I would never use it as a source for anything.

jcims 3y ago
just because I appreciate it when people do it for me waste -> vast https://www.merriam-webster.com/dictionary/vast https://www.merriam-webster.com/dictionary/vast
- s3p 3y ago
  Thank you for this. Is 'waste' used in a specific vernacular? I've never heard of someone saying waste instead of vast before.
  - deleted 3y ago
    [deleted]
  - RheingoldRiver 3y ago
    No, it was almost certainly a typo. There is no condition under which "waste majority" makes sense, but the poster was talking about waste, and the two words share 3 letters in common, so an easy mistake to make when typing quickly. But for anyone who's not 100% comfortable with English, "the vast majority" is not simply a case of a descriptive adjective modifying the noun "majority," but it's actually a common phrase. People don't say "the big majority" or "the large majority," it's specifically "the vast majority." If you wanted to use a different adjective, you could say "a large majority," and that would mean something like "most but not all and the 'but not all' is kind of significant" where as "the vast majority" means "nearly all of them, and the 'not all' is insignificant."

samus 3y ago

Most satellites are deorbited in a planned fashion and thus generate very little if any space debris. If the orbit is low enough, the orbit will decay by themselves by aerodynamic braking after a few years. Compared to that, anti-satellite missile bust a satellite into pieces and carry indeed the danger of creating a Kessler syndrome. In case these would be used on a large scale, WW III would be imminent anyways. Apart from that, missiles are too expensive to knock out Starlink satellites, and the latter are comparatively easy to replace.