3 ms·

Serious comment: I've thought about this idea a lot since I heard about it, and my mind immediately goes to "can't we deflect these things?" Assuming that the

Serious comment: I've thought about this idea a lot since I heard about it, and my mind immediately goes to "can't we deflect these things?" Assuming that the dangerous orbiting debris is in a few "layers" (like a shell at a certain distance from the earth) which conflict with satellites operating at the same layer, it should only come in at any of 360° angles on a semi-2D plane. Like, it's not going to strike a satellite from much of an angle above or below, because then it would by definition not be in orbit, correct? Could we not reasonably launch a series of deflective plates or shields in the same plane through the "danger zones" encircling important satellites, or creating a safe zone for passage with shuttles? Obviously we can't create a ring around the entire globe, nor protect all satellites, but it seems that a few well-placed shields in the worst areas would accumulate a growing "cleanup score" over time.

aidenn0 7y ago
When something hits a deflective plate, it could ablate part of the plate, thus increasing the amount of debris in that particular orbit.
- deleted 7y ago
  [deleted]
mumblemumble 7y ago
> Like, it's not going to strike a satellite from much of an angle above or below, because then it would by definition not be in orbit, correct? It sounds like you're assuming that orbits are typically close to circular. I have no idea how true that is, but I imagine that a Kessler-type chain reaction would tend to make it less true.
- GlenTheMachine 7y ago
  1) it’s not true, and it becomes less true over time. Gravitational perturbations change the orbital planes of the debris. 2) It’s hard to get your head around the relative velocities you can get from orbital debris. A bullet travels at around 750 miles per hour. A satellite in low-earth orbit travels at 17,500 miles per hour. Orbital debris could impact a spacecraft at something like a cosine loss of that number, which depending on the exact inclination could be on the order of 10,000 miles per hour. So a factor of 15 faster than a bullet. Shielding takes mass. Mass is expensive. It costs $5000/pound to launch mass into low earth orbit;
  - pg_is_a_butt 7y ago
    Need to make the shield self assemble using the mass of any colliding debris.
  - ThisIsTheWay 7y ago
    > 1) it’s not true, and it becomes less true over time. Gravitational perturbations change the orbital planes of the debris. I can't imagine gravitational perturbations in LEO are going to significantly alter eccentricity. I'm trying to find some data that supports this, will report back.
    - GlenTheMachine 7y ago
      Well, to be clear, when I say "gravitational perturbations" I don't mean GRAVITATIONAL perturbations ;) I mean any terms other than the strict 2-body problem dynamics: gravitational perturbations, third body gravitational effects, solar pressure, atmospheric drag, especially acting on non-spherical bodies, etc. See: https://www.researchgate.net/publication/292745544_Perturbations_in_orbital_elements_of_a_low_earth_orbiting_satellite https://www.researchgate.net/publication/292745544_Perturbat...
      - mumblemumble 7y ago
        So, my imagination is lacking, so let me make sure I've got this right: The main gravitational perturbation you're thinking of isn't interaction with other small satellites or Earth's varying density; a bigger effect is going to be because the Moon, which is also moving relative to everything else is also a part of the equation. Out of curiosity, wouldn't atmospheric drag have a circularizing effect on eccentric orbits? I'd have guessed that, since drag is greatest when the satellite is at its perigee, it's going to have a much larger relative effect on the apogee.
        GlenTheMachine 7y ago
        I am making no claim about what effects would be bigger (other than atmospheric drag, which is always the biggest effect in LEO). All I’m saying is that in general, all those nonlinear effects we tend to ignore, when integrated over long periods of time, tend to make orbits change their eccentricity and inclination, and that makes them more of a collision hazard because the relative velocity is higher than it would be if they were in more similar orbits to the thing they collide with.
yk 7y ago
> Could we not reasonably launch a series of deflective plates or shields in the same plane through the "danger zones" encircling important satellites, or creating a safe zone for passage with shuttles? No, the problem is, while the probability to collide with any one debris particle is low, there are just a lot of them. So when your plate collides with some, there are still a lot of them.
pg_is_a_butt 7y ago
> it's not going to strike a satellite from much of an angle above or below, because then it would by definition not be in orbit, correct? Incorrect. Orbits are not all circular... elliptical orbits exist that could cross paths with every possible circular orbit. It's called the "eccentricity" of the orbit. If you knock something out of circular orbit, you may knock it into an elliptical orbit now making it a potential problem for a lot more satellites not in the original orbit.

aidenn0 7y ago

When something hits a deflective plate, it could ablate part of the plate, thus increasing the amount of debris in that particular orbit.

deleted 7y ago
[deleted]

mumblemumble 7y ago

> Like, it's not going to strike a satellite from much of an angle above or below, because then it would by definition not be in orbit, correct? It sounds like you're assuming that orbits are typically close to circular. I have no idea how true that is, but I imagine that a Kessler-type chain reaction would tend to make it less true.

GlenTheMachine 7y ago
1) it’s not true, and it becomes less true over time. Gravitational perturbations change the orbital planes of the debris. 2) It’s hard to get your head around the relative velocities you can get from orbital debris. A bullet travels at around 750 miles per hour. A satellite in low-earth orbit travels at 17,500 miles per hour. Orbital debris could impact a spacecraft at something like a cosine loss of that number, which depending on the exact inclination could be on the order of 10,000 miles per hour. So a factor of 15 faster than a bullet. Shielding takes mass. Mass is expensive. It costs $5000/pound to launch mass into low earth orbit;
- pg_is_a_butt 7y ago
  Need to make the shield self assemble using the mass of any colliding debris.
- ThisIsTheWay 7y ago
  > 1) it’s not true, and it becomes less true over time. Gravitational perturbations change the orbital planes of the debris. I can't imagine gravitational perturbations in LEO are going to significantly alter eccentricity. I'm trying to find some data that supports this, will report back.
  - GlenTheMachine 7y ago
    Well, to be clear, when I say "gravitational perturbations" I don't mean GRAVITATIONAL perturbations ;) I mean any terms other than the strict 2-body problem dynamics: gravitational perturbations, third body gravitational effects, solar pressure, atmospheric drag, especially acting on non-spherical bodies, etc. See: https://www.researchgate.net/publication/292745544_Perturbations_in_orbital_elements_of_a_low_earth_orbiting_satellite https://www.researchgate.net/publication/292745544_Perturbat...
    - mumblemumble 7y ago
      So, my imagination is lacking, so let me make sure I've got this right: The main gravitational perturbation you're thinking of isn't interaction with other small satellites or Earth's varying density; a bigger effect is going to be because the Moon, which is also moving relative to everything else is also a part of the equation. Out of curiosity, wouldn't atmospheric drag have a circularizing effect on eccentric orbits? I'd have guessed that, since drag is greatest when the satellite is at its perigee, it's going to have a much larger relative effect on the apogee.
      - GlenTheMachine 7y ago
        I am making no claim about what effects would be bigger (other than atmospheric drag, which is always the biggest effect in LEO). All I’m saying is that in general, all those nonlinear effects we tend to ignore, when integrated over long periods of time, tend to make orbits change their eccentricity and inclination, and that makes them more of a collision hazard because the relative velocity is higher than it would be if they were in more similar orbits to the thing they collide with.

yk 7y ago

> Could we not reasonably launch a series of deflective plates or shields in the same plane through the "danger zones" encircling important satellites, or creating a safe zone for passage with shuttles? No, the problem is, while the probability to collide with any one debris particle is low, there are just a lot of them. So when your plate collides with some, there are still a lot of them.

pg_is_a_butt 7y ago

> it's not going to strike a satellite from much of an angle above or below, because then it would by definition not be in orbit, correct? Incorrect. Orbits are not all circular... elliptical orbits exist that could cross paths with every possible circular orbit. It's called the "eccentricity" of the orbit. If you knock something out of circular orbit, you may knock it into an elliptical orbit now making it a potential problem for a lot more satellites not in the original orbit.