2 ms·

Explain to the class why Kessler Syndrome isn’t possible with large LEO constellations.

crewindream 2mo ago
In a form of a question: does low earth orbit has big enough drag to be effectively do automatic cleanup every several years?
- nine_k 2mo ago
  The answer is positive. LEO satellites need orbital corrections every few weeks, and some, several times a week.
mayama 2mo ago
In case of collision in LEO, wouldn't the debris have chance to go high altitude and cause further collisions?
- cyberax 2mo ago
  No. It'll stay in essentially the same orbit. During collision, some of the energy will be lost, so the fragments will necessarily have a lower orbit. The only thing that can accelerate fragments into a substantially higher orbit is the energy of elastic deformation of material during the explosion.
  - lanstin 2mo ago
    Can’t two solid object with equal kinetic energy collide in such a way that most of the energy goes into one of them, giving it a velocity that boosts its orbit while the other one has lower velocity and de-orbits? Or one object explode into two fragments, equal and opposite relative velocity, again pushing the one half into a higher orbit and de-orbiting the other half? (Honest question, math major, never took orbital mechanics or played KSP much).
    - cyberax 2mo ago
      > Can’t two solid object with equal kinetic energy collide in such a way that most of the energy goes into one of them, giving it a velocity that boosts its orbit while the other one has lower velocity and de-orbits? Sure, you can. Imagine shooting a bullet into a tungsten cube. The cube will go into a higher orbit, and the bullet will bounce back (and maybe de-orbit). But the kicker here is that for this to work, the bullet has to be in a _higher_ orbit than the cube initially. So the end result is still fewer objects in higher orbits. Another option is momentum transfer via elastic deformation - you shoot a bullet into a 45-degree facet of that tungsten cube, and the bullet then ricochets into a higher orbit. It ultimately works by momentarily storing the energy of the projectile as a plastic deformation of the facet. So it can't accelerate more than a few small fragments.
SiempreViernes 2mo ago
It is in fact possible to have the Kessler syndrome in LEO, the debris doesn't just immediately fall out of the sky so in practice you just need to put more satellites into a specific orbit to reach the critical density where one satellite breaking leads to a runaway chain reaction. In actual reality it's estimated that several segments of LEO have already reached criticality, especially around 600 km: https://conference.sdo.esoc.esa.int/proceedings/sdc9/paper/305/SDC9-paper305.pdf https://conference.sdo.esoc.esa.int/proceedings/sdc9/paper/3...

In a form of a question: does low earth orbit has big enough drag to be effectively do automatic cleanup every several years?

nine_k 2mo ago
The answer is positive. LEO satellites need orbital corrections every few weeks, and some, several times a week.

mayama 2mo ago

In case of collision in LEO, wouldn't the debris have chance to go high altitude and cause further collisions?

cyberax 2mo ago
No. It'll stay in essentially the same orbit. During collision, some of the energy will be lost, so the fragments will necessarily have a lower orbit. The only thing that can accelerate fragments into a substantially higher orbit is the energy of elastic deformation of material during the explosion.
- lanstin 2mo ago
  Can’t two solid object with equal kinetic energy collide in such a way that most of the energy goes into one of them, giving it a velocity that boosts its orbit while the other one has lower velocity and de-orbits? Or one object explode into two fragments, equal and opposite relative velocity, again pushing the one half into a higher orbit and de-orbiting the other half? (Honest question, math major, never took orbital mechanics or played KSP much).
  - cyberax 2mo ago
    > Can’t two solid object with equal kinetic energy collide in such a way that most of the energy goes into one of them, giving it a velocity that boosts its orbit while the other one has lower velocity and de-orbits? Sure, you can. Imagine shooting a bullet into a tungsten cube. The cube will go into a higher orbit, and the bullet will bounce back (and maybe de-orbit). But the kicker here is that for this to work, the bullet has to be in a _higher_ orbit than the cube initially. So the end result is still fewer objects in higher orbits. Another option is momentum transfer via elastic deformation - you shoot a bullet into a 45-degree facet of that tungsten cube, and the bullet then ricochets into a higher orbit. It ultimately works by momentarily storing the energy of the projectile as a plastic deformation of the facet. So it can't accelerate more than a few small fragments.

SiempreViernes 2mo ago

It is in fact possible to have the Kessler syndrome in LEO, the debris doesn't just immediately fall out of the sky so in practice you just need to put more satellites into a specific orbit to reach the critical density where one satellite breaking leads to a runaway chain reaction. In actual reality it's estimated that several segments of LEO have already reached criticality, especially around 600 km: https://conference.sdo.esoc.esa.int/proceedings/sdc9/paper/305/SDC9-paper305.pdf https://conference.sdo.esoc.esa.int/proceedings/sdc9/paper/3...