4 ms·
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
by 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 agoNeed 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 agoWell, 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 agoSo, 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 agoI 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.