3 ms·

Instead of de-orbiting it towards earth, why don't they de-orbit it in the other direction, away from earth. Wouldn't that be safer?

by r3pl4y 3y ago

chrisamiller 3y ago
The amount of energy needed to get out of earth's gravity well is incredibly high. It would be silly to try to boost a massive object like the ISS out.
mwint 3y ago
Much more expensive (in delta-v terms) to hit escape velocity, I’m guessing?
hinoki 3y ago
Escape velocity energy from an orbit is sqrt(2) times the energy it takes to get to that orbit. But it’s more than ~41% more fuel, since you need more fuel to push the fuel, and more fuel than that to get it to orbit in the first place. Much cheaper to let the atmosphere drag it down, which is something that is going to happen anyways.
- dotancohen 3y ago
  So achieving escape velocity from geosynchronous orbit requires more delta v than from LEO? I kind of see it, as the surface velocity of a GEO satellite is near zero yet the surface velocity of a LEO bird is measured in the thousands of KPH. However so much more energy was invested in raising the satellite so high up, I have a difficult time imagining that actually more energy is now required to bring it to escape velocity. Is not escape velocity at GEO altitudes lower than escape velocity at LEO?
anonymousiam 3y ago
This is done for GEO satellites, but as mentioned in other comments here, it's impossible for LEO satellites such as the ISS. https://en.wikipedia.org/wiki/List_of_orbits https://en.wikipedia.org/wiki/List_of_orbits https://en.wikipedia.org/wiki/Graveyard_orbit https://en.wikipedia.org/wiki/Graveyard_orbit https://www.esa.int/ESA_Multimedia/Images/2008/03/Mitigation_scenarios_Graveyard_orbit_300_km_above_GEO https://www.esa.int/ESA_Multimedia/Images/2008/03/Mitigation...
_fat_santa 3y ago
That would take way to much energy for little benefit. They expect the ISS to burn up in the atmosphere so there wouldn't be a safety issue to people/things on earth.

Instead of de-orbiting it towards earth, why don't they de-orbit it in the other direction, away from earth. Wouldn't that be safer?

by r3pl4y 3y ago

Instead of de-orbiting it towards earth, why don't they de-orbit it in the other direction, away from earth. Wouldn't that be safer?

chrisamiller 3y ago

The amount of energy needed to get out of earth's gravity well is incredibly high. It would be silly to try to boost a massive object like the ISS out.

mwint 3y ago

Much more expensive (in delta-v terms) to hit escape velocity, I’m guessing?

hinoki 3y ago

Escape velocity energy from an orbit is sqrt(2) times the energy it takes to get to that orbit. But it’s more than ~41% more fuel, since you need more fuel to push the fuel, and more fuel than that to get it to orbit in the first place. Much cheaper to let the atmosphere drag it down, which is something that is going to happen anyways.

dotancohen 3y ago
So achieving escape velocity from geosynchronous orbit requires more delta v than from LEO? I kind of see it, as the surface velocity of a GEO satellite is near zero yet the surface velocity of a LEO bird is measured in the thousands of KPH. However so much more energy was invested in raising the satellite so high up, I have a difficult time imagining that actually more energy is now required to bring it to escape velocity. Is not escape velocity at GEO altitudes lower than escape velocity at LEO?

anonymousiam 3y ago

This is done for GEO satellites, but as mentioned in other comments here, it's impossible for LEO satellites such as the ISS. https://en.wikipedia.org/wiki/List_of_orbits https://en.wikipedia.org/wiki/List_of_orbits https://en.wikipedia.org/wiki/Graveyard_orbit https://en.wikipedia.org/wiki/Graveyard_orbit https://www.esa.int/ESA_Multimedia/Images/2008/03/Mitigation_scenarios_Graveyard_orbit_300_km_above_GEO https://www.esa.int/ESA_Multimedia/Images/2008/03/Mitigation...

_fat_santa 3y ago

That would take way to much energy for little benefit. They expect the ISS to burn up in the atmosphere so there wouldn't be a safety issue to people/things on earth.