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You could put in an orbit that would have a predefined reentry in the future. Design the satellite to survive reentry and somehow safely land in a way that reli

by moftz 9y ago

You could put in an orbit that would have a predefined reentry in the future. Design the satellite to survive reentry and somehow safely land in a way that relies on a mechanical system that wouldn't degrade like electronics in space would.

sigstoat 9y ago
> You could put in an orbit that would have a predefined reentry in the future. it isn't clear what you mean by this, but there's no picking where something will reenter hundreds of years in the future. if you just want to ensure that it will reenter, sooner or later, that's easily done. > Design the satellite to survive reentry and somehow safely land in a way that relies on a mechanical system that wouldn't degrade like electronics in space would. chunks of satellites are far more likely to survive reentry already than you might expect. i expect it would be feasible now to produce an insert sphere filled with information etched on nickel-superalloy plates that would survive uncontrolled reentry and impact with the earth's surface. i'd suggest storing the information in something covered with retro-reflectors, and dropping it onto the moon's surface, though. need more delta-V to get it there and retrieve it, but it'd be a simpler object to construct, and then later deconstruct.
- moftz 9y ago
  You can calculate an estimate of reentry from atmospheric drag. It's not going to be exact but anything you throw up into LEO is going to come down someday and as long as the atmosphere doesn't change too much, it should be fairly close. http://www.sws.bom.gov.au/Category/Educational/Space%20Weather/Space%20Weather%20Effects/SatelliteOrbitalDecayCalculations.pdf http://www.sws.bom.gov.au/Category/Educational/Space%20Weath...
- Sir_Cmpwn 9y ago
  >it isn't clear what you mean by this, but there's no picking where something will reenter hundreds of years in the future. if you just want to ensure that it will reenter, sooner or later, that's easily done. Well, you could schedule a deorbit burn, assuming the hardware is still in working order far into the future.
walrus01 9y ago
You can't do this on a long term scale with something that's below geostationary orbit, because random solar flares and solar phenomena cause expansion and contraction of the earth's atmosphere at unpredictable times. If you have a satellite in an orbit that is low enough to gradually degrade through atmospheric drag (even if it's a very high-LEO orbit or molniya orbit that won't reenter for an estimated 300 years), the exact time that it will re-enter can't be predicted with any confidence. At least not if you are talking about a very long time scale. Short-term (3, 5 or 7 year time scale) orbit degradation of things in LEO is predictable based on orbital height and known atmospheric density at a given altitude, but beyond that any re-entry predictions become much more fuzzy. for reference: https://arxiv.org/abs/1305.0233 https://arxiv.org/abs/1305.0233 If you want to put something in orbit that will stay in a predictable location, you don't want it to re-enter at all, you want to put it in an orbit that is high enough to not be affected by atmospheric drag on a geologic time scale. Something slightly beyond geostationary will still be there in 200,000 years.

by moftz 9y ago

sigstoat 9y ago

> You could put in an orbit that would have a predefined reentry in the future. it isn't clear what you mean by this, but there's no picking where something will reenter hundreds of years in the future. if you just want to ensure that it will reenter, sooner or later, that's easily done. > Design the satellite to survive reentry and somehow safely land in a way that relies on a mechanical system that wouldn't degrade like electronics in space would. chunks of satellites are far more likely to survive reentry already than you might expect. i expect it would be feasible now to produce an insert sphere filled with information etched on nickel-superalloy plates that would survive uncontrolled reentry and impact with the earth's surface. i'd suggest storing the information in something covered with retro-reflectors, and dropping it onto the moon's surface, though. need more delta-V to get it there and retrieve it, but it'd be a simpler object to construct, and then later deconstruct.

moftz 9y ago
You can calculate an estimate of reentry from atmospheric drag. It's not going to be exact but anything you throw up into LEO is going to come down someday and as long as the atmosphere doesn't change too much, it should be fairly close. http://www.sws.bom.gov.au/Category/Educational/Space%20Weather/Space%20Weather%20Effects/SatelliteOrbitalDecayCalculations.pdf http://www.sws.bom.gov.au/Category/Educational/Space%20Weath...
Sir_Cmpwn 9y ago
>it isn't clear what you mean by this, but there's no picking where something will reenter hundreds of years in the future. if you just want to ensure that it will reenter, sooner or later, that's easily done. Well, you could schedule a deorbit burn, assuming the hardware is still in working order far into the future.

walrus01 9y ago

You can't do this on a long term scale with something that's below geostationary orbit, because random solar flares and solar phenomena cause expansion and contraction of the earth's atmosphere at unpredictable times. If you have a satellite in an orbit that is low enough to gradually degrade through atmospheric drag (even if it's a very high-LEO orbit or molniya orbit that won't reenter for an estimated 300 years), the exact time that it will re-enter can't be predicted with any confidence. At least not if you are talking about a very long time scale. Short-term (3, 5 or 7 year time scale) orbit degradation of things in LEO is predictable based on orbital height and known atmospheric density at a given altitude, but beyond that any re-entry predictions become much more fuzzy. for reference: https://arxiv.org/abs/1305.0233 https://arxiv.org/abs/1305.0233 If you want to put something in orbit that will stay in a predictable location, you don't want it to re-enter at all, you want to put it in an orbit that is high enough to not be affected by atmospheric drag on a geologic time scale. Something slightly beyond geostationary will still be there in 200,000 years.