6 ms·

If someone makes a mistake and the satellite deorbits in the wrong place, am I likely to be impaled by a satellite screw or something travelling at terminal vel

If someone makes a mistake and the satellite deorbits in the wrong place, am I likely to be impaled by a satellite screw or something travelling at terminal velocity?

latchkey 3y ago
China is still working on those reusable rockets... https://www.youtube.com/watch?v=sDufpRp57ok https://www.youtube.com/watch?v=sDufpRp57ok
oconnor663 3y ago
No, they burn up. You can think of how much work goes into the heat shields on spacecraft that are supposed to survive reentry. Satellites have none of that.
- scottlamb 3y ago
  I also think a screw at terminal velocity might not be particularly dangerous, similar to the popular "will a penny dropped off the empire skyscraper kill you?" question. ...which I suppose is closely related. The deorbiting satellite burns up because all that potential energy goes into heat because of the ~friction~ [edit: compression, thanks for the correction] that limits it to that low terminal velocity.
  - iamgopal 3y ago
    Heat is Not because of friction but compression of air
- m4rtink 3y ago
  Starlinks are actually built so that nothing sizeable remains at all after reentry. This even delayed the laser coms a bit, as the original laser mirrors were too sturdy & so pieces of them could theoretically make it through.
mlindner 3y ago
Actually the person you replied to somewhat incorrectly. They're not targeted re-entries because the on-board propulsion of Starlink is too low to precisely control the re-entry location. However instead the satellites are designed to be intentionally "demisable" meaning that every portion of the satellite should vaporize/turn to char/dust during re-entry. Put another way, every kilogram of Starlink spacecraft has as much energy "stored" in it's motion as around 4-5 tons of TNT.
- weregiraffe 3y ago
  You mean 4-5 kg of TNT. Starlink is not relativistic yet.
  - mlindner 3y ago
    I mistyped the comment. It should be 4-5 tons of TNT for the entire satellite.
- qayxc 3y ago
  > Actually the person you replied to somewhat incorrectly. They're not targeted re-entries because the on-board propulsion of Starlink is too low to precisely control the re-entry location. SpaceX says otherwise, see [1] SpaceX spokesman James Gleeson, when asked about the 10 satellites, said SpaceX is “performing a controlled de-orbit of several first iteration Starlink satellites,” using onboard propulsion. There's a difference between unscheduled deorbiting (as happened to about 40 satellites after a solar storm in February 2022) and a scheduled deorbiting manoeuvre trigged by ground control. Starlink satellites use electric on-board propulsion (Krypton powered Hall thrusters) that doesn't run out as quickly as chemical or cold gas gas thrusters. There's also not much precision needed to avoid major population centres - Earth is pretty big after all. [1] https://spacenews.com/spacex-launches-fourth-batch-of-starlink-satellites-tweaks-satellite-design/ https://spacenews.com/spacex-launches-fourth-batch-of-starli...
  - mlindner 3y ago
    And I'm telling you that the statement is incorrect. Starlink is not equipped with propulsion capable of doing that. They use electric propulsion, which means they can't target a re-entry. They can de-orbit it on a time scale, but they cannot do what is conventionally described as a controlled de-orbit. Meaning they cannot precisely target a general area of the Earth. They can target re-entry within a couple hours to days, but that's still all over the world. Now, none of this is an actual problem as they're entirely demisable, but the statement that they can achieve controlled de-orbit is false.

If someone makes a mistake and the satellite deorbits in the wrong place, am I likely to be impaled by a satellite screw or something travelling at terminal velocity?

latchkey 3y ago

China is still working on those reusable rockets... https://www.youtube.com/watch?v=sDufpRp57ok https://www.youtube.com/watch?v=sDufpRp57ok

oconnor663 3y ago

No, they burn up. You can think of how much work goes into the heat shields on spacecraft that are supposed to survive reentry. Satellites have none of that.

scottlamb 3y ago
I also think a screw at terminal velocity might not be particularly dangerous, similar to the popular "will a penny dropped off the empire skyscraper kill you?" question. ...which I suppose is closely related. The deorbiting satellite burns up because all that potential energy goes into heat because of the ~friction~ [edit: compression, thanks for the correction] that limits it to that low terminal velocity.
- iamgopal 3y ago
  Heat is Not because of friction but compression of air
m4rtink 3y ago
Starlinks are actually built so that nothing sizeable remains at all after reentry. This even delayed the laser coms a bit, as the original laser mirrors were too sturdy & so pieces of them could theoretically make it through.

mlindner 3y ago

Actually the person you replied to somewhat incorrectly. They're not targeted re-entries because the on-board propulsion of Starlink is too low to precisely control the re-entry location. However instead the satellites are designed to be intentionally "demisable" meaning that every portion of the satellite should vaporize/turn to char/dust during re-entry. Put another way, every kilogram of Starlink spacecraft has as much energy "stored" in it's motion as around 4-5 tons of TNT.

weregiraffe 3y ago
You mean 4-5 kg of TNT. Starlink is not relativistic yet.
- mlindner 3y ago
  I mistyped the comment. It should be 4-5 tons of TNT for the entire satellite.
qayxc 3y ago
> Actually the person you replied to somewhat incorrectly. They're not targeted re-entries because the on-board propulsion of Starlink is too low to precisely control the re-entry location. SpaceX says otherwise, see [1] SpaceX spokesman James Gleeson, when asked about the 10 satellites, said SpaceX is “performing a controlled de-orbit of several first iteration Starlink satellites,” using onboard propulsion. There's a difference between unscheduled deorbiting (as happened to about 40 satellites after a solar storm in February 2022) and a scheduled deorbiting manoeuvre trigged by ground control. Starlink satellites use electric on-board propulsion (Krypton powered Hall thrusters) that doesn't run out as quickly as chemical or cold gas gas thrusters. There's also not much precision needed to avoid major population centres - Earth is pretty big after all. [1] https://spacenews.com/spacex-launches-fourth-batch-of-starlink-satellites-tweaks-satellite-design/ https://spacenews.com/spacex-launches-fourth-batch-of-starli...
- mlindner 3y ago
  And I'm telling you that the statement is incorrect. Starlink is not equipped with propulsion capable of doing that. They use electric propulsion, which means they can't target a re-entry. They can de-orbit it on a time scale, but they cannot do what is conventionally described as a controlled de-orbit. Meaning they cannot precisely target a general area of the Earth. They can target re-entry within a couple hours to days, but that's still all over the world. Now, none of this is an actual problem as they're entirely demisable, but the statement that they can achieve controlled de-orbit is false.