Re:DirecTV races to decommission broken satellite before it ...
by mark-r on Friday January 24, 2020 @02:09PM
(#22141410)
How much of a danger is debris from an exploded satellite? Each fragment is going to be independent and have its own orbit. Any orbit higher or lower than the geostationary belt won't be a problem. Any orbit equal to the original satellite's won't be a problem either. Only those pieces maintaining the same altitude but a different direction will ever intersect the belt, and that will be a rare occurrence.
Re:DirecTV races to decommission broken satellite before it ...
by Floegipoky on Friday January 24, 2020 @03:41PM
(#22142228)
You're correct that each fragment will have its own independent orbit, based on the delta-v that it gained from the explosion. But they won't circularize; each of those new orbits will intersect the original orbit at the point where it exploded. The orbital periods of the fragments will also not match the original, meaning that the relative intersection will shift along the original orbit every time. So an explosion in geostationary orbit would be a Really Big Deal and could potentially threaten the whole geostationary fleet.
Re:DirecTV races to decommission broken satellite before it ...
by Aperocky on Friday January 24, 2020 @02:27PM
(#22141595)
Orbit can be both higher and lower, actually, any deltaV except purely in the axis of movement will result in exactly that.
Yes. you can accelerate away from the Earth and have a lower periapsis (conversely, you can accelerate towards the Earth and have a higher apoapsis). The only way you can maintain the same periapsis is by accelerating in the same direction you're going. Highly impossible in an explosion.
Also note, it is impossible to raise periapsis in a single event (or single time frame), except by leaving Earth orbit entirely (i.e. eject to planetary space)
Re:DirecTV races to decommission broken satellite before it ...
by Aperocky on Friday January 24, 2020 @01:45PM
(#22141197)
Wernher von Kerman approves this message.
So we're in a stable orbit with a high periapsis (closest part of our orbit to earth). To de-orbit we need to lower the periapsis so that it touches the atmosphere, and on each pass the satellite will slow down, further lowering the apoapsis and periapsis. The problem is that to do this we have to burn all that horizontal velocity that's keeping us in orbit in the first place, which is a crapload.
An alternative is to instead change the orbit so it's no longer in geostationary orbit and potentially interfering with live satellites, so instead they just push the satellite further out into the "graveyard orbit".
There's 100x difference in the needed energy for the two methods, and I'm sure you can see why most would opt for the graveyard orbit.
EDIT: To add, it's actually rather difficult to "plunge into earth". To do this you need to burn all of your horizontal velocity (I think that's around 3.07 km/s in geostationary orbit?). Reaching the sun is actually really difficult as well for the same reason, you have to lose all of your horizontal velocity, and earth has a ton.