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comment by kleinbl00
kleinbl00  ·  1525 days ago  ·  link  ·    ·  parent  ·  post: DirecTV fears explosion risk from satellite with damaged battery

Wonder why they can't just vent it in graveyard orbit.





steve  ·  1525 days ago  ·  link  ·  

Some bean counter somewhere is deciding if it’s worth the financial risk.

kleinbl00  ·  1525 days ago  ·  link  ·  

Naaah, that's not it, I think they're required to vent it prior to parking for reasons I don't fully understand. This is where my understanding of orbital mechanics is inadequate to the task.

I suspect they aren't pointing it dirtward because it's a longer trajectory but all I can do is suspect.

demure  ·  1523 days ago  ·  link  ·  

Venting is required to mitigate the risk of accidental explosions (see pp. 14-15, particularly pp. 15 in the footnotes). Presumably there are fewer knock-on effects of an accidental explosion outside the parking orbit, though yeah, I'm also not quite clear why it needs to be vented prior to getting there.

Dirtward is no-go because of how fucking high geostationary orbit is. Way easier (in terms of delta-v) to boost it up 300 km than changing the perigee to something < 500 km (roughly the height of SpaceX's current Starlink sats, which will deorbit and burn in a few years at that altitude, thus mitigating space junk risk) from 35,786 km (geo orbit).

Edit: venting propellant prior to moving to parking orbit would mean less delta-v required to move the thing to parking orbit in the first place (less mass to move), so that's my educated guess...they might not have enough delta-v to get there without venting first.

kleinbl00  ·  1523 days ago  ·  link  ·  

Your edit gets to the core of my question - "not enough delta-V to get there without venting first."