2
$\begingroup$

SpaceX's Starlink and other mega-constellation plans highlight safe de-orbiting features but does this also extend to altitudes higher than 1,000 kms?

My concern is whether these smaller sats will have enough propulsion to de-orbit from ~1,110 kms altitude orbit (vs ~450kms altitude orbit)

$\endgroup$
4
$\begingroup$

It's a valid question. The Starlinks would require larger tanks but we're still only talking about a few percent of their 227 kg mass because they use high solar-electric propulsion rather than conventional rockets.

I estimated about 2.3 kg of liquid krypton for the lower orbiting Starlink satellites in this answer. That included orbit raising from 445 to 550 km (58 m/s), keeping it there against drag for five years (20 m/s) and then bringing it back down from 550 to 350 km (112 m/s) at which point nature (drag) would complete the deorbit fairly quickly.

Drag will be far lower at 1100 km, so we can ignore that.

So if they had to raise themselves from 450 km to 1100 km and then lower back to 350 km, that would be a delta-v of 736 m/s. If they were placed at 1100 km and only needed to deorbit, that's only 396 m/s.

Assuming an electric Isp of 2000 seconds (and so exhaust velocity of about 20,000 m/s) those would require 3.68% and 1.98% of the spacecraft's 227 kg mass as reaction mass, or 8.35 and 4.49 kg of liquid krypton, respectively

Your milage may vary.

Also possibly of interest:

| improve this answer | |
$\endgroup$
  • 1
    $\begingroup$ ~4% of mass sounds like significant but still feasible trade-off then! So I surmise they will manage to do this. Thanks! $\endgroup$ – pat_nafs Dec 7 '19 at 13:28

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.