I wonder what is the approach to replace let's say: 5 defective Starlink satellites, each one in a different orbit? I guess that it can't be done with just one launch as the krypton ion thrusters delta-v is low and should be used to avoid collision, orbit raising and re-entering.
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asked Jan 28, 2020 at 10:03
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1$\begingroup$ I ballpark-estimated 190 m/s for a Starlink's delta-v, that gets you about 8 to 10 degrees of plane change if you blow it all at once, so yeah, they'd have to have some kind of enhancement gizmo to put each in a different plane. $\endgroup$– uhohCommented Jan 28, 2020 at 10:10
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2$\begingroup$ Wellcome to stackexchange. Good first question! I guess they will use some analog to this xkcd joke. As soon as a high enough number of satellites in a plane is defect they will simply replace the whole plane as most likely more will fail soon too. $\endgroup$– ChristophCommented Jan 28, 2020 at 11:36
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1$\begingroup$ I would expect they are launched with spares in each plane, so when one fails a standby takes over. $\endgroup$– user20636Commented Jan 28, 2020 at 12:20
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$\begingroup$ @JCRM is most likely correct: just as with GPS satellites, the point of having a bunch of them is so performance does not significantly degrade if a few go bad. $\endgroup$– Carl WitthoftCommented Jan 28, 2020 at 12:40
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There are a lot of possibilities. A few things to keep in mind.
- The early days of Starlink will not have guaranteed 100% uptime.
- Starlink requires a 40 degree above the horizon line of sight. This is actually very large, many satellites only require 10 or even 5 degrees. This means that there has to be a lot more Starlink satellites, but there might be a bit of spare capacity if you spread them out.
- Eventually the increase in satellite count will be more dictated on increased capacity, and not on redundancy. A few single missing satellites won't make a huge difference.
For the early days, I predict they will space out the satellites in the same plane a bit more for the short term. For the long term, they will have a few on-orbit spares, or new launches, where one of the satellites will be put in an orbit to gradually move it to the correct plane.
For later days, there will probably be some spares in the plane, so simply moving one of those around can be done, and will only take a few days. That will leave a "hole" where periodically the capacity will drop slightly, but that probably isn't a huge issue in the grand scheme of things.
answered Jan 28, 2020 at 12:40
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1$\begingroup$ Line of Sight. Will fix that. $\endgroup$– PearsonArtPhoto ♦Commented Jan 28, 2020 at 12:56
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1$\begingroup$ You're right, at following FCC document at page 1, SpaceX says that will use up to two spares per plane, and they will not operate their communications payloads, only will perform station-keeping and debris avoidance maneuvers. More info at: licensing.fcc.gov/myibfs/download.do?attachment_key=1158350 $\endgroup$ Commented Jan 31, 2020 at 13:54