We've been noticing the lack of orbit updates for the most recent batch of Starlinks, and the reentry of several. Well, it turns out things did not go well for this launch. SpaceX now say increased drag due to a recent geomagnetic storm forced them to put the sats in safemode buta bunch of them failed to exit safemode and can't orbit raise. So the majority (perhaps 40 of the 49) will reenter shortly after only a few days in orbit
Ouch. Do you think they are insured? How could the atmospheric density prevent the satellites from exitting the safe mode?
Quote from: JayWee on 02/09/2022 12:08 amOuch. Do you think they are insured? How could the atmospheric density prevent the satellites from exitting the safe mode?My guess is that that means the force of atmospheric drag is now greater than the thrust Starlink's ion propulsion can produce, making orbit-raising physically impossible. Properly deploying the solar arrays to maximize power generation (probably necessary for max-thrust orbit-raising) would also drastically increase that drag.
Quote from: eeergo on 02/09/2022 07:12 amQuote from: vaporcobra on 02/09/2022 12:14 amQuote from: JayWee on 02/09/2022 12:08 amOuch. Do you think they are insured? How could the atmospheric density prevent the satellites from exitting the safe mode?My guess is that that means the force of atmospheric drag is now greater than the thrust Starlink's ion propulsion can produce, making orbit-raising physically impossible. Properly deploying the solar arrays to maximize power generation (probably necessary for max-thrust orbit-raising) would also drastically increase that drag.There can be several effects at play here: one is the overwhelming of the control authority they are able to muster (i.e. their attitude might have been unstable due to drag making them tumble). They presumably use control rods and gyros for that, perhaps coupled with help from the ion thrusters (?), although the gyros may only be for fine-pointing the optical links.Then there can be the thrust issue you mention, by itself or in combination with the above (if they can't keep the edge-on attitude well locked, then drag will increase too, making control harder and increasing drag, in a vicious circle)... although that seems unlikely -or a major design flaw- since this extremely quick deorbit would mean they aren't even able to *hold* their current orbit (whose apogee is quite a bit higher than 200-something km), not just raise it. If this minor storm was an issue (50% extra sounds like a lot, but let's keep in mind this means less than twice the drag than previous occasions, which is NOT a lot, especially with this being a well-known and consistently measured effect). Considering we've been going through one of the quietest solar minima on record, it doesn't bode well for the system's deployment over the next few years as the Sun gets rowdy again.Another issue can be within the electric propulsion itself: too high an ambient free electron density and you will get arcing between the thruster's cathode and its neutralizer, which will fault the EP and can altogether prevent its operation.Then there are the radiation effects of course (both over the poles and the SAA), although the release doesn't seem to focus on them, and levels don't appear to have significantly increased.Has anyone seen any news concerning other satellites (in general) and Starlinks (in particular)? There should be >150 S/C undergoing orbit-raising experiencing similar issues - even if not so severe as to bring them down in a matter of hours, there can have been issues with them as well, especially for the 4-6 group launched just a few days prior.This event has single-handedly doubled early mortality numbers for Starlink.The issue was primarily the temporary increase of up to 50% in atmospheric density at the deployment altitude. Even so, some of the current batch managed to navigate through it.Everything at a higher altitude will be fine. No need for opportunistic concern trolling.👍
Quote from: vaporcobra on 02/09/2022 12:14 amQuote from: JayWee on 02/09/2022 12:08 amOuch. Do you think they are insured? How could the atmospheric density prevent the satellites from exitting the safe mode?My guess is that that means the force of atmospheric drag is now greater than the thrust Starlink's ion propulsion can produce, making orbit-raising physically impossible. Properly deploying the solar arrays to maximize power generation (probably necessary for max-thrust orbit-raising) would also drastically increase that drag.There can be several effects at play here: one is the overwhelming of the control authority they are able to muster (i.e. their attitude might have been unstable due to drag making them tumble). They presumably use control rods and gyros for that, perhaps coupled with help from the ion thrusters (?), although the gyros may only be for fine-pointing the optical links.Then there can be the thrust issue you mention, by itself or in combination with the above (if they can't keep the edge-on attitude well locked, then drag will increase too, making control harder and increasing drag, in a vicious circle)... although that seems unlikely -or a major design flaw- since this extremely quick deorbit would mean they aren't even able to *hold* their current orbit (whose apogee is quite a bit higher than 200-something km), not just raise it. If this minor storm was an issue (50% extra sounds like a lot, but let's keep in mind this means less than twice the drag than previous occasions, which is NOT a lot, especially with this being a well-known and consistently measured effect). Considering we've been going through one of the quietest solar minima on record, it doesn't bode well for the system's deployment over the next few years as the Sun gets rowdy again.Another issue can be within the electric propulsion itself: too high an ambient free electron density and you will get arcing between the thruster's cathode and its neutralizer, which will fault the EP and can altogether prevent its operation.Then there are the radiation effects of course (both over the poles and the SAA), although the release doesn't seem to focus on them, and levels don't appear to have significantly increased.Has anyone seen any news concerning other satellites (in general) and Starlinks (in particular)? There should be >150 S/C undergoing orbit-raising experiencing similar issues - even if not so severe as to bring them down in a matter of hours, there can have been issues with them as well, especially for the 4-6 group launched just a few days prior.This event has single-handedly doubled early mortality numbers for Starlink.
Has anyone seen any news concerning other satellites (in general) and Starlinks (in particular)? There should be >150 S/C undergoing orbit-raising experiencing similar issues - even if not so severe as to bring them down in a matter of hours, there can have been issues with them as well, especially for the 4-6 group launched just a few days prior.This event has single-handedly doubled early mortality numbers for Starlink.
Quote from: eeergo on 02/09/2022 07:12 amHas anyone seen any news concerning other satellites (in general) and Starlinks (in particular)? There should be >150 S/C undergoing orbit-raising experiencing similar issues - even if not so severe as to bring them down in a matter of hours, there can have been issues with them as well, especially for the 4-6 group launched just a few days prior.This event has single-handedly doubled early mortality numbers for Starlink.jcm updated his plots with data through yesterday for the previous 3 launches (4-4, 4-5, and 4-6) , and they all look like they are continuing to operate normally. "Normally" means raising to ~350 km, which starts within 36 hours of launch, and then drifting to precess until they are in plane to continue raising. There are plenty of sats both drifting and raising as of yesterday, and it all looks nominal.The 4-7 batch are now 9 days post-launch and never started the L+36 hour raise. They are clearly behaving much differently then the previous 3 launches. I don't think there's anything here to worry about for the earlier launches. https://planet4589.org/space/stats/star/starstats.html
