8 ms·
Eu_sst: 20% probability for large satellite collision
- AlphaGeekZulu 6y agoThe two satellites involved are: OPS 6182 (10820, 1978-042A): https://www.n2yo.com/satellite/?s=10820 https://www.n2yo.com/satellite/?s=10820 SL-8 R/B (12443, 1981-041B): https://www.n2yo.com/satellite/?s=12443 https://www.n2yo.com/satellite/?s=12443 They are on head-on course. With a probability of about 80 percent they will miss each other. With a probability of more than 20 percent they will impact at a speed of more than 50000 km/h in an altitude of 780 km. The two objects are not important (an old Russian rocket piece and an old US weather satellite). But upon impact, the objects will create a large cloud of debris, that might collide with more objects, in the worst case in a chain reaction. The danger is not falling debris, but that they will produce more damage in their orbit, maybe hitting more essential space equipment in the future. No need to hide in a bunker.
- cassianoleal 6y agoExcellent explanation, thanks very much!
- moring 6y agoCan somebody give a layman explanation why the debris would stay in the same orbit? I would expect a lot of energy to go into destroying both objects, especially in a head-on collision.
- hn_throwaway_99 6y agoConservation of momentum. All of the teeny little bits of the two colliding objects still have the exact same average momentum of the two original objects, now there are just hundreds of thousands of them flying off in slightly different directions. The movie Gravity actually gives a fairly good, if overly dramatized, example of what happens when objects collide in space.
- eqvinox 6y agoPut quite simply - the energy doesn't go into destroying objects. There's only a very small amount going into heating things up from mechanical deformation [and a bit into spinning], but fundamentally, splitting something in a million pieces just means you have a million pieces that have the same total kinetic energy in orbit. However, they also exchange kinetic energy & impulse with each other, meaning you get a mix of slower and faster pieces. This is what the Gabbard diagram shows: https://twitter.com/EU_SST/status/1380443036862316545 https://twitter.com/EU_SST/status/1380443036862316545 Anything that is sped up in the collision (i.e. "steals" energy from another piece) has the same perigee (orbit low point) but a higher apogee (orbit high point.) The reverse happens to anything slowed down / stolen from. That's why the graph looks like open scissors. Some pieces with lower perigee will friction against earth atmosphere and burn up, but the ones with higher apogee become a serious problem... (also, for anyone who can't remember to distinguish apogee & perigee: think of your periphery, it's the things close to you :D)
- JshWright 6y agoI think of "peripheral" as being "far from the center of my vision". Fortunately, years of Kerbal Space Program means the apo/peri prefixes are pretty solidly ingrained.
- eqvinox 6y agoAh crap :/ …well I guess the "center of vision" is the center of the orbit ellipse… ;D (just trying to salvage the mnemonic aid for myself)
- _0ffh 6y agoMy mental crutch was always Apogee Software. It's more intuitive that someone calls their company "High Point Software" than "Low Point Software".
- ithkuil 6y agoMy mental crutch is "apotheosis" (the high point of something)
- mnw21cam 6y agoA lot of the debris won't stay in the same orbit. It'll be like a mini-explosion, spraying out debris in every direction, but then add the existing velocity to that. So yes, the debris will be in another orbit. The question is, how much of a change occurs. In the twitter thread, there is a Gabbard diagram that shows a prediction of the orbits that the pieces will end up in. The satellites currently have a reasonably circular orbit, with apogee (highest point) and perigee (lowest point) about 800km. After the collision, the apogee is likely to be higher and the perigee is likely to be lower, so the orbits won't be circular any more. The way this happens is - if the debris piece is knocked directly backwards, then its apogee will be about the same, but its perigee will be lower. If it is knocked forwards (yes, that can happen), then the apogee will be raised, and the perigee will be about the same, and the piece could remain in orbit for a long time. If it is knocked up or down, then both the perigee will be lowered and the apogee will be raised. If the perigee is low enough, then the pieces will scrape through the upper levels of the atmosphere, and de-orbit eventually. It looks like the prediction is for the lowest perigee to be about 200km. It may take a long time for even those pieces to de-orbit.
- brandmeyer 6y agoIt doesn't. It splatters into many related orbits. https://twitter.com/EU_SST/status/1380443036862316545/photo/1 https://twitter.com/EU_SST/status/1380443036862316545/photo/...
- stonesweep 6y agoDoes the debris have a degrading orbit and eventually get pulled earthward and burn up on entry? Or is that chaff out there floating around forever just outside the gravitational pull?
- toomuchtodo 6y agoIn the case of these objects, at ~800km, the time for orbital decay is often measured in decades.
- londons_explore 6y agoTry millennia...
- mnw21cam 6y agoSome of the pieces will have a lower orbit, which might be low enough for them to scrape the atmosphere and bring them down. Some of the pieces will be placed into a higher orbit (although the lowest point won't be raised).
- theginger 6y agoDid they miss? Both those links show them still there, but I suspect they are calculated not real time
- londons_explore 6y agoThey missed
- deleted 6y ago[deleted]
- superkuh 6y agoHere's the text without having to execute arbitrary code from twitter. --- Update: according to #EUSST's latest estimates using data from its surveillance radars, the close approach between #space objects SL-8 R/B & OPS 6182 expected by tomorrow will have a miss distance under 10m and a Scaled Probability of Collision over 20%! +updates to follow soon See the below plot for the conjunction plane at Time of Close Approach (TCA) #EUSST #spacedebris #space https://pbs.twimg.com/media/EycvaPZWQAMXjV2?format=png&name=large https://pbs.twimg.com/media/EycvaPZWQAMXjV2?format=png&name=... Update: #EUSST simulations indicate that the potential collision between the two #space objects would generate more than 4 million fragments. This plot shows the Delta-V distribution of the whole cloud of fragments #spacedebris https://pbs.twimg.com/media/EyhGxpjXMAE-pmM?format=jpg&name=small https://pbs.twimg.com/media/EyhGxpjXMAE-pmM?format=jpg&name=... More than 400 of the fragments generated by the potential collision would be larger than 20cm. Gabbard diagram shows the extent of orbital regimes that these simulated fragments would reach. #EUSST continues monitoring the probability of collision. Stay tuned for more updates. https://pbs.twimg.com/media/EyhQ_InWYAI5V5a?format=jpg&name=small https://pbs.twimg.com/media/EyhQ_InWYAI5V5a?format=jpg&name=... Latest update: according to #EUSST the close approach between #space objects SL-8 R/B and OPS 6182 remains stable in geometry and in Scaled Probability of Collision. Miss distance would be ~21m and Scaled PoC over 20%. This should be the last estimate until TCA. https://pbs.twimg.com/media/EyiBCnsXEAAgrCu?format=jpg&name=small https://pbs.twimg.com/media/EyiBCnsXEAAgrCu?format=jpg&name=...
- cassianoleal 6y agoAre you able to translate this to layman's terms? Should I find a bunker?
- nwah1 6y agoI assume the fear of this sort of thing is the potential for causing Kessler Syndrome.
- soldehierro 6y agoNo, there's not a risk of space debris.
- artemonster 6y agoHow likely is a massive satellite collapse is to happen in nearest future? Are there any educated guesses/estimates?
- londons_explore 6y agoThe thing to look up is "Kessler syndrome". It appears we have already passed the threshold at some altitudes, so a satellite collapse will happen in the future, but probably not for hundreds of years.
- yetihehe 6y agoAnyone knows above where it could happen? I see that it's almost 800km above earth, but what about nearest lat/lon?
- AlphaGeekZulu 6y ago67.820°N 176.552°O (north-east Russia)
- undecisive 6y agoIn summary, a rocket body and an old weather satellite want to have a nice big hug. At high speed. Producing a cloud of 4 million fragments. 400 of which will bigger than 20cm. Except that they'll probably miss (by about 10m). Probably. Really interesting how much of this is statistical probabilities, and how much we can model about this. Right down to particle sizes. And yet, I still have so many questions. Mostly involving the maths from https://what-if.xkcd.com/13/ https://what-if.xkcd.com/13/ and whether we could push either of them out of the way...
- scanny 6y agoI’m curious as to how they get those sizes and quantities! Too they have cad models of both objects or are they just taking the radar returns and material and making an estimate?
- bagels 6y agoFor well known objects like these, the mass and approximate size is known. You can Google them to find values even. The positional uncertainty and lack of data about attitude lead to modelling the objects as spheres as not so bad a choice. One algorithm that is sometimes used: https://link.springer.com/article/10.1007/BF03546397 https://link.springer.com/article/10.1007/BF03546397
- bagels 6y agoIt would probably take longer than the notice you might get of a potential collision (5-7 days)
- SethTro 6y agoLeolabs is tracking as well. Their data suggests a slightly lower but >2% chance of collision https://twitter.com/LeoLabs_Space/status/1380549507390259203 https://twitter.com/LeoLabs_Space/status/1380549507390259203
- ISL 6y agoThat's somewhat more comforting, but alas, hope alone is not a strategy.
- 1-6 6y agoPuts away popcorn
- joezydeco 6y agoThe Leolabs Visualizer is pretty amazing. I didn't understand what the red gates were on the map until I looked inward - they're running their own radar sites in different parts of the world to track the objects privately. That's cool. https://platform.leolabs.space/visualization https://platform.leolabs.space/visualization
- Buttons840 6y agoDo near misses (hopefully) like this happen without us knowing, or do we track almost everything in orbit?
- bagels 6y agoYes, but more frequently between small anonymous debris pieces (due to their quantity)
- the_duke 6y agoThe current tracking infrastructure detects pieces down to 10cm. All of those are catalogued, get identification numbers, and are tracked. Active sats often do small collision avoidance maneuvers.
- temp0826 6y agohttps://en.wikipedia.org/wiki/Kessler_syndrome https://en.wikipedia.org/wiki/Kessler_syndrome
- m463 6y agodate -d "2021-04-09T17:18:21 UTC" result: time in your timezone (on linux)
- swsieber 6y agoSo, in about an hour.
- gmuslera 6y agoWith a bit of luck, Sandra Bullock won't be involved in a satellite collision this time.
- hinkley 6y ago"Houston, I have a bad feeling about this mission."
- polishdude20 6y agoYou can watch a map of both here! https://www.n2yo.com/?s=12443|10820 https://www.n2yo.com/?s=12443|10820
- mikewarot 6y agoTangent: I went to find UTC, and they've redesigned time.gov, it looks great on my desktop. https://time.gov/ https://time.gov/
- meowster 6y agoIt happened about a year ago, and I think one of the developers commented on HN: https://news.ycombinator.com/item?id=22272966 https://news.ycombinator.com/item?id=22272966
- salamander014 6y agoMy personal favorite time/NTP website is https://time.is/ https://time.is/ https://time.is/UTC https://time.is/UTC
- gerikson 6y agoLove time.is. You can embed JS from them in your own webpages for custom clocks.
- capableweb 6y agotime.is is pretty great! Their calendar is real handy as well, especially to see duration between two dates: https://time.is/calendar https://time.is/calendar
- Black101 6y agoI never realized that there was two time zones in Arizona...
- spzb 6y agoHow soon after the event will we find out whether they collided?
- marshmallow_12 6y agoit's 2021 now. They have presumably been tracking the orbits of there large objects for years now. Yes this is literally rocket science, but this collision is only a few hours away. Why can't they do better then a vague 20%?
- iSnow 6y agoMy guess would be because sats are not perfect spheres but - esp in the case of a rocket stage like here - complex objects which have non-trivial rotation patterns because the center of gravity might be off the visible center. So I doubt they model each and every piece of space junk out there to get a super detailed prediction - after all, what can you do if you know 95% it's going to be a hit between do dead sats vs if you know 80%. Radar resolution of civil orgs might also be a limit.
- junon 6y agoYou're right; do some analysis yourself and tell us your findings ASAP please :)
- marshmallow_12 6y agovery funny. My sums should take me just a couple of hours...
- iSnow 6y agoSnarky replies aren't really helpful as an answer to a question - even if it was in loaded form.
- junon 6y agoIt wasn't snark. This is how peer review works.
- kilotaras 6y agoBecause the difference between collision and safely pass is less than 0.01% on the scale they model it.
- AlphaGeekZulu 6y agoBrace, brace, brace ...
- the0nyx 6y agoCRISIS AVERTED
- civilian 6y agocitation?
- polishdude20 6y agoIs it? Or are the current satellite view websites just showing predicted paths?
- marshmallow_12 6y agodid they hit or miss?
- hinkley 6y agoYou're off by a day. We just passed 24 hours to minimum distance.
- civilian 6y agoedit: nevermind
- smithza 6y agoAll of those corporations are in the business of development and integration of satellites as well as satellite operations for commercial, public, and military customers.
- mckirk 6y agoWorst case: Our planet ends up with Kessler syndrome and nobody will launch a satellite for quite a while... But in the bright side, I'm fairly sure your stocks wouldn't be alone in tanking if that happened.
- keithwhor 6y agoFor anybody interested, they missed: https://www.n2yo.com/?s=12443|10820 https://www.n2yo.com/?s=12443|10820 (Link further in thread.)
- yetihehe 6y agoWe don't know yet. Satellites (especially defunct) don't have active live tracking like ships. Satellite sites show them based on calculated trajectories. Edit: as of 2021-04-09T20:21:00Z EUSST thinks they missed. https://twitter.com/EU_SST/status/1380601898164744199 https://twitter.com/EU_SST/status/1380601898164744199
- jepler 6y agoleolabs' next anticipated contact with SL-8 R/B 12443 is at 21:06UTC https://platform.leolabs.space/catalog/L5136#next-planned-passes https://platform.leolabs.space/catalog/L5136#next-planned-pa... next anticipated contact with OPS 6182 at 20:00UTC https://platform.leolabs.space/catalog/L11618#next-planned-passes https://platform.leolabs.space/catalog/L11618#next-planned-p... So what's that, about 90 minutes from now assuming I've got the right info?
- runarberg 6y agoAre these satellites visible by telescope, can someone in e.g. Ankara try to spot SL-8 R/B 12443 as it as it flies over there in a few seconds?
- sitkack 6y agoIs there an automated amateur run satellite tracking network? Just tracking points of light at dusk/dawn is an easy thing and wouldn't even require pointing, imagers could be fixed.
- terom 6y agoMissed? https://twitter.com/EU_SST/status/1380601898164744199 https://twitter.com/EU_SST/status/1380601898164744199 > UPDATE: #EUSST’s network of sensors has only detected a single object or echo at passes over three radars after close approach. Most likely, the collision between SL-8 R/B and OPS 6182 did not take place. We will continue observing the objects to confirm this assessment.