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Those are two massive objects (2800kg or 6100 lbs) with a high relative velocity (14km/s or 31,000 mph) basically head on, so a crash would be a disaster.
by MarkMarine 6y ago
Those are two massive objects (2800kg or 6100 lbs) with a high relative velocity (14km/s or 31,000 mph) basically head on, so a crash would be a disaster.
- kortilla 6y agoSorry if stupid, but why? Wouldn’t the head-on nature mean most of the energy goes into destroying each other’s velocity and they just fall into the atmosphere?
- TeMPOraL 6y agoAt these velocities, the objects behave as if being made of glass or water. Upon collision, we can expect a large number of small fragments flying out in pretty much every direction - some still fast enough to retain orbital velocity. And given the altitude of the event, 991 km, even those fragments that fall down may shred something on their way down.
- raverbashing 6y agoBut if they are on LEO the atmospheric drag shouldn't be too negligible no?
- lmm 6y ago991km is pretty high for LEO - ISS is at ~400km, Hubble is at ~500km.
- mikewarot 6y agoFrom up stream in the comments, one was launched 31 years ago... so yeah, this stuff could stick around a while.
- threatripper 6y agoFor every 100-200 km in height the lifetime seems to increase by a factor of 10. At 900 km the lifetime of big objects is 1000 years. Smaller objects can still orbit 10s to 100s of years.
- yetihehe 6y agoThose fragments will scatter in all directions. Some will go down, some will go up or in eccentric orbits, some wil go sideways, some will stay in the same or similar orbits. There will be A LOT of those fragments, all going at orbital speeds in various directions.
- TeMPOraL 6y agoIt isn't negligible on the timescales we care about. Skimming through the graphs in [0], at 900km we're talking 100+ years of orbital lifetime. And even if most fragments were to disappear sooner[1] - giving them a generous 20 years - that's still 20 years of dealing with a swarm of untrackable hypervelocity bullets coming at you from random directions. While space is big, it's not that big in LEO, and any such bullet will, upon impact, spawn more bullets. I don't think we'll have a catastrophic cascade leading to Kessler syndrom even if these two satellites collide today, but few more such events might be enough. EDIT: Also, the collision will be off-center and, eyeballing the orbital diagrams, some 15 degrees shy of being head-on. That means you can expect most of the both satellites not being directly involved in the collision, but instead gaining spin and breaking apart under stress. Those surviving pieces will then keep most of their orbital velocity and heading, but scatter like buckshot, each piece on slightly different orbit, migrating further over time. -- [0] - https://www.spaceacademy.net.au/watch/debris/orblife.htm https://www.spaceacademy.net.au/watch/debris/orblife.htm [1] - Orbital decay due to atmospheric drag is a function of mass to area ratio. I'm not sure whether the debris from a hypervelocity collision tends to be more like irregular, high-drag shatter, or like low-drag spheres of superheated metal that cooled off radiatively.
- dmurray 6y ago> Also, the collision will be off-center and, eyeballing the orbital diagrams, some 15 degrees shy of being head-on. How can we tell it will be off-centre if there's enough uncertainty in the orbital prediction that they are only "1% to 20%" to collide at all?
- TeMPOraL 6y agoBecause if there's 1% to 20% chance they'll collide at all, then the chance they'll collide centrally is even smaller.
- nabla9 6y agoIt depends on LEO altitude (exponentially) and aerodynamic properties of the object. ~ 150 km making single orbit becomes impossible. ~ 300 km orbital decay is ~km/month, so it already takes years to fall down to earth. ISS is at 400 km and decays 2 km/month. It has unfavourable mass to area ratio due to all those solar panels. ~ 500 km it takes few decades to fall down. (Hubble space telescope is here) 990 km is the altitude where these two satellites might collide. Debris can stay up thousands of years .
- xvector 6y agoKessler syndrome - hundreds of thousands of tiny shards would explode at the point of impact ripping into other satellites and rendering them defunct (causing more collisions). An exponential growth would occur which would result in Earth orbit being unusable. This might effectively lock use of Earth orbit away for centuries. See the video by Kurzgesagt - “End of Space: Creating a Prison for Humanity.” [1] [1]: https://youtube.com/watch?v=yS1ibDImAYU https://youtube.com/watch?v=yS1ibDImAYU
- staticassertion 6y agoCan't wait to be boiled alive on this stupid planet because we filled space with garbage.
- ladberg 6y agoIf it makes you feel any better it's pretty much impossible to make Earth less habitable than anywhere else in a few light years, so I wouldn't worry about missing out on a space-paradise!
- jyriand 6y agoSo, will it be something similar to the collision scene in "Gravity", movie?
- MarkMarine 6y agoYup. Not good for anything in LEO
- jfoster 6y agoFor anyone who hasn't seen the movie: https://www.youtube.com/watch?v=vKW-Gd_S_xc https://www.youtube.com/watch?v=vKW-Gd_S_xc What's the likelihood of any given collision like this initiating a space debris chain reaction? I'm guessing it's fairly low for any given collision, but quite high if we continue to allow collisions to happen. Would love to hear from someone who knows better than I do, though.
- slazaro 6y agoThere's lots of info around that here: https://en.wikipedia.org/wiki/Kessler_syndrome https://en.wikipedia.org/wiki/Kessler_syndrome