Here's my rough impression of what we may expect to see if the collision happens. Note that the collision isn't going to be perfectly heads-on, and is statistically unlikely for the centers of mass to collide.<p>BEFORE:<p><pre><code> ^ /
| |
| o - CZ-4C R/B
| /
| |
| /
|/
|
*
/|
| |
/ |
/ o - COSMOS 2004
| |
/ |
v |
</code></pre>
AFTER:<p><pre><code> aaa^ /
aaaa |
aaaa |
aa /
b aa b b
bb b bb b b
ccc b b
ccccc b b
b ccccc b b
b b ccc
b b b b b
b a |
aa |
aaa |
aaa |
aaa |
</code></pre>
Legend:<p>a - Shattered fragments of the parts of satellites that weren't involved in direct hypervelocity collision, but got torn off and spun. Essentially like a shotgun discharge, but in space. These will carry most of their original kinetic energy and follow close to their satellite's original trajectory, slowly spreading over time and becoming untrackable. These will stay around the longest.<p>b - Pieces that were close to or directly involved in the collision, retaining enough orbital velocity to stay in space. May be on highly eccentric orbits. Should decay faster than pieces labeled "a" (I think, I'm not sure).<p>c - Pieces that lost enough velocity to fall either straight down, or fly upwards and then fall straight down. These may cause some damage on their way down to ground, but should disappear quickly.<p>For reference, here are some (much prettier) diagrams of the 2009 collision, that happened at close to 90 degree angle: <a href="http://celestrak.com/events/collision/" rel="nofollow">http://celestrak.com/events/collision/</a>.
Probability of collision between 1% and 20%.<p>These are extraordinarily high numbers.<p><a href="https://en.wikipedia.org/wiki/Kessler_syndrome" rel="nofollow">https://en.wikipedia.org/wiki/Kessler_syndrome</a>
Leolabs has updated maximum likely encounter distance to 12 meters, >10% chance of collision. [1]<p>The objects are a Russian Parus navigation satellite (see [2] for image) and a Chinese expended rocket booster, the third stage of a Chang Zheng 4C rocket (see [3] for image).<p>[1] <a href="https://twitter.com/LeoLabs_Space/status/1316410780552699909" rel="nofollow">https://twitter.com/LeoLabs_Space/status/1316410780552699909</a>
[2] <a href="https://space.skyrocket.de/doc_sdat/parus.htm" rel="nofollow">https://space.skyrocket.de/doc_sdat/parus.htm</a>
[3] <a href="https://space.skyrocket.de/doc_lau_det/cz-4c.htm" rel="nofollow">https://space.skyrocket.de/doc_lau_det/cz-4c.htm</a>
SOCRATES seemed to see a much smaller probability for this event when it recalculated around the same time:<p><a href="https://celestrak.com/SOCRATES/search-results.php?IDENT=NAME&NAME_TEXT1=COSMOS+2004&NAME_TEXT2=&CATNR_TEXT1=&CATNR_TEXT2=&ORDER=MAXPROB&MAX=25&B1=Submit" rel="nofollow">https://celestrak.com/SOCRATES/search-results.php?IDENT=NAME...</a><p>I wonder why?
Now would be a good time to push one of the satellites out of the way (softly). Maybe one of those big airborne lasers [1]<p>Every piece of junk we put in space should be able to de-orbit on command.<p>[1] I know, I know the ranges are way off, but it _could_ work if something on the outside of the object would gas off and provide a propellant <a href="https://en.wikipedia.org/wiki/Boeing_YAL-1" rel="nofollow">https://en.wikipedia.org/wiki/Boeing_YAL-1</a>
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.
Considering they have nearly opposite velocities, would any debris have enough velocity to stay in orbit after a collision?<p>I'd assume the majority would fall out of orbit while maybe a few smaller pieces stay up, but if anyone knows of similar past events or simulations for reference then I'd be interested in seeing them!
This is the satellite [1] - launched in 1989 [2]. At least it doesn’t have a nuclear reactor as many other soviet military sats do.<p>[1] - <a href="https://en.m.wikipedia.org/wiki/Parus_(satellite)" rel="nofollow">https://en.m.wikipedia.org/wiki/Parus_(satellite)</a><p>[2] - <a href="https://www.n2yo.com/satellite/?s=19826" rel="nofollow">https://www.n2yo.com/satellite/?s=19826</a>
Given how much cheaper and frequent it is becoming to get into space with SpaceX launches. how long until we start seeing high-risk-debris deorbit missions?<p>I think these would be good candidates for well used falcon stages that might fail since I doubt the payload would be that expensive in hte form of a small'ish, mass-produced, short-life robot that separates from the stage, grabs on to the debrit and pushes. (Yet I know I am glossing over a lot of technical details, still cheaper than what we normally send up).<p>Robot is disposable and goes down with the debris. Falcon-9 returns to land for the next robot.<p>But in my super-fantastical dream, the robot would detach from the nearby falcon 9 stage, do the pushing on the debris, then return and reattach to the falcon-9 (Opening and closing fairing) and the falcon 9 brings the robot back.<p>Refuel and repeat.
The people at the South Pole stations will be able to catch some interesting fireworks. At 900 km it should be above the horizon about 3000 km away, so it'll be pretty high in the sky for them.
A couple of questions:<p>1. How likely is it that a collision like this (two large satellites, high enough for the fragments to have a long orbital lifetime) occurs in any given year?<p>2. This announcement popped up on HN a couple of days before the event. Are we not able to project potential collisions farther ahead? I would think objects of this size are well tracked.<p>I'm wondering how difficult it would be to detect these far enough in advance to send something up to nudge one of the dead satellites out of the way.
I believe this should be a live-track of these two objects on NORAD: <a href="https://www.n2yo.com/?s=36123|19826" rel="nofollow">https://www.n2yo.com/?s=36123|19826</a>
I am trying to wrap my head around this, assuming collision, what would be the likely secondary effects - many satellites knocked out? Communications grids down? Falling debris doing real damage (seems unlikely to me, but maybe airplanes?)<p>The first two seem likely given Kessler syndrome.
If there were a collision, and a chain reaction that led to disruption of other satellites, what is the chances that certain world leaders use it as an excuse to declare state of emergency, and if so does that effect election dates?