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Space Policy Online has an article from yesterday titled 'AUSTIN: NO PLANS TO SHOOT DOWN ERRANT CHINESE ROCKET STAGE'.

Which made me wonder - is that even plausible? If you shoot it in space, first how easy is that to really do, and second how would creating that cloud of debris affect the overall risk presented by the object?

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    $\begingroup$ Please don't do that ucsusa.org/sites/default/files/2019-09/… $\endgroup$ Commented May 7, 2021 at 20:58
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    $\begingroup$ It is possible to shoot down a bird or an airplane in air. But there is no shoot down of a rocket stage in orbit. The cloud of debris will be still in orbit $\endgroup$
    – Uwe
    Commented May 7, 2021 at 22:59
  • $\begingroup$ Unless you manage to momentum-transfer it appropriately. $\endgroup$
    – ikrase
    Commented May 7, 2021 at 23:57
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    $\begingroup$ Possible, yes. Even easy, nowadays. USA, Russia, China and maybe EU has anti-sat rockets in their military inventory that can do exactly this. Practical? Not so much, it is very likely to worsen the problem, causing a large number of fragments to be ejected to a higher apogee orbit, causing all sorts of grief for LEO. $\endgroup$ Commented May 8, 2021 at 7:32
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    $\begingroup$ @PcMan don't forget India too! $\endgroup$ Commented May 8, 2021 at 15:04

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It's entirely possible to shoot a spent rocket stage or a satellite in low earth orbit with an Anti-Satellite (ASAT) weapon, and in fact it has been done at least twice.

However, as you correctly suspect it's possible but not practical as it doesn't solve the problem. The chance that the stage will cause damage or injury is extremely low, and shooting it will just create a debris field that is a far greater problem.

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  • $\begingroup$ Provided you did it only just as reentry began, and so minimized the risk of impacts with other things in orbit, how small would the pieces have to be in order to be harmless on re-entry? I imagine terminal velocity goes down and the fraction that burns up rises as objects get smaller. $\endgroup$ Commented May 8, 2021 at 4:54
  • $\begingroup$ @KristofferSjöö How small must the pieces be to be harmless? About.... Well, anything smaller than the 76-tonne Skylab has been proven to be harmless, so let's use that as a baseline. $\endgroup$ Commented May 8, 2021 at 7:34
  • $\begingroup$ A kinetic impactor would make some nice small pieces and, if brought in from above, would slow and reduce the altitude of anything it hits. Good practice for the new Space Force, doing Long March a big favor. $\endgroup$ Commented May 8, 2021 at 11:42
  • $\begingroup$ Wikipedia has (had) a nice article covering the pro and con of anti sub orbital Intercontinental missiles system. It is somehow related to this thread. $\endgroup$
    – Alchimista
    Commented May 8, 2021 at 20:53
  • $\begingroup$ Intercepts by ASAT weapons cause not one but two sprays of debris. The first is the larger shower of debris from the target, the center of mass of which is slightly altered from its original orbit by the intercept. The second small spray of debris is from the remains of the interceptor vehicle itself along the direction of the interceptor, The latter usually returns to Earth quickly but an LEO target's debris may take years to come down while damaging other satellites in the meantime. A small bit of paint left a crater about 2 cm in diameter in the Shuttle's front window. Scary pic. $\endgroup$
    – Chris Ison
    Commented May 8, 2021 at 23:45
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This is a great question and I wish I'd asked it first! I saw Scott Kelly's answer when viewing this for an answer to Is it possible to know where the Long March 5B will be landed approximately? and so I'll add it here as well.

Let's ask an Astronaut

because they know stuff about practicality and risk

From CNN's Rocket debris expected to crash into Earth soon

CNN’s Kate Bolduan: The military said that they’re not going to shoot it down, why do you think that that is not a preferred option right now? Is it about the level of risk?

Ret. US Astronaut2 Scott Kelley: (Smiles demurely/dismissively at the thought of it) You know I just think that that is... for one it’s complicated and for two it could make the situation worse perhaps… I don’t think it’s really necessary. [...] my guess is that it’s going to land in the Pacific Ocean; often when I was on the (International) Space Station, you look out the window, and it’s the Pacific Ocean, so my bet is that it’s going to land there.

Scott Kelley on CNN

2 cmdr STS-118, EXP-26, EXP-45, EXP-46

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