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Comment by inglor_cz | Hacker News Reader

We will need a cosmic vacuum cleaner one day.

Won't work because cosmos is mostly vacuum already :) But there are some neat tricks with lasers that can help https://en.wikipedia.org/wiki/Laser_broom

When really scares me is how easy it would be for a malicious actor to kickstart the process. Imagine a cylinder filled with ball bearings painted black and an explosive device in the middle. Launch that to a mega-constellation altitude and at the very least that orbital altitude is no longer inhabitable.

> Won't work because cosmos is mostly vacuum already

How else to clean a vacuum but with a vacuum cleaner? :-)

With Newtons 3rd law :) You use opposite of a vacuum to decelerate the objects. I.E. shoot gas moving in other direction at them.

Could perhaps ferromagnetic pieces be collected using a giant magnet?

Yup, magnetic drag is a definitely a thing, see https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/202... . To have a real effect the magnet would need to be ginormous, specifically effectiveness would be proportional to a ratio of distance between magnet poles and the target object. The distance between poles is important because if both poles are equidistant to an object the net effect would be 0.

So with that constraint in mind I doubt anything we can do at our current Kardashev scale can top Earths magnetic field. (Note the above is for a permanent magnet, it is possible that electromagnet would fare better. However given that magnetic force strength decays proportionally to distance squared, a magnet powerful enough to be effective would mess up real satellites too.

The ball bearings would suck for optical tracking but, most stuff is tracked by radar so the black paint really wouldn't do much more than add to the debris field as radiation would eventually cause it to flake off the metal and solar bleaching would turn it back to white.

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