[BurningFrog]

I don't have a good feel for the numbers either, but surely if you make the Space Sponge big enough, things will get caught in it.

There is almost certainly a better material to use as well, but I don't think either of these practical concerns invalidates the idea.

Of course, big enough Space Sponges to make a practical difference would be very visible to the naked eye.

[MauranKilom]

Well, the reason why I brought up Newton's impact depth formula is that it quite clearly shows you have to have enough "braking" material up there. Distributing it over a greater area reduces the effectiveness proportionally.

The problem in the end is launch costs. Yes, we're getting better, but that doesn't mean we can shoot up a "visible to the naked eye"-sized impactor. Not to mention what difficulties an object of that size would bring for non-garbage that also occupies those orbits.

Lastly, I have no idea how much research there has been in containing the fragmentation of hypervelocity impacts. But presumably it would be an important part of the mission to not generate more garbage.

[BurningFrog]

OK, you've convinced me.

Even if launching costs ever makes this feasible, any Space Sponge big enough to be efficient would be a big collision problem in itself.