Imagine we have a particle-assembly device which we can trustily feed raw components and out comes planned assemblies. We could call this thing, a "3D printer"

Imagine we have a particle-assembly device which we can trustily feed raw components and out comes planned assemblies. We could call this thing, a "3D printer" because it allows us to print things but in this particular case its literally the best 3D printer in the known universe, because: it recycles everything it prints. So, we have this ideal device, and we send it up to one of these asteroids, in some form of redundancy of course (i.e. there is more than one ideal device, rather now a fleet of them), and the first thing that happens is that the fleet duplicates itself. Then, we have the ability to remotely send print jobs, some sort of .. inter-spacial network of some variety or brand or another .. whereby anyone on Good Ol'^WNew Earth can send something to the print queue. If the job is printable (it is/will be) then the asteroid is consumed, bit-by-bit. These bits fly themselves back to Earth for use. OR! They fly themselves somewhere else in space, for use ... Okay, I think I'm getting a nice video game idea from this article at least. Time for some science!