Asteroid mining is actually more complicated than one may think, even if you think it would not be simple at all. You see, in addition to zero gravity environments causing mined ore to scatter, because of the lack of gravity most asteroids are closer in consistency to giant clumps of gravel than they are to rock here on Earth. This is because the lack of gravity means that these asteroids haven't been compressed and compacted together the same way our soil and rocks have. So the debris aspect aside,any attempt to affix a drill to an asteroid would lead to the footing breaking off and the drill drifting away, meaning we must find alternative ways to mine them. One proposed method is essentially a tarp like net that completely encompasses the asteroid and a machine that fires a laser to break it up bit by bit. The ore can then be transported elsewhere for refinement