Hi All, I'm hoping some of you with more expertise in such matters can help me out with the plausibility of a scenario for a novel I'm working on. I know you guys must get stupid hypothetical questions like this frequently, so if I'm out of line just let me know and I'll just slink back to my word processor and keep working. This is a somewhat near future setting without super advanced technology. All of the technology is based on at least either what we can do now or what we can speculate we can do in the near future. Basically, what's happening is that there are independent colonies spread throughout the solar system that are being conquered by earth. The colonies hatch a plan to deal with earth by creating a cloud of debris around the planet that makes space flight too hazardous to be practical for several years (or more). Space ships are still essentially tin cans but with more advanced propulsion, so a pebble can still punch right through one of them. My idea for creating the cloud is this... A near earth asteroid (or comet) is going to make a pass by earth within a few earth-moon distances. A bomb (regular nuke or possibly antimatter) will be detonated on the surface, or under the surface of the asteroid to adjust the orbit enough to collide with the moon and knock massive amounts of regolith out of the moon's gravity well and into earth orbit. I'm assuming such an impact done in a precise enough way could knock up a lot of rock and with enough velocity to escape the moons orbit, but how big would the impactor have to be to saturate the space around earth with hazardous amounts of debris? Would your average hazardous NEO be large enough if it hit just the right way? Say 1.5km to 10km? Or do I have to start looking at freakishly large unknown comets instead? And could you create an explosion large enough to divert an asteroid (that's about a month away from a 1-2 earth-moon distance pass) so it would smash into the moon? The idea is, that the amount of time before impact should be short enough so that earth couldn't respond by detonating another bomb to make it miss. Keep in mind, large amounts (100's of kg) of antimatter atoms could be written in easily if nukes are insufficient. Thanks in advance for whatever input you can offer.