[candiodari]

Why is that necessary ? We can control the speed of asteroid impacts without crashing them into the Moon.

Nobody (I hope) is suggesting just putting an asteroid on a crash course with earth. Rather the idea is to bring the asteroids in an orbit around the earth and/or the moon and then leave them there, biting off small chunks and deorbiting them one at a time. So what would impact would be something like 10-100 tons at a time, in 10 tons-at-a-time chunks, maybe even less (enough weight so they survive reentry, or maybe we package them to "fly"/crashland like the space shuttle)

So capturing an asteroid refers to moving them into a parking orbit around earth, nothing more.

And don't worry. Earth orbit is an unbelievably big place. If you don't want to be at special places (like geosync orbit, or just as close as possible), there is no shortage of space whatsoever.

[M_Grey]

Why take the risk? If anything goes wrong you either lose the asteroid with unpredictable results, or worse, it crashes uncontrollably. With the moon, you really don't have to care. It's also a useful "base" for any other exploration or industry we'd care to have, without having to overcome the Delta-v of something like Mars.

[candiodari]

I don't think you quite realize just how much energy we're talking about here. Most asteroids have enough mass, which at a realistic speed could shatter the moon.

If we shatter the moon, well, let's put it this we : at that point we're fucked. As in close to end of human race fucked. There will be worldwide constant meteor showers for years, which will impact with enough force to penetrate nuclear bunkers. Oceans will boil for years.