Hi. Yes, using asteroids and rocks in general as kinetic energy weapons has been thought of. In fact, that scenario has been described in numerous novels, including The Expanse series, as well as Heinlein’s famous “The Moon Is a Harsh Mistress” from the 1950s.
All technology creates risk. The greatest technology related risks today are not space exploration not even global warming, but tabletop gene editing and artificial intelligence that carries the prospect of eventually leading to artificial “general intelligence”.
With technology, we have a universal choice: say “no” and live like the Amish, or accept the technology and attempt to manage the risks. There really is no inbetween choice. I don’t condemn the Amish for their choice — it is a valid choice. Their choice might prove to be the better one.
The real reason so many people want to embark on space exploration is not an immediately practical reason: they have a dream, and the dream is to — as Musk puts it — become an “interplanetery species”. The reason so many sci fi books (hundreds of thousands?) have been written about humans becoming an interplanetary species is that it is compelling to so many. Just visit a bookstore if you can still find one, and browse through the sci fi section.
To say “no” to it is to kill the dream of millions. I myself — now 63 — had given up on it, with considerable disgust and anger. When I was a teenager, I just assumed that by the year 2000 I would be able to travel to Mars and the moon — that these things would have become commonplace. But our government failed us, as governments almost always do. Now the dream is alive again, thanks to a few “rocket billionaires”.
Ironically, in all of Heinlein’s books, he predicts that: that governments will fail us with space exploration, and private individuals will lead the way. He turned out to be right.
Of course, all endeavors that might affect a-lot of people require governance. The National Geographic series “Mars” does an excellent job of exploring the governance issues and other issues for Mars settlement.
Governance is one thing; saying “no you can’t do that” is another. Articles that say “no, humans should not go to Mars”, etc., attempt to speak for all humans, as if we all have a single set of values. We don’t, and those articles make a-lot of people angry, just as someone saying “no, you cannot pursue your dream because I value something else” would make anyone angry.
