A reality of physics, and one that doesn't get much play in science fiction, is that as soon as humanity gains space travel, anyone in the asteroid mining or space travel business will have city-busting capabilities at their fingertips.
It's there in classic sci-fi, but not so much recently.
This discussion was started in the comments to:
http://lesswrong.com/lw/gln/a_brief_history_of_ethically_concerned_scientists/
In the "Ethically Concerned Scientists" post, Izeinwinter commented:
, I have given some thought to this specific problem - not just asteroids, but the fact that any spaceship is potentially a weapon, and as working conditions go, extended isolation does not have the best of records on the mental stability front.
Likely solutions: Full automation and one-time-pad locked command and control - This renders it a weapon as well controlled as nuclear arsenals, except with longer lead times on any strike, so even safer from a MAD perspective. (... and no fully private actor ever gets to run them. ) Or if full automation is not workable, a good deal of effort expended on maintaining crew sanity - Psyc/political officers - called something nice, fluffy, and utterly anodyne to make people forget just how much authority they have, backed up with a remote controlled self destruct. Again, one time pad com lock. It's not going to be a libertarian free for-all as industries go, more a case of "Extremely well paid, to make up for the conditions and the sword that will take your head if you crack under the pressure" Good story potential in that, though.
A great start to a discussion here.
You've considered people going loons and some general security, but it would then become a hacker war along the lines of who could break the security and gain control of the space ships.
It doesn't address the problem of the leaders using the ships as threat weapons, since they have legitimate control, but can still make terrorist decisions.
And I'm terrified of your idea of turning spaceflight, which I see as the ultimate freedom, along the lines of Niven's Belters, into a state-controlled affair like the Soviet navy with political officers.
Now, one thing I think is a useful safety control that doesn't lead to worse problems is the destruct option. All major rockets have them right now, since if it goes out of control it's a huge hazard for a great distance. And although I don't like the idea of all personal spaceships being under a safety officers thumb, it might be better than the alternative of terrorist groups gaining control of asteroid mines and holding the world hostage.
You're right about great story potential though, in any of these scenarios.
How do you know that's the reality? Could you go into more detail? Especially if you have enough telescope satellites to monitor all mining activities and some nuclear weapons to attack asteroids that get redirected?
Will a company like Planetary Resources, Inc have the ability to blow up a city when it gets it's mining working?
I think the idea is that active defensive measures (as opposed to just watching with telescopes) are a lot more difficult to set up, and there's little motivation considering that the space activities aren't military-oriented. Although I suppose if we'd be far enough in space exploration to have asteroid mining there'd also be some contingency plans for extinction-grade bricks on a collision course; plans that can probably be adapted to include 'hostile local' handling.
Regarding the physics, do not underestimate heavy things flying very fast, especially if they're good at staying in one piece - a ship/asteroid may well destroy a city when dropped at 10~30km/sec, and attackers will aim.