If you're going to bombard something for military purposes, the most effective technique involves using a very large number of nuclear weapons, which is well within the capabilities of anyone who would try to bombard the earth from space.
Back during the Space Race, the idea that the Russians could put something into orbit wasn't just a wound to the national pride, it was a technical demonstration of the fact that they could build ICBM's. If you have the rocket power necessary to lift something into orbit, you have the rocket power necessary to put a warhead on a ballistic trajectory to any point on the earth's surface. So if you can go into space and redirect asteroids, you can obviously launch an ICBM. And at this juncture, it's probably easier to develop the technology for nuclear weapons than the technology to capture asteroids and bombard the earth with them. The only way you could do more damage more cost-effectively with asteroids is if you had an extinction-level asteroid, but there's obviously no strategic value to that.
Bear in mind, I'm only talking about how scary it is, which isn't quite the same as discussing how militarily effective it is. By which I mean--obviously orbital bombardment can be worthwhile, but it would cause no more damage than nuclear weapons, and any magnitude of orbital bombardment that wouldn't trigger a MAD reaction would have to cause strictly less damage.
However, it's easier to claim that a mining asteroid crashing into your enemy was an act of sabotage/accident/non-national terrorism than a rain of nukes with your signature on them.
An interesting thing is that ballistic missiles that go through space, like the V2 and Scud, are dramatically easier than getting into orbit. Like 10% of the energy cost. Getting your ballistic missile to the other side of the Earth, though, does seem like it would require only epsilon less energy and precision than putting it in orbit. (I haven't done the math, so I could be wrong.)
> If you're going to bombard something for military purposes, the most effective technique involves using a very large number of nuclear weapons...
Only if you don't intend to occupy that land in the next 500 years, though. I'd imagine a tungsten telephone pole dropped from orbit has better deep-ground penetration than a nuke, too.
Sorry, this is a common misunderstanding. Modern nuclear weapons are generally very fuel efficient, while there are some short lived nucleotides that are brought on by the activation of elements exposed to the gamma ray flux during detonation, unless you actively try to make it 'dirty' (and thus long lived) you can go back to living there in a couple of months. The only cities which were atomically bombed are completely livable today (much less than 500 years).
The dangers of a large nuclear exchange are widespread climate change and economic disruptions brought about by entire supply chains being removed. Not 'wastelands' of bombed out cities too radioactive to visit.
Military applications may divert a couple billions into developing the technologies needed for peaceful applications. Even with traditional government inefficiencies, that's the equivalent of a couple hundred millions in private enterprise. Not entirely bad and consider we here at HN are not the first people to think about it.
Don't forget the Redstone and Atlas rockets that carried the Mercury capsules were (not very) modified ICBMs.
This scary thought makes up much of the backdrop for one of my favourite scifi stories, The Moon is a Harsh Mistress. Definitely worth a (re)read given this latest news!
