“(b) Secondly, while the great powers may see military use for smaller scale orbital bombardment weapons (i.e. ones capable of causing sub-global or Tunguska-like asteroid events), these are only as destructive as nuclear weapons and similarly cannot be used without risking nuclear retaliation.”
I don’t think this is necessarily right. First, an asteroid impact is easier to seem like a natural event, therefore being less likely to result in mutually assured destruction. Also, just because we can’t think of a reason for a nation to use an asteroid strike, doesn’t mean there isn’t one. Accidental deflection of a small planetary body into an Earth-intersecting orbit is possible. And I don’t necessarily think that only great powers will have access to asteroid deflection technology in the future. As the technology develops, it will be possible for smaller and smaller groups to access it.
Given the relatively low probability of asteroid impacts on short-term timescales, it wouldn’t take that much of an increased risk from the deflection dilemma to make developing deflection technology not worth it.
I think improving detection technology might be a safer option to leave our options open while having a similarly positive effect.
Fair enough! I probably wasn’t clear—what I had in mind was one country detecting an asteroid first, then deflecting it into Earth before any other country/‘the global community’ detects it. Just recently we detected a 1.5 km near Earth object that has an orbit which intersects with Earth. The scenario I had in mind was that one country detects this (but probably a smaller one ~50 m) first, then deflects it.
We detect ~50 m asteroids as they make their final approach to Earth all the time, so detecting one first by chance could be a strategic advantage.
I take your other points, though.